# The Next Generation Virgo Cluster Survey (NGVS). XL. The Morphological Classification of Virgo Cluster Galaxies

Max M Kurzner, Patrick Côté, Laura Ferrarese, Kaixiang Wang, Eric W

Peng, Scott Wilkinson, Joel C Roediger, Chelsea Spengler, Toby Brown,

Chengze Liu, et al.

► To cite this version:

Max M Kurzner, Patrick Côté, Laura Ferrarese, Kaixiang Wang, Eric W Peng, et al.. The Next Generation Virgo Cluster Survey (NGVS). XL. The Morphological Classification of Virgo Cluster Galaxies. The Astronomical Journal, 2025, 170, 10.3847/1538-3881/ae1616 . insu-05410912

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# The Next Generation Virgo Cluster Survey (NGVS). XL. The Morphological Classification of Virgo Cluster Galaxies

Max M. Kurzner¹ ID, Patrick Côté² ID, Laura Ferrarese² ID, Kaixiang Wang³ ID, Eric W. Peng⁴ ID, Scott Wilkinson¹ ID, Joel C. Roediger⁵ ID, Chelsea Spengler¹ ID, Toby Brown² ID, Chengze Liu⁶ ID, Sungsoon Lim⁷ ID, Rubén Sánchez-Janssen⁸ ID, Elisa Toloba⁹ ID, Puragra Guhathakurta¹⁰ ID, John P. Blakeslee⁴ ID, Patrick R. Durrell¹¹ ID, Ariane Lançon¹² ID, J. Christopher Mihos¹³ ID, Matthew A. Taylor¹⁴ ID, Tyrone E. Woods¹⁵ ID, Solveig Thompson¹⁴ ID, and Lauren A. MacArthur¹⁶ ID

¹ Department of Physics and Astronomy, University of Victoria, Victoria, BC V8P 1A1, Canada; mkurzner@uvic.ca

² National Research Council of Canada, Herzberg Astronomy & Astrophysics Research Centre, Victoria, BC, V9E 2E7, Canada

³ Department of Astronomy, Peking University, Beijing, China Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing, People's Republic of China

⁴ NSF's NOIRLab, 950 N. Cherry Avenue, Tucson, AZ 85719, USA

⁵ Canadian Space Agency, 6767 Route de l'Aéroport, Saint-Hubert, QC J3Y 8Y9, Canada

⁶ State Key Laboratory of Dark Matter Physics, Shanghai Key Laboratory for Particle Physics and Cosmology, School of Physics and Astronomy & Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China

⁷ Division of Science Education, Kangwon National University, Chuncheon, Republic of Korea

⁸ UK Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK

⁹ Department of Physics and Astronomy, University of the Pacific, Stockton, CA, USA

¹⁰ UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California Santa Cruz, Santa Cruz, CA, USA

¹¹ Department of Physics, Astronomy, GIS, Geology and Environmental Sciences, Youngstown State University, One Tressel Way, Youngstown, OH 44555, USA

¹² Université de Strasbourg, CNRS, Observatoire Astronomique de Strasbourg, UMR 7550, 11 rue de l'Université, F-67000 Strasbourg, France

¹³ Department of Astronomy, Case Western Reserve University, Cleveland, OH 44106, USA

¹⁴ University of Calgary, 2500 University Drive NW, Calgary Alberta T2N 1N4, Canada

¹⁵ Department of Physics and Astronomy, Allen Building, 30A Sifton Road, University of Manitoba, Winnipeg, MB R3T 2N2, Canada

¹⁶ Princeton University, Department of Astrophysical Sciences, Princeton, NJ 08544, USA

Received 2025 April 7; revised 2025 September 24; accepted 2025 October 20; published 2025 December 1

## Abstract

We present a study of morphologies, based on deep $u*g'i'z' imaging of the Virgo Cluster from the Next Generation Virgo Cluster Survey, for 3689 Virgo cluster members spanning a mass range of ~$10^{11}$–$10^5 M_\odot$. Our analysis introduces a new, two-component visual classification scheme developed to capture the morphological diversity of galaxies over more than 6 orders of magnitude in stellar mass. Our morphological classifications use two parameters to describe the global structure and star formation activity of each galaxy. Structural subcodes denote features such as spiral arms, bars, disks, shells, and streams, while star formation subcodes indicate the form and location of the current star formation activity (e.g., in cores, clumps, filaments). These visual classifications rely on deep $g'$-band images, supplemented by $u*g'i'$ color images, as well as unsharp-masked images for a subset of objects. We compare our classifications to previous results for bright member galaxies that used more established schemes, finding good agreement. We also measure quantitative classification statistics (e.g., CASGM$_{20}$) for a subset of the brighter galaxies, and present catalogs for some galaxy types of special interest, including structurally compact galaxies, ultradiffuse galaxies, candidate ultracompact dwarf transition objects, as well as candidate postmerger systems. These morphological classifications may be useful as a training set in the application of machine learning tools to the next generation of wide-field imaging surveys.

*Unified Astronomy Thesaurus concepts: Galaxy clusters (584); Galaxy evolution (594); Galaxy classification systems (582)*

## 1. Introduction

How is the general appearance of a galaxy connected to its evolutionary history and physical properties? This question has occupied astronomers for nearly a century (see, e.g., the review of C. J. Conselice 2014). A series of foundational papers by Edwin Hubble established what later came to be known as the Hubble Sequence—a classification framework that dominated the field throughout much of the 20th century (E. P. Hubble 1926, 1936; E. Hubble 1927).

Numerous revisions and modifications to this system added the flexibility needed to capture the diversity of features

observed in real galaxies, such as bars, rings, lenses, and spiral arm patterns (e.g., G. de Vaucouleurs 1959; S. van den Bergh 1960a, 1960b, 1976; A. Sandage 1961; J. Sérsic 1963; A. Sandage & G. A. Tammann 1981; D. M. Elmegreen & B. G. Elmegreen 1987). Over time, researchers, motivated by a desire to connect appearances to physical properties, began to use more quantitative methods to describe the light distribution within galaxies (E. Holmberg 1958; W. W. Morgan 1959; M. S. Roberts 1963; M. S. Roberts & M. P. Haynes 1994; P. D. Allen et al. 2006; J. P. Blakeslee et al. 2006; C. J. Conselice 2006; C. J. Conselice 2014). This approach has its roots in early analytic models of galaxy light profiles. The $r^{1/4}$ law for elliptical galaxies (G. de Vaucouleurs 1948) and its generalization by J. Sérsic (1963) laid the foundation for decades of quantitative classifications, in which de Vaucouleurs and Sérsic profiles were fitted to spiral bulges and

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elliptical galaxies (e.g., S. M. Kent 1985). Such measurements
helped establish empirical scaling relations that link structural
parameters to internal kinematics, such as the Tully–Fisher
relation for disk galaxies, the Faber–Jackson relation for
ellipticals, and the fundamental plane (e.g., S. Faber &
R. E. Jackson 1976; R. B. Tully & J. R. Fisher 1977;
S. Djorgovski & M. Davis 1987).

More recent efforts have used tools such as GALFIT
(C. Y. Peng et al. 2002; Y.-j. Peng et al. 2010) to model galaxy
light distributions using Sérsic, bulge-disk, and multicompo-
nent decompositions across large surveys (e.g., A. W. Graham
& S. P. Driver 2005; L. Simard et al. 2011; A. Meert et al.
2015). These quantitative approaches have become central to
modern morphological analysis and continue to evolve through
the development of new pipelines and deeper imaging datasets
(e.g., P. Dimauro et al. 2018; C. Gilhuly & S. Courteau 2018;
J. P. Nogueira-Cavalcante et al. 2018; S. Casura et al. 2022).
Such tools are expected to play a central role in upcoming
wide-field surveys such as Euclid (R. Laureijs et al. 2011;
Euclid Collaboration et al. 2023). Parametric fitting techniques
have proven especially effective for describing the structure of
massive, well-resolved galaxies, where features such as bulges
and disks are prominent and can be robustly modeled.
Nevertheless, their effectiveness may diminish for low-mass
galaxies, where irregular morphologies, diffuse light profiles,
and strong environmental processing challenge the assump-
tions of smooth, symmetric models (e.g., A. Boselli &
G. Gavazzi 2006; T. Lisker et al. 2006).

At the same time, the introduction of “nonparametric”
structural parameters—such as the concentration, asymmetry,
and smoothness (CAS) system (R. G. Abraham et al. 1996;
M. A. Bershady et al. 2000; C. J. Conselice et al. 2000)—
allowed researchers to explore important physical processes,
such as star formation and mergers, using measurements
performed on digital images. Other parameters, such as the
Gini coefficient (J. M. Lotz et al. 2004) and the M<sub>20</sub> statistic
(J. M. Lotz et al. 2008), gained popularity as diagnostics of
mergers and star formation activity. Additional nonparametric
methods and statistics continue to be developed, including
those of Z. Z. Wen et al. (2014), E. Curtis-Lake et al. (2016),
Z. Z. Wen & X. Z. Zheng (2016), and M. M. Pawlik et al.
(2016), to name just a few.

Studies have utilized such nonparametric statistics to explore
and characterize the morphologies of distinct and unique galaxy
populations detected in deep and/or wide surveys, as well as
galaxies generated in cosmological numerical simulations (e.g.,
D. Nelson et al. 2019; W. J. Pearson et al. 2019; V. Rodriguez-
Gomez et al. 2019; I. D. Roberts & L. C. Parker 2020;
A. Whitney et al. 2021; L. Ferreira et al. 2022; I. Vega-Acevedo
& A. M. Hidalgo-Gámez 2022; S. Wilkinson et al. 2022;
D. Pandey et al. 2024). Increasingly, machine learning and neural
network techniques are being developed to classify and
characterize galaxy morphologies, using both “classical”
(e.g., A. Naim et al. 1995; N. M. Ball et al. 2006; M. Huertas-
Company et al. 2008, 2011; C. J. Lintott et al. 2008; M. Banerji
et al. 2010) and more complex tools (S. Dieleman et al. 2015;
H. Domínguez Sánchez et al. 2018; P. H. Barchi et al. 2020;
R. Hausen & B. E. Robertson 2020; G. Martin et al. 2020;
T.-Y. Cheng et al. 2021; C. Tohill et al. 2021; M. Walmsley
et al. 2022). These techniques are expected to see widespread use
during the coming era of ultradeep and ultrawide-field imaging
surveys, like Rubin Observatory’s Legacy Survey of Space and

Time (LSST; Ž. Ivezić et al. 2019), Euclid (R. Laureijs et al. 2011), and Roman (D. Spergel et al. 2013), where the analysis of huge galaxy samples will require fast, flexible, and robust classification tools. At the same time, nonparametric and machine learning algorithms require training sets based on carefully selected samples of galaxies in the local Universe that have been classified using traditional approaches. Such training sets will be especially important for intermediate- and low-mass galaxies; these populations have long been underrepresented in imaging programs but will be common in future surveys conducted with ground- and space-based telescopes.

A natural target for morphological studies of galaxies in the local Universe is the Virgo cluster—the nearest rich cluster of galaxies. At its distance of *D* ≈ 16.5 Mpc (S. Mei et al. 2007; J. P. Blakeslee et al. 2009), 1" corresponds to ≈80 pc, so individual galaxies can be studied at a level of detail that will never be possible in more distant clusters, even those at modest redshifts. Past studies of galaxies in Virgo, as well as other nearby groups and clusters (A. Dressler 1980; B. M. Tinsley 1980; H. Butcher & A. J. Oemler 1984; B. Moore et al. 1996, 1998; G. Kauffmann et al. 2004; M. Cappellari et al. 2006; S. M. Faber et al. 2007; A. Boselli & G. Gavazzi 2014; R. J. Buta et al. 2015), revealed an impressive morphological diversity. Virgo itself is a complex, irregular system that, in some ways, mirrors the structure observed in some high-redshift clusters. It contains several thousand members, including virtually all known galaxy types, and spans a wide range in density and environment, from its periphery to dense core. Virgo and its surroundings thus provide a unique testbed for exploring how galaxy morphologies evolve—before, during, and after cluster infall.

The Virgo Cluster Catalog (VCC; B. Binggeli et al. 1985)—a photographic survey of the Virgo cluster that identified 2096 confirmed or possible member galaxies within a 140 deg² region centered on the cluster—established our baseline understanding of galaxy morphologies in a cluster environment. Indeed, the most enduring legacy of the VCC, aside from the galaxy catalog itself, may be its homogeneous database of morphologies, which continues to be utilized by astronomers to this day. A recent expansion of the VCC, based largely on the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7; K. N. Abazajian et al. 2009), is the Extended Virgo Cluster Catalog (EVCC) of S. Kim et al. (2014), which surveyed a broader region than the original VCC to study galaxy morphologies in the outskirts of Virgo and beyond.

In this paper, we present a new study of galaxy
morphologies in the Virgo cluster using multiband imaging
from the Next Generation Virgo Cluster Survey (NGVS;
L. Ferrarese et al. 2012). While numerous classification
schemes have been developed to describe galaxy morpholo-
gies, most have been tailored to, and designed explicitly for,
high-mass galaxies; thus, they rely on features such as well-
defined spiral arms, bars, and bulges, which are less distinct or
absent in lower-mass systems (e.g., B. Binggeli et al. 1985;
T. Lisker et al. 2006). Dwarf galaxies, which dominate the
low-mass end of the galaxy population, often exhibit more
irregular structures, weak or absent disk features, and a greater
susceptibility to environmental processes such as tidal
interactions and ram pressure stripping (e.g., L. Mayer et al.
2001, 2006; A. Boselli & G. Gavazzi 2006; R. Smith et al.
2013). Traditional classification schemes, including both
visual and automated approaches, struggle to robustly
categorize such galaxies, particularly when their structures are faint or diffuse. Our study addresses this gap by leveraging the depth, resolution, and multiband coverage of the NGVS (L. Ferrarese et al. 2012) to develop a morphological classification framework that is specifically designed to capture the diversity of low-mass cluster galaxies while being agnostic to labels and classifications based on stellar mass.

As we show in Section 2, the NGVS significantly improves on the VCC in terms of overall sample size ($N \sim 3700$), limiting magnitude, angular resolution, and the availability of color information. The NGVS imaging allows us to characterize galaxy morphologies over roughly 6 orders of magnitude, from brightest cluster galaxies ($M_* \gtrsim 10^{11} M_\odot$) down to the scale of dwarf galaxies, with stellar masses comparable to those of faint Milky Way satellites ($M_* \sim 10^5 M_\odot$). Indeed, low-mass galaxies dominate the NGVS sample, with ~94% of the cataloged galaxies having stellar masses below $10^9 M_\odot$.

Our analysis builds on a series of NGVS papers focused on galaxy evolution and the role of a cluster environment in shaping galaxy populations. Previous NGVS papers relevant to the present analysis include: the galaxy color-magnitude relation and red sequence relation (J. C. Roediger et al. 2017); the luminosity function and stellar populations of galaxies (J. Grossauer et al. 2015; L. Ferrarese et al. 2016); distance measurements using the method of surface brightness fluctuations (M. Cantiello et al. 2018, 2024); the properties of structurally compact (C. Liu et al. 2015, 2020; H.-X. Zhang et al. 2018) or diffuse galaxies (E. Toloba et al. 2018, 2023; S. Lim et al. 2020; Junais et al. 2022), and the evolutionary processes that may link them (A. Guérou et al. 2015; K. Wang et al. 2023); galaxy shapes and nucleation properties (C. Spengler et al. 2017; R. Sánchez-Janssen et al. 2019a, 2019b); plus targeted analyses of unusual or noteworthy galaxies and groups (F. Arrigoni Battaia et al. 2012; S. Paudel et al. 2013, 2017). This work also complements the search for low surface brightness features, including tidal streams and tails, in the NGVS and other datasets carried out by E. Sola et al. (2025).

This paper is structured as follows. In Section 2, we describe the NGVS imaging and data products used in this study. Our discussion of galaxy morphologies and a comparison to previous results for Virgo cluster galaxies is presented in Section 3, while Section 4 presents an analysis of our morphological classifications. A discussion of our findings, including an overview of some morphologically or structurally interesting galaxies, is presented in Section 5. We conclude and summarize in Section 6.

## 2. Data and Observations

### 2.1. Survey Design and Observations

We use images and data products from the NGVS (L. Ferrarese et al. 2012) to visually classify 3689 confirmed, probable, or possible members of the Virgo Cluster—roughly 2200 of which represent new discoveries (for details, see L. Ferrarese et al. 2025, in preparation). We introduce a customized classification system designed to avoid some of the limitations of past schemes, most notably the separate treatment of high- and low-mass galaxies (i.e., so-called “giant” and “dwarf” galaxies). In this section, we briefly describe the survey itself, including the imaging products and catalog measurements used in our study.

The NGVS is a Large Program that was carried out with the MegaPrime instrument on the 3.6 m Canada-France-Hawaii Telescope (CFHT). The NGVS was performed in the $u^*g'r'i'z'$ bands, covering Virgo's two major subclusters (A and B; B. Binggeli et al. 1987) out to their virial radii. The survey footprint, covering 104 deg$^2$, was tiled with 117 distinct MegaCam pointings overlapping by $3'$, each covering an area of roughly $1^\circ \times 1^\circ$ (after stacking of multiple, dithered exposures).

Each of these fields was observed in four MegaCam filters, $u^*g'i'z'$, whose bandpasses, with the exception of $u'$, closely resemble those of their SDSS counterparts. The original NGVS survey strategy called for coverage in the $r'$ band as well, but $r'$-band exposures were only obtained for the core of the cluster plus a few additional fields, due to time lost to weather and mechanical problems, so this coverage is largely ignored in this work. Two separate image stacks were obtained for each field: a long exposure, reaching a 10σ point-source limit of 25.9 mag in the $g'$ band, and a short exposure designed to recover the centers of galaxies that saturate in the long exposures, as shown in Table 2 in L. Ferrarese et al. (2012). For all long exposures, the observing strategy followed a “step-dither” pattern described in L. Ferrarese et al. (2020), whereby the dithered exposures that would normally be acquired in a continuous sequence for each individual field and each filter are applied, instead, to a *block* of fields.

The NGVS images reach 5σ limiting magnitudes, for point sources, of 26.3, 26.6, 25.8, and 24.8 mag in the stacked $u'$, $g'$, $i'$, and $z'$ images, respectively. For extended sources, the NGVS reaches a surface brightness limit of $\mu_{g'} \sim 29$ mag arcsec$^{-2}$, enabling the detection of galaxies at the faint end of the luminosity function. The NGVS thus supersedes previous optical surveys of Virgo in terms of depth, number of passbands, and areal coverage, including the landmark study of B. Binggeli et al. (1985).

For reference, the 5σ point-source limits of the stacked NGVS images differ from the expected 10 yr depths of LSST by +0.7, -0.3, -0.5, and -0.8 mag in the $u'$, $g'$, $i'$, and $z'$ passbands, respectively (Ž.IVEZIĆ et al. 2019). These differences are in the sense that the NGVS depth exceeds that of LSST in the $u'$ band, and is slightly shallower in the remaining bands.

### 2.2. Image Analysis and Data Products

The NGVS observing strategy adopted a method commonly used in near-infrared observations, as outlined in T. Erben et al. (2005), which allowed for the application of the Elixir-LSB reduction package (L. Ferrarese et al. 2012). Elixir-LSB is important for NGVS observations, especially for the low-surface-brightness (LSB) galaxies observed in Virgo, as it creates an accurate map of the spatially varying component of the sky and scattered light background by median averaging all fields observed in a continuous sequence for a given filter. This map is then subtracted from each individual exposure within the sequence before stacking. Typical residuals in the Elixir-LSB-processed, scattered light-subtracted images are 0.2% of the sky background in all filters, corresponding to a surface brightness of ~29 mag arcsec$^{-2}$ (see P.-A. Duc et al. 2015 for a detailed discussion). As discussed there, some faint background variations are still visible after the Elixir-LSB processing. Nevertheless, the stacked, Elixir-LSB images are useful for morphological
classification given their sensitivity to extended, LSB features like shells, halos, and stellar streams.

The intrachip regions (measuring ~13" wide between columns and ~80" wide between rows) are recovered by the dithering strategy but do not reach the full exposure time and therefore have a lower signal-to-noise ratio (S/N). Moreover, bright, saturated foreground stars can be surrounded by faint (surface brightness ≥26.5 mag arcsec⁻² in the g' band) extended stellar halos, while scattered light from Galactic cirrus also affects the images at g-band surface brightnesses ≤27 mag arcsec⁻². We do not correct for any of these effects, and as shown by the simulations employed in L. Ferrarese et al. (2020), about 10% of artificial galaxies injected in the frames are not recovered by the automated detection algorithm precisely because they fall in a region of variable background, due to either high surface brightness or low S/N. However, these objects are ultimately recovered based on visual inspection, leading to the detection limit for low-mass galaxies being set by noise, rather than residual background variations.

To visually classify each galaxy and to measure nonparan-
metric morphological parameters, we use fitted two-dimen-
sional model images and residuals available from the NGVS.
The model images were created with either the IRAF
ELLIPSE task (R. I. Jedrzejewski 1987) or through fitting of
two-dimensional Sérsic models using the GALFIT code
(C. Y. Peng et al. 2002; Y.-j. Peng et al. 2010), as detailed
in L. Ferrarese et al. (2020). Residual images generated by
subtracting these models from individual galaxy images were
also useful for identifying, with SAOImage DS 9 (Smithsonian
Astrophysical Observatory 2000), certain morphological
features, such as spiral arms, bars, central nuclear star clusters,
and irregular or twisted isophotes. For brighter galaxies with
higher-S/N imaging, unsharp-masked images (D. F. Malin
1977) were also generated; by sharpening the contrast, these
images proved useful for classifying certain faint, extended
features.

Our classifications also made use of color “thumbnail”
images created from the stacked i’g’u* NGVS images using a
customized Python code. Such images are especially useful
when examining the stellar populations of individual galaxies
and their subcomponents.

## 2.3. Supplementary Information

Our classifications also make use of some other NGVS data
products and catalogs that provide information on the structure
and stellar content of individual galaxies and their surround-
ings. These include catalogs of candidate globular clusters
selected from the NGVS on the basis of magnitude, colors, and
inverse concentrations (P. R. Durrell et al. 2014; S. Lim et al.
2024, 2025) and catalogs of candidate ultracompact dwarf
(UCD) galaxies (C. Liu et al. 2015, 2020; K. Wang et al. 2023)
as well as cataloged LSB features from the Burrell Schmidt
survey of J. C. Mihos et al. (2005, 2015, 2017), including tidal
tails, shells, plumes, and diffuse halos (E. Sola et al. 2025).

Our sample is defined using NGVS membership probabilities
from L. Ferrarese et al. (2020) that distinguish Virgo galaxies
from contaminants, particularly when redshift data are unavail-
able. These probabilities rely on multidimensional color–
magnitude space, trained on objects with known spectroscopic
redshifts, and incorporate structural parameters—such as sur-
face brightness, Sérsic index, and effective radius—as well as
spatial clustering (given that Virgo members are more centrally

concentrated than background field galaxies). Preprocessing
techniques like object masking and ring filtering (J. Secker
1995) were utilized to help suppress bright sources that could
obscure LSB galaxies. Candidate Virgo members were then
selected based on structural and photometric properties, with
diagnostic plots (e.g., isophotal area versus surface brightness)
aiding separation from contaminants. Two-dimensional Sérsic
profile fitting with GALFIT (Y.-j. Peng et al. 2010) refined these
measurements, and spectroscopic redshifts supersede photo-
metric classifications when available. Even at the faint end of
the luminosity function, where spectroscopic completeness is
low, combining photometric and structural priors enabled a
robust probabilistic classification. Ultimately, membership
probabilities are assigned by weighting multiple independent
criteria to maximize agreement with a training set of known
cluster members, ensuring reliable Virgo galaxy selection while
minimizing contamination.

We also make use of the NGVS stellar masses (J. C. Roedi-
ger et al. 2025, in preparation). The derivation of stellar masses
for NGVS galaxies follows a methodology designed to ensure
consistency across the full mass range of the sample. Stellar
masses are estimated by fitting multiband photometry to stellar
population synthesis models. The inclusion of NGVS u\*g'i'z'
photometry allows for robust constraints on age and dust
attenuation, minimizing systematic uncertainties in mass
estimates. For galaxies with spectroscopic data, the photo-
metric masses are cross-validated against spectroscopically
derived mass-to-light ratios. This approach ensures reliable
mass determinations, even for the low-mass dwarf population,
where single-band mass-to-light ratio assumptions can intro-
duce significant biases.

**3. Methodology**

3.1. *Classification Scheme*

The overall usefulness of morphological classifications for
studies of galaxy formation and evolution can be a matter of
debate. On one hand, visual classifications are known to have
drawbacks: e.g., being subjective in nature, they can vary
between classifiers; the classifications can depend on the
source materials (such as the wavelength, depth, and resolution
of the imaging used in the analysis); and some popular
classification schemes are focused heavily—sometimes exclu-
sively—on high-mass galaxies, whereas low-mass systems
dominate galaxy populations by number.

On the other hand, morphologies have played a prominent
role in many past investigations, and nearly every previous
imaging survey of Virgo galaxies has provided classifications
of some sort (e.g., G. Reaves 1983; B. Binggeli et al. 1985;
N. Trentham & S. Hodgkin 2002; T. Lisker et al. 2007; S. Kim
et al. 2014). Moreover, history has shown that morphological
classifications can enjoy usage long after the original imaging
materials have been superseded: i.e., the Hubble tuning fork
system (E. P. Hubble 1926) endures to this day, and the
classifications of B. Binggeli et al. (1985) are still widely used
four decades after the publication of the original VCC catalog.

We have therefore devised a visual classification scheme
that builds on previous morphological classifications while
taking advantage of the depth, angular resolution, and
multiwavelength coverage of the NGVS. Each member galaxy
is assigned two parameters that broadly describe its global
structure and current level of star formation activity. For the
<figure><img src="image_4.png" /><figcaption>High Mass (M. > 10⁹ M⊙) NGVS Morphologies</figcaption></figure>

**Figure 1.** A schematic illustration of the NGVS morphological classification scheme for a selection of high-mass ($M_* \ge 10^9 M_\odot$) galaxies. The six possible structural codes are arranged roughly from early to late types (E → S → I), including "transitional" categories (ES, SI, EI). The three rows correspond to the three possible star formation codes: Quiescent (Q), Intermediate (I), and Active (A). Galaxies are labeled by their NGVS *identification number*—or VCC number if the galaxy was previously cataloged in the VCC (B. Binggeli et al. 1985)—*morphology* and *stellar mass*. Empty entries in this matrix, denoted by an “X,” are either galaxies that do not exist in nature or plausibly exist but are not found in the NGVS, as explained in the text.

first parameter, galaxies are divided into six broad categories, with the following defining characteristics:

**E:** Smooth and regular in appearance, having *elliptical* isophotes.

**ES:** Intermediate in properties between E and S. ES galaxies often exhibit a largely spheroidal outer light distribution consistent with elliptical galaxies, but contain inner features such as weak or embedded disks, bars, or shell-like structures that indicate a dynamically colder component. Some edge-on systems are also placed in this category when flattened light profiles or dust lanes suggest hidden disk components. These galaxies often lie near the boundary between classic ellipticals and lenticular (S0) galaxies. For examples, see VCC122, VCC534, and VCC34 in Figures 1 and 2.

**S:** A *spiral* galaxy morphology, with features that may include bars, spiral arms, or flattened disks.

**SI:** Intermediate in properties between S and I. SI galaxies often show a global disklike structure but are more irregular, with patchy, asymmetric, or clumpy features replacing coherent spiral arms. Many show active star formation in irregular patterns or dust lanes that distort the underlying morphology. See VCC1450 and VCC119 in Figures 1 and 2.

**I:** An *irregular*, patchy, or filamentary appearance lacking an obvious spiral or ellipsoidal structure.

**EI:** Intermediate in properties between I and E. EI galaxies have broadly elliptical envelopes but show significant irregularities in their inner structure, including off-centered, star-forming knots, clumps, or mild asymmetries. These features suggest either a disturbed morphology or residual star formation that disrupts the appearance of a smooth spheroid. Examples include VCC1554 and VCC83 in Figures 1 and 2.

The three intermediate structural classes—ES, SI, and EI—are used for galaxies that do not fit cleanly into a single structural type, often exhibiting transitional morphologies or complex structures. These types are especially useful for classifying systems with intermediate masses or galaxies impacted by evolutionary processes that appear to have altered or reshaped their morphologies.

The ES class in our scheme includes most of the high-mass galaxies that, in the canonical Hubble system, would likely be classified as S0 galaxies or, less frequently, early-type spirals. Rather than enforce a strict division between ellipticals and spirals, our scheme provides a more flexible description that reflects the observed continuity in structural properties, particularly among galaxies that show both spheroidal envelopes and disklike substructure. In this way, ES types
Low Mass (M. < 10⁹ M☉) NGVS Morphologies

<figure><img src="image_5.png" /><figcaption>**Figure 2.** Same as the previous figure, except for the case of low-mass ($M_* \le 10^9 M_{\odot}$) galaxies. The classification categories in terms of structural and star formation properties are applicable across the full range of stellar mass probed by the NGVS.</figcaption></figure>

overlap substantially with the traditional S0 class, but also
accommodate edge-on systems and shell-bearing galaxies, as
well as low-mass galaxies with disklike structures that do not
fit cleanly within the Hubble tuning fork.

For the second parameter in our visual classification
scheme, galaxies are divided into three categories on the basis
of their apparent state of star formation:

Q: Quiescent, galaxies with negligible or no recent star formation, characterized by red optical colors with little or no *u*\* band emission.

I: Intermediate, galaxies exhibiting sporadic or low-level star formation, either localized (e.g., in specific knots or regions) or fading globally, often associated with weak *u*\* band emission and moderate optical colors.

A: Active, galaxies with vigorous star formation across significant portions of the disk, often visible in blue optical colors and structured features like star-forming clumps or filaments.

The NGVS classifications rely primarily on stacked g'-band
images. Our decision to use the g'-band images as our primary
classification resource is a compromise between a desire to
trace the underlying stellar mass in each galaxy and the need
for sensitivity to recent star formation; it also allows for a
direct connection to earlier photographic classifications carried
out using blue-sensitive plates. Our two-parameter classifica-
tion system differs from most previous schemes (such as the
"extended Hubble" scheme employed in the VCC; see

A. Sandage & G. A. Tammann (1981) and A. Sandage &
B. Binggeli (1984)) but has the advantage that it can be applied
equally well to high- and low-mass galaxies, thus avoiding the
introduction of conceptual “dichotomies” due to the scheme
itself (e.g., “giants” versus “dwarfs”; J. Kormendy et al. 2009).

This flexibility is illustrated in Figures 1 and 2, which show
the application of this scheme to a representative sample of
high- and low-mass galaxies, respectively. Note that some
spaces in this matrix are unpopulated because no examples
exist in nature: i.e., there are no examples of Active
Ellipticals, or Quiescent Irregulars. Other ele-
ments of the matrix might exist, at least in principle, but no
such galaxies appear in our current database for the Virgo
cluster.

In Figure 3, we show some more examples of transitional
types—ES, SI, and EI galaxies with intermediate masses.
Galaxies are labeled with both the VCC and NGVS
classifications. While such transitional systems comprise a
modest fraction of the NGVS sample, they exhibit properties
that are not easily captured within the simple E, S, and I
classes.

3.2. *Internal Comparisons and Consistency Checks*

In this section, we describe the classification subsamples
and results, which provide insights into overall repeatability
and possible biases. These issues are common to all visual
classification schemes, including the one used here, which are
<figure><img src="image_6.png" /><figcaption>**Figure 3.** As in Figures 1 and 2, but highlighting transitional NGVS structural codes (ES, SI, and EI). Thumbnails are annotated (top to bottom) with the VCC identifier and VCC type from B. Binggeli et al. (1985), the compact NGVS code, and the stellar mass.</figcaption></figure>

inherently subjective in nature. It is thus important to verify that the classifiers are coming to the same general conclusions when attempting to connect classifications to the physics of galaxy formation and evolution.

Initially, classifications according to the scheme that forms the basis of our analysis were carried out for roughly 1000 galaxies by one of the authors (PC, hereafter Classifier 1 = C1). Following a joint review by C1 and MMK (hereafter C2) of a training set large enough to include all galaxy types, including rare systems, classifications were then performed independently by C2.

We consider two different subsamples for our internal comparison. First, a subsample of 100 galaxies was randomly selected from the full catalog for classification by C2. These galaxies span the full range in magnitude of Virgo cluster members and include many of the brightest and most structurally complex objects. We find very good agreement between the independent classifications for this subsample, the results of which are shown in the third column of Table 1.

For the 100 galaxies in this sample, 91% are classified with the same structural code, and 93% are assigned the same star formation code. Moreover, in the few cases where the assigned codes differ, the discrepancy nearly always amounts to a difference of one subcode (i.e., E versus ES, or A versus I). This high level of agreement demonstrates that the classifiers are broadly identifying the same structural or star formation patterns when making their classifications.

As a second comparison, two independent sets of classifications were carried out for 1275 galaxies with magnitudes $18 \lesssim g' \lesssim 24.4$. These galaxies represent the faintest third of

the sample that lacked prior classifications and account for precisely half of all newly classified galaxies in this magnitude range. Results in this case are shown in the fourth column of Table 1.

<table><caption>**Table 1**</caption><caption>Comparison of C1 NGVS and C2 Codes for Structural and Star Formation Classification</caption><thead><tr><th>C1 Code</th><th>C2 Code</th><th>N (Random 100)</th><th>N (Faint Third)</th></tr></thead><tbody><tr><td colspan="4" style="text-align:center; font-weight:bold;">Structural Code Comparison</td></tr><tr><td>E</td><td>E</td><td>84</td><td>1194</td></tr><tr><td>ES</td><td>E</td><td>1</td><td>5</td></tr><tr><td>I</td><td>I</td><td>3</td><td>...</td></tr><tr><td>EI</td><td>E</td><td>1</td><td>21</td></tr><tr><td>E</td><td>ES</td><td>2</td><td>...</td></tr><tr><td>ES</td><td>ES</td><td>4</td><td>9</td></tr><tr><td>ES</td><td>EI</td><td>1</td><td>1</td></tr><tr><td>EI</td><td>ES</td><td>2</td><td>2</td></tr><tr><td>S</td><td>S</td><td>...</td><td>3</td></tr><tr><td>E</td><td>EI</td><td>...</td><td>9</td></tr><tr><td>EI</td><td>EI</td><td>...</td><td>22</td></tr><tr><td colspan="4" style="text-align:center; font-weight:bold;">Star Formation Code Comparison</td></tr><tr><td>Q</td><td>Q</td><td>87</td><td>1163</td></tr><tr><td>I</td><td>Q</td><td>5</td><td>51</td></tr><tr><td>A</td><td>Q</td><td>1</td><td>1</td></tr><tr><td>Q</td><td>I</td><td>...</td><td>3</td></tr><tr><td>I</td><td>I</td><td>3</td><td>37</td></tr><tr><td>I</td><td>A</td><td>1</td><td>3</td></tr><tr><td>A</td><td>A</td><td>3</td><td>11</td></tr><tr><td>A</td><td>I</td><td>...</td><td>2</td></tr></tbody></table>
<figure><img src="image_7.png" /><figcaption>**Figure 4.** Comparison of our morphological classifications to those from the Virgo Cluster Catalog of B. Binggeli et al. (1985). The pie charts show the breakdown of our NGVS classifications for each of six major morphological categories from the VCC: Es; S0s; dEs/dE, Ns; dS0s/dS0, Ns; spirals (Sa—Sm); and irregulars (Im).</figcaption></figure>

Once again, the two sets of classifications are in very good agreement, with 97.1% and 95.5% of galaxies having the same structural and star formation codes, respectively. Note that this subsample is heavily weighted toward faint, low-mass galaxies, which are dominated by apparently compact, LSB galaxies typically assigned E-Q types.

Student's t-tests (Student 1908) were performed on the independent classifications to see if the observed breakdowns in structural and star formation codes are consistent with their belonging to the same distribution. We find that all labeled structure codes and star formation codes are similar, with mean classifications within one standard deviation in code versus absolute magnitude space, with *p*-values ≥0.05 indicating a high level of internal agreement. These *p*-values provide strong evidence that the samples are drawn from the same underlying parent distribution. As a final step in the calibration and standardization of the classifications, a third classifier (LF = C3) performed an independent review of all classifications, identifying a small fraction of systems with discrepant structural or star formation codes, which were then resolved jointly to ensure maximum internal consistency across the full dataset.

We conclude on the basis of these tests and comparisons that there is very good internal consistency for the NGVS morphologies. With this established, we now examine how our morphological classifications compare to previous results for the Virgo cluster.

### 3.3. Comparison to the Virgo Cluster Catalog

The survey of B. Binggeli et al. (1985) provides an obvious comparison point for our classifications. Their survey consisted of confirmed or probable cluster members that were identified

using photographic B-band imaging taken with the duPont 2.5 m telescope at Las Campanas Observatory. From a visual inspection of these blue-sensitive plates, they placed each galaxy within the Hubble classification system, including its extension to late-type spirals and irregular galaxies. They also presented an extension into the regime of dwarf galaxies, for both early- and late-type systems. Full details on the classification system are presented in A. Sandage & G. A. Tammann (1981) and A. Sandage & B. Binggeli (1984), with the individual classifications tabulated in B. Binggeli et al. (1985).

Of the 2096 galaxies in the VCC, 1466 lie within the NGVS footprint and have been classified by the NGVS as confirmed, probable, or possible members of the Virgo cluster. This sample forms the basis of the comparison below. A wide diversity is available within this sample—from massive quenched elliptical galaxies, to grand-design spirals, to star-forming irregulars, and to many different types of dwarfs scattered throughout the cluster. Like their high-mass counterparts, these dwarfs show a range in star formation activity; in some cases, this activity was likely triggered by interactions with other cluster galaxies, or with the cluster itself.

Figure 4 compares the VCC and NGVS classifications in the form of pie charts. Each chart shows the division of NGVS types for six of the most common galaxy types in the VCC. From left to right, these are E galaxies, S0 (lenticular) galaxies, dE galaxies, dS0 galaxies, spiral galaxies (types Sa through Sm), and Im galaxies. Each pie chart shows the division of structural codes according to the NGVS classifications.<fnref n="17" />

<footnote n="17">¹⁷ Another 174 galaxies in the overlap sample have uncertain classifications (with catalog entries of ?) or represent very rare types in the VCC; as a result, they are not included in this comparison.</footnote>
<figure><img src="image_8.png" /><figcaption>**Figure 5.** Fractional confusion matrix comparing VCC and NGVS structural classifications. Each row corresponds to a VCC morphological class, and the color shading indicates the fraction of galaxies assigned to each NGVS structural category.</figcaption></figure>

To complement these pie charts, we present in Figure 5 a confusion matrix that shows the fractional breakdown of NGVS structural classifications for each of the six major VCC classes. This heatmap provides a more quantitative view of the classification overlap between the two catalogs. As expected, early-type classes (e.g., E, S0, dE, and dS0) show very good alignment with NGVS E and ES classifications. Later-type systems exhibit more diversity, with VCC spirals often classified as ES or, less frequently, other types (SI, EI, I) in the NGVS. VCC irregulars show a broad spread, including a surprising number of galaxies with regular elliptical morphologies in their LSB outskirts. These findings underscore the importance of deep imaging when analyzing galaxy structural properties.

For the sample of galaxies classified as Es in the VCC, we find good agreement, with 82.1% of these objects similarly classified in the NGVS; the remaining 17.9% are classified as ES galaxies, meaning that we see some evidence for disklike or intermediate properties in the CFHT imaging. Similarly, 77.8% of S0 galaxies in the VCC are classified as ES types, which is expected given that this NGVS-defined class corresponds most closely to the traditional S0 class. The remaining 22.2% of S0 galaxies in the VCC are assigned E or S classifications in the NGVS, which is again understandable given the transitional nature of the S0 class as originally defined.

The dE class dominates this comparison sample with 984 galaxies classified as such in the VCC. The vast majority (89.8%) of these objects are similarly classified as E types in the NGVS, with a small number of exceptions classified as either ES, EI, or I galaxies. The dS0 class is much less common in the VCC, with just 25 examples in its catalog. As expected, these galaxies are usually classified as ES galaxies in

the NGVS (88%), with the remaining objects assigned E or EI types, meaning that a disky nature was not obvious in the deep CFHT imaging. Overall, though, we find good agreement with the early-type classes in the VCC (i.e., the E and S0 galaxies as well as their low-mass counterparts).

There is a greater diversity in the classifications for the two later-type classes in the VCC. Roughly half (49.6%) of the galaxies classified as spirals in the VCC are similarly classified in the NGVS, but fully a third (36.8%) are assigned ES types due to the clear presence of diffuse, extended, and roughly elliptical components in which the star-forming regions are embedded. The remaining systems (13.6%) are divided among the SI, EI, and I types (roughly 5% in each case). There is even greater diversity in the case of the 99 galaxies classified as Im types in the VCC. In only 10.1% of cases do we assign an I-type structural code. In 32.3% of the cases, we find a predominant E-type morphology: our deeper imaging reveals more regular elliptical isophotes in these galaxies, resulting in fewer pure I classifications and instead favoring more transitional morphologies. This shows that many of these systems, while not entirely devoid of star formation activity or substructures, appear more regular and elliptical than suggested by the VCC Im designations. The remaining Im galaxies from the VCC have ES or EI structural codes (in 13.1% and 44.4% of the cases, respectively). Again, the deep CFHT imaging points to more transitional morphologies, rather than pure I systems.

### 3.4. Comparison to the Extended Virgo Cluster Catalog

A second important comparison sample is provided by the EVCC of S. Kim et al. (2014). The EVCC expanded on the original VCC by using SDSS DR7 data (K. N. Abazajian et al. 2009) to carry out a census of galaxies within a 725 deg²
<figure><img src="image_9.png" /><figcaption>**Figure 6.** Comparison of our morphological classifications to those from the EVCC of S. Kim et al. (2014). The pie charts show the breakdown of our NGVS classifications for each of four primary morphological categories in the EVCC: ellipticals, disk galaxies, irregulars, and early-type dwarfs.</figcaption></figure>

region centered on the cluster—an area 5.2 times larger than the VCC and reaching to a projected distance of ~3.5 virial radii. The EVCC utilized both SDSS imaging and spectroscopic data, defining a *primary morphology* (based on monochromatic *g*-, *r*-, and *i*-band images as well as combined *gri* color images) as well as a *secondary morphology*, determined from the spectral energy (SED).

The EVCC contains a total of 1589 galaxies, 676 of which do not appear in the VCC. Cataloged galaxies were selected spectroscopically, with a requirement that radial velocities be less than 3000 km s⁻¹. A total of 1324 galaxies were selected on the basis of SDSS redshifts, while an additional 265 galaxies without SDSS spectra were identified using redshifts collected from the NASA Extragalactic Database.<fnref n="18" /> The EVCC covers a much larger area than the NGVS, but our comparison is naturally limited to galaxies in common between the two surveys, which amounts to just 766 galaxies that can be matched directly to the NGVS—all in the inner region of the EVCC. Still, as we show below, this matched sample exhibits broad morphological diversity and thus provides a useful point of comparison.

The EVCC primary classifications are based on optical CCD imaging from the SDSS (D. G. York et al. 2000). S. Kim et al. (2014) employed a classification scheme that differs from the one used here, dividing galaxies into four categories: *ellipticals*, *disk galaxies*, *irregulars*, and *early-type dwarfs*. These classes are assigned respective digital codes of 100, 200, 300, and 400 in the EVCC catalog, subclasses excluded. The overlap between the two studies is limited by the depth of the SDSS photometry and spectroscopy, and includes only galaxies brighter than $g' \sim 20$.

Figure 6 shows a comparison of the NGVS morphologies to those from the EVCC. The four panels correspond to the main EVCC morphological classes, as labeled in the figure.

The number of matched galaxies in each EVCC category is also labeled in the figure. The pie charts show the breakdown of NGVS structural codes within these four EVCC classes.

An alternate comparison between the EVCC and NGVS structural classifications is shown in Figure 7. Here we display a fractional confusion matrix, akin to Figure 5, where now each row corresponds to one of the four primary EVCC morphological classes. The figure highlights the strong consistency for early-type dwarfs and ellipticals, with every matched EVCC elliptical being classified as *E* in the NGVS, and 97% of early-type dwarfs being assigned either *E* or *ES* types. Disk galaxies show a broader spread but still largely fall within disklike NGVS classifications (i.e., 91% are classified as having *ES*-, *S*-, or *SI*-type morphologies). Irregular galaxies display the widest distribution of structural types in the NGVS. Only 7% are classified as *I*, while 63% are labeled as *EI*, meaning that a significant fraction of Irregular EVCC galaxies appear more elliptical-like than in their original EVCC designation, as was the case for *Im* galaxies in the VCC.

Several conclusions can be drawn from this comparison. The sample is, unsurprisingly, dominated by galaxies belonging to the EVCC's early-type dwarf class, which comprises 57% (434/766) of the entire sample. 422 of these 434 galaxies are assigned either *E* or *ES* types in the NGVS; the remaining 12 are classified as *EIs*: i.e., transitional objects that show some signs of a later morphological type. Among the 188 objects classified as disk galaxies in the EVCC, 167 are classified as either *ES*, *S*, or *SI* in the NGVS, meaning they show some disklike features in the deeper CFHT imaging; the remaining 21 objects are classified as *E*, *EI*, or *I*. Among the 116 galaxies classified as irregular in the EVCC, nearly 70% are found to have *EI* or *I* types in the NGVS. In fact, a sizable number of galaxies in this EVCC class are assigned earlier-type morphologies in the NGVS (i.e., 14 and 21 objects are classified as *E* or *ES*, respectively), which we interpret as the result of more regular, diffuse features appearing in the deeper CFHT imaging. Finally, we find excellent agreement among

<footnote n="18">¹⁸ The NASA/IPAC Extragalactic Database (NED) is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.</footnote>
<figure><img src="image_10.png" /><figcaption>**Figure 7.** Same as Figure 5 for comparing the primary morphological classifications in the EVCC with NGVS structural codes.</figcaption></figure>

the 27 (high-mass) galaxies classified as *elliptical* in the EVCC, with every object similarly classified as E in the NGVS. Despite the differing classification schemes, the agreement between the two studies is very good, especially for EVCC ellipticals, disk galaxies, and early-type dwarfs.

Figure 8 compares our classifications to the *secondary* morphologies from the EVCC. As explained in S. Kim et al. (2014), there are four categories for these secondary morphologies, which are based on a combination of SDSS optical spectroscopy and broadband SEDs: red absorption (RA), red emission (RE), blue absorption (BA), or blue emission (BE). Galaxies are classified as “red” if their spectrum matches that of a model for an early-type galaxy (ETG) and “blue” if their spectrum matches that of a blue, star-forming galaxy; the absorption or emission criteria are determined from the appearance of Hα in either absorption or emission.

Most galaxies with secondary morphologies (74.8% of the matched sample) fall into the BE and RA categories, as would be expected from the broad separation of galaxies into star-forming and quiescent populations (e.g., I. Strateva et al. 2001; G. Kauffmann et al. 2003; I. K. Baldry et al. 2004; K. Schawinski et al. 2014). This general picture is supported by the NGVS classifications: 98.5% of the RA galaxies have E or ES structural codes, whereas 88% of BE galaxies have some level of morphological structure, and are not smooth E galaxies (mainly ES, EI, or S). In terms of star formation codes, 97.5% of BE galaxies are classified as A or I types, while 76.1% of RA galaxies are classified as Q.

Of course, it is worth noting that the SDSS spectral classifications utilized in the EVCC are based on spectra taken through a 3" fiber, meaning they reflect conditions in the

central region of the galaxy rather than its global properties. In contrast, our classification accounts for the entire galaxy, so some discrepancies between the two methods may be expected —for instance, a galaxy that appears quiescent overall but hosts a central starburst or AGN could be classified differently, as could a star-forming disk with a central old bulge.

The rarer and more anomalous secondary types—the RE and BA classes—provide a glimpse into the often complex evolutionary processes operating in the cluster. Visual inspection of the 50 galaxies belonging to the RE class (6.5% of the matched sample) reveals these objects to have predominantly late-type morphologies and low levels of star formation, or disklike emission embedded with the elliptical isophotes typical of older, redder stellar populations (in some cases with appreciable dust content). This class also includes a small number of E galaxies that appear quiescent but evidently exhibit nuclear emission from their centers, likely the signature of centrally concentrated star formation or emission from an active nucleus.

The 42 BA galaxies (5.5% of the sample) appear to trace similar populations but are generally comprised either of objects with more elliptical morphologies and embedded/distributed star formation, or galaxies with transition-type morphologies having red central stellar populations and offset star formation. These complexities are well captured by the classification scheme introduced here, which includes several transitional, or mixed, structural and star formation categories.

Taken together, the comparisons to the VCC and EVCC reveal some consistent trends. In both cases, we find excellent agreement for massive ETGs and early-type dwarfs, which are overwhelmingly classified as E or ES in the NGVS.
<figure><img src="image_11.png" /><figcaption>**Figure 8.** Secondary morphologies from the EVCC compared to our structural and star formation codes (left and right panels, respectively). The symbol size is proportional to the number of galaxies at each point on this grid, with the number of galaxies labeled in each case. Note that most of the 661 galaxies in this comparison have either RA or BE morphologies in the EVCC.</figcaption></figure>

<table><caption>**Table 2**
Distribution of Star Formation and Structural Codes</caption><thead><tr><th>Star Formation Code</th><th>N</th><th>P (%)</th><th>Structural Code</th><th>N</th><th>P (%)</th></tr></thead><tbody><tr><td colspan="6" style="text-align: center;">Full Sample (N = 3689)</td></tr><tr><td>Q</td><td>3037</td><td>82.33% ± 1.49</td><td>E</td><td>3099</td><td>84.01% ± 1.51</td></tr><tr><td>I</td><td>510</td><td>13.82% ± 0.61</td><td>ES</td><td>276</td><td>7.48% ± 0.45</td></tr><tr><td>A</td><td>138</td><td>3.74% ± 0.32</td><td>S</td><td>86</td><td>2.33% ± 0.25</td></tr><tr><td>...</td><td>...</td><td>...</td><td>SI</td><td>10</td><td>0.27% ± 0.09</td></tr><tr><td>...</td><td>...</td><td>...</td><td>EI</td><td>192</td><td>5.20% ± 0.38</td></tr><tr><td>...</td><td>...</td><td>...</td><td>I</td><td>25</td><td>0.68% ± 0.14</td></tr><tr><td colspan="6" style="text-align: center;">High-Mass Sample (N = 236)</td></tr><tr><td>Q</td><td>104</td><td>44.07% ± 4.32</td><td>E</td><td>52</td><td>22.03% ± 3.06</td></tr><tr><td>I</td><td>75</td><td>31.78% ± 3.67</td><td>ES</td><td>115</td><td>48.73% ± 4.54</td></tr><tr><td>A</td><td>55</td><td>23.31% ± 3.14</td><td>S</td><td>62</td><td>26.27% ± 3.34</td></tr><tr><td>...</td><td>...</td><td>...</td><td>SI</td><td>1</td><td>0.42% ± 0.42</td></tr><tr><td>...</td><td>...</td><td>...</td><td>EI</td><td>5</td><td>2.12% ± 0.95</td></tr><tr><td colspan="6" style="text-align: center;">Low-Mass Sample (N = 3431)</td></tr><tr><td>Q</td><td>2921</td><td>85.14% ± 1.58</td><td>E</td><td>3034</td><td>88.43% ± 1.61</td></tr><tr><td>I</td><td>429</td><td>12.50% ± 0.60</td><td>ES</td><td>155</td><td>4.52% ± 0.36</td></tr><tr><td>A</td><td>79</td><td>2.30% ± 0.26</td><td>S</td><td>22</td><td>0.64% ± 0.14</td></tr><tr><td>...</td><td>...</td><td>...</td><td>SI</td><td>9</td><td>0.26% ± 0.09</td></tr><tr><td>...</td><td>...</td><td>...</td><td>EI</td><td>186</td><td>5.42% ± 0.40</td></tr><tr><td>...</td><td>...</td><td>...</td><td>I</td><td>25</td><td>0.73% ± 0.15</td></tr></tbody></table>

Differences are most apparent among late-type systems: galaxies originally classified as spirals or irregulars are often assigned intermediate types such as ES, EI, or even E in the NGVS, likely reflecting features revealed thanks to the greater depth and spatial resolution of the CFHT imaging. For example, the CFHT imaging allows us to detect diffuse outer envelopes or regular isophotes that may have been missed in earlier, shallower surveys. While the EVCC includes a spectroscopically motivated secondary classification scheme, mismatches with NGVS star formation classes may be largely attributable to differences in spatial coverage, as EVCC spectroscopy is confined to the central 3", while NGVS classifications are based on the galaxy as a whole.

Finally, we briefly examined classifications from Galaxy Zoo 2 (GZ2; K. W. Willett et al. 2013), which provided morphological votes for ~300,000 SDSS galaxies with $m_r < 17$. Although Virgo systems are underrepresented in GZ2, owing to their low redshift, large angular sizes, and the tendency of the SDSS pipeline to mis-handle nearby galaxies through shredding, deblending, or crowding effects (M. R. Blanton et al. 2005; C. Lintott et al. 2011; K. W. Willett et al. 2013), we identified 117 NGVS galaxies with one-to-one positional matches (within 3"). All matched galaxies were classified as “smooth” in the primary GZ2 task, broadly consistent with their predominantly early-type morphologies. However, this agreement is largely superficial: 62.3% were flagged as potential mergers, and 57.6% had bar vote fractions $P_{bar} > 0.5$, suggesting structural features not reflected in the dominant vote. Additionally, all matched galaxies were also classified as having “no bulge” in the GZ2 bulge task. These inconsistencies highlight the limitations of crowdsourced classifications for faint, compact, or LSB galaxies in SDSS imaging, and underscore the importance of high-resolution visual classifications from the NGVS.

# 4. Results

## 4.1. Breakdown of Morphological Types

We consider the implications of our classifications for the evolution of the cluster and its member galaxies, including the interpretation of the color–magnitude relation, the morphology–density relation, and other galaxy scaling relations. Before doing so, however, we examine the breakdown of morphological subtypes within the cluster. This global breakdown is reported in Table 2, which summarizes the distribution of galaxies by both structural and star formation code.

For the cluster as a whole, the vast majority of galaxies are classified as quiescent (Q) in star formation properties (82.3% ± 1.5%) and E-like in structure (84.0% ± 1.5%). This preponderance is unsurprising given that galaxies in clusters are known to be quenched when they enter the cluster potential (D. Fabjan et al. 2010; D. S. Taranu et al. 2014; A. Paccagnella et al. 2016), after preprocessing at the group
scale (R. Sánchez-Janssen et al. 2008; C. P. Haines et al. 2015; Y. L. Jaffé et al. 2018; L. Cortese et al. 2021; A. Boselli et al. 2022). This is especially true for the low-mass galaxies ($\lesssim 10^9 M_\odot$) that dominate the NGVS sample: i.e., 3431 out of the 3689 galaxies in the NGVS sample are in the low-mass regime (93.0%). Most low-mass galaxies are found to be quiescent (85.1% $\pm$ 1.6%) and have an E-like structure (88.4% $\pm$ 1.6%). The rest of the low-mass systems predominantly exhibit transitional structures and intermediate levels of star formation.

Although they comprise only a small fraction of the sample overall, galaxies with irregular, transition-type morphologies are more common within the low-mass sample. The low-mass sample, outside of elliptical galaxies, is dominated by ES (4.5% $\pm$ 0.4%) and EI (5.4% $\pm$ 0.4%) structure codes, but they are rarely seen to be actively forming stars (2.3% $\pm$ 0.3%); more often, they are classified as having intermediate levels of star formation activity (12.5% $\pm$ 0.6%). This may be the result of the short quenching times for dwarf galaxies in the cluster; alternatively, it may point to the onset of incompleteness for very faint and blue galaxies in the NGVS sample (see the discussion in L. Ferrarese et al. 2020). Environmental processes such as ram pressure stripping and tidal interactions likely accelerate quenching, rapidly transforming star-forming dwarfs into quiescent systems before they can be detected (A. Boselli & G. Gavazzi 2006, 2014; L. Ferrarese et al. 2020). Additionally, the detection of diffuse, LSB galaxies may be biased due to incomplete recovery of their surface brightness profiles (J. I. Davies et al. 2016; L. Ferrarese et al. 2020). It is also true that, for the faintest and most compact galaxies in our sample, the limited S/N and relatively small number of spatial resolution elements may make it difficult to discern subtle structural peculiarities or clearly identify low levels of star formation activity.

To estimate the extent of incompleteness in our sample, we make use of the simulations presented in Section 4 of L. Ferrarese et al. (2020), to which we refer the reader for full details. Briefly, the NGVS catalog is 50% complete at $M_g = -9.1$, and we detect 403 galaxies fainter than this limit, including 28 systems with ($u - i$) < 1.0, indicative of blue stellar populations. Assuming 50% completeness, we infer that an additional ~400 faint galaxies, including ~30 faint, blue systems, could be undetected. This hypothetical population of “missing” galaxies could partially explain the apparent paucity of blue, actively star-forming dwarfs at the faintest magnitudes.

At the high-mass end ($M_* \ge 10^9 M_\odot$), late-type morphologies such as S (26.3% $\pm$ 3.3%) and ES (48.7% $\pm$ 4.5%) systems are at their peak abundance, with intermediate (I) (31.8% $\pm$ 3.7%) and active (A) star-forming galaxies (23.3% $\pm$ 3.1%) combining to form a slight majority of the high-mass sample. This abundance of star-forming systems is less pronounced at the highest stellar masses: among the 236 high-mass galaxies, 52 are quenched ellipticals (E and Q), corresponding to 22.0% $\pm$ 3.1%. Massive, quenched ellipticals are usually located in the densest cluster regions and are responsible for much of the quenching of lower-mass satellite galaxies (A. Dressler 1980; D. Thomas et al. 2005; A. Boselli & G. Gavazzi 2006; Y.-j. Peng et al. 2010; A. van der Wel et al. 2010; N. J. McConnell & C.-P. Ma 2013; C.-P. Ma et al. 2014; J. M. Gabor & R. Davé 2015; M. Cappellari 2016; A. Boselli et al. 2022). It is thus expected that, compared to

field galaxy populations, Virgo will contain a richer diversity of galaxy morphologies. This should be true even at the highest masses given the frequency of mergers, galaxy interactions, and feedback processes, including bursts of star formation triggered in a dense cluster environment (J. E. Gunn & J. R. I. Gott 1972; W. H. Press & P. Schechter 1974; S. D. M. White & M. J. Rees 1978; A. Dressler 1980; G. Kauffmann et al. 2004; R. J. Smith et al. 2012; A. R. Wetzel et al. 2013). Notably, pure I structure codes are not found at the high-mass end, as these galaxies tend to be classified more frequently as transition-types (e.g., ES, EI) due to their underlying structural complexity. A purely irregular classification requires significant morphological disturbance without any discernible ordered structure, a criterion rarely met by high-mass galaxies. This follows the trend identified in A. Sandage et al. (1985), where no Im galaxies were found with $B_T \lesssim 14$, with more massive irregulars typically exhibiting features characteristic of more complicated transition-type morphologies. Our classification similarly reflects this trend, reinforcing the expectation that truly irregular, high-mass galaxies should be exceedingly rare.

The morphological complexity of galaxies in Virgo is captured by our classification scheme, which allows us to broadly map galaxy properties to observables from the NGVS catalog. In Section 5.1, we will use our morphological classifications, catalog measurements, and nonparametric morphologies to highlight the full diversity of galaxies in the Virgo cluster and identify members of rare, unusual, or otherwise noteworthy galaxy classes.

## 4.2. Ensemble Properties

How are the different morphological subpopulations distributed within the cluster and across the color-magnitude relation? Figure 9 shows a map for the full sample of NGVS galaxies inside the survey footprint; individual galaxies are labeled by structural and star formation code in the left and right panels, respectively. The dominance of galaxies with early-type morphologies and quiescent star formation codes is apparent in both panels. In fact, it is this large population of mainly quiescent, E-like galaxies that most clearly defines the main subclusters and filaments within the cluster. The highest-density regions are marked principally by these early-type populations, consistent with previous findings (e.g., B. Binggeli et al. 1987; B. Binggeli & L. M. Cameron 1991; S. Schindler et al. 1999).

A useful way to explore possible trends with the environment is to connect the visual morphologies to local density. The left and right panels of Figure 10 show cumulative distribution functions for local surface density as a function of the structural and star formation code, respectively, with the median density for each code overlaid. The surface densities used in this analysis were calculated directly from the NGVS catalog using the areas inscribed within the radial distance to the 10th nearest neighbor. In both panels, the distributions for the subpopulations show considerable overlap, presumably due to projection effects. Galaxies with late-type structural codes (S) and disturbed morphologies (EI, I) or elevated star formation rates (I, A) reach their peaks at low densities, as would be expected if these objects preferentially occupy the outer cluster regions where infall is underway. Nevertheless, we see signs that some of these morphologically complex or active galaxies are found in denser regions. The peak of SI
<figure><img src="image_12.png" /><figcaption>**Figure 9.** (Left panel) Distribution in the sky of 3689 confirmed or probable Virgo cluster members from the NGVS. Symbol colors indicate different morphological structural codes, as indicated in the legend. For reference, the large red circles indicate the virial radii of Virgo's two major subclusters, centered on M87 (A) and M49 (B). The footprint of the NGVS is shown in light gray. (Right panel) Same as the previous panel, except now with symbols showing different star formation codes.</figcaption></figure>

<figure><img src="image_13.png" /><figcaption>**Figure 10.** Cumulative distribution functions of the local surface density for 3675 NGVS galaxies with measured surface density (out of the 3689 total in the sample). The left panel shows the distribution by structural code, while the right panel presents the distribution by star formation code. Dotted lines indicate the median density for each classification.</figcaption></figure>

galaxies in slightly denser regions suggests that these transitional, late-type galaxies may be associated with galaxy interactions and mergers. This likely points to episodes of star formation triggered by recent interactions or close passes with companion galaxies. It is also possible that some of these galaxies appear in denser environments because of projection effects rather than physical associations. Given the lack of clear merger signatures, projection may, in some cases, be a more plausible explanation.

Building on these observed qualitative trends, we conducted a more rigorous statistical analysis of the local density distributions across star formation and morphological codes

in the NGVS sample using both Kolmogorov–Smirnov (KS; A. Kolmogorov 1933; N. Smirnov 1948) and Anderson–Darling (AD; T. W. Anderson & D. A. Darling 1952; F. W. Scholz & M. A. Stephens 1987) tests. A KS test confirmed a strong correlation between star formation activity and environment, with Q and A galaxies exhibiting a highly significant difference ($p \approx 0.001$). I and A galaxies also differ (KS $p \approx 0.041$; AD $p \approx 0.001$), indicating that star formation activity is environmentally regulated. Q and I galaxies likewise show a significant separation ($p \approx 0.001$ in both tests). The AD test consistently yields higher significance than the KS test, reflecting its greater sensitivity to differences in
<figure><img src="image_14.png" /><figcaption>**Figure 11.** Surface density profiles for Virgo cluster galaxies. Profiles are measured in circular annuli centered on M87. The left and right panels show profiles found for subsets of the galaxy population after dividing by structural code and star formation code, respectively. The vertical dashed lines show the radii at which the total (i.e., full sample) surface density profile falls to one-half ($r_{50}$) and one-tenth ($r_{10}$) of its peak value.</figcaption></figure>

<table><caption>**Table 3**
Profile Results for Structural and Star Formation Codes</caption><thead><tr><th>Type</th><th>r<sub>50</sub><br>(arcmin)</th><th>r<sub>10</sub><br>(arcmin)</th><th>Peak<br>Density<br>(N deg<sup>-2</sup>)</th></tr></thead><tbody><tr><td colspan="4" style="text-align: center;">Full Sample</td></tr><tr><td>All Structural Codes</td><td>138.4 ± 6.3</td><td>360.1 ± 4.4</td><td>94.3</td></tr><tr><td>All Star Formation<br>Codes</td><td>138.4 ± 6.3</td><td>360.1 ± 4.4</td><td>94.0</td></tr><tr><td colspan="4" style="text-align: center;">Structural Code</td></tr><tr><td>E</td><td>135.9 ± 4.3</td><td>346.1 ± 5.6</td><td>85.7</td></tr><tr><td>ES</td><td>143.6 ± 55.6</td><td>405.8 ± 9.8</td><td>5.1</td></tr><tr><td>S</td><td>95.7 ± 121.8</td><td>408.9 ± 15.2</td><td>0.9</td></tr><tr><td>SI</td><td>110.2 ± 44.2</td><td>322.5 ± 139.3</td><td>0.1</td></tr><tr><td>EI</td><td>288.9 ± 92.3</td><td>413.4 ± 6.2</td><td>2.5</td></tr><tr><td>I</td><td>198.3 ± 107.6</td><td>397.4 ± 42.5</td><td>0.3</td></tr><tr><td colspan="4" style="text-align: center;">Star Formation Code</td></tr><tr><td>Q</td><td>135.9 ± 4.5</td><td>344.4 ± 5.8</td><td>84.0</td></tr><tr><td>I</td><td>161.0 ± 55.6</td><td>405.0 ± 7.0</td><td>9.2</td></tr><tr><td>A</td><td>293.4 ± 130.3</td><td>413.9 ± 5.7</td><td>1.4</td></tr></tbody></table>

**Note.** $r_{10}$ and $r_{50}$ denote the projected radii where the observed density falls to one-tenth and one-half its peak value, respectively.

the distribution tails. Together, these results reinforce the conclusion that local density significantly influences star formation activity.

For morphological codes, both the KS and AD tests identify strong environmental differences between E and S, with $p \approx 0.001$ in both tests. This finding supports the well-established trend that ellipticals preferentially reside in denser environments, while spirals are more common in lower-density regions (e.g., A. Dressler 1980; M. Postman & M. J. Geller 1984; T. Goto et al. 2003). ES and S show only marginal separation in the KS test ($p \approx 0.068$), but the AD test indicates

a highly significant difference ($p \approx 0.001$). This discrepancy suggests that the median densities of these two populations are similar, but their extremes differ in a statistically meaningful way, which is captured by the AD test. Ellipticals and transition ellipticals (E versus EI) also differ significantly (KS $p \approx 0.002$; AD $p \approx 0.001$), with both tests agreeing on the environmental distinction.

Beyond these key contrasts, many comparisons among intermediate categories (e.g., EI versus I, S versus SI) yield weak or nonsignificant results in the KS test, yet the AD test often reports differences at the ~0.003 level. This pattern underscores the complementarity of the two tests: the KS test is most sensitive to differences near the median of the distributions, while the AD test is more sensitive to differences in the tails. For highly significant results where p-values approach numerical limits, we report them as $p \approx 0.001$, though they may in fact be smaller. Overall, the KS and AD tests converge on the broad trends—especially in distinguishing E from S and separating Q from A, but the AD test highlights additional differences that are less apparent in the KS test. This emphasizes the importance of applying both methods together to fully capture the environmental dependence of galaxy morphology and star formation activity.

To further highlight trends with position, Figure 11 shows density profiles for the different morphological populations, with structural code and star formation code shown in the left and right panels, respectively. Profiles are calculated using five radial bins in Virgocentric radius. We see the expected (albeit gentle) morphology–density relation wherein S and other late-type structure codes are found at preferentially larger distances from the center of the cluster, while early-type, quiescent galaxies are especially dominant at smaller radii. The overall density profile for cluster members (shown as the gray curves in each panel) is dominated by E-like, quiescent galaxies with quiescent star formation, as noted above. We summarize these
<figure><img src="image_15.png" /><figcaption>**Figure 12.** (Left panel) CMDs for 3689 members of the Virgo cluster from the NGVS. The distribution of galaxies in the *g*–(*u*–*i*) plane is shown with symbols color coded according to the NGVS structural code, as indicated in the legend. Note that power-law fits for the SI and I structural codes are not shown due to the sparsity of data. (Right panel) Same as the previous panel, except with color coding based on the NGVS star formation code.</figcaption></figure>

trends more qualitatively in Table 3. From left to right, this table records, for each morphological subpopulation, the peak density and the projected radii where the profiles fall to one-half (*r*<sub>50</sub>) and one-tenth (*r*<sub>10</sub>) of these peak values.

Figure 12 shows how the different morphological sub-
populations are distributed across the color–magnitude dia-
gram (CMD). Results are shown after dividing by structural
code (on the left) and star formation code (on the right). We
parameterize the overall behavior by fitting power laws to each
subpopulation having enough data points to fit reliably. The
various loci are most clearly delineated in terms of star
formation, where there is a clear connection between
integrated color and star formation code: i.e., bluer galaxies
tend to be actively forming stars, while red galaxies are
overwhelmingly classified as quiescent.

Dividing by structural code results in greater overlap among
the power-law fits, making it more difficult to meaningfully
distinguish between different structural codes in color–
magnitude space. This is understandable given the high degree
of structural complexity captured by each code and the fact
that the most common morphological type (E) extends from
the highest-mass ellipticals down to some of the faintest
dwarfs in the cluster. These caveats aside, the CMDs
demonstrate that the NGVS classifications are reflecting—
independent of integrated color—expectations that the red
sequence is composed of mostly quenched, passively evolving
galaxies having smooth, elliptical-like structures, while the
blue cloud is populated by later types exhibiting active or
intermediate star formation (J. C. Roediger et al. 2017).

Our conclusions are consistent with previous findings, based
on significantly smaller samples, that the Virgo cluster—
despite its relatively unrelaxed state—exhibits a clear morph-
ology–density relation, with early-type (red sequence) systems
dominating its high-density regions (e.g., B. Binggeli et al.
1987; S. Phillipps et al. 1998; N. Trentham & S. Hodgkin
2002; S. Lieder et al. 2012). This observation is usually taken
as evidence that these low-mass galaxies correspond to
subhalos that have experienced strong mass loss, or spent
extended periods inside massive halos (T. Lisker et al. 2009).

**5. Discussion**

5.1. *Galaxy Types of Special Interest*

Previous studies of the Virgo (B. Binggeli et al. 1985;
L. Ferrarese et al. 2006; T. Lisker et al. 2006; S. Kim et al.
2014) and Fornax clusters (H. C. Ferguson & A. Sandage
1989; A. Venhola et al. 2019) have compiled catalogs of
galaxies with unusual or notable morphologies. We do the
same in this section, focusing on galaxy types that may be of
particular interest for future study. Tables 4–7 provide basic
data for these noteworthy objects, including morphological
classifications and brief notes; similar data for the complete
sample of NGVS galaxies will be presented in the upcoming
NGVS galaxy catalog (L. Ferrarese et al. 2025, in preparation).

5.1.1. *Compact Galaxies*

In cluster environments, quiescent galaxies with small sizes
are generally thought to be byproducts of interactions with
massive companions or the mean cluster gravitational field.
Such interactions are known to strip the lower-mass galaxy of
much of its star-forming disk, leaving behind a dense core with
little or no star-forming gas (K. Bekki et al. 2001, 2003;
A. Meza et al. 2003; L. Ferrarese et al. 2016), although other
formation channels are certainly possible (see, e.g., M. Du
et al. 2019, and references therein). Such “compact elliptical
galaxies” (cEs) are similar in structure and morphology to the
archetypal Local Group galaxy, M32, which is thought to have
been heavily influenced by tidal interaction with M31
(K. Bekki et al. 2001; R. Ibata et al. 2001; P. I. Choi et al.
2002; R. D’Souza & E. F. Bell 2018). This class of galaxy was
therefore referred to as “M32-type” systems by B. Binggeli
et al. (1985), who identified a handful of compact, inter-
mediate-luminosity, high-surface-brightness ellipticals in
Virgo (see their Table XIII).

Virgo is also known to contain a number of blue compact
dwarf (BCD) galaxies—compact, metal-poor galaxies that exhibit
bursts of star formation: i.e., L. Searle et al. (1973), H. Gerola
et al. (1980), T. X. Thuan & G. E. Martin (1981), A. Sandage &
B. Binggeli (1984), T. X. Thuan & G. E. Martin (1981),
<table><caption>Table 4
Candidate Compact Galaxies</caption><thead><tr><th>#</th><th>ID [NGVSJ]</th><th>NGVS</th><th>VCC</th><th>α(2000)<br>(deg)</th><th>δ(2000)<br>(deg)</th><th>g'(mag)</th><th>Type</th><th>Notes</th></tr></thead><tbody><tr><td>1</td><td>12:10:35.68+11:45:38.9</td><td>26</td><td>24</td><td>182.65</td><td>11.76</td><td>15.37</td><td>ES(di|du)-I(c|d)</td><td>ES galaxy with dust and star formation. Possible compact central region offset from the photocenter, probably due to dust absorption. Candidate UCG. Classified as a “certain” member. Cross ID: VCC24</td></tr><tr><td>2</td><td>12:11:02.73+12:06:14.4</td><td>34</td><td>32</td><td>182.76</td><td>12.10</td><td>13.94</td><td>E(n-):Q</td><td>Smooth ETG with possible compact nucleus and hint of other nuclear substructure. Candidate UCG. Classified as a “certain” member. Cross ID: VCC32</td></tr><tr><td>3</td><td>12:11:45.94+13:17:09.7</td><td>50</td><td>...</td><td>182.94</td><td>13.29</td><td>18.18</td><td>E(n)-Q</td><td>Nucleated, compact, round ETG. Candidate UCG. Classified as a “certain” member</td></tr><tr><td>4</td><td>12:13:13.68+13:31:22.1</td><td>89</td><td>...</td><td>183.31</td><td>13.52</td><td>16.07</td><td>E(du:|b-):I(c-)</td><td>Compact, intermediate-luminosity ETG with boxy isophotes. star formation (SF) in the central region with a possible bar-like structure. Candidate UCG. Classified as a “certain” member</td></tr><tr><td>5</td><td>12:14:43.05+10:31:59.3</td><td>131</td><td>...</td><td>183.68</td><td>10.53</td><td>18.07</td><td>ES-I(c-)</td><td>Compact, possibly faint ES galaxy seen face-on, with possible blue core and clumpy central structure surrounded by a lower-surface-brightness, regular envelope. Candidate UCG. Classified as a “certain” member</td></tr><tr><td>6</td><td>12:14:53.50+09:40:11.8</td><td>140</td><td>...</td><td>183.72</td><td>9.67</td><td>17.69</td><td>E-I(c)</td><td>Compact, elongated ETG with possible irregular structure in the core. Candidate UCG. Classified as a “certain” member</td></tr><tr><td>7</td><td>12:15:27.29+10:30:44.5</td><td>164</td><td>...</td><td>183.86</td><td>10.51</td><td>17.60</td><td>EI-I(c|f)</td><td>Compact EI galaxy with SF in the inner core, in patches and filaments. Candidate UCG. Classified as a “certain” member</td></tr><tr><td>8</td><td>12:16:34.04+10:12:22.8</td><td>231</td><td>...</td><td>184.14</td><td>10.21</td><td>17.48</td><td>EI-I(c|g-)</td><td>Compact EI galaxy with complex, irregular morphology and possible central star formation. Candidate UCG. Classified as a “certain” member</td></tr><tr><td>9</td><td>12:16:47.81+08:02:57.0</td><td>244</td><td>207</td><td>184.20</td><td>8.05</td><td>17.02</td><td>EI(di-):I(c|p|d)</td><td>Compact EI galaxy with active star formation. The peak of emission is offset from the photocenter. The galaxy, which has a velocity of 2588 km s<sup>-1</sup>, might be associated with VCC180 (11.2 to the southwest, v = 2239 km s<sup>-1</sup>) and VCC190 (16.2 to the southwest, v = 2354 km s<sup>-1</sup>). Candidate UCG. Classified as a “certain” member. Cross ID: VCC207</td></tr><tr><td>10</td><td>12:17:28.07+12:55:56.0</td><td>279</td><td>...</td><td>184.37</td><td>12.93</td><td>17.07</td><td>ES(di|du-):I(d|c|p)</td><td>Compact ES galaxy seen edge-on with star formation and dust in the disk. Candidate UCG. Classified as a “certain” member</td></tr><tr><td>11</td><td>12:18:17.99+07:07:41.0</td><td>332</td><td>...</td><td>184.57</td><td>7.13</td><td>16.60</td><td>E(du-):I(c)</td><td>Compact ETG with star formation and possible dust in the core. Candidate UCG. Classified as a “certain” member</td></tr><tr><td>12</td><td>12:19:23.09+05:47:41.3</td><td>400</td><td>344</td><td>184.85</td><td>5.79</td><td>15.11</td><td>E(n-):Q</td><td>Compact ETG with possible nucleus. The galaxy, which has a measured velocity of 2038 km s<sup>-1</sup> might be part of a small group with VCC345 as the brightest member (v = 2202 km s<sup>-1</sup>), VCC340 (v = 1506 km s<sup>-1</sup>), VCC336 (v = 3016 kms s<sup>-1</sup>), and VCC358 (v 2514 kms s<sup>-1</sup>), all of which are between 2 and 7 effective radii of VCC345 (108"-308"). No sign of tidal interaction, but there is some isophotal twisting. Galaxy is elongated in the inner regions, becoming round at large radius. Candidate UCG. Classified as a “certain” member. Cross ID: VCC344</td></tr><tr><td>13</td><td>12:20:21.89+12:11:15.4</td><td>485</td><td>410</td><td>185.09</td><td>12.19</td><td>17.21</td><td>EI-I(f|p)</td><td>Compact EI galaxy with active star formation. Primary star formation is in patches and filaments offset from the galaxy's photocenter. Candidate UCG. Classified as a “certain” member. Cross ID: VCC410</td></tr><tr><td>14</td><td>12:20:30.91+06:38:23.9</td><td>503</td><td>...</td><td>185.13</td><td>6.64</td><td>18.09</td><td>E-I(c-)</td><td>Compact ETG with a high-surface-brightness blue core, central substructure, and an extended, lower-surface-brightness elongated envelope. Candidate UCG. Classified as a “certain” member</td></tr><tr><td>15</td><td>12:23:18.39+05:36:25.5</td><td>827</td><td>...</td><td>185.83</td><td>5.61</td><td>16.58</td><td>ES(di-):I(d|c)</td><td>Compact, high-surface-brightness ES galaxy seen edge-on, with SF in disk and patches. Candidate UCG. Classified as a “certain” member</td></tr><tr><td>16</td><td>12:24:35.32+06:01:58.8</td><td>1006</td><td>...</td><td>186.15</td><td>6.03</td><td>16.71</td><td>E-I(c)</td><td>Compact ETG with SF in core. Candidate UCG. Classified as a “certain” member</td></tr><tr><td>17</td><td>12:24:54.85+16:48:38.9</td><td>1041</td><td>...</td><td>186.23</td><td>16.81</td><td>17.37</td><td>E(n-):I(c)</td><td>Compact, round ETG with star formation in blue core and possible nucleus. Candidate UCG. Classified as a “certain” member</td></tr><tr><td>18</td><td>12:26:21.55+06:40:10.4</td><td>1289</td><td>890</td><td>186.59</td><td>6.67</td><td>16.57</td><td>EI(du-):I(c)</td><td>Compact EI galaxy with active star formation in its core. Candidate UCG. Classified as a “certain” member. Cross ID: VCC890</td></tr><tr><td>19</td><td>12:27:26.96+05:11:16.9</td><td>1515</td><td>...</td><td>186.86</td><td>5.19</td><td>16.55</td><td>E-I(c|f)</td><td>Compact, elongated ETG with star formation in the core and filaments. Candidate UCG. Classified as a “certain” member</td></tr></tbody></table>
<table><caption>Table 4
(Continued)</caption><thead><tr><th>#</th><th>ID [NGVSJ]</th><th>NGVS</th><th>VCC</th><th>α(2000)<br>(deg)</th><th>δ(2000)<br>(deg)</th><th>g'(mag)</th><th>Type</th><th>Notes</th></tr></thead><tbody><tr><td>20</td><td>12:29:21.29+08:09:23.8</td><td>1840</td><td>1178</td><td>187.34</td><td>8.16</td><td>12.95</td><td>E(n)-Q</td><td>Nucleated ETG with strong isophote twisting suggestive of tidal influence from VCC1226. The galaxy, which has velocity v = 1243 km s<sup>-1</sup>, is located 677" to the northwest of M49 (VCC1226, v = 989 km s<sup>-1</sup>). Candidate UCG. Classified as a "certain" member. Cross ID: VCC1178</td></tr><tr><td>21</td><td>12:29:34.99+08:03:28.8</td><td>1877</td><td>1199</td><td>187.40</td><td>8.06</td><td>15.94</td><td>E(n)-Q</td><td>Compact ETG with a small envelope and a bright nucleus. The galaxy, which has velocity v = 1395 km s<sup>-1</sup>, is located 271" to the northwest of M49 (VCC1226, v = 989 km s<sup>-1</sup>). Candidate UCG. Classified as a "certain" member. Cross ID: VCC1199</td></tr><tr><td>22</td><td>12:30:31.97+12:29:24.6</td><td>2065</td><td>1297</td><td>187.63</td><td>12.49</td><td>13.76</td><td>E(n)-Q</td><td>Compact ETG with an LSB envelope and bright nucleus. The galaxy, which has a velocity v = 1554 km s<sup>-1</sup>, is located 438" to the northwest of M87 (VCC1316, v = 1284 km s<sup>-1</sup>) and is considered a classical example of a UCG due to interaction with M87 itself. Classified as a "certain" member. Cross ID: VCC1297, NGC 4486B</td></tr><tr><td>23</td><td>12:30:42.00+05:52:43.8</td><td>2090</td><td>...</td><td>187.68</td><td>5.88</td><td>17.23</td><td>EI(du|di:-)I(c|<br>f|d:)</td><td>Compact EI galaxy with SF in disk or filament embedded in slightly elliptical isophotes. Candidate UCG. Classified as a "certain" member</td></tr><tr><td>24</td><td>12:30:48.58+12:02:42.7</td><td>2112</td><td>1313</td><td>187.70</td><td>12.05</td><td>16.94</td><td>EI-I(p)</td><td>Very compact EI galaxy with very active star formation displaced from the photocenter of the older, more smoothly distributed component. The galaxy, which has velocity v = 1260 km s<sup>-1</sup>, is located 1245" to the southwest of M87 (VCC1316, v = 1284 km s<sup>-1</sup>). Candidate UCG. Classified as a "certain" member. Cross ID: VCC1313</td></tr><tr><td>25</td><td>12:30:57.77+12:16:15.5</td><td>2141</td><td>1327</td><td>187.74</td><td>12.27</td><td>12.87</td><td>E(di|du:-)Q</td><td>ETG projected 3" from a very bright star. ACSVCS images reveal a compact edge-on disk with dust. The galaxy, which has a velocity of v = 758 km s<sup>-1</sup>, is located in the Virgo core, 449" to the southeast of M87 (VCC1316, v = 1284 km s<sup>-1</sup>). Candidate UCG. Classified as a "certain" member. Cross ID: VCC1327</td></tr><tr><td>26</td><td>12:31:52.90+12:15:59.1</td><td>2275</td><td>...</td><td>187.97</td><td>12.27</td><td>17.80</td><td>E(n)-Q</td><td>Round, compact, very LSB ETG with compact envelope and bright nucleus. Candidate UCG. Classified as a "certain" member</td></tr><tr><td>27</td><td>12:32:33.52+09:10:25.2</td><td>2392</td><td>1437</td><td>188.14</td><td>9.17</td><td>14.79</td><td>EI(n:|sh|du)-I(c)</td><td>Possibly nucleated compact EI galaxy with dust and active star formation in its core. Candidate UCG. Classified as a "certain" member. Cross ID: VCC1437</td></tr><tr><td>28</td><td>12:35:37.25+12:22:55.4</td><td>2784</td><td>1627</td><td>188.91</td><td>12.38</td><td>14.94</td><td>E(n)-Q</td><td>Nucleated ETG. May be associated with VCC1619, which is located 9.8 to the southwest and has a similar velocity (266 km s<sup>-1</sup> for VCC1627 and 420 km s<sup>-1</sup> for VCC1619), and VCC1632 (v = 339 km s<sup>-1</sup>), located 10.4 to the north. Candidate UCG. Classified as a "certain" member. Cross ID: VCC1627</td></tr><tr><td>29</td><td>12:38:15.49+06:59:39.1</td><td>3040</td><td>1750</td><td>189.56</td><td>6.99</td><td>16.66</td><td>EI(st:-)I(c|p|g)</td><td>Compact EI with low-level star formation throughout, and a more intense patch of star formation offset from the core. Isophotes appear distorted at large radius. May be associated with VCC1726, which is located 10.0 to the northwest and has a similar velocity (-112 km s<sup>-1</sup> for VCC1750 and 45 km s<sup>-1</sup> for VCC1726). Candidate UCG. Classified as a "certain" member. Cross ID: VCC1750</td></tr><tr><td>30</td><td>12:41:01.08+09:43:06.3</td><td>3238</td><td>...</td><td>190.25</td><td>9.72</td><td>17.78</td><td>EI-I(c)</td><td>Compact EI galaxy with complex morphology, central star formation, and LSB, regular, elongated envelope. Candidate UCG. Classified as a "certain" member</td></tr></tbody></table>
<table><caption>Table 5
Candidate UDGs</caption><thead><tr><th>#</th><th>Sample</th><th>ID [NGVSJ]</th><th>NGVS</th><th>VCC</th><th>α(2000)<br>(deg)</th><th>δ(2000)<br>(deg)</th><th>g'</th><th>mag</th><th>Type</th><th>log R<sub>e</sub><br>(arcsec)</th><th>μ<sub>e,g</sub><br>(mag arcsec<sup>-2</sup>)</th><th>μ<sub>e,g</sub><br>(mag arcsec<sup>-2</sup>)</th><th>Notes</th></tr></thead><tbody><tr><td colspan="13" style="text-align:center; font-weight:bold;">Certain NGVS Members</td></tr><tr><td>1</td><td>Primary</td><td>12:16:32.59+13:09:51.3</td><td>227</td><td>197</td><td>184.14</td><td>13.16</td><td>16.77</td><td>E(n|st)-Q</td><td>1.79</td><td>28.85</td><td></td><td>27.72</td><td>Nucleated, very elongated, very LSB ETG, possibly due to a tidal stripping event. Candidate UDG. Classified as a "certain" member. Cross ID: VCC197</td></tr><tr><td>2</td><td>Primary</td><td>12:19:36.96+15:27:16.8</td><td>421</td><td>360</td><td>184.90</td><td>15.45</td><td>16.61</td><td>EI-I(g:)</td><td>1.53</td><td>26.80</td><td></td><td>26.25</td><td>Very LSB EI galaxy with irregular morphology. Candidate UDG. Classified as a "certain" member. Cross ID: VCC360</td></tr><tr><td>3</td><td>Primary</td><td>12:25:37.61+10:14:58.6</td><td>1160</td><td>811</td><td>186.41</td><td>10.25</td><td>16.96</td><td>E-I(g)</td><td>1.53</td><td>27.10</td><td></td><td>26.60</td><td>Extended, very LSB ETG. A faint and compact LSB galaxy, NGVS 1148, is located 90" to the southwest, although the velocity of either galaxy is unknown. Candidate UDG. Classified as a "certain" member. Cross ID: VCC811</td></tr><tr><td>4</td><td>Primary</td><td>12:27:31.55+09:35:44.3</td><td>1528</td><td>1017</td><td>186.88</td><td>9.60</td><td>14.55</td><td>EI(sh|st|:<br>du:|a)-<br>I(g)</td><td>1.73</td><td>25.83</td><td></td><td>25.19</td><td>Very LSB EI galaxy that is star-forming at a relatively low level. Shell-like structures (and generally disturbed appearance) at large radius. May be interacting with VCC983 (264" to the northwest) and VCC993 (163 to the southwest), with connecting diffuse light, although neither galaxy has a measured velocity. Candidate UDG. Classified as a "certain" member. Cross ID: VCC1017</td></tr><tr><td>5</td><td>Primary</td><td>12:27:55.22+12:22:09.5</td><td>1593</td><td>1052</td><td>186.98</td><td>12.37</td><td>16.06</td><td>E-I(g|f)</td><td>1.68</td><td>27.00</td><td></td><td>26.43</td><td>Extended, extremely LSB EI galaxy with disturbed morphology. Possible low-level star formation. Located 80" to the south of NGVS 1552 (VCC1036) and NGVS 1588 (VCC1047), which likely form a physical pair. A compact, very LSB ETG, NGVS1586, is located 57" to the northwest. Candidate UDG. Classified as a "certain" member. Cross ID: VCC1052</td></tr><tr><td>6</td><td>Primary</td><td>12:30:08.68+09:42:56.2</td><td>1993</td><td>...</td><td>187.54</td><td>9.72</td><td>17.09</td><td>E-Q</td><td>1.55</td><td>27.27</td><td></td><td>26.84</td><td>Extended, extremely LSB ETG. Apparent member of an LSB pair, with the second member, NGVS 2001, located 57" to the east. Neither galaxy has a measured velocity. A third, possibly connected LSB ETG, NGVS 2031, is located 175" to the east. Candidate UDG. Classified as a "certain" member</td></tr><tr><td>7</td><td>Primary</td><td>12:30:24.43+13:58:54.5</td><td>2045</td><td>1287</td><td>187.60</td><td>13.98</td><td>15.71</td><td>E-Q</td><td>1.66</td><td>26.58</td><td></td><td>26.01</td><td>Extended very LSB ETG with no obvious nucleus. Candidate UDG. Classified as a "certain" member. Cross ID: VCC1287</td></tr><tr><td>8</td><td>Secondary</td><td>12:33:29.59+15:14:02.8</td><td>2531</td><td>...</td><td>188.37</td><td>15.23</td><td>17.51</td><td>E-Q</td><td>1.43</td><td>27.24</td><td></td><td>26.67</td><td>Extended, extremely LSB ETG. Located 356" to the west of the bright LTG NGVS 2568 (VCC1524), with which it shares almost identical velocity (260 vs. 296 km s<sup>-1</sup>). Candidate UDG. Classified as a "certain" member</td></tr><tr><td>9</td><td>Secondary</td><td>12:40:21.21+12:43:02.8</td><td>3190</td><td>1835</td><td>190.09</td><td>12.72</td><td>18.23</td><td>E-Q</td><td>1.39</td><td>27.62</td><td></td><td>27.16</td><td>Extended, extremely LSB ETG. Candidate UDG. Classified as a "certain" member. Cross ID: VCC1835</td></tr><tr><td>10</td><td>Primary</td><td>12:41:39.34+09:12:30.5</td><td>3272</td><td>1884</td><td>190.41</td><td>9.21</td><td>16.20</td><td>E-Q</td><td>1.59</td><td>26.69</td><td></td><td>26.16</td><td>Extended, very LSB ETG. Candidate UDG. Classified as a "certain" member. Cross ID: VCC1884</td></tr></tbody></table>
<table><caption>Table 5
(Continued)</caption><thead><tr><th>#</th><th>Sample</th><th>ID [NGVSJ]</th><th>NGVS</th><th>VCC</th><th>α(2000)<br>(deg)</th><th>δ(2000)<br>(deg)</th><th>g'(mag)</th><th>Type</th><th>log R<sub>e</sub><br>(arcsec)</th><th>μ<sub>e,g</sub><br>(mag arcsec<sup>-2</sup>)</th><th>⟨μ<sub>e,g</sub>⟩<br>(mag arcsec<sup>-2</sup>)</th><th>Notes</th></tr></thead><tbody><tr><td colspan="12" style="text-align:center; font-weight:bold;">Probable NGVS Members</td></tr><tr><td>11</td><td>Secondary</td><td>12:20:11.38+11:53:56.5</td><td>466</td><td>...</td><td>185.05</td><td>11.90</td><td>19.78</td><td>E(n:|<br>st:)-Q</td><td>1.24</td><td>28.65</td><td>27.96</td><td>Extended, extremely LSB ETG with possible tidal stream. Candidate UDG. Classified as a "probable" member</td></tr><tr><td>12</td><td>Primary</td><td>12:24:01.84+13:51:56.4</td><td>935</td><td>...</td><td>186.01</td><td>13.87</td><td>18.39</td><td>E(n)-Q</td><td>1.52</td><td>28.32</td><td>27.95</td><td>Extended, extremely LSB ETG with a possible bright nucleus. Several faint galaxies (NGVS 878, NGVS 952, NGVS 971 and NGVS 978) are located within 153" and 327", while a brighter galaxy (NGVS 904 == VCC674) is located 147" to the north. Candidate UCD transition object. Candidate UDG. Classified as a "probable" member</td></tr><tr><td>13</td><td>Primary</td><td>12:24:42.06+13:31:00.6</td><td>1017</td><td>...</td><td>186.18</td><td>13.52</td><td>17.60</td><td>E(n:)-Q</td><td>1.51</td><td>27.85</td><td>27.15</td><td>Extended, extremely LSB ETG with a possible bright nucleus. Candidate UCD transition object. Candidate UDG. Classified as a "probable" member</td></tr><tr><td>14</td><td>Primary</td><td>12:26:38.25+13:04:44.2</td><td>1353</td><td>927</td><td>186.66</td><td>13.08</td><td>18.19</td><td>E-Q</td><td>1.41</td><td>28.15</td><td>27.25</td><td>Extended, extremely LSB ETG with bright nucleus. Candidate UCD transition object. Candidate UDG. Classified as a "probable" member. Cross ID: VCC927</td></tr><tr><td>15</td><td>Primary</td><td>12:26:48.36+13:21:17.7</td><td>1397</td><td>...</td><td>186.70</td><td>13.35</td><td>18.97</td><td>E-Q</td><td>1.45</td><td>28.88</td><td>28.19</td><td>Extended, extremely LSB ETG. Candidate UDG. Classified as a "probable" member</td></tr><tr><td>16</td><td>Secondary</td><td>12:27:15.75+13:26:56.1</td><td>1478</td><td>...</td><td>186.82</td><td>13.45</td><td>18.91</td><td>E-Q</td><td>1.32</td><td>28.28</td><td>27.51</td><td>Extended, extremely LSB ETG. Another very LSB ETG, NGVS 1476, is located 135" to the south. Candidate UDG. NGVS 1478 and NGVS 1479 are identified here as two separate galaxies, with NGVS 1479 located 4" to the north. However, this could also be a single, asymmetric galaxy. Classified as a "probable" member</td></tr><tr><td>17</td><td>Primary</td><td>12:28:10.07+12:43:29.4</td><td>1632</td><td>...</td><td>187.04</td><td>12.72</td><td>18.42!</td><td>E-Q</td><td>1.50</td><td>28.30</td><td>27.89</td><td>Extended, extremely LSB ETG. Candidate UDG. Classified as a "probable" member</td></tr><tr><td>18</td><td>Primary</td><td>12:28:37.88+12:51:42.0</td><td>1721</td><td>...</td><td>187.16</td><td>12.86</td><td>18.75</td><td>E-Q</td><td>1.46</td><td>28.46</td><td>28.02</td><td>Extended, extremely LSB ETG. Three bright galaxies are found nearby, although physical association cannot be assessed given that NGVS 1721 does not have a measured velocity: NGVS1693 (VCC1104, 198" to the southwest, v = 1709 km s<sup>-1</sup>), NGVS 1731 (VCC1122, 203" to the north, v = 465 km s<sup>-1</sup>), and NGVS 1742 (VCC1129, 214" to the southeast, v = 12 km s<sup>-1</sup>). Candidate UDG. Classified as a "probable" member</td></tr><tr><td>19</td><td>Primary</td><td>12:30:37.30+10:20:53.0</td><td>2079</td><td>...</td><td>187.66</td><td>10.35</td><td>17.45</td><td>E-Q</td><td>1.67</td><td>28.25</td><td>27.77</td><td>Extended, extremely LSB ETG. Candidate UDG. Classified as a "probable" member</td></tr><tr><td>20</td><td>Primary</td><td>12:31:48.01+12:21:33.1</td><td>2268</td><td>...</td><td>187.95</td><td>12.36</td><td>19.75</td><td>E-Q</td><td>1.33</td><td>28.83</td><td>28.38</td><td>Extended, extremely LSB ETG. Candidate UDG. Classified as a "probable" member</td></tr><tr><td>21</td><td>Primary</td><td>12:32:22.52+12:19:32.1</td><td>2365</td><td>...</td><td>188.09</td><td>12.33</td><td>19.20</td><td>E-Q</td><td>1.57</td><td>29.75</td><td>29.05</td><td>Extended, extremely LSB ETG. Candidate UDG. Classified as a "probable" member</td></tr></tbody></table>
<table><caption>Table 5
(Continued)</caption><thead><tr><th>#</th><th>Sample</th><th>ID [NGVSJ]</th><th>NGVS</th><th>VCC</th><th>α(2000)<br>(deg)</th><th>δ(2000)<br>(deg)</th><th>g'(mag)</th><th>Type</th><th>log R<sub>e</sub><br>(arcsec)</th><th>μ<sub>e,g</sub><br>(mag arcsec<sup>-2</sup>)</th><th>⟨μ<sub>e,g</sub>⟩<br>(mag arcsec<sup>-2</sup>)</th><th>Notes</th></tr></thead><tbody><tr><td>22</td><td>Primary</td><td>12:33:02.20+13:42:14.0</td><td>2458</td><td>...</td><td>188.26</td><td>13.70</td><td>20.03</td><td>E-Q</td><td>1.35</td><td>29.13</td><td>28.74</td><td>Extended, extremely LSB ETG. Candidate UDG. Classified as a "probable" member</td></tr><tr><td>23</td><td>Primary</td><td>12:35:12.86+07:03:22.4</td><td>2731</td><td>...</td><td>188.80</td><td>7.06</td><td>18.09</td><td>E-Q</td><td>1.64</td><td>28.82</td><td>28.26</td><td>Extended, extremely LSB ETG. Candidate UDG. Classified as a "probable" member</td></tr><tr><td>24</td><td>Primary</td><td>12:38:09.93+10:47:17.6</td><td>3032</td><td>...</td><td>189.54</td><td>10.79</td><td>20.66</td><td>E-Q</td><td>1.19</td><td>29.25</td><td>28.61</td><td>Extremely LSB ETG. Candidate UDG. Classified as a "probable" member</td></tr><tr><td>25</td><td>Secondary</td><td>12:39:21.99+12:05:34.6</td><td>3116</td><td>...</td><td>189.84</td><td>12.09</td><td>20.76</td><td>E(n-):Q</td><td>1.10</td><td>29.10</td><td>28.24</td><td>Extremely LSB ETG with a possible bright nucleus. Candidate UCD transition object. Candidate UDG. Classified as a "probable" member</td></tr><tr><td>26</td><td>Secondary</td><td>12:39:48.00+07:18:47.2</td><td>3146</td><td>...</td><td>189.95</td><td>7.31</td><td>18.12</td><td>E(n-):Q</td><td>1.41</td><td>27.68</td><td>27.13</td><td>Extended, extremely LSB ETG. Candidate UDG. Classified as a "probable" member</td></tr><tr><td>27</td><td>Primary</td><td>12:40:56.41+14:15:16.3</td><td>3225</td><td>...</td><td>190.24</td><td>14.25</td><td>19.46</td><td>E-Q</td><td>1.31</td><td>28.66</td><td>27.98</td><td>Extended, extremely LSB ETG. Candidate UDG. Seemingly part of a triplet of galaxies, although none has a measured velocity: NGVS 3225 is at the farther western position, the more compact and brighter NGVS 3231 (VCC1862) is 58" to the southeast, and NGVS 3233 is 55" to the northeast. Classified as a "probable" member</td></tr><tr><td>28</td><td>Secondary</td><td>12:40:58.86+14:15:57.6</td><td>3233</td><td>...</td><td>190.25</td><td>14.27</td><td>19.50</td><td>E-Q</td><td>1.29</td><td>28.26</td><td>27.94</td><td>Extended, extremely LSB ETG. Seemingly part of a triplet of galaxies, although none has a measured velocity: NGVS 3225 is at the farther western position, the more compact and brighter NGVS 3231 (VCC1862) is 58" to the southeast, and NGVS 3233 is 55" to the northeast. Candidate UDG. Classified as a "probable" member</td></tr><tr><td>29</td><td>Secondary</td><td>12:43:07.09+16:28:42.0</td><td>3365</td><td>...</td><td>190.78</td><td>16.48</td><td>19.38</td><td>E-Q</td><td>1.32</td><td>28.24</td><td>27.97</td><td>Extended, extremely LSB ETG. Candidate UDG. Classified as a "probable" member</td></tr><tr><td colspan="12" style="text-align:center; font-weight:bold;">Possible NGVS Members</td></tr><tr><td>30</td><td>Primary</td><td>12:16:20.63+06:56:52.9</td><td>213</td><td>...</td><td>184.09</td><td>6.95</td><td>18.47</td><td>E-Q</td><td>1.57</td><td>28.80</td><td>28.31</td><td>Extended, extremely LSB ETG. Candidate UDG. Classified as a "possible" member</td></tr><tr><td>31</td><td>Secondary</td><td>12:24:11.52+12:11:41.0</td><td>960</td><td>...</td><td>186.05</td><td>12.19</td><td>21.69</td><td>E-Q</td><td>1.04</td><td>29.45</td><td>28.89</td><td>Extended, extremely LSB ETG. Located 151" to the west of the bright LTG NGVS 934 (VCC692). Another extended, extremely LSB ETG, NGVS 955, is located 108" to the southwest. Candidate UDG. Classified as a "possible" member</td></tr><tr><td>32</td><td>Primary</td><td>12:26:55.95+12:59:40.0</td><td>1418</td><td>...</td><td>186.73</td><td>12.99</td><td>19.21</td><td>E-Q</td><td>1.46</td><td>29.08</td><td>28.49</td><td>Extended, extremely LSB ETG. Candidate UDG. Classified as a "possible" member</td></tr><tr><td>33</td><td>Primary</td><td>12:27:15.01+12:50:55.9</td><td>1473</td><td>...</td><td>186.81</td><td>12.85</td><td>18.98</td><td>E-Q</td><td>1.49</td><td>28.67</td><td>28.40</td><td>Highly elongated, extended, extremely LSB ETG with a possible offset nucleus. Candidate UDG. Classified as a "possible" member</td></tr><tr><td>34</td><td>Primary</td><td>12:29:20.27+12:01:16.4</td><td>1836</td><td>...</td><td>187.33</td><td>12.02</td><td>18.58</td><td>E-Q</td><td>1.48</td><td>28.28</td><td>27.98</td><td>Extended, extremely LSB ETG. Candidate UDG. Classified as a "possible" member</td></tr><tr><td>35</td><td>Secondary</td><td>12:30:09.41+09:16:45.3</td><td>1995</td><td>...</td><td>187.54</td><td>9.28</td><td>21.56</td><td>E-Q</td><td>1.01</td><td>29.41</td><td>28.59</td><td>Extremely LSB ETG. Candidate UDG. Classified as a "possible" member</td></tr></tbody></table>
<table><caption>Table 5
(Continued)</caption><thead><tr><th>#</th><th>Sample</th><th>ID [NGVSJ]</th><th>NGVS</th><th>VCC</th><th>α(2000)<br>(deg)</th><th>δ(2000)<br>(deg)</th><th>g'(mag)</th><th>Type</th><th>log R<sub>e</sub><br>(arcsec)</th><th>μ<sub>e,g</sub><br>(mag arcsec<sup>-2</sup>)</th><th>⟨μ<sub>e,g</sub>⟩<br>(mag arcsec<sup>-2</sup>)</th><th>Notes</th></tr></thead><tbody><tr><td>36</td><td>Primary</td><td>12:32:18.20+10:17:29.0</td><td>2355</td><td>...</td><td>188.08</td><td>10.29</td><td>15.89</td><td>E-Q</td><td>1.91</td><td>27.81</td><td>27.41</td><td>Extended, extremely LSB ETG. A bright ES galaxy, NGVS 2348 (VCC1422, v = 1300 km s<sup>-1</sup>), is located 155" to the northeast. Candidate UDG. Classified as a "possible" member</td></tr><tr><td>37</td><td>Secondary</td><td>12:32:18.91+13:44:35.6</td><td>2359</td><td>...</td><td>188.08</td><td>13.74</td><td>21.90</td><td>E-Q</td><td>0.96</td><td>29.84</td><td>28.70</td><td>Extremely LSB ETG. Candidate UDG. Classified as a "possible" member</td></tr><tr><td>38</td><td>Secondary</td><td>12:35:47.22+12:47:40.8</td><td>2802</td><td>...</td><td>188.95</td><td>12.79</td><td>21.88</td><td>E-Q</td><td>1.02</td><td>29.55</td><td>28.94</td><td>Extended, extremely LSB ETG. Candidate UDG. Classified as a "possible" member</td></tr><tr><td>39</td><td>Primary</td><td>12:37:38.91+14:18:45.6</td><td>2981</td><td>...</td><td>189.41</td><td>14.31</td><td>22.34</td><td>E-Q</td><td>1.11</td><td>31.20</td><td>29.88</td><td>Extremely LSB ETG. Candidate UDG. Classified as a "possible" member</td></tr><tr><td>40</td><td>Primary</td><td>12:37:51.81+16:11:45.7</td><td>3004</td><td>...</td><td>189.47</td><td>16.20</td><td>18.41</td><td>E-Q</td><td>1.70</td><td>29.47</td><td>28.89</td><td>Extended, extremely LSB ETG. Two compact LSB ETG, NGVS 2992 and NGV3002, are located 97" and 102", respectively, to the southwest. Candidate UDG. Classified as a "possible" member</td></tr><tr><td>41</td><td>Secondary</td><td>12:41:03.65+09:40:54.5</td><td>3240</td><td>...</td><td>190.27</td><td>9.68</td><td>21.17</td><td>E-Q</td><td>1.11</td><td>29.27</td><td>28.72</td><td>Extended, extremely LSB ETG. Candidate UDG. Classified as a "possible" member</td></tr><tr><td>42</td><td>Secondary</td><td>12:43:49.88+14:26:54.0</td><td>3404</td><td>...</td><td>190.96</td><td>14.45</td><td>19.12</td><td>EI(sh:st)-<br>I(f)</td><td>1.33</td><td>27.94</td><td>27.75</td><td>Extremely LSB EI galaxy with irregular structure and possible filaments or streams. Candidate UDG. Classified as a "possible" member</td></tr><tr><td>43</td><td>Primary</td><td>12:45:05.47+13:54:28.4</td><td>3477</td><td>...</td><td>191.27</td><td>13.91</td><td>18.15</td><td>E-Q</td><td>1.67</td><td>28.72</td><td>28.50</td><td>Extended, extremely LSB ETG. Candidate UDG. Classified as a "possible" member</td></tr><tr><td>44</td><td>Primary</td><td>12:45:17.82+15:31:56.1</td><td>3492</td><td>...</td><td>191.32</td><td>15.53</td><td>18.31</td><td>E-Q</td><td>1.58</td><td>28.72</td><td>28.19</td><td>Extended, extremely LSB ETG. Candidate UDG. Classified as a "possible" member</td></tr><tr><td>45</td><td>Primary</td><td>12:45:44.41+12:35:14.3</td><td>3516</td><td>...</td><td>191.44</td><td>12.59</td><td>18.78</td><td>E-Q</td><td>1.61</td><td>29.24</td><td>28.82</td><td>Extended, extremely LSB ETG. Candidate UDG. Classified as a "possible" member</td></tr><tr><td>46</td><td>Secondary</td><td>12:47:04.44+09:48:45.4</td><td>3551</td><td>...</td><td>191.77</td><td>9.81</td><td>21.59</td><td>E-Q</td><td>1.00</td><td>29.55</td><td>28.57</td><td>Extremely LSB ETG. Candidate UDG. Classified as a "possible" member</td></tr><tr><td>47</td><td>Secondary</td><td>12:49:19.72+11:52:54.2</td><td>3626</td><td>...</td><td>192.33</td><td>11.88</td><td>20.77</td><td>E-Q</td><td>1.24</td><td>28.98</td><td>28.96</td><td>Extended, extremely LSB ETG. Candidate UDG. Classified as a "possible" member</td></tr><tr><td>48</td><td>Secondary</td><td>12:49:24.40+13:23:22.3</td><td>3628</td><td>...</td><td>192.35</td><td>13.39</td><td>21.31</td><td>E-Q</td><td>1.13</td><td>29.18</td><td>28.96</td><td>Extremely LSB ETG. Candidate UDG. Classified as a "possible" member</td></tr><tr><td>49</td><td>Primary</td><td>12:51:08.90+11:28:36.4</td><td>3659</td><td>...</td><td>192.79</td><td>11.48</td><td>18.81</td><td>E-Q</td><td>1.48</td><td>28.88</td><td>28.20</td><td>Extended, extremely LSB ETG. Located 118" to the west of the very LSB ETG NGVS 3654. Candidate UDG. Classified as a "possible" member</td></tr><tr><td>50</td><td>Primary</td><td>12:51:12.85+13:05:45.1</td><td>3661</td><td>...</td><td>192.80</td><td>13.10</td><td>19.61</td><td>E-Q</td><td>1.33</td><td>28.96</td><td>28.27</td><td>Extended, extremely LSB ETG. Candidate UDG. Classified as a "possible" member</td></tr></tbody></table>
<figure><img src="image_16.png" /><figcaption>**Figure 13.** Scaling relations for NGVS galaxies with $log M_* \le 10$. Panels: (a) size–magnitude ($log r_{e,g}$ vs. $M_g$), (b) effective surface brightness ($\mu_{e,g}$ vs. $M_g$), (c) mean surface brightness within one effective radius ($\langle\mu\rangle_{e,g}$ vs. $M_g$), and (d) color–magnitude ($u-i$ vs. $M_g$). Black curves show polynomial fits to the NGVS population; long-dashed black lines mark the ±2.5σ envelopes. UDG candidates (blue) and compact galaxies (red) are highlighted. Marker shape encodes how many relations the object is an outlier in: circles = 1, triangles = 2, squares = 3. Outliers are defined as points lying outside the ±2.5σ envelope of the corresponding fit.</figcaption></figure>

S. Amrutha et al. (2024). Table XII of B. Binggeli et al. (1985) gives a catalog of BCD candidates selected from the VCC. Once thought to be young galaxies undergoing their first bursts of star formation (W. L. W. Sargent & L. Searle 1970; J. Lequeux & F. Viallefond 1980; D. Kunth et al. 1988), the prevailing view now holds that BCDs are subject to repeated bursts of star formation caused by interactions with massive galaxies and/or the cluster potential (T. X. Thuan 1991; P. Papaderos et al. 1996; L. M. Cairós et al. 2001a, 2001b; G. de Paz et al. 2003; D. A. Hunter & B. G. Elmegreen 2004; L. M. Cairós et al. 2010). As a class, BCDs are sometimes referred to as dwarf irregulars and may be subject to the same extreme tidal forces that give rise to M32-type galaxies (K. Bekki 2008; E. Kado-Fong et al. 2020; H.-X. Zhang et al. 2020a; D. N. Chhatkuli et al. 2023).

Since the exact definition of what constitutes a BCD or cE is still a topic of debate (B. Ekta & J. N. Chengalur 2010; J. Yin et al. 2011; F. Lelli et al. 2012; S. Shen et al. 2014; T. Hsyu et al. 2018), we proceed by restricting the sample selection to structurally compact galaxies: i.e., galaxies located at the extreme end of the NGVS galaxy size distribution. Following S. Lim et al. (2020, hereafter L20), we use several scaling

relations to identify structurally extreme sizes: compact galaxies and ultradiffuse galaxies (UDGs; discussed in Section 5.1.2). From left to right, the first three panels of Figure 13 show the relationship between absolute g-band magnitude, $M_g$, and effective radius, $r_e$, effective surface brightness, $\mu_{e,g}$, and mean effective surface brightness, $\langle\mu_{e,g}\rangle$, respectively. All 3601 confirmed, probable, and possible cluster members with $log M_*/M_{\odot} \le 10$ are plotted as gray points, where the high-mass galaxies are excluded in order to reduce the potential bias in the trend introduced by the highest-mass galaxies, which are best treated as a separate class of galaxies entirely. The fourth panel of this figure shows the CMD for this same sample, with ($u-i$) as the color index.

For this analysis, we use similar scaling relations as L20, who identified UDGs and studied their globular cluster systems. We define compact galaxies as those objects that deviate by at least 2.5σ from the mean scaling relations, though in the opposite direction of UDGs (i.e., we select outliers with small size and high surface brightness). Table 4 lists properties for the 30 compact galaxies that are outliers in at least two of the three scaling relations in Figure 13. From left to right, this table records the NGVS ID, NGVS
<figure><img src="image_17.png" /><figcaption>**Figure 14.** A mosaic of the 30 compact galaxies listed in Table 4. The sample includes both M32-like objects, BCD galaxies, as well as intermediate systems. Each panel measures 1.5 × 1.5 with north at the top and east to the left. The sample includes both M32-like objects (e.g., NGVS50 and NGVS400) and BCD galaxies (e.g., NGVS1515 and NGVS231).</figcaption></figure>

“nickname,” VCC number (if available), R.A., decl., g-band magnitude, and morphological classification. The final column gives brief notes from the visual classifications.

Rather than separating M32-like galaxies and BCDs, once we exclude the most massive galaxies, we simply select galaxies that fall at least 2.5σ below a polynomial curve in log r<sub>e,g</sub>–M<sub>g</sub> space and at least 2.5σ above the respective surface brightness curves. These are the regions where we expect to find the most concentrated objects. In fitting each scaling relation, we found that a cubic polynomial was able to capture the overall trends in the data while imposing few additional restrictions on the sample. Note that the polynomials used in L20 are fourth-order polynomials determined by maximum likelihood fitting of the observed scaling relations in the Virgo core region and differ slightly from those used here.

Inherent in this method is the assumption of uniform scatter in the standard deviation at all magnitudes, instead of assigning magnitude-dependent confidence intervals based on the scatter within magnitude bins. Our approach is more robust given the relative sparsity of objects in the tails of our distributions (i.e., we wish to avoid biases that might be introduced by using a more complicated functional form).

As is evident from Table 4, the compact galaxies are predominantly early-type in structure, with E systems comprising 16/30 (53%), alongside 10 EI (33%) and four ES (13%) galaxies. Consistent with the thumbnails in Figure 14, this indicates modest morphological diversity within an overall early-type population. The star formation codes likewise show some diversity in the properties of these galaxies: 21/30 (70%) are classified as I, while the remaining
9/30 (30%) are quiescent ☉). The varied star formation types are additional evidence that a sample of compact galaxies selected in size–magnitude space is populated by both star-forming and quiescent compact galaxies belonging to distinct subpopulations. This diversity is also apparent in the right panel of Figure 13. The CMD in the figure shows that the compact galaxy sample includes both very red and very blue objects.

This color spread hints at the different evolutionary pathways within compact galaxies. The redder compact galaxies may be the remnants of once more massive systems that have undergone significant stripping, while the bluer objects could be more akin to BCDs, which have retained or recently reignited star formation. Altogether, the sample thus provides a snapshot of the evolutionary channels that drive morphological changes within the cluster. The varied star formation modes provide additional evidence that a sample of compact galaxies selected in size–magnitude space includes both star-forming and quiescent subpopulations. This apparent bimodality follows the agreed-upon picture that compact galaxies can follow different evolutionary pathways, with some retaining or reigniting star formation while others remain quenched.

Interestingly, only eight galaxies in this sample were classified as either M32-like or BCD systems by B. Binggeli et al. (1985). Of these eight galaxies, five were classified as cEs and three as BCDs. We attribute this modest overlap to the superior depth and resolution provided by the NGVS, bearing in mind that some discrepancies will be inevitable given differing definitions of “compact.” Our selection criteria have the advantage of being based on quantitative and uniform cuts in the size–magnitude surface brightness–magnitude diagrams, but some caution is advisable since a few galaxies usually considered to cE-type systems (e.g., VCC1192, VCC1440, VCC1545, etc) just fail to satisfy our selection criteria.

### 5.1.2. Ultradiffuse Galaxies

Although large diffuse low-mass galaxies had been known for some time (A. Sandage & B. Binggeli 1984; B. Binggeli et al. 1985; C. Impey et al. 1988; C. D. Impey et al. 1996; J. J. Dalcanton et al. 1997; M. R. Blanton et al. 2005), the UDG class was introduced by P. G. van Dokkum et al. (2015) for Coma cluster galaxies with large effective radii ($r_{e,g} \ge 1.5$ kpc) which were also exceptionally faint and diffuse ($\mu_g \ge 24$).<fnref n="19" />

Recent work on UDGs has revealed some strange and seemingly contradictory properties. Some UDGs without dark matter have been reported (P. van Dokkum et al. 2018, 2019; S. Trujillo-Gomez et al. 2022; E. Toloba et al. 2023), posing a potential challenge to $\Lambda$CDM (J. S. Bullock & M. Boylan-Kolchin 2017). At the same time, other UDGs have been found to be dark-matter-dominated in their central regions (E. W. Peng & S. Lim 2016; M. A. Beasley et al. 2016; P. van Dokkum et al. 2017; E. Toloba et al. 2018, 2023; T. Carleton et al. 2019). More work is needed to understand these seemingly contradictory results and ascertain their homogeneity as a class.

Using the same methodology as in Section 5.1.1, we identify 50 UDGs as diffuse outlier galaxies in our scaling relations.

These galaxies are labeled in Figure 13 and listed in Table 5. A natural comparison for our analysis is the catalog of UDGs presented in L20. These authors defined a sample of 44 UDGs, 26 in a “primary” sample of objects that are at least $2.5\sigma$ outliers in each of three scaling relations (i.e., magnitude versus effective radius, effective surface brightness, and mean effective surface brightness). They further defined a “secondary” sample of 18 galaxies that are $2.5\sigma$ outliers in at least one of these scaling relations, bringing their sample to 44 galaxies.

For our UDG sample selection, we opt to utilize the same $2.5\sigma$ outlier selection used in Section 5.1.1 while also adopting the approach of defining primary and secondary samples. We focus on the galaxies that lie at least $2.5\sigma$ above the best-fit curve derived from our polynomial fits, rather than those in L20, in each of the scaling relations to present a uniform and consistent sample of UDGs across all mass regimes. By design, we are less stringent with our selection criteria than L20, which limited their sample only to “certain” and “probable” NGVS members (membership classes 0 and 1, respectively), whereas, by contrast, we include “possible” NGVS members (class 2) in our sample in order to compile a more complete sample of UDG candidates. In total, 33 of our galaxies fall into our primary sample, while another 17 objects belong to our secondary sample.

Some galaxies are absent from either our sample or that of L20 due to slight differences in how we define UDGs. In total, 30 galaxies in our sample are also present in L20, while 14 galaxies are exclusive to L20, and 21 galaxies are unique to our catalog. For images of some of these galaxies, we refer the reader to L20, where they present visual representations of their UDG sample as part of their analysis. The 14 galaxies found only in the L20 sample fall just outside our outlier regions; however, we still consider them viable UDG candidates that narrowly missed our slightly different selection criteria.

An additional method to study the evolutionary properties of UDGs in cluster environments is to look for signs of nucleation, i.e., the presence of a compact nuclear star cluster (NSC). NSCs are dense stellar systems, typically only a few parsecs in size but reaching masses up to $10^{7-8} M_\odot$, and are among the most common central components of low- and intermediate-mass galaxies (T. Böker et al. 2002; P. Côté et al. 2006; N. Neumayer et al. 2020). Their incidence depends on both galaxy mass and environment, and nucleation fractions provide important clues to the formation and survival of galaxies in clusters (F. Antonini et al. 2015; I. Y. Georgiev et al. 2016; R. Leaman & G. van de Ven 2022). Within our sample, 44 galaxies show no visual evidence for a nucleus, 4 are classified as potentially nucleated, and only 2 exhibit a clear nucleus. We further investigated these systems using structural decompositions with GALFIT (Y.-j. Peng et al. 2010), following the approach of L20. In that analysis, 48 galaxies were found to be nonnucleated, 1 was deemed likely nonnucleated, and 2 were confirmed to host a nucleus. Both approaches, therefore, converge on the conclusion that nuclear star clusters are rare in UDGs, with an occupation fraction of only $(2-6)/50 = 4\%–12\%$. This is markedly lower than the typical nucleation fractions of 20\%–60% found in galaxies of comparable luminosity in Coma and Virgo (S. Lim et al. 2018, 2020; R. Sánchez-Janssen et al. 2019a). Although the precise mass ranges of the two UDG samples differ, both

<footnote n="19">¹⁹ Table XIV of B. Binggeli et al. (1985) gives a compilation of “dwarfs of very large size and LSB”.</footnote>
analyses consistently point to a suppressed nucleation fraction in UDGs relative to normal galaxies at fixed stellar mass.

Table 5 shows that most of our UDG candidates are quiescent (38/42 ≃ 90%) and roughly elliptical in structure (40/42 ≃ 95%). This is consistent with past work on UDGs (R. F. J. van der Burg et al. 2016; Y. Rong et al. 2017, 2020). However, even though we expect the majority of the UDG population to be faint, diffuse, and quiescent, we are most likely missing some information on UDG structure and star formation due to the challenging nature of these objects for in-depth study. For example, there is a chance that some of our Class 2 objects may actually be very faint image artifacts (see the discussion in L. Ferrarese et al. 2020).

Unlike compact galaxies, which span both quiescent and star-forming regimes, UDGs in our sample are almost exclusively quiescent. Of the 50 UDGs, 46 (≈92%) are classified as quiescent, while only four (=8%) show intermediate or irregular star formation signatures. This reinforces the picture of UDGs as diffuse, red systems that largely follow passive evolutionary tracks, with star-forming cases being the exception rather than the rule.

A handful of morphologically interesting systems warrant mention. NGVS 227 (VCC197) is a quiescent elliptical that nevertheless hosts an embedded nucleus, likely the result of a tidal stripping event. NGVS 421 (VCC360) is a diffuse EI galaxy with irregular structure and evidence of residual star formation throughout its body. NGVS 1160 (VCC811) is an extended LSB system possibly interacting with a nearby faint LSB companion. NGVS 1528 (VCC1017) is an EI system with multiple shell-like features suggesting recent interactions. NGVS 1593 (VCC1052) shows a disturbed morphology and hints of low-level star formation. Finally, NGVS 3404, although only a possible cluster member, exhibits EI structure with filaments or streams.

Taken together, these few exceptions highlight that most UDGs in Virgo appear structurally simple and quiescent, but a minority do retain signatures of star formation or environmental disturbance. The full degree of morphological complexity exhibited by these objects, however, will be better assessed using resolved stellar populations based on future space-based studies.

### 5.1.3. UCD Transition Objects

UCD galaxies are dense, compact stellar systems with luminosities comparable to faint dwarf galaxies but sizes roughly an order of magnitude smaller ($10 \lesssim r_e \lesssim 50$ pc). Located between globular clusters and classical dwarf galaxies in the size-magnitude relation, the origin of these objects has been debated since their discovery more than two decades ago (M. Hilker et al. 1999; M. J. Drinkwater et al. 2000; S. Phillipps et al. 2001). It was quickly recognized that these systems did not fit neatly into the context of dwarf galaxy formation (B. Moore et al. 1996; K. Bekki et al. 2001), which led to suggestions that they arise from tidal “threshing” of nucleated dwarf galaxies (K. Bekki et al. 2003; S. Mieske et al. 2008). Early studies established that some UCDs do indeed show evidence for tidal distortion (M. J. Drinkwater et al. 2003; M. Haşegan et al. 2005), supporting this interpretation. However, other formation mechanisms remain feasible, at least in some cases, including the coalescence of superstellar clusters formed in gas-rich mergers (M. Fellhauer & P. Kroupa 2002, 2005) or formation

from small-scale peaks in the primordial dark matter power spectrum (M. J. Drinkwater et al. 2004).

Recent studies (e.g., H.-X. Zhang et al. 2015; K. Fahrion et al. 2020; H. Mahani et al. 2021; R. J. Mayes et al. 2021; T. Saifollahi et al. 2021; N. R. Napolitano et al. 2022) have tried to discern the most likely formation channels for UCDs. In the Virgo cluster, C. Liu et al. (2015, 2020) used NGVS imaging to assemble a sample of 612 confirmed or candidate UCDs distributed across the entire cluster. They showed that these UCDs are concentrated toward the most massive galaxies and noted an apparent connection between local density and envelope size for UCDs and nucleated dwarf galaxies (dE, N), suggestive of an evolutionary link. This connection was examined in more detail by K. Wang et al. (2023), who presented a quantitative link between location within the cluster and the prominence of the diffuse component surrounding both UCDs and the nuclei of dE, N galaxies.

Our visual inspection of NGVS galaxies bears directly on a possible evolutionary link between UCDs and nucleated dwarfs. According to the threshing scenario, some of these transition-type galaxies may be the progenitors of UCDs. As a byproduct of our morphological analysis, we identified an initial sample of galaxies as candidate UCD “transition objects”: i.e., galaxies that appear to contain an especially prominent nucleus, or a small, diffuse, or elongated envelope that could be the sign of advanced tidal stripping.

To refine this initial sample, we impose additional criteria to select galaxies with prominent nuclei and faint, compact, or elongated envelopes.

Our final sample of 115 candidates is presented in Table 6.

A key question is how our sample compares with that of K. Wang et al. (2023), who used surface-brightness profile fitting to study the connection between UCDs and nucleated dwarfs. Crossmatching their 48 “strongly nucleated” systems to our UCD transition catalog yields 31 galaxies in common (≈65% of their sample and ≈27% of our sample). This difference reflects complementary selection criteria: our morphology-driven approach, focusing on asymmetric/irregular, LSB envelopes, naturally admits many systems at intermediate stripping phases, whereas the profile-fitting strategy of K. Wang et al. (2023) favors objects with smooth, well-behaved diffuse components. Taken together, the two samples bracket different points along the stripping sequence: our nonoverlap objects plausibly represent earlier, more disturbed phases, while their nonoverlap systems tend to be more regular and may be further along in the transformation.

Our identified UCD transition candidates display a wide range of morphologies, from elongated, asymmetric systems to compact galaxies dominated by bright nuclei. Several candidates (e.g., NGVS 308, NGVS 1032, NGVS 1719, NGVS 1849, NGVS 2024, NGVS 2244, NGVS 2681, NGVS 2785, NGVS 3099) exhibit elongated or irregular LSB envelopes, consistent with ongoing tidal interactions. Others (e.g., NGVS 149, NGVS 787, NGVS 1032) show bright nuclei embedded in only small, faint envelopes, suggestive of systems in advanced stages of stripping where most of the diffuse component has already been lost (K. Wang et al. 2023). In addition, NGVS 317 stands out as having a possible offset or double nucleus, while NGVS 935 is classified as both a candidate UDG and a UCD transition system, reflecting the extreme tidal effects shaping its morphology. This morphological diversity highlights the transitional status of these
<table><caption>**Table 6**
Candidate UCD Transition Objects</caption><thead><tr><th>#</th><th>ID [NGVSJ]</th><th>NGVS</th><th>VCC</th><th>α(2000)<br>(deg)</th><th>δ(2000)<br>(deg)</th><th>g'(mag)</th><th>Type</th><th>Notes</th></tr></thead><tbody><tr><td>1</td><td>12:15:04.86+13:24:33.5</td><td>149</td><td>...</td><td>183.77</td><td>13.41</td><td>20.38</td><td>E(n)-Q</td><td>Very compact, extremely LSB ETG and bright nucleus. Candidate UCD transition object. Classified as a "possible" member</td></tr><tr><td>2</td><td>12:15:19.21+07:58:56.2</td><td>159</td><td>...</td><td>183.83</td><td>7.98</td><td>20.34</td><td>E(n)-Q</td><td>Compact, extremely LSB ETG with a small envelope and a bright, offset nucleus. Candidate UCD transition object. Classified as a "possible" member</td></tr><tr><td>3</td><td>12:17:55.31+07:33:24.3</td><td>308</td><td>...</td><td>184.48</td><td>7.56</td><td>20.63</td><td>E(n:)-Q</td><td>Compact, very elongated, very LSB ETG with possible bright, offset nucleus. Candidate UCD transition object. Classified as a "probable" member</td></tr><tr><td>4</td><td>12:18:04.41+15:10:43.7</td><td>317</td><td>...</td><td>184.52</td><td>15.18</td><td>18.48</td><td>E(n:)-Q</td><td>Extended, very LSB ETG with possible offset (double) nucleus. Candidate UCD transition object. Classified as a "certain" member</td></tr><tr><td>5</td><td>12:20:22.73+16:43:17.0</td><td>486</td><td>...</td><td>185.09</td><td>16.72</td><td>20.41</td><td>E(n:)-Q</td><td>Extremely LSB ETG with a possible bright nucleus. Candidate UCD transition object. Classified as a "possible" member</td></tr><tr><td>6</td><td>12:20:26.70+11:31:24.7</td><td>495</td><td>...</td><td>185.11</td><td>11.52</td><td>17.80</td><td>E(n)-Q</td><td>Very LSB ETG with bright nucleus. Candidate UCD transition object. Classified as a "certain" member</td></tr><tr><td>7</td><td>12:20:38.25+07:18:43.1</td><td>514</td><td>...</td><td>185.16</td><td>7.31</td><td>20.34</td><td>E(n)-Q</td><td>Compact, extremely LSB ETG with bright nucleus. Candidate UCD transition object. Classified as a "probable" member</td></tr><tr><td>8</td><td>12:21:51.50+07:01:26.6</td><td>630</td><td>...</td><td>185.46</td><td>7.02</td><td>20.23</td><td>E(n)-Q</td><td>Compact, extremely LSB ETG with a small envelope and bright nucleus. Candidate UCD transition object. Classified as a "probable" member</td></tr><tr><td>9</td><td>12:22:22.50+11:27:45.2</td><td>685</td><td>...</td><td>185.59</td><td>11.46</td><td>20.96</td><td>E(n)-Q</td><td>Nucleated, very compact, extremely LSB ETG. Candidate UCD transition object. Classified as a "possible" member</td></tr><tr><td>10</td><td>12:22:53.78+12:23:20.2</td><td>763</td><td>595</td><td>185.72</td><td>12.39</td><td>19.12</td><td>E(n)-Q</td><td>Compact, very LSB ETG with a small envelope and bright nucleus. Candidate UCD transition object. Classified as a "probable" member. Cross ID: VCC595</td></tr><tr><td>11</td><td>12:22:56.69+14:21:46.7</td><td>778</td><td>...</td><td>185.74</td><td>14.36</td><td>19.49</td><td>E(n)-Q</td><td>Extremely LSB ETG with bright nucleus. Candidate UCD transition object. Classified as a "probable" member</td></tr><tr><td>12</td><td>12:23:01.30+13:59:19.1</td><td>787</td><td>...</td><td>185.76</td><td>13.99</td><td>21.98</td><td>E(n:)-Q</td><td>Very compact, extremely LSB ETG with a possible bright nucleus. Candidate UCD transition object. Classified as a "possible" member</td></tr><tr><td>13</td><td>12:23:04.54+12:20:43.8</td><td>795</td><td>...</td><td>185.77</td><td>12.35</td><td>20.57</td><td>E(n)-Q</td><td>Nucleated, compact, extremely LSB ETG with faint, small envelope. Candidate UCD transition object. Classified as a "probable" member</td></tr><tr><td>14</td><td>12:23:04.59+12:00:53.4</td><td>796</td><td>615</td><td>185.77</td><td>12.01</td><td>17.25</td><td>E(n:)-Q</td><td>Very LSB ETG with a possible bright nucleus. Candidate UCD transition object. Classified as a "certain" member. Cross ID: VCC615</td></tr><tr><td>15</td><td>12:23:11.59+13:25:06.4</td><td>812</td><td>624</td><td>185.80</td><td>13.42</td><td>18.65</td><td>E(n)-Q</td><td>Compact LSB ETG with round isophotes and a bright nucleus. Candidate UCD transition object. Classified as a "certain" member. Cross ID: VCC624</td></tr><tr><td>16</td><td>12:23:22.80+13:00:07.8</td><td>835</td><td>...</td><td>185.84</td><td>13.00</td><td>18.95</td><td>E(n)-Q</td><td>Compact, very LSB ETG with a small, LSB envelope and bright nucleus. Candidate UCD transition object. Classified as a "certain" member</td></tr><tr><td>17</td><td>12:23:39.21+07:47:43.9</td><td>876</td><td>...</td><td>185.91</td><td>7.80</td><td>19.98</td><td>E(n:)-Q</td><td>Compact, extremely LSB ETG with a possible bright nucleus. Candidate UCD transition object. Classified as a "probable" member</td></tr><tr><td>18</td><td>12:23:52.90+12:46:23.1</td><td>906</td><td>678</td><td>185.97</td><td>12.77</td><td>17.58</td><td>E(n)-Q</td><td>Very LSB ETG with round isophotes and a bright nucleus. Candidate UCD transition object. Classified as a "certain" member. Cross ID: VCC678</td></tr><tr><td>19</td><td>12:24:01.84+13:51:56.4</td><td>935</td><td>674</td><td>186.01</td><td>13.87</td><td>18.39</td><td>E(n:)-Q</td><td>Extended, extremely LSB ETG with a possible bright nucleus. Several faint galaxies (NGVS 878, NGVS 952, NGVS 971, and NGVS 978) are located within 153" and 327", while a brighter galaxy (NGVS 904 == VCC674) is located 147" to the north. Candidate UCD transition object. Candidate UDG. Classified as a "probable" member</td></tr><tr><td>20</td><td>12:24:42.06+13:31:00.6</td><td>1017</td><td>...</td><td>186.18</td><td>13.52</td><td>17.60</td><td>E(n:)-Q</td><td>Extended, extremely LSB ETG with a possible bright nucleus. Candidate UCD transition object. Candidate UDG. Classified as a "probable" member</td></tr><tr><td>21</td><td>12:24:48.19+07:32:11.3</td><td>1032</td><td>...</td><td>186.20</td><td>7.54</td><td>20.47</td><td>E(n)-Q</td><td>Nucleated, very compact, elongated, extremely LSB ETG with a small envelope. Candidate UCD transition object. Classified as a "possible" member</td></tr><tr><td>22</td><td>12:24:58.09+09:37:17.9</td><td>1048</td><td>...</td><td>186.24</td><td>9.62</td><td>20.42</td><td>E(n:)-Q</td><td>Extremely LSB ETG. Possible double nucleus. Candidate UCD transition object. Classified as a "possible" member</td></tr><tr><td>23</td><td>12:25:09.21+12:09:18.5</td><td>1075</td><td>...</td><td>186.29</td><td>12.16</td><td>21.65</td><td>E(n:|st:)-Q</td><td>Compact, extremely LSB ETG with possible nucleus and faint streams. Candidate UCD transition object. Classified as a "possible" member</td></tr></tbody></table>
<table><caption>**Table 6**
(Continued)</caption><thead><tr><th>#</th><th>ID [NGVSJ]</th><th>NGVS</th><th>VCC</th><th>α(2000)<br>(deg)</th><th>δ(2000)<br>(deg)</th><th>g'(mag)</th><th>Type</th><th>Notes</th></tr></thead><tbody><tr><td>24</td><td>12:25:23.69+12:40:30.3</td><td>1119</td><td>800</td><td>186.35</td><td>12.68</td><td>19.42</td><td>E(n)-Q</td><td>Compact, very LSB ETG with a small envelope and bright nucleus. Located 43" to the east of NGVS 1128 (VCC800), although the velocity of either galaxy is unknown. Additionally, both galaxies are located ~300" to the west of VCC836 and might be part of a small group containing, besides VCC836, NGVS 1133, VCC871, and VCC838. Candidate UCD transition object. Classified as a "certain" member. Cross ID: VCC796</td></tr><tr><td>25</td><td>12:25:35.64+12:10:01.8</td><td>1153</td><td>...</td><td>186.40</td><td>12.17</td><td>20.05</td><td>E(n)-Q</td><td>Extremely LSB ETG with a very LSB envelope and possibly bright, offset nucleus. Candidate UCD transition object. Classified as a "probable" member</td></tr><tr><td>26</td><td>12:25:36.62+12:50:58.9</td><td>1157</td><td>814</td><td>186.40</td><td>12.85</td><td>18.24</td><td>E(n)-Q</td><td>Very LSB ETG with bright nucleus. Located 499" to the southeast of M84. Candidate UCD transition object. Classified as a "certain" member. Cross ID: VCC814</td></tr><tr><td>27</td><td>12:25:55.70+11:48:03.8</td><td>1212</td><td>853</td><td>186.48</td><td>11.80</td><td>18.92</td><td>E(n)-Q</td><td>Compact, very LSB ETG with faint envelope and bright nucleus. Candidate UCD transition object. Classified as a "certain" member. Cross ID: VCC853</td></tr><tr><td>28</td><td>12:25:55.79+10:43:13.2</td><td>1214</td><td>852</td><td>186.48</td><td>10.72</td><td>18.50</td><td>E(n)-Q</td><td>Extended, extremely LSB ETG with possible offset nucleus. Candidate UCD transition object. Classified as a "certain" member. Cross ID: VCC852</td></tr><tr><td>29</td><td>12:26:05.19+12:03:01.3</td><td>1239</td><td>...</td><td>186.52</td><td>12.05</td><td>19.75</td><td>E(n)-Q</td><td>Compact, very LSB ETG with a small, faint envelope and bright nucleus. Candidate UCD transition object. Classified as a "probable" member</td></tr><tr><td>30</td><td>12:26:25.15+11:18:36.9</td><td>1298</td><td>915</td><td>186.60</td><td>11.31</td><td>21.01</td><td>E(n)-Q</td><td>Very compact, extremely LSB ETG with a possible bright nucleus. Located 158" to the northwest of the brighter ETG NGVS 1331 (VCC915), although neither galaxy has a measured velocity. Candidate UCD transition object. Classified as a "possible" member</td></tr><tr><td>31</td><td>12:26:36.32+12:48:10.0</td><td>1342</td><td>923</td><td>186.65</td><td>12.80</td><td>17.89</td><td>E(n)-Q</td><td>Nucleated, very LSB ETG with round isophotes. The galaxy is located 629" to the southeast of M86 (ν = -233 km s<sup>-1</sup>) and has a similar velocity (168 km s<sup>-1</sup>), suggesting it might be part of the M86 group. Candidate UCD transition object. Classified as a "certain" member. Cross ID: VCC923</td></tr><tr><td>32</td><td>12:26:38.25+13:04:44.2</td><td>1353</td><td>927</td><td>186.66</td><td>13.08</td><td>18.19</td><td>E(n)-Q</td><td>Extended, extremely LSB ETG with bright nucleus. Candidate UCD transition object. Candidate UDG. Classified as a "probable" member. Cross ID: VCC927</td></tr><tr><td>33</td><td>12:26:42.50+09:53:54.8</td><td>1368</td><td>...</td><td>186.68</td><td>9.90</td><td>20.22</td><td>E(n)-Q</td><td>Compact, extremely LSB ETG with compact envelope and possible bright nucleus. Candidate UCD transition object. Classified as a "possible" member</td></tr><tr><td>34</td><td>12:26:43.31+12:17:44.0</td><td>1370</td><td>...</td><td>186.68</td><td>12.30</td><td>18.39</td><td>E(n)-Q</td><td>Very LSB ETG with bright nucleus. Candidate UCD transition object. Classified as a "probable" member</td></tr><tr><td>35</td><td>12:26:51.99+12:39:08.2</td><td>1407</td><td>...</td><td>186.72</td><td>12.65</td><td>20.54</td><td>E(n)-Q</td><td>Compact, extremely LSB ETG with bright, possibly offset nucleus. Candidate UCD transition object. Classified as a "probable" member</td></tr><tr><td>36</td><td>12:27:03.75+14:48:54.0</td><td>1439</td><td>...</td><td>186.77</td><td>14.81</td><td>20.73</td><td>E(n)-Q</td><td>Extremely LSB ETG with a possible bright nucleus. Candidate UCD transition object. Classified as a "probable" member</td></tr><tr><td>37</td><td>12:27:16.78+12:32:07.8</td><td>1482</td><td>...</td><td>186.82</td><td>12.54</td><td>21.27</td><td>E(n)-Q</td><td>Very compact, very LSB ETG with a small LSB envelope and a bright nucleus. Candidate UCD transition object. Classified as a "possible" member</td></tr><tr><td>38</td><td>12:27:17.61+06:46:05.7</td><td>1484</td><td>988</td><td>186.82</td><td>6.77</td><td>18.77</td><td>E(n)-Q</td><td>Extremely LSB ETG with a small envelope and bright nucleus. Candidate UCD transition object. Classified as a "certain" member. Cross ID: VCC988</td></tr><tr><td>39</td><td>12:27:19.26+13:51:01.9</td><td>1488</td><td>...</td><td>186.83</td><td>13.85</td><td>21.07</td><td>E(n)-Q</td><td>Very compact, extremely LSB ETG with a very small envelope and bright nucleus. Candidate UCD transition object. Classified as a "probable" member</td></tr><tr><td>40</td><td>12:27:44.67+07:56:43.0</td><td>1568</td><td>...</td><td>186.94</td><td>7.95</td><td>19.03</td><td>E(n)-Q</td><td>Extremely LSB ETG with bright nucleus. Candidate UCD transition object. Classified as a "possible" member</td></tr><tr><td>41</td><td>12:28:03.74+12:46:41.2</td><td>1612</td><td>...</td><td>187.02</td><td>12.78</td><td>21.04</td><td>E(n)-Q</td><td>Very compact, extremely LSB ETG with a small envelope and bright nucleus. Candidate UCD transition object. Classified as a "possible" member</td></tr><tr><td>42</td><td>12:28:06.26+08:03:43.7</td><td>1620</td><td>1067</td><td>187.03</td><td>8.06</td><td>18.14</td><td>E(n)-Q</td><td>Extended, extremely LSB ETG with possible extended blue nucleus and boxy structure. Candidate UCD transition object. Classified as a "certain" member. Cross ID: VCC1067</td></tr><tr><td>43</td><td>12:28:06.77+12:58:43.2</td><td>1622</td><td>1070</td><td>187.03</td><td>12.98</td><td>18.99</td><td>E(n)-Q</td><td>Very LSB ETG with bright nucleus. Candidate UCD transition object. Classified as a "certain" member. Cross ID: VCC1070</td></tr><tr><td>44</td><td>12:28:14.47+08:59:51.3</td><td>1649</td><td>...</td><td>187.06</td><td>9.00</td><td>18.12</td><td>E(n)-Q</td><td>Round, very LSB ETG with a small envelope and bright nucleus. Candidate UCD transition object. Classified as a "certain" member</td></tr><tr><td>45</td><td>12:28:15.85+12:52:12.0</td><td>1653</td><td>...</td><td>187.07</td><td>12.87</td><td>19.09</td><td>E(n)-Q</td><td>Extremely LSB ETG with bright nucleus. Candidate UCD transition object. Classified as a "probable" member</td></tr></tbody></table>
<table><caption>**Table 6**
(Continued)</caption><thead><tr><th>#</th><th>ID [NGVSJ]</th><th>NGVS</th><th>VCC</th><th>α(2000)<br>(deg)</th><th>δ(2000)<br>(deg)</th><th>g'(mag)</th><th>Type</th><th>Notes</th></tr></thead><tbody><tr><td>46</td><td>12:28:18.72+10:59:33.2</td><td>1658</td><td>...</td><td>187.08</td><td>10.99</td><td>19.97</td><td>E(n:-)Q</td><td>Extremely LSB ETG with a possible extended and bright nucleus. Candidate UCD transition object. Classified as a “possible” member</td></tr><tr><td>47</td><td>12:28:25.96+09:53:13.8</td><td>1686</td><td>...</td><td>187.11</td><td>9.89</td><td>18.65</td><td>E(n:-)Q</td><td>Very LSB ETG with possible offset, extremely bright blue nucleus. Candidate UCD transition object. Classified as a “certain” member</td></tr><tr><td>48</td><td>12:28:34.01+07:34:16.7</td><td>1712</td><td>1113</td><td>187.14</td><td>7.57</td><td>18.77</td><td>E(n)-Q</td><td>Very LSB ETG with bright nucleus. Candidate UCD transition object. Classified as a “certain” member. Cross ID: VCC1113</td></tr><tr><td>49</td><td>12:28:37.53+07:54:05.1</td><td>1719</td><td>...</td><td>187.16</td><td>7.90</td><td>19.04</td><td>E(n)-Q</td><td>Nucleated, elongated, extremely LSB ETG with very LSB and compact envelope. Candidate UCD transition object. Classified as a “probable” member</td></tr><tr><td>50</td><td>12:28:46.92+12:38:31.5</td><td>1747</td><td>...</td><td>187.20</td><td>12.64</td><td>19.94</td><td>E(n)-Q</td><td>Compact, extremely LSB ETG with bright nucleus. Candidate UCD transition object. Classified as a “certain” member</td></tr><tr><td>51</td><td>12:28:59.15+12:02:30.4</td><td>1784</td><td>...</td><td>187.25</td><td>12.04</td><td>20.41</td><td>E(n)-Q</td><td>Nucleated, compact, extremely LSB ETG with bright nucleus. Candidate UCD transition object. Classified as a “possible” member</td></tr><tr><td>52</td><td>12:28:59.50+11:55:23.4</td><td>1786</td><td>...</td><td>187.25</td><td>11.92</td><td>19.47</td><td>E(n:-)Q</td><td>Round, extremely LSB ETG with a possible bright nucleus. Candidate UCD transition object. Classified as a “probable” member</td></tr><tr><td>53</td><td>12:29:05.13+12:09:13.6</td><td>1801</td><td>1162</td><td>187.27</td><td>12.15</td><td>19.38</td><td>E(n)-Q</td><td>Very LSB ETG with bright nucleus. Candidate UCD transition object. Classified as a “certain” member. Cross ID: VCC1162</td></tr><tr><td>54</td><td>12:29:10.21+07:56:27.7</td><td>1813</td><td>...</td><td>187.29</td><td>7.94</td><td>20.57</td><td>E(n)-Q</td><td>Extremely LSB ETG with a small envelope and bright nucleus. Projected in the Virgo B subcluster. Candidate UCD transition object. Classified as a “probable” member</td></tr><tr><td>55</td><td>12:29:17.39+15:44:56.7</td><td>1831</td><td>...</td><td>187.32</td><td>15.75</td><td>19.84</td><td>E(n:-)Q</td><td>Compact, extremely LSB ETG with possible nucleus and round isophotes. Candidate UCD transition object. Classified as a “probable” member</td></tr><tr><td>56</td><td>12:29:23.56+14:53:48.9</td><td>1849</td><td>...</td><td>187.35</td><td>14.90</td><td>20.83</td><td>E(n)-Q</td><td>Very compact, very elongated, very LSB ETG with elongated, LSB envelope and bright blue nucleus. Candidate UCD transition object. Classified as a “probable” member</td></tr><tr><td>57</td><td>12:29:38.10+13:05:18.2</td><td>1889</td><td>...</td><td>187.41</td><td>13.09</td><td>20.88</td><td>E(n)-Q</td><td>Compact, extremely LSB ETG with bright nucleus. Candidate UCD transition object. Classified as a “possible” member</td></tr><tr><td>58</td><td>12:29:38.67+10:58:51.0</td><td>1894</td><td>...</td><td>187.41</td><td>10.98</td><td>21.10</td><td>E(n)-Q</td><td>Very compact, extremely LSB ETG with a small envelope and bright nucleus. Candidate UCD transition object. Classified as a “possible” member</td></tr><tr><td>59</td><td>12:29:41.39+11:34:19.3</td><td>1911</td><td>...</td><td>187.42</td><td>11.57</td><td>19.72</td><td>E(n:-)Q</td><td>Extremely LSB ETG with a possible bright nucleus. Candidate UCD transition object. Classified as a “probable” member</td></tr><tr><td>60</td><td>12:29:52.34+06:03:32.1</td><td>1943</td><td>1234</td><td>187.47</td><td>6.06</td><td>19.41</td><td>E(n:-)Q</td><td>Very LSB ETG with a possible bright nucleus. Candidate UCD transition object. Classified as a “certain” member. Cross ID: VCC1234</td></tr><tr><td>61</td><td>12:29:56.34+13:13:12.3</td><td>1956</td><td>1244</td><td>187.48</td><td>13.22</td><td>17.70</td><td>E(n)-Q</td><td>Compact, very LSB ETG and bright nucleus. Candidate UCD transition object. Classified as a “certain” member. Cross ID: VCC1244</td></tr><tr><td>62</td><td>12:29:57.10+11:24:03.1</td><td>1957</td><td>1217</td><td>187.49</td><td>11.40</td><td>19.47</td><td>E(n:-)Q</td><td>Extremely LSB ETG with a possible bright nucleus. Although its velocity is unknown, the galaxy is located 199" to the west of the bright LTG NGVS 1916 (VCC1217). Candidate UCD transition object. Classified as a “certain” member</td></tr><tr><td>63</td><td>12:30:12.55+09:42:56.3</td><td>2001</td><td>...</td><td>187.55</td><td>9.72</td><td>18.70</td><td>E(n:-)Q</td><td>Extremely LSB ETG with possible nucleus. Apparent member of an LSB pair, with the second member, NGVS 1993, located 57" to the west. Neither galaxy has a measured velocity. A third, possibly connected LSB ETG, NGVS 2031, is located 124" to the east. Candidate UCD transition object. Classified as a “certain” member</td></tr><tr><td>64</td><td>12:30:18.15+14:40:52.7</td><td>2024</td><td>1274</td><td>187.58</td><td>14.68</td><td>19.40</td><td>E(n)-Q</td><td>Nucleated, very elongated, very LSB ETG. A fainter LSB ETG, NGVS 2038, is located 63" to the southeast, while the brighter LSB ETG NGVS 2016 (VCC1274) is located 83" to the north. None of the galaxies has a measured velocity. Candidate UCD transition object. Classified as a “certain” member. Cross ID: VCC1276</td></tr><tr><td>65</td><td>12:30:31.24+06:23:19.2</td><td>2063</td><td>...</td><td>187.63</td><td>6.39</td><td>19.68</td><td>E(n)-Q</td><td>Extremely LSB ETG with bright nucleus. Candidate UCD transition object. Classified as a “certain” member</td></tr><tr><td>66</td><td>12:30:33.15+08:07:47.6</td><td>2069</td><td>1226</td><td>187.64</td><td>8.13</td><td>19.94</td><td>E(n:-)Q</td><td>Compact, extremely LSB ETG with possible bright offset nucleus. The galaxy, which has velocity v = 830.11 km s<sup>-1</sup>, is located 831" to the northeast of M49 (VCC1226, v = 989 km s<sup>-1</sup>). Candidate UCD transition object. Classified as a “probable” member</td></tr></tbody></table>
<table><caption>**Table 6**
(Continued)</caption><thead><tr><th>#</th><th>ID [NGVSJ]</th><th>NGVS</th><th>VCC</th><th>α(2000)<br>(deg)</th><th>δ(2000)<br>(deg)</th><th>g'(mag)</th><th>Type</th><th>Notes</th></tr></thead><tbody><tr><td>67</td><td>12:30:36.82+06:34:49.0</td><td>2075</td><td>...</td><td>187.65</td><td>6.58</td><td>19.36</td><td>E(n:-)Q</td><td>Extremely LSB ETG with a possible bright nucleus. Although its velocity is unknown, the galaxy is located in the Virgo core, close (324" to the northwest) of M87. Candidate UCD transition object. Classified as a "probable" member</td></tr><tr><td>68</td><td>12:30:45.94+09:00:44.9</td><td>2101</td><td>1303</td><td>187.69</td><td>9.01</td><td>18.29</td><td>E(n)-Q</td><td>Compact, very LSB ETG with bright nucleus. A bright ES galaxy (NGVS 2087, VCC1303) is located very close, 79" to the west. Candidate UCD transition object. Classified as a "certain" member. Cross ID: VCC1306</td></tr><tr><td>69</td><td>12:30:53.59+06:36:32.7</td><td>2128</td><td>1320</td><td>187.72</td><td>6.61</td><td>18.62</td><td>E(n)-Q</td><td>Compact, very LSB ETG with a small envelope and bright nucleus. Candidate UCD transition object. Classified as a "certain" member. Cross ID: VCC1320</td></tr><tr><td>70</td><td>12:31:08.79+14:36:04.0</td><td>2162</td><td>...</td><td>187.79</td><td>14.60</td><td>20.34</td><td>E(n:-)Q</td><td>Extremely LSB ETG with a possible bright nucleus. Candidate UCD transition object. Classified as a "probable" member</td></tr><tr><td>71</td><td>12:31:19.44+07:14:29.4</td><td>2191</td><td>...</td><td>187.83</td><td>7.24</td><td>20.36</td><td>E(n)-Q</td><td>Compact, extremely LSB ETG with bright nucleus. Candidate UCD transition object. Classified as a "certain" member</td></tr><tr><td>72</td><td>12:31:25.90+08:20:02.4</td><td>2204</td><td>1360</td><td>187.86</td><td>8.33</td><td>18.40</td><td>E(n)-Q</td><td>Very LSB ETG with bright nucleus and nearly round isophotes. Candidate UCD transition object. Classified as a "certain" member. Cross ID: VCC1360</td></tr><tr><td>73</td><td>12:31:37.17+05:23:02.5</td><td>2244</td><td>...</td><td>187.90</td><td>5.38</td><td>20.07</td><td>E(n:-)Q</td><td>Elongated, extremely LSB ETG with a possible bright nucleus. Candidate UCD transition object. Classified as a "probable" member</td></tr><tr><td>74</td><td>12:31:38.75+11:49:44.7</td><td>2249</td><td>...</td><td>187.91</td><td>11.83</td><td>21.14</td><td>E(n)-Q</td><td>Very compact, extremely LSB ETG with a small envelope and bright nucleus. Candidate UCD transition object. Classified as a "possible" member</td></tr><tr><td>75</td><td>12:31:39.76+13:38:53.7</td><td>2253</td><td>...</td><td>187.92</td><td>13.65</td><td>19.30</td><td>E(n)-Q</td><td>Compact, very LSB ETG with a small, very diffuse envelope and bright nucleus. Candidate UCD transition object. Classified as a "probable" member</td></tr><tr><td>76</td><td>12:31:44.79+11:13:59.1</td><td>2259</td><td>...</td><td>187.94</td><td>11.23</td><td>19.37</td><td>E(n)-Q</td><td>Compact, very LSB ETG with bright nucleus. Candidate UCD transition object. Classified as a "certain" member</td></tr><tr><td>77</td><td>12:31:47.77+06:55:56.9</td><td>2266</td><td>...</td><td>187.95</td><td>6.93</td><td>19.11</td><td>E(n)-Q</td><td>Very compact, extremely LSB ETG with bright nucleus. Candidate UCD transition object. Classified as a "possible" member</td></tr><tr><td>78</td><td>12:31:56.03+08:42:02.2</td><td>2291</td><td>...</td><td>187.98</td><td>8.70</td><td>21.73</td><td>E(n:-)Q</td><td>Compact, extremely LSB ETG with a small envelope and a possible bright nucleus. Candidate UCD transition object. Classified as a "possible" member</td></tr><tr><td>79</td><td>12:32:12.37+13:35:21.6</td><td>2341</td><td>...</td><td>188.05</td><td>13.59</td><td>19.09</td><td>E(n)-Q</td><td>Extremely LSB ETG with bright nucleus. Candidate UCD transition object. Classified as a "probable" member</td></tr><tr><td>80</td><td>12:32:12.92+09:18:56.7</td><td>2343</td><td>1421</td><td>188.05</td><td>9.32</td><td>17.16</td><td>E(n:-)Q</td><td>Extremely LSB ETG with a possible bright and blue nucleus. Candidate UCD transition object. Classified as a "certain" member. Cross ID: VCC1421</td></tr><tr><td>81</td><td>12:32:54.13+07:05:53.5</td><td>2442</td><td>...</td><td>188.23</td><td>7.10</td><td>20.57</td><td>E(n:-)Q</td><td>Compact, extremely LSB ETG with a possible bright nucleus. A second LSB ETG, NGVS 2436, is located 54" to the northwest, although neither galaxy has a measured velocity. Candidate UCD transition object. Classified as a "certain" member</td></tr><tr><td>82</td><td>12:33:06.41+13:18:11.1</td><td>2472</td><td>1477</td><td>188.28</td><td>13.30</td><td>18.22</td><td>E(n)-Q</td><td>Round, very LSB ETG with bright nucleus. Candidate UCD transition object. Classified as a "certain" member. Cross ID: VCC1477</td></tr><tr><td>83</td><td>12:33:15.05+11:13:49.6</td><td>2499</td><td>...</td><td>188.31</td><td>11.23</td><td>18.39</td><td>E(n)-Q</td><td>Extremely LSB ETG with bright blue nucleus. Located 86" to the northwest of the LSB ETG NGVS 2491, although the velocity of either galaxy is unknown. Candidate UCD transition object. Classified as a "certain" member</td></tr><tr><td>84</td><td>12:33:21.31+10:22:25.2</td><td>2514</td><td>...</td><td>188.34</td><td>10.37</td><td>19.40</td><td>E(n)-Q</td><td>Compact, extremely LSB ETG with bright nucleus. Candidate UCD transition object. Classified as a "probable" member</td></tr><tr><td>85</td><td>12:34:07.83+11:45:48.1</td><td>2606</td><td>...</td><td>188.53</td><td>11.76</td><td>20.60</td><td>E(n)-Q</td><td>Very compact, extremely LSB ETG with bright nucleus. Candidate UCD transition object. Classified as a "probable" member</td></tr><tr><td>86</td><td>12:34:23.11+12:20:21.3</td><td>2641</td><td>...</td><td>188.60</td><td>12.34</td><td>20.59</td><td>E(n:-)Q</td><td>Extremely LSB ETG with a possible very bright nucleus. Candidate UCD transition object. Classified as a "possible" member</td></tr><tr><td>87</td><td>12:34:25.91+12:45:38.2</td><td>2647</td><td>...</td><td>188.61</td><td>12.76</td><td>20.89</td><td>E(n:-)Q</td><td>Extremely LSB ETG with a possible bright nucleus. Candidate UCD transition object. Classified as a "possible" member</td></tr><tr><td>88</td><td>12:34:44.66+13:43:09.5</td><td>2681</td><td>...</td><td>188.69</td><td>13.72</td><td>20.31</td><td>E(n)-Q</td><td>Compact, extremely LSB ETG with extremely diffuse, elongated envelope and bright nucleus. Candidate UCD transition object. Classified as a "possible" member</td></tr></tbody></table>
<table><caption>**Table 6**
(Continued)</caption><thead><tr><th>#</th><th>ID [NGVSJ]</th><th>NGVS</th><th>VCC</th><th>α(2000)<br>(deg)</th><th>δ(2000)<br>(deg)</th><th>g'(mag)</th><th>Type</th><th>Notes</th></tr></thead><tbody><tr><td>89</td><td>12:34:52.53+08:40:42.1</td><td>2695</td><td>...</td><td>188.72</td><td>8.68</td><td>21.42</td><td>E(n)-Q</td><td>Very compact, extremely LSB ETG with a small LSB envelope and bright nucleus. Candidate UCD transition object. Classified as a "probable" member</td></tr><tr><td>90</td><td>12:35:37.87+08:05:55.1</td><td>2785</td><td>...</td><td>188.91</td><td>8.10</td><td>21.13</td><td>E(n)-Q</td><td>Compact, extremely elongated, extremely LSB ETG with bright nucleus. Candidate UCD transition object. Classified as a "probable" member</td></tr><tr><td>91</td><td>12:36:32.59+12:31:05.8</td><td>2878</td><td>1672</td><td>189.14</td><td>12.52</td><td>18.11</td><td>E(n)-Q</td><td>Compact, extremely LSB ETG with a very LSB isophote envelope and bright nucleus. Candidate UCD transition object. Classified as a "probable" member. Cross ID: VCC1672</td></tr><tr><td>92</td><td>12:36:59.28+07:52:22.5</td><td>2918</td><td>...</td><td>189.25</td><td>7.87</td><td>18.25</td><td>E(n)-Q</td><td>Very LSB ETG with diffuse, compact envelope and possible nucleus. Candidate UCD transition object. Classified as a "certain" member</td></tr><tr><td>93</td><td>12:37:25.09+12:35:11.0</td><td>2960</td><td>...</td><td>189.35</td><td>12.59</td><td>20.47</td><td>E(n)-Q</td><td>Very compact, extremely LSB ETG with a very small envelope and a possible bright nucleus. Candidate UCD transition object. Classified as a "possible" member</td></tr><tr><td>94</td><td>12:37:36.26+09:12:24.8</td><td>2978</td><td>1723</td><td>189.40</td><td>9.21</td><td>18.75</td><td>E(n)-Q</td><td>Compact, very LSB ETG with bright nucleus. Candidate UCD transition object. Classified as a "certain" member. Cross ID: VCC1723</td></tr><tr><td>95</td><td>12:37:49.73+07:49:23.1</td><td>2999</td><td>...</td><td>189.46</td><td>7.82</td><td>19.50</td><td>E(n)-Q</td><td>Extremely LSB ETG with a possible offset bright nucleus. Candidate UCD transition object. Classified as a "probable" member</td></tr><tr><td>96</td><td>12:38:12.15+10:42:06.6</td><td>3038</td><td>1749</td><td>189.55</td><td>10.70</td><td>18.37</td><td>E(n)-Q</td><td>Compact, very LSB ETG with a small envelope and bright nucleus. Candidate UCD transition object. Classified as a "certain" member. Cross ID: VCC1749</td></tr><tr><td>97</td><td>12:39:12.23+08:09:20.6</td><td>3099</td><td>...</td><td>189.80</td><td>8.16</td><td>20.32</td><td>E(n)-Q</td><td>Compact, very elongated, extremely LSB ETG with a possible bright nucleus. Candidate UCD transition object. Classified as a "certain" member</td></tr><tr><td>98</td><td>12:39:20.34+11:26:20.0</td><td>3112</td><td>1798</td><td>189.83</td><td>11.44</td><td>20.16</td><td>E(n)-Q</td><td>Extremely LSB ETG with faint envelope and bright nucleus. Candidate UCD transition object. Located 177" to the southwest of the extended, extremely LSB ETG BGVS3128 (VCC1798). Classified as a "probable" member</td></tr><tr><td>99</td><td>12:39:21.99+12:05:34.6</td><td>3116</td><td>...</td><td>189.84</td><td>12.09</td><td>20.76</td><td>E(n)-Q</td><td>Extremely LSB ETG with a possible bright nucleus. Candidate UCD transition object. Candidate UDG. Classified as a "probable" member</td></tr><tr><td>100</td><td>12:39:24.84+10:29:56.2</td><td>3117</td><td>...</td><td>189.85</td><td>10.50</td><td>19.49</td><td>E(n)-Q</td><td>Extremely LSB ETG with a possible bright nucleus. One member of an apparent pair of candidate UCD transition objects, the second one being NGVS 3119, located 20" to the northeast, although neither galaxy has a measured velocity. Classified as a "possible" member</td></tr><tr><td>101</td><td>12:39:25.72+10:30:12.3</td><td>3119</td><td>...</td><td>189.86</td><td>10.50</td><td>21.00</td><td>E(n)-Q</td><td>Very compact, extremely LSB ETG with a small LSB envelope and a possible bright nucleus. Candidate UCD transition object. Member of an apparent pair of candidate UCD transition objects, the second one being NGVS 3117, located 20" to the southwest, although neither galaxy has a measured velocity. Classified as a "possible" member</td></tr><tr><td>102</td><td>12:39:48.45+09:49:46.6</td><td>3149</td><td>...</td><td>189.95</td><td>9.83</td><td>19.14</td><td>E(n)-Q</td><td>Compact, unusual, very LSB ETG with a small envelope and a possible bright, possibly resolved nucleus. Candidate UCD transition object. Classified as a "certain" member</td></tr><tr><td>103</td><td>12:40:01.63+11:52:44.7</td><td>3164</td><td>1815</td><td>190.01</td><td>11.88</td><td>19.20</td><td>E(n)-Q</td><td>Compact, very LSB ETG with bright nucleus (and possible offset dual nucleus). NGVS 3156 (VCC1815) is located 119" to the northwest. Candidate UCD transition object. Classified as a "certain" member</td></tr><tr><td>104</td><td>12:40:01.95+09:57:25.1</td><td>3167</td><td>1826</td><td>190.01</td><td>9.96</td><td>19.06</td><td>E(n)-Q</td><td>Very LSB ETG with round isophotes and a bright nucleus. Located 30" to the south of the fainter LSB ETG NGVS 3165, whose velocity is unknown. May be associated with VCC1826, which is located 4.3 to the southeast and has a similar velocity (1974 km s<sup>-1</sup> for VCC1826 and 1845 km s<sup>-1</sup> for VCC1817). Candidate UCD transition object. Classified as a "certain" member. Cross ID: VCC1817</td></tr><tr><td>105</td><td>12:41:32.64+15:55:54.2</td><td>3267</td><td>...</td><td>190.39</td><td>15.93</td><td>20.62</td><td>E(n)-Q</td><td>Extremely LSB ETG with a small envelope and a possible bright nucleus. Candidate UCD transition object. Classified as a "probable" member</td></tr><tr><td>106</td><td>12:42:22.80+11:41:06.2</td><td>3317</td><td>1903</td><td>190.60</td><td>11.69</td><td>19.74</td><td>E(n)-Q</td><td>Nucleated, compact, very LSB ETG. Candidate UCD transition object. Located 331" to the northeast of NGVS 3296 (VCC1903, M59). Classified as a "certain" member</td></tr><tr><td>107</td><td>12:43:20.88+14:02:02.9</td><td>3379</td><td>...</td><td>190.84</td><td>14.03</td><td>18.77</td><td>E(n)-Q</td><td>Extended, extremely LSB ETG with a possible bright blue nucleus. Candidate UCD transition object. Classified as a "probable" member</td></tr><tr><td>108</td><td>12:43:57.77+11:52:50.5</td><td>3413</td><td>1986</td><td>190.99</td><td>11.88</td><td>17.94</td><td>E(n)-Q</td><td>Compact, very LSB ETG with bright nucleus. Possible tidal streams. Candidate UCD transition object. Classified as a "certain" member. Cross ID: VCC1986</td></tr></tbody></table>
<table><caption>**Table 6**
(Continued)</caption><thead><tr><th>#</th><th>ID [NGVSJ]</th><th>NGVS</th><th>VCC</th><th>α(2000)<br>(deg)</th><th>δ(2000)<br>(deg)</th><th>g'(mag)</th><th>Type</th><th>Notes</th></tr></thead><tbody><tr><td>109</td><td>12:44:23.92+08:47:29.1</td><td>3434</td><td>...</td><td>191.10</td><td>8.79</td><td>18.88</td><td>E(n:)-Q</td><td>Very LSB ETG with a possible offset blue nucleus. Candidate UCD transition object. Classified as a “certain” member</td></tr><tr><td>110</td><td>12:44:45.00+11:48:03.5</td><td>3455</td><td>...</td><td>191.19</td><td>11.80</td><td>18.94</td><td>E(n)-Q</td><td>Extremely LSB ETG with round isophotes and a bright nucleus. Candidate UCD transition object. Classified as a “certain” member</td></tr><tr><td>111</td><td>12:45:54.08+10:39:29.5</td><td>3522</td><td>...</td><td>191.48</td><td>10.66</td><td>19.44</td><td>E(n)-Q</td><td>Compact, very LSB ETG with a small envelope and bright nucleus. Candidate UCD transition object. Classified as a “probable” member</td></tr><tr><td>112</td><td>12:46:31.37+13:19:33.0</td><td>3538</td><td>...</td><td>191.63</td><td>13.33</td><td>19.07</td><td>E(n)-Q</td><td>Extremely LSB ETG with bright nucleus. Candidate UCD transition object. Classified as a “probable” member</td></tr><tr><td>113</td><td>12:47:47.50+12:41:42.5</td><td>3582</td><td>...</td><td>191.95</td><td>12.70</td><td>19.60</td><td>E(n)-Q</td><td>Extremely LSB ETG with bright nucleus. Candidate UCD transition object. Classified as a “probable” member</td></tr><tr><td>114</td><td>12:47:49.44+15:43:28.9</td><td>3584</td><td>...</td><td>191.96</td><td>15.72</td><td>20.53</td><td>E(n:)-Q</td><td>Compact, extremely LSB ETG with a small envelope and possible nucleus. Candidate UCD transition object. Classified as a “probable” member</td></tr><tr><td>115</td><td>12:49:00.69+09:00:42.2</td><td>3619</td><td>...</td><td>192.25</td><td>9.01</td><td>19.47</td><td>E(n:)-Q</td><td>Compact LSB ETG with a small, round envelope and a possible extended nucleus. Candidate UCD transition object. Classified as a “probable” member</td></tr></tbody></table>
objects and their potential role in bridging nucleated dwarfs and bona fide UCDs.

Our sample of candidate transition objects provides an opportunity to investigate the physical processes driving envelope disruption during an apparently short-lived evolutionary phase. These objects may be attractive targets for future spectroscopic and photometric studies aimed at understanding the role of tidal stripping in UCD growth. In particular, a quantitative comparison of envelope sizes and luminosities between our sample and those of K. Wang et al. (2023) could further clarify whether these differences arise due to selection effects or reflect intrinsic variations in the stripping process.

By characterizing the structural properties of these objects in detail and comparing them to both intact nucleated dwarfs and fully stripped UCDs, it may be possible to refine models of tidal stripping and nuclear survival. Future work will explore the implications of these findings for the structural evolution of low-mass galaxies in cluster environments (e.g., K. Wang et al. 2025, in preparation), while a broader investigation of nuclear star clusters in Virgo galaxies will be presented in a future paper in this series.

### 5.1.4. Candidate Merger and Postmerger Galaxies

Mergers, both major and minor, are recognized as important drivers of galaxy evolution (G. Efstathiou & J. Silk 1983; G. R. Blumenthal et al. 1984; J. Silk & R. F. G. Wyse 1993) since they affect the growth and morphological transformation of galaxies. Their importance as a function of the environment and galaxy mass is a topic of active study (S. Jogee et al. 2009; D. W. Darg et al. 2010; D. Thomas et al. 2010; D. D. Kocevski et al. 2012; S. L. Ellison et al. 2019; B. Vulcani et al. 2021; S. P. Driver et al. 2022). This is particularly true in cluster environments (e.g., Y.-K. Sheen et al. 2012; S. Oh et al. 2016, 2018, 2019; D. Kim et al. 2024; F. Piraino-Cerda et al. 2024; E. Sola et al. 2025) and specific examples of merger and postmerger systems in Virgo may bear on the structure of the cluster itself (H. Böhringer et al. 1994; Y. Lee et al. 2021).

Our visual analysis reveals a number of Virgo galaxies that show signs of interactions or tidal encounters—stellar streams, tails, plumes, shells, or disturbed isophotes. While the NGVS structure and star formation codes record such features when present, some galaxies appear sufficiently disturbed to suggest an ongoing or recent merger. In this section, we discuss such systems, noting that they are best described as *candidate* merger or postmerger galaxies given that our classifications have been made on the basis of visual appearance alone, without the benefit of the kinematic observations or numerical modeling that is usually needed to identify such systems unambiguously.

A sample of 66 candidate merger or postmerger galaxies is presented in Table 7. As noted above, these candidates were identified purely from their visual appearance: i.e., based on the presence of prominent shells, filaments, twisted isophotes, misaligned spiral arms, and distorted morphologies that are indicative of ongoing or recent mergers. Many galaxies in the cluster show such features, so only the most prominent cases are listed in Table 7. The sample is thus somewhat subjective in nature and should not be considered complete.

Figure 15 presents thumbnail images for these 66 candidates. Each panel measures 3' × 3' (i.e., 14.4 kpc on a side at the

distance of Virgo). The telltale signs of ongoing or recent mergers are readily apparent in most cases. As expected, the galaxies span a broad range in mass ($6.47 \le \log(M_*/M_{\odot}) \le 10.81$) and are distributed across the cluster ($182^{\circ}087 \le \alpha \le 192^{\circ}415, 5^{\circ}181 \le \delta \le 15^{\circ}679$), encompassing a wide range of structural and star formation codes.

This compilation may be useful for future studies of mergers in cluster environments, particularly among intermediate- and low-mass galaxies. The median galaxy mass is log $M^*/M_{\odot} = 7.89$, placing the majority of our sample in the dwarf galaxy regime. Additionally, 53/66 (80%) of our postmerger galaxies have $\log M^*/M_{\odot} \le 9$, indicating that our sample is mostly comprised of dwarfs.

We also note the inclusion of three dwarf mergers previously identified as early-type dwarfs with shell-like features by S. Paudel et al. (2017): VCC1361 (NGVS 2205), VCC1447 (NGVS 2402), and VCC1668 (NGVS 2871). Although the faint and extended nature of these shells makes them difficult to discern in NGVS imaging, they remain indicative of recent merger activity that has perturbed the morphologies of these galaxies. Our sample additionally includes more striking and strongly disturbed dwarf merger systems such as VCC848 and VCC479, known dwarf-dwarf mergers whose NGVS imaging has been used in the respective studies of H.-X. Zhang et al. (2020a, 2020b) and W. Sun et al. (2025). While our visually identified sample of postmerger systems in Virgo is necessarily incomplete due to the subjective nature of classification, we nonetheless observe a significant presence of merger activity. The diversity of morphological signatures within our sample, from subtle tidal features to well-defined merger remnants, underscores the prevalence of interactions among low-mass galaxies and highlights the broad range of dynamical states they exhibit within the cluster.

## 5.2. Nonparametric Measurements

### 5.2.1. statmorph Measurements of the NGVS

Nonparametric morphological statistics can be used to supplement traditional galaxy classifications. Such statistics have usually been used to classify galaxies automatically with little or no human intervention, and have never been applied to a large cluster sample dominated by low-mass, faint galaxies, as is the case here. We have run the *statmorph* code of V. Rodriguez-Gomez et al. (2019) on our NGVS sample to measure nonparametric morphological statistics for as many Virgo galaxies as possible. Before describing our selection criteria, we briefly review the utility of nonparametric morphological statistics. For more thorough reviews, the reader is directed to the deeper dives on nonparametric morphological statistics in S. Wilkinson et al. (2022), V. Rodriguez-Gomez et al. (2019), and the section on nonparametric morphologies in the review on galaxy structure formation by C. J. Conselice (2014).

We focus on some of the most commonly applied nonparametric morphology statistics. These statistics are the CAS system (C. J. Conselice 2003) and Gini-$M_{20}$ statistics (J. M. Lotz et al. 2004). Concentration (C) (M. A. Bershady et al. 2000; C. J. Conselice 2003), asymmetry (A) (D. Schade et al. 1995; R. G. Abraham et al. 1996; C. J. Conselice et al. 2000) and smoothness (S) C. J. Conselice (2003) define the CAS system, which quantifies different aspects of a galaxy's
<table><caption>Table 7
Candidate Merger and Postmerger Galaxies</caption><thead><tr><th>#</th><th>ID [NGVSJ]</th><th>NGVS</th><th>VCC</th><th>α(2000)<br>(deg)</th><th>δ(2000)<br>(deg)</th><th>g'(mag)</th><th>Type</th><th>Notes</th></tr></thead><tbody><tr><td>1</td><td>12:08:20.90+12:30:07.8</td><td>7</td><td>...</td><td>182.09</td><td>12.50</td><td>18.01</td><td>EI(sp:|du:|b:|sh:|pm:)-I<br>(c|p|g)</td><td>Possible EI galaxy with irregular structure and star formation. Postmerger system? Classified as "a<br>certain" member</td></tr><tr><td>2</td><td>12:09:50.60+12:54:09.8</td><td>16</td><td>...</td><td>182.46</td><td>12.90</td><td>17.42</td><td>E(n:|pm:)-I(c:)</td><td>Unusual elongated LSB ETG, very likely the result of an ongoing merger event between two LSB<br>ETG galaxies, each with a bright blue nucleus. A high-surface-brightness blue filament connects<br>the two nuclei. Possible postmerger remnant. Classified as a "certain" member</td></tr><tr><td>3</td><td>12:10:03.30+11:42:48.3</td><td>19</td><td>...</td><td>182.51</td><td>11.71</td><td>16.86</td><td>ES(pm:)-I(c)</td><td>ES galaxy with SF in patches and filaments embedded in elliptical isophotes. Possible postmerger<br>system. Classified as "a certain" member</td></tr><tr><td>4</td><td>12:11:45.72+13:01:27.4</td><td>49</td><td>37</td><td>182.94</td><td>13.02</td><td>17.74</td><td>ES(n|pm:)-Q</td><td>Nucleated ES galaxy with apparent disk. Possible flared or bow-tie morphology. Possible postmerger<br>remnant. Classified as a "certain" member. Cross ID: VCC37</td></tr><tr><td>5</td><td>12:13:35.81+13:02:04.4</td><td>94</td><td>85</td><td>183.40</td><td>13.03</td><td>17.37</td><td>EI(sh|pm)-I(g|e)</td><td>Structurally complex galaxy with active star formation. Galaxy contains a series of loops and shells.<br>Peak of star formation offset from the centroid of light. Postmerger remnant. Classified as a<br>"certain" member. Cross ID: VCC85</td></tr><tr><td>6</td><td>12:15:35.69+13:37:11.0</td><td>171</td><td>155</td><td>183.90</td><td>13.62</td><td>15.04</td><td>ES(di:|b:|sp:|du|pm:)-I<br>(c|d)</td><td>Complex ES galaxy with old stellar population, but streams and possible intermediate-age bar, disk,<br>or lens. Possible postmerger remnant. Classified as "a certain" member. Cross ID: VCC155</td></tr><tr><td>7</td><td>12:16:23.01+07:47:54.5</td><td>220</td><td>190</td><td>184.10</td><td>7.80</td><td>17.14</td><td>EI(pm:)-I(g|e)</td><td>Extended LSB EI galaxy with distributed star formation, LTG with peculiar structure suggestive of a<br>postmerger remnant. Irregular appearance with low-level star formation and several compact<br>clumps are found scattered near the center. Classified as a "certain" member. Cross ID: VCC190</td></tr><tr><td>8</td><td>12:17:09.91+07:11:29.3</td><td>268</td><td>222</td><td>184.29</td><td>7.19</td><td>11.99</td><td>ES(n|di:|sp:|sh|st|du|<br>pm:)-I(g)</td><td>Nucleated ES galaxy seen nearly edge-on. Low-level star formation in a disk, with dust. Bow-shaped<br>streams at both ends of the disk. Possible postmerger remnant. Classified as a "certain" member.<br>Cross ID: VCC222</td></tr><tr><td>9</td><td>12:17:14.54+08:56:32.4</td><td>272</td><td>227</td><td>184.31</td><td>8.94</td><td>14.64</td><td>ES(n|sh|st|b|pm:)-I(g)</td><td>ES galaxy with complex structure comprising a series of shells and streams. Possible postmerger<br>remnant. Bright compact nucleus. Possible inner bar or disk. Classified as a "certain" member.<br>Cross ID: VCC227</td></tr><tr><td>10</td><td>12:18:15.35+13:44:56.8</td><td>330</td><td>281</td><td>184.56</td><td>13.754</td><td>15.39</td><td>ES(sh|du:|sp:|pm:)-I(c)</td><td>ES galaxy with smoothly distributed older component and star formation, and dust in the core. Dust<br>may be distributed in an arc. Apparent shell to the northwest. Possible postmerger remnant.<br>Classified as a "certain" member. Cross ID: VCC281</td></tr><tr><td>11</td><td>12:18:57.69+08:38:41.4</td><td>363</td><td>...</td><td>184.74</td><td>8.64</td><td>18.41</td><td>E(sh:|pm:)-Q</td><td>LSB ETG with irregular structure. Possible shells. Possible postmerger product. Classified as a<br>"certain" member</td></tr><tr><td>12</td><td>12:19:05.14+13:58:51.9</td><td>371</td><td>322</td><td>184.77</td><td>13.98</td><td>15.37</td><td>EI(sh:|st:|pm:)-A(g)</td><td>Complex galaxy with shells, ripples, and some central star formation. Possibly interacting with<br>VCC319 (v = 421 km s<sup>-1</sup>), located 0.7 to the west, and sharing a common envelope. Also possibly<br>associated with VCC334 (v = -246 km s<sup>-1</sup>), located 6.3 to the southeast. VCC322 velocity is<br>-195 km s<sup>-1</sup>. Likely postmerger system. Classified as "a certain" member. Cross ID: VCC322</td></tr><tr><td>13</td><td>12:19:15.56+06:17:38.0</td><td>388</td><td>331</td><td>184.81</td><td>6.29</td><td>15.43</td><td>ES(n|sp|sh|pm:)-I(c)</td><td>ES galaxy with offset nucleus, extended star-forming core or disk superimposed on older population with<br>ripples, arms, or shells. Possible postmerger remnant. Located 48'' to the south of the similarly bright<br>VCC332, although the two galaxies have significantly different velocities (2257 and 660 km s<sup>-1</sup>). A<br>third galaxy, NGVS 393, with unknown velocity, is located 110'' to the northeast. Classified as a<br>"certain" member. Cross ID: VCC331</td></tr><tr><td>14</td><td>12:19:16.39+15:23:46.3</td><td>389</td><td>335</td><td>184.82</td><td>15.40</td><td>17.32</td><td>EI(sh:|pm:)-I(c)</td><td>Complex EI galaxy with a series of shells and lobes. Possible postmerger product. Cross ID: VCC360<br>is located 6' to the northeast. Classified as a "certain" member. Cross ID: VCC335</td></tr><tr><td>15</td><td>12:19:22.13+05:54:38.1</td><td>398</td><td>340</td><td>184.84</td><td>5.91</td><td>14.65</td><td>E(sh|st|du|pm:)-A(c)</td><td>Complex ETG or possibly EI galaxy with a possible nucleus, blue and dusty inner regions, and a shell<br>to the south. Might be part of a small group that includes VCC340 (v = 1506 km s<sup>-1</sup>), VCC329<br>(v = 1618 km s<sup>-1</sup>), located 5.0 to the northwest, VCC315 (v = 1594 km s<sup>-1</sup>), located 12.2 to the<br>northwest, VCC341 (v = 1838 km s<sup>-1</sup>), located 11.2 to the north, VCC379 (v = 1453 km s<sup>-1</sup>),<br>located 9.0 to the northeast. Located close to a prominent stellar stream that emanates from VCC336.<br>Possible tidal or postmerger features. Classified as a "certain" member. The presence of a nucleus is<br>impossible to assess due to the presence of dust or other contaminants. Cross ID: VCC340</td></tr></tbody></table>
<table><caption>Table 7
(Continued)</caption><thead><tr><th>#</th><th>ID [NGVSJ]</th><th>NGVS</th><th>VCC</th><th>α(2000)<br>(deg)</th><th>δ(2000)<br>(deg)</th><th>g'(mag)</th><th>Type</th><th>Notes</th></tr></thead><tbody><tr><td>16</td><td>12:20:43.91+14:37:52.0</td><td>519</td><td>429</td><td>185.18</td><td>14.63</td><td>16.64</td><td>EI(sh|pm:)-I(c|g|p)</td><td>EI galaxy with active star formation in its core and "lobes" or clumps along its major axis. Shells in its inner regions. Possible postmerger remnant. Classified as a "certain" member. Cross ID: VCC429</td></tr><tr><td>17</td><td>12:20:58.89+08:51:55.4</td><td>537</td><td>447</td><td>185.25</td><td>8.87</td><td>19.03</td><td>E(pm:)-Q</td><td>Elongated LSB ETG with unusual peanut-like morphology. Possible postmerger remnant. Classified as a "probable" member. Cross ID: VCC447</td></tr><tr><td>18</td><td>12:21:03.68+07:04:39.4</td><td>543</td><td>450</td><td>185.27</td><td>7.08</td><td>15.38</td><td>ES(di|sh|st|du|pm:)-<br>I(c)</td><td>ES galaxy with dust and very weak star formation offset from the center. A series of outer faint shells or streams, suggestive of past merger or accretion. The galaxy is likely associated (and may be interacting) with VCC439, which is located 3.3 to the southwest and has almost identical velocity (2326 km s<sup>-1</sup> for VCC439 and 2358 km s<sup>-1</sup> for VCC450) and VCC415 (v = 2560 km s<sup>-1</sup>), located 13.8 to the southwest. Classified as a "certain" member. Cross ID: VCC450</td></tr><tr><td>19</td><td>12:21:29.23+08:09:04.6</td><td>586</td><td>479</td><td>185.37</td><td>8.15</td><td>16.32</td><td>EI(sh|pm:)-I(c)</td><td>EI galaxy with active star formation in its core. Shell-like structure and S-shaped distortion at large radius. Possible postmerger system. Classified as a "certain" member. Cross ID: VCC479</td></tr><tr><td>20</td><td>12:21:42.72+09:21:19.3</td><td>612</td><td>496</td><td>185.43</td><td>9.36</td><td>17.51</td><td>ES(di|st|sh|pm:)-Q</td><td>Complex ES galaxy with central structure and dumbbell appearance, including possible shells. Possible postmerger remnant. Classified as "a certain" member. Cross ID: VCC496</td></tr><tr><td>21</td><td>12:21:47.10+05:59:20.8</td><td>620</td><td>...</td><td>185.45</td><td>5.99</td><td>16.86</td><td>E(n|sh|pm:)-I(c)</td><td>ETG with a blue nucleus and core, and possible outer shells. Possible postmerger system. Classified as a "certain" member</td></tr><tr><td>22</td><td>12:22:19.98+15:40:46.6</td><td>680</td><td>...</td><td>185.58</td><td>15.68</td><td>18.75</td><td>ES(di|pm:)-Q</td><td>Elongated ES galaxy with extended tails. Possible S-shaped morphology. Bow-tie morphology at large radii. The smaller and more compact NGVS 687 is located 64" to the southeast, although neither galaxy has a known velocity. Possible postmerger remnant. Classified as "a possible" member</td></tr><tr><td>23</td><td>12:22:21.67+10:36:06.4</td><td>683</td><td>546</td><td>185.59</td><td>10.60</td><td>15.65</td><td>E(di|sh|du|pm:)-I(g|d)</td><td>Unusual ETG with prominent shells. Twisted isophotes, with the galaxy having a bow-shaped or bent appearance at large radius. Possible postmerger remnant. Classified as a "certain" member. Cross ID: VCC546</td></tr><tr><td>24</td><td>12:22:28.32+12:53:55.6</td><td>696</td><td>...</td><td>185.62</td><td>12.90</td><td>18.35</td><td>EI(sh|st|pm:)-I(c|g)</td><td>Possible postmerger remnant with fans and shells, plus central SF. Classified as a "possible" member</td></tr><tr><td>25</td><td>12:23:21.46+07:35:30.4</td><td>833</td><td>633</td><td>185.84</td><td>7.59</td><td>17.10</td><td>E(sh|pm:)-I(c:)</td><td>Elongated LSB ETG with bow-tie or boxy structure at large radius. Possible postmerger remnant. Classified as a "certain" member. Cross ID: VCC633</td></tr><tr><td>26</td><td>12:24:03.22+05:10:51.3</td><td>937</td><td>693</td><td>186.01</td><td>5.18</td><td>14.81</td><td>E(di|b|sp|sh|st|du|<br>pm)-A(g|e)</td><td>Morphologically complex galaxy with strong star formation, but a series of streams and shells that do not resemble organized spiral arms. Likely postmerger remnant. Classified as a "certain" member. Cross ID: VCC693</td></tr><tr><td>27</td><td>12:24:07.55+06:36:27.4</td><td>949</td><td>699</td><td>186.03</td><td>6.61</td><td>13.74</td><td>EI(di|sp|sh|st|du|<br>pm:)-I(d)</td><td>EI galaxy object with a series of rings/shells at a large radius, and a central irregular star-forming component. Possible postmerger remnant. Classified as a "certain" member. Cross ID: VCC699</td></tr><tr><td>28</td><td>12:25:52.42+05:48:32.9</td><td>1204</td><td>848</td><td>186.47</td><td>5.81</td><td>14.77</td><td>EI(b|sh|du|pm)-A(g|<br>b|e:)</td><td>EI galaxy and likely postmerger system. The galaxy is roughly face-on and includes a bar and a chaotic series of shells that extend to a large radius. Classified as a "certain" member. Cross ID: VCC848</td></tr><tr><td>29</td><td>12:27:11.68+09:25:13.8</td><td>1463</td><td>979</td><td>186.80</td><td>9.42</td><td>11.83</td><td>ES(di|b|sp|sh|du|pm:)-I<br>(c|f)</td><td>Morphologically complex ES galaxy with dust filaments and star formation in the inner bar. Faint, incomplete spiral structure and possible shells at large radius. Possible postmerger remnant. Classified as a "certain" member. Cross ID: VCC979</td></tr><tr><td>30</td><td>12:27:11.68+09:25:13.8</td><td>1524</td><td>1013</td><td>186.88</td><td>9.34</td><td>16.68</td><td>EI(sh|pm:)-I(c|p|f|g)</td><td>EI galaxy with star formation throughout and filamentary/patchy formation in the core. Likely shell or "shelf" to the northwest. Possible postmerger remnant. Classified as a "certain" member. Cross ID: VCC1013</td></tr><tr><td>31</td><td>12:27:45.65+13:00:31.9</td><td>1570</td><td>1043</td><td>186.94</td><td>13.01</td><td>10.92</td><td>EI(di|sh|st|du|pm)-At<br>(g|f|p|e)</td><td>Catastrophically disturbed galaxy, classified as EI, which is possibly interacting with VCC1030 (NGVS 1550, located 263" to the N), although the two galaxies have significantly different velocities (70 km s<sup>-1</sup> for NGVS 1570, and 793 km s<sup>-1</sup> for NGVS1550). Two additional galaxies are located nearby: NGVS1567 (92" to the southwest, with v = -142 km s<sup>-1</sup>) and NGVS 1587 (171" to the southeast, unknown velocity). The galaxy is also located 23" to the southeast of M86 (v = -233 km s<sup>-1</sup>) and has a similar velocity, suggesting it might be part of the M86 group. Dust and star formation, with very disturbed morphology. Classified as a "certain" member. Cross ID: VCC1043</td></tr></tbody></table>
<table><caption>Table 7
(Continued)</caption><thead><tr><th>#</th><th>ID [NGVSJ]</th><th>NGVS</th><th>VCC</th><th>α(2000)<br>(deg)</th><th>δ(2000)<br>(deg)</th><th>g'(mag)</th><th>Type</th><th>Notes</th></tr></thead><tbody><tr><td>32</td><td>12:28:11.34+09:45:37.0</td><td>1638</td><td>1078</td><td>187.05</td><td>9.75</td><td>15.68</td><td>ES(n:di:|sp|sh|st|pm:)-<br>I(c)</td><td>ES galaxy with a slightly blue core, a series of shells or clumps along the major axis, and an offset<br>nucleus. S-shaped isophotes at large radius, suggestive of a tidal encounter with VCC1078, which<br>is located 3.2 to the southeast and has a similar velocity (547 km s<sup>-1</sup> for VCC1062 and 530 km s<sup>-1</sup> for VCC1078). Possible postmerger remnant. Classified as a "certain" member. Cross ID:<br>VCC1078</td></tr><tr><td>33</td><td>12:28:33.75+08:38:24.6</td><td>1711</td><td>1114</td><td>187.14</td><td>8.64</td><td>14.41</td><td>EI(n:|sh|du|pm)-I(g|p)</td><td>Elongated EI galaxy with shells and a disturbed outer structure. Possible, maybe an offset nucleus and<br>off-centered clump of star formation in the inner region. Boxy structure in the outer regions.<br>Classified as a "certain" member. Cross ID: VCC1114</td></tr><tr><td>34</td><td>12:28:41.01+11:07:58.4</td><td>1727</td><td>1121</td><td>187.17</td><td>11.13</td><td>16.81</td><td>EI(sp:|sh|pm:)-I(g)</td><td>EI galaxy with star formation in shells and arcs. Possible weak spiral structure. Forms a very close<br>pair with NGVS 1732, which has similar morphology and is located 12" to the southeast. A very<br>bright star is projected close to the center. Possible postmerger remnant. Classified as a "certain"<br>member. Cross ID: VCC1121</td></tr><tr><td>35</td><td>12:28:41.73+11:07:51.1</td><td>1732</td><td>...</td><td>187.17</td><td>11.13</td><td>16.72</td><td>EI(pm)-I(g:)</td><td>Complex galaxy. Forms a very close pair with NGVS 1727, which has similar morphology and is<br>located 12" to the northwest. Interpretation is made difficult by the presence of a nearby star.<br>Likely postmerger remnant. Classified as "a probable" member</td></tr><tr><td>36</td><td>12:29:28.02+08:44:59.2</td><td>1859</td><td>1190</td><td>187.37</td><td>8.75</td><td>11.75</td><td>ES(di:sp:|du|pm:)-I<br>(c|d)</td><td>Edge-on ES galaxy with a weakly star-forming disk and prominent dust lanes and patches. Dust gives<br>the galaxy an "X-shaped" appearance in the inner regions. Classified as a "certain" member. The<br>presence of a nucleus is impossible to assess due to the presence of dust or other contaminants.<br>Possible postmerger remnant. Cross ID: VCC1190</td></tr><tr><td>37</td><td>12:30:57.11+11:29:00.7</td><td>2135</td><td>1326</td><td>187.74</td><td>11.48</td><td>12.96</td><td>ES(n:di:|b|sh:|st|du|<br>pm:)-I(c)</td><td>ES galaxy with complex inner structure highlighted by arcs, streams, dust, star formation, and a<br>possible nucleus. Possible shells at large radii. Possible postmerger product. Classified as a<br>"certain" member. Cross ID: VCC1326</td></tr><tr><td>38</td><td>12:31:02.08+06:07:20.0</td><td>2149</td><td>1332</td><td>187.76</td><td>6.12</td><td>18.06</td><td>E(sh|pm:)-Q</td><td>LSB EI or ETG galaxy with asymmetric, irregular structure and shells. Possible SF. Possible merger<br>product. Classified as a "certain" member. Cross ID: VCC1332</td></tr><tr><td>39</td><td>12:31:27.11+09:44:00.5</td><td>2205</td><td>1361</td><td>187.86</td><td>9.73</td><td>17.19</td><td>E(sh|pm:)-I(c)</td><td>Peculiar ETG galaxy with old stellar populations and a series of lobes or clumps along the major axis.<br>Possible postmerger remnant. Galaxy resembles Cross ID: VCC429. Classified as a "certain"<br>member. Cross ID: VCC1361</td></tr><tr><td>40</td><td>12:31:53.86+14:18:23.4</td><td>2280</td><td>1400</td><td>187.97</td><td>14.31</td><td>15.53</td><td>E(n:di:|sh|pm:)-I(c:)</td><td>Nucleated ETG. Galaxy has ba oxy, almost bow-tie or X-shaped appearance, with possible flaring or<br>shells at large radius. Located 416" to the south of the bright LTG NGVS 2297 (VCC1401),<br>although the two galaxies have significantly different velocities (2283 vs. 460 km s<sup>-1</sup>). Possible<br>postmerger remnant. Classified as a "certain" member. Cross ID: VCC1400</td></tr><tr><td>41</td><td>12:32:05.63+11:49:03.6</td><td>2318</td><td>1411</td><td>188.02</td><td>11.82</td><td>15.37</td><td>ES(n:sp:|sh|du|f|pm:)-<br>I(c|d:|p)</td><td>ES galaxy with significant star formation in its core and a possible offset nucleus. Shells and<br>filaments. May be associated with VCC1407, which is located 4.4 to the north and has a similar<br>velocity (906 km s<sup>-1</sup> for VCC1411 and 1005 km s<sup>-1</sup> for VCC1407), and VCC1426 (v = 832<br>km s<sup>-1</sup>), which is located 6.3 to the northeast. Possible postmerger remnant. Classified as a<br>"certain" member. Cross ID: VCC1411</td></tr><tr><td>42</td><td>12:32:38.67+10:45:34.7</td><td>2402</td><td>1447</td><td>188.16</td><td>10.76</td><td>19.41</td><td>E(st|sh|pm:)-I(c:)</td><td>Compact ETG with extended streams and prominent stellar shells and possible star formation in the<br>core. Possible postmerger remnant. Classified as a "probable" member. Cross ID: VCC1447</td></tr><tr><td>43</td><td>12:33:13.43+09:23:50.4</td><td>2493</td><td>1488</td><td>188.31</td><td>9.40</td><td>14.63</td><td>E(sh|di:|pm:)-I(c)</td><td>ETG with a possible blue lens/disk in the core and a series of shells or ripples along the major axis.<br>Isophotes become boxy at large radius. May be associated with VCC1509, which is located 5.8 to<br>the northeast and has a similar velocity (808 km s<sup>-1</sup> for VCC1509 and 1079 km s<sup>-1</sup> for<br>VCC1488). Possible postmerger remnant. Classified as a "certain" member. Cross ID: VCC1488</td></tr><tr><td>44</td><td>12:33:24.70+08:41:26.7</td><td>2519</td><td>1501</td><td>188.35</td><td>8.69</td><td>15.45</td><td>ES(di:|b:|sh|st|pm:)-<br>I(c)</td><td>ES galaxy with central star formation and numerous shells and streams. A larger LTG, NGVS 2534<br>(VCC1508), is located 153" to the southeast and has a similar velocity (1219 vs. 1403 km s<sup>-1</sup>).<br>Possible merger remnant. Classified as a "certain" member. Cross ID: VCC1501</td></tr></tbody></table>
<table><caption>Table 7
(Continued)</caption><thead><tr><th>#</th><th>ID [NGVSJ]</th><th>NGVS</th><th>VCC</th><th>α(2000)<br>(deg)</th><th>δ(2000)<br>(deg)</th><th>g'(mag)</th><th>Type</th><th>Notes</th></tr></thead><tbody><tr><td>45</td><td>12:34:31.29+09:37:23.4</td><td>2652</td><td>1567</td><td>188.63</td><td>9.62</td><td>14.42</td><td>ES(n|di:|b:|sh:|pm:)-Q</td><td>Nucleated ETG. Galaxy is very boxy (bar-like) in the inner regions and becomes peanut-shaped (bone- or bow-tie shaped) at large radius. Possible postmerger remnant. Classified as a "certain" member. Cross ID: VCC1567</td></tr><tr><td>46</td><td>12:34:31.81+13:30:13.3</td><td>2654</td><td>1569</td><td>188.63</td><td>13.50</td><td>15.38</td><td>EI(di:|b:|sp:|sh:|pm:)-I<br>(c|d|g)</td><td>EI with star formation, mostly in the inner regions. Possible weak spiral structure. Possible post-merger product. Classified as a "certain" member. Cross ID: VCC1569</td></tr><tr><td>47</td><td>12:34:42.49+14:13:23.2</td><td>2676</td><td>1582</td><td>188.68</td><td>14.22</td><td>16.77</td><td>EI(sh|pm:)-I(g)</td><td>EI galaxy with widespread, low-level star formation. Galaxy shows a generally disturbed morphology, with a series of faint loops and shells. Possible postmerger remnant. Classified as a "certain" member. Cross ID: VCC1582</td></tr><tr><td>48</td><td>12:35:24.15+06:30:04.3</td><td>2753</td><td>1611</td><td>188.85</td><td>6.50</td><td>18.38</td><td>ES(di|pm:)-Q</td><td>ES galaxy with boxy isophotes and strong disk flaring. Bow-tie morphology. Possible postmerger remnant. Classified as a "probable" member. Cross ID: VCC1611</td></tr><tr><td>49</td><td>12:36:20.09+13:17:36.9</td><td>2850</td><td>...</td><td>189.08</td><td>13.29</td><td>19.58</td><td>E(n:|pm:)-Q</td><td>Very elongated, extremely LSB ETG with faint envelope and possible nucleus. Isophotal flaring at large radii. Possible postmerger remnant. Classified as a "possible" member</td></tr><tr><td>50</td><td>12:36:30.13+13:32:33.2</td><td>2871</td><td>1668</td><td>189.13</td><td>13.54</td><td>17.73</td><td>ES(b:|di:|sh:|pm:)-Q</td><td>Unusual ES galaxy with bar-like, or bow-tie, morphology, and possible shells that define an abrupt edge to the galaxy. Possible postmerger remnant. Classified as a "certain" member. Cross ID: VCC1668</td></tr><tr><td>51</td><td>12:36:34.93+08:03:16.7</td><td>2884</td><td>1675</td><td>189.15</td><td>8.05</td><td>14.24</td><td>ES(n|di:|b|sp|du|pm:)-I<br>(c|p|n)</td><td>Nucleated ES galaxy with a weak spiral pattern and a small, star-forming bar. Possible postmerger remnant. Classified as a "certain" member. Cross ID: VCC1675</td></tr><tr><td>52</td><td>12:36:39.42+11:06:06.4</td><td>2894</td><td>1684</td><td>189.16</td><td>11.10</td><td>14.97</td><td>EI(di:|sh|du|pm:)-I(c)</td><td>EI galaxy with star formation in the core, aligned along a thick disk. Peanut-shaped isophotes at large radii. Located 189" to the south of NGVS 2887 (VCC1681), whose velocity is unknown. Possible postmerger remnant. Classified as a "certain" member. Cross ID: VCC1684</td></tr><tr><td>53</td><td>12:38:06.92+10:09:53.5</td><td>3028</td><td>1744</td><td>189.53</td><td>10.16</td><td>16.63</td><td>EI(n:|sh|pm:)-I(c|p)</td><td>EI galaxy with active star formation and a possible offset nucleus. The peak of star formation occurs in a small patch that is slightly displaced from the photocenter. A series of shells are visible along the major axis. May be associated with VCC1743, which is located 4.9 to the south and has a similar velocity (1273 km s<sup>-1</sup> for VCC1743 and 1139 km s<sup>-1</sup> for VCC1744), although there is no sign of an interaction. Possible postmerger remnant. Classified as a "certain" member. Cross ID: VCC1744</td></tr><tr><td>54</td><td>12:38:17.90+13:06:35.9</td><td>3046</td><td>1757</td><td>189.53</td><td>13.11</td><td>13.33</td><td>ES(n:|d|sp|sh|du|pm:)-I(c)</td><td>Face-on ES galaxy with faint residual spiral pattern and clear shell-like structures at large radius. Several point sources project near the photocenter, one of which might be an offset nucleus. Possible postmerger remnant. Classified as a "certain" member. Cross ID: VCC1757</td></tr><tr><td>55</td><td>12:39:04.08+13:21:49.4</td><td>3094</td><td>1778</td><td>189.77</td><td>13.36</td><td>14.03</td><td>EI(n|sh|du|di:|pm:)-I(c)</td><td>Structurally complex EI galaxy with faint nucleus, small dust disk, ongoing star formation, and outer shells that fan out along the major axis. Likely postmerger remnant. Classified as a "certain" member. Cross ID: VCC1778</td></tr><tr><td>56</td><td>12:39:14.07+15:37:36.1</td><td>3103</td><td>1784</td><td>189.81</td><td>15.63</td><td>16.53</td><td>EI(n:|b:|sp:|sh|pm:)-I(c)</td><td>Disturbed EI galaxy with low-level star formation. Twisted isophotes, with prominent S-shaped distortion or possible spiral arms at large radius. Possible offset nucleus and even a misaligned bar. Possible postmerger remnant?. Classified as a "certain" member. Cross ID: VCC1784</td></tr><tr><td>57</td><td>12:40:19.56+14:42:54.0</td><td>3187</td><td>1836</td><td>190.08</td><td>14.71</td><td>14.31</td><td>ES(di:|b|sp:|r:|du:|pm:)-I(g)</td><td>ES galaxy with complex structure, including a bar, a possible ring, and spiral arms. Possible post-merger remnant. Classified as a "certain" member. Cross ID: VCC1836</td></tr><tr><td>58</td><td>12:41:54.28+13:46:22.4</td><td>3285</td><td>1897</td><td>190.48</td><td>13.77</td><td>14.03</td><td>E(n|sh|pm:)-Q</td><td>Nucleated, extremely boxy ETG with shells along the major axis. An unsharp-masked image shows the entire galaxy to have a bow-tie appearance. Possible postmerger remnant. Classified as a "certain" member. Cross ID: VCC1897</td></tr><tr><td>59</td><td>12:42:03.23+12:28:48.1</td><td>3300</td><td>1905</td><td>190.51</td><td>12.48</td><td>17.49</td><td>E(sh|pm:)-Q</td><td>Very LSB ETG with shells or arcs. Possible merger remnant. Classified as a "certain" member. Cross ID: VCC1905</td></tr><tr><td>60</td><td>12:42:17.76+10:01:47.4</td><td>3311</td><td>...</td><td>190.57</td><td>10.03</td><td>19.93</td><td>ES(pm:)-I(c)</td><td>Possible ES galaxy with dumbbell lobes and central core. Possible postmerger remnant. Classified as a "possible" member</td></tr></tbody></table>