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# The galaxy cluster AC114 - II. Stellar populations and the mass-metallicity relation

Ivo Saviane, Irina Yegorova, Dominique Proust

► To cite this version:

Ivo Saviane, Irina Yegorova, Dominique Proust. The galaxy cluster AC114 - II. Stellar populations and the mass-metallicity relation. Monthly Notices of the Royal Astronomical Society, 2023, 526, pp.2458-2478. 10.1093/mnras/stad2620. insu-04848708

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# The galaxy cluster AC114 – II. Stellar populations and the mass–metallicity relation

Ivo Saviane<sup>1,★</sup> Irina Yegorova<sup>2</sup> and Dominique Proust<sup>3</sup>

Accepted 2023 August 24. Received 2023 August 6; in original form 2022 November 30

## ABSTRACT

We investigate the mass–metallicity relation (MZR) for galaxies in the Abell cluster AC114 from 7 h of VIMOS/MR data collected at the European Southern Observatory–Very Large Telescope in 2009. The dynamical analysis completed in our previous paper allowed us to select cluster members, whose spectra are here analysed with stellar population synthesis models. Active and passive galaxies are identified based on the presence/absence of the [O II] λ3727, [O III] λλ4959, 5007 and/or Hβ emission lines, depending on the galaxy redshift. We find that active galaxies have lower average masses than passive ones, and have lower average metallicities. The MZR of the cluster is found to be steeper than that for galaxies in the local universe.

**Key words:** galaxies: abundances – galaxies: clusters: general – galaxies: distances and redshifts – galaxies: stellar content.

## 1 INTRODUCTION

The mass–metallicity relation (MZR) is one of the fundamental constraints to galaxy evolution, and for this reason it is the subject of a substantial body of literature (see Maiolino & Mannucci 2019, for a review), with a section of that literature looking at its evolution with redshift: indeed, studies of the MZR of galaxies are now available up to $z \sim 8$ (Jones et al. 2020).

However, metallicities at different redshifts are obtained with different methods, owing to abundance-sensitive spectral features moving across the optical-infrared range. This makes a comparison of both absolute and relative trends across cosmic time rather difficult. Furthermore, spectra of high-redshift objects cannot be obtained at high resolution, so metallicity indices calibrated with nearby galaxies must be used. For example in the case of star-forming galaxies, abundance indicators are calibrated based on local H II regions, but physical conditions of the interstellar medium (ISM) at high-redshift might be different than those at present day, thus adding further uncertainty to the process.

Interestingly, up to $z \sim 0.5$ emission lines that are used to compute abundances and physical conditions of the ISM, still fall in the optical range, and sufficiently good spectra can be obtained with 10-m class telescopes, with reasonable exposure times. Thus, a few years ago we identified the galaxy cluster AC114 as an interesting target to obtain emission-line spectra of galaxies spanning a range of masses: the cluster sits at $z \sim 0.32$, and as explained in Saviane et al. (2014), we expect that star-forming galaxies at that epoch are a factor ~1.4 more metal-poor than those in the local universe. Therefore, obtaining gas-phase metallicities of AC114 cluster members gives us the possibility to check the evolution of the MZR in the last ~4 Gyr, with abundances obtained with the exact same method used for local star-forming regions.

The substantial body of work on the cluster has been reviewed in our previous paper (Proust et al. 2015), nevertheless we summarize here the key features that make it relevant for the current study. The cluster is classified as Bautz–Morgan type II–III (Abell et al. 1989) with a galaxy distribution that tends to be diffuse. Indeed, X-ray emission has an irregular morphology, with two components dominating the soft part of the spectrum (below 0.5 keV): a tail extends about 400 kpc from the central emission to the southeast (see De Filippis et al. 2004). Its compact core is dominated by a cD galaxy and has strong lensing power with several bright arcs and multiple image sources (Smail et al. 1995; Natarajan et al. 1998; Campusano et al. 2001). Note, however, that it is also classified as a ‘non-cool core’ cluster by Zhang et al. (2016), meaning that a central supermassive black hole shall not be present. AC114 has a higher fraction of blue, late-type galaxies compared with lower redshift clusters (up to 60 per cent outside the core region; Couch et al. 1998; Sereno et al. 2010), making it a prototypical Butcher–Oemler cluster. Having many active members is a crucial property when studying the MZR based on H II regions.

In the course of data reduction, we realized that abundance-sensitive absorption features can also be reliably measured in our VIMOS spectra, therefore a study of the stellar component of AC114 galaxies is presented in this work, while ISM abundances will be the subject of a forthcoming paper. It shall be noted that a recent study of stellar populations can also be found in Rodríguez Del Pino et al. (2014), who targeted 13 disc galaxies with integral field spectroscopy. While most galaxies in their sample to not display emission lines, they still host a young stellar population; this is not centrally concentrated therefore it is suggested that star formation was recently truncated by gradual processes such as ram-pressure stripping or weak galaxy–galaxy interactions.

The present study builds on a dynamical analysis of the velocities of galaxies in our sample, which was performed in Proust et al. (2015) hereafter referred to as Paper I. As explained in that paper, thanks to a sample that reaches 1 mag fainter ($R \sim 21$), and which is about

<footnote n="1"><sup>1</sup>European Southern Observatory, Alonso de Cordova 3107, Vitacura, Casilla 19001, Santiago de Chile 19, Chile</footnote>

<footnote n="2"><sup>2</sup>Departamento de Ciencias Físicas, Universidad Andres Bello, Fernandez Concha 700, Las Condes, Santiago, Chile</footnote>

<footnote n="3"><sup>3</sup>GEPI, Observatoire de Paris, F92195 Meudon Principal CEDEX, France</footnote>

<footnote>* E-mail: isaviane@eso.org</footnote>
<figure><img src="image_3.png" /><figcaption>**Figure 1.** Distribution in redshift of all galaxies. The vertical and horizontal segments mark the limits of redshift ranges that are used later in the analysis. These limits are consistent with redshift clustering presented in Paper I, which are based on a larger sample including literature data (magenta histogram).</figcaption></figure>

30 per cent larger than those in previous studies, we could revisit the structure and dynamics of the cluster, which helped us select cluster members.

## 1.1 Main results from Paper I

The mean redshift obtained in Paper I is $z = 0.31665 \pm 0.0008$ and the velocity dispersion is $\sigma = 1893_{-82}^{+73}$ km s$^{-1}$ based on a catalogue of 524 velocities. The distribution in redshift of all galaxies is shown in Fig. 1 with bins $z = 0.01$ widths (magenta histogram). The cluster has a very elongated main radial filament spanning 12 000 km s$^{-1}$ in redshift space. In addition, a radial foreground structure was detected within the central $0.5$ h$^{-1}$ Mpc radius, recognizable as a redshift group at the same central redshift value. A

background structure could also be identified (see also Fig. 2). Two hundred and sixty five galaxy members were identified, which yield a dynamical mass $M_{200} = (4.3 \pm 0.7) \times 10^{15}$ M$_\odot$ h$^{-1}$ for AC114 and $M_v = (5.4 \pm 0.7 \pm 0.6) \times 10^{15}$ M$_\odot$ h$^{-1}$ from the intrinsic velocity dispersion out to a radius of $3.98$ h$^{-1}$ Mpc.

## 1.2 Analysis of the stellar populations based on Paper I and new data

Once the redshift is known, the spectrum can be corrected to the rest frame: this exercise led to the identification of a number of galaxies whose redshift value needed revision, mainly because of their low signal-to-noise (S/N) values, in particular when the R value of the correlation peak is lower or close to 3, except for emission-line objects (see Section 2). A few redshifts could be determined from the position of the most prominent emission and absorption lines: O II and Ca I H&K.

The new distribution in redshift of all galaxies is shown in Fig. 1 (black lines) where objects are clearly clustered in a few redshift intervals whose limits are identified by the vertical lines and horizontal segments. The limits are listed in Table 1. Galaxies belonging to the cluster are defined as those within the lower and upper limits of rows 3 and 4 of Table 1: they span a ~5σ range of velocities.

In this paper, we re-analyse the data obtained in Paper I. Section 2 presents the observations and reduction of the data and Section 3 analyses the stellar populations properties; these properties are used in Section 4 to construct and interpret the MZR, and finally Section 5 presents the conclusions based on the global results obtained for AC114.

## 2 OBSERVATIONS AND REDUCTIONS

A complete account of the observations and data reduction is given in Paper I, so just a summary is given here. VIMOS (Le Fèvre et al.

<figure><img src="image_4.png" /><figcaption>**Figure 2.** 3D representation of objects in the sky area covered by our VIMOS observations, with blue dots identifying active galaxies, and red dots identifying passive ones. AC114 is the clump of objects near $cz = 100\,000$ km s$^{-1}$. The transversal scale has been greatly amplified to better show structures surrounding the cluster: at the redshift of the cluster, the 16 arcmin of RA span of VIMOS, convert into 4.8 Mpc linear distance, while the linear distance spanned by the redshift limits of the cluster is ~300 Mpc (see Wright 2006, for the calculations).</figcaption></figure>
<table><caption>**Table 1.** Redshift limits used to group galaxies. Galaxies belonging to AC114 are defined as those within the lower and upper limits of rows 3 and 4.</caption><thead><tr><th>No.</th><th>z</th><th>c z (km s<sup>-1</sup>)</th><th>Notes</th></tr></thead><tbody><tr><td>1</td><td>0.1503</td><td>45 059</td><td></td></tr><tr><td>2</td><td>0.1900</td><td>56 961</td><td></td></tr><tr><td>3</td><td>0.2840</td><td>85 141</td><td>Lower limit</td></tr><tr><td>4</td><td>0.3310</td><td>99 231</td><td>Upper limit</td></tr><tr><td>5</td><td>0.4558</td><td>136 645</td><td></td></tr><tr><td>6</td><td>0.5487</td><td>164 496</td><td></td></tr><tr><td>7</td><td>0.6048</td><td>181 314</td><td></td></tr><tr><td>8</td><td>0.6678</td><td>200 201</td><td></td></tr></tbody></table>

<table><caption>**Table 2.** Observations log (OB = Observing Block).</caption><thead><tr><th>Date</th><th>OB start<sup>a</sup></th><th>Exp. time<sup>b</sup></th><th>Filter</th><th>Grism</th></tr></thead><tbody><tr><td>2009-09-17</td><td>02:37</td><td>2250</td><td>GG475</td><td>HR red</td></tr><tr><td>2009-09-17</td><td>03:32</td><td>2250</td><td>GG475</td><td>HR red</td></tr><tr><td>2009-09-17</td><td>04:11</td><td>2250</td><td>GG475</td><td>HR red</td></tr><tr><td>2009-09-17</td><td>04:50</td><td>2250</td><td>GG475</td><td>HR red</td></tr><tr><td>2009-09-17</td><td>05:28</td><td>2250</td><td>GG475</td><td>HR red</td></tr><tr><td>2009-09-17</td><td>06:07</td><td>2250</td><td>GG475</td><td>HR red</td></tr><tr><td>2009-09-21</td><td>03:54</td><td>2250</td><td>GG475</td><td>HR red</td></tr><tr><td>2009-08-16</td><td>05:25</td><td>2250</td><td>GG475</td><td>MR</td></tr><tr><td>2009-08-16</td><td>06:15</td><td>2250</td><td>GG475</td><td>MR</td></tr><tr><td>2009-08-16</td><td>06:55</td><td>2250</td><td>GG475</td><td>MR</td></tr><tr><td>2009-08-21</td><td>07:24</td><td>2250</td><td>GG475</td><td>MR</td></tr><tr><td>2009-08-21</td><td>06:11</td><td>2250</td><td>GG475</td><td>MR</td></tr><tr><td>2009-09-25</td><td>04:02</td><td>2250</td><td>GG475</td><td>MR</td></tr><tr><td>2009-09-25</td><td>04:53</td><td>2250</td><td>GG475</td><td>MR</td></tr></tbody></table>

Notes.ª Beginning of the observation block, UT time.

ᵇ Exposure time of the science part, in seconds.

2003) was used to carry out observations in service mode at the Very Large Telescope (VLT), under program 083.A-0566, between 2009 August 16 and September 25 (see Table 2). Seven exposures for each grism HR red and MR were obtained, for a total shutter time of ~4.4 h for each setup. The MR grism has a spectral resolution of 580 for a 1 arcsec slit, over the 500–1000 nm spectral range, while the HR-red grism has a spectral resolution of 2500 for a 1 arcsec slit, over the 630–870 nm spectral range.

The galaxy selection was made from the pre-imaging frames of the cluster. To construct the masks, initially, the SIMBAD catalogue was used without imposing any restriction criteria. As a first step we identified already known galaxies of the cluster. Then, we selected the non-stellar objects in this region by eye in order to punch a maximum number of slits in each of the four quadrants. Such a visual inspection allows to discriminate between extended objects and stars.

## 2.1 Data reduction

The VIMOS pipeline was used to reduce the data. We reduced separately the data taken with the grism HR red and MR. Each scientific frame was bias subtracted and flat-field corrected, the cosmic rays were removed, and sky emission lines subtracted (the same procedure was done for the standard stars). The spectra were wavelength calibrated and seven frames for each VIMOS quadrant were combined. This gave us S/N = 20 pixel⁻¹ on the average at the continuum level on the final spectra. Since the continuum of most of the galaxies is too weak we did not use the spectra extracted

by the pipeline. Instead, we extracted 1D spectra with MIDAS. Flux calibration was obtained with spectrophotometric standards from Hamuy et al. (1992, 1994).

In this work, only MR data are used, while HR spectroscopy is used in the forthcoming paper on the nebular abundances, to resolve N II from Hα emission lines.

Apparent magnitudes in the R band were obtained by computing the integrated flux of our spectra in the range 4897.5–9785.5 Å and calibrating it using objects in common with the superCOSMOS database (Maddox et al. 1990a, b). Photometry could also have been obtained from pre-imaging frames, but these are observed under variable sky conditions, so magnitudes would have to be calibrated on the superCOSMOS system anyway. The precision of our calibration was estimated in paper I as ≃0.5 mag, which is comparable with that of superCOSMOS. Furthermore, synthetic photometry can be obtained with vastly more efficient means compared to reducing pre-imaging frames from scratch, and we show in the sections below that luminosities and masses obtained this way yield well-defined MZRs. As shown in Paper I, our galaxy sample reaches luminosities as faint as R ~ 21, but it starts to suffer from incompleteness at R ~ 20.

We obtained a total of 163 redshifts, combining and checking those already obtained in Paper I. The complete redshift values with their individual error measurements are published in Table 5 and correspond to the highest R value obtained from the cross-correlations (Tonry & Davis 1979). UK–J B<sub>j</sub> and UK–J R<sub>j</sub> magnitudes are from superCOSMOS.

The content of this table is as follows:

(i) number of the object in each quadrant from slit position;

(ii) right ascension (J2000);

(iii) declination (J2000);

(iv) UK–J B<sub>j</sub> magnitude from superCOSMOS;

(v) UK–J R<sub>j</sub> magnitude from superCOSMOS;

(vi) R<sub>comp</sub> computed magnitude from spectra;

(vii) redshift;

(viii) redshift error;

(ix) R value from the cross-correlation (Tonry & Davis 1979);

(x) notes.

In the course of data analyses, we identified two objects that were removed from the table, as their spectra tricked the cross-correlation algorithm, which returned wrong redshift values; indeed objects Q4/39 and Q4/59 were identified as M-dwarf stars, after finding that their D<sub>n</sub>(4000) values were too high for their supposed mass (see below).

Using data from Table 5, Fig. 2 shows the spatial distribution of all galaxies in our VIMOS sample with a measured spectrum, with blue and red dots marking active and passive galaxies, respectively. The cluster is clearly visible as the dense agglomeration of objects near c z = 100 000 km s⁻¹, and it appears that most of its galaxies are not actively forming stars, although in the cluster periphery there are some that do. Couch et al. (2001) note that in AC114 the star formation rate (SFR) from the Hα emission is not exceeding 4 M☉ yr⁻¹ and that the Hα luminosity function is an order of magnitude below that observed for field galaxies at the same redshift. As anticipated in Section 1.1, Fig. 2 also suggests the existence of two other structures, which appear as filaments extending for 10 000 km s⁻¹, one of them seemingly connected to the cluster core. Fig. 3 shows a zoom into the 3D representation of the cluster. It is clear that the cluster has a very elongated structure spanning ≃10 000 km s⁻¹.
<figure><img src="image_5.png" /></figure>

**Figure 3.** A zoom into the 3D representation of AC114. The three segments show velocity values from 90 000 to 100 000 km s⁻¹ in steps of 5000 km s⁻¹. The transversal scale has been amplified by a factor ~10 compared to the radial scale, but it is still clear that the cluster is a very elongated structure. Note that gaps in the object density are artefacts of the partial sky coverage of the VIMOS footprint.

## 2.2 Classification of galaxies

After correcting spectra to rest frame, the 163 galaxies were classified as ‘active’ or ‘passive’ based on the presence/absence of [O II] λ3727, [O III] λλ4959, 5007 and/or Hβ emission lines, depending on the galaxy redshift, with the following procedure.

The first step consisted in blindly scanning all spectra for the presence of [O III] λ5007 and/or Hβ: a linear fit to the continuum was subtracted, and a maximum in flux was searched in the window 4800 ≤ λ ≤ 4841 for Hβ and in the window 4980 ≤ λ ≤ 5090 for [O III] λ5007. A Gaussian fit was then attempted, provided that the peak in flux is three times larger than the continuum noise (assumed to be the semi-quartile of the flux variation in the spectral window). To estimate errors, the fit was repeated for the nominal continuum level, and by assuming a higher or lower continuum by the amount of noise. The result of this procedure was that, for each spectrum where a fit is possible, and for each of the two lines, the central wavelength, its full width at half-maximum (FWHM) and error, and the area of the Gaussian and its error are obtained. After this first screening, a quality parameter *q* is assigned to each spectrum, defined as the sum for the two lines, of their Gaussian area divided by its error. Spectra are then sorted by fit quality, and plotted one by one to visually check the quality of the fit. We find that spectra with *q* ≥ 4 show unambiguous presence of emission lines, so galaxies that satisfy this criterion were classified as ‘active’, while the rest were classified as ‘passive’. While performing the visual checks, a few galaxies preliminarily classified as ‘passive’ were noticed having a clear [O II] λ3727 emission line, and were added to the list of ‘active’ objects: their spectra are shown in Fig. A1 of Appendix A. While some passive galaxies might have very weak emission lines that are not detected by our methods, the sections below show that the two galaxy classes have very different properties, thus our classification must be broadly correct.

Table D1 summarizes the results, and adds further remarks on some galaxies, such as those actually identified as local M-dwarf stars, and those having low-quality spectra that are not further considered in this paper.

In order to show the redshift evolution of their spectral energy distribution (SED), Figs 4 and 5 show the co-added spectra of the two galaxy classes, in the redshift ranges defined in Table 1.

<figure><img src="image_6.png" /></figure>

**Figure 4.** For each redshift range from Table 1, this figure shows the co-added spectra of active galaxies. The vertical blue bars mark the position of the following emission lines: [S II] λλ6716,6731, Hα, [O III] λλ4959,5007, Hβ, Hγ, Hδ, [O II] λ; and Ca H and K absorption lines (3968 Å, 3934 Å).

<figure><img src="image_7.png" /></figure>

**Figure 5.** Same as Fig. 4 for co-added spectra of passive galaxies.

It can be seen that, in the redshift range of AC114, the majority of galaxies are passive: there are 30 galaxies classified as such (59 per cent), versus 21 classified as active (41 per cent). This confirms the visual impression given by Fig. 2.
<figure><img src="image_8.png" /><figcaption>**Figure 6.** To select the best SSP model that fits the co-added spectrum of active galaxies in AC114, the dispersion of the model-to-data ratio is plotted as a function of age and metallicity: this figure shows that the minimum value is reached for a model age of 2 Gyr, and a metallicity $Z=0.008$.</figcaption></figure>

<figure><img src="image_9.png" /><figcaption>**Figure 7.** Same as Fig. 6, for the co-added spectrum of passive galaxies in AC114. In this case, the best model fit is reached for an age of 10 Gyr, and a metallicity $Z=0.02$.</figcaption></figure>

# 3 STELLAR POPULATIONS

## 3.1 Representative age and metallicity of active and passive galaxies in AC114

As a first step towards the characterization of galaxies in AC114, we fitted the co-added spectra obtained above in the redshift range of the cluster, with stellar population synthesis models from Bruzual & Charlot (2003), following the prescriptions of Saviane & Jerjen (2007). Briefly, model spectra were degraded to the resolution of our VIMOS data, and then for each model spectrum, the steps were the following:

(i) select the spectral range from 3800 to 6000 Å;

(ii) remove emission lines from co-added spectra, before fitting: that is, remove regions near $H\beta$ and [O III];

(iii) normalize both model and co-added spectra to maximum flux within the fit range;

(iv) compute ratio of model to observed spectrum;

(v) compute average and dispersion of spectral ratio;

(vi) select the best-fitting model as the one that gives the lowest dispersion of the spectral ratio.

The results of this procedure are shown in Figs 6 and 7, for active and passive galaxies, respectively: the typical age of active galaxies in the cluster is 2 Gyr, and their metallicity is $Z=0.008$; while in the case of passive galaxies, the best fit is reached for an age of

<figure><img src="image_10.png" /><figcaption>**Figure 8.** The co-added spectrum of all passive galaxies in AC114 redshift range (black) fitted with the best model of Bruzual & Charlot (2003) in red. This gives the typical age and metallicity of the underlying stellar population.</figcaption></figure>

<figure><img src="image_11.png" /><figcaption>**Figure 9.** Same as Fig. 8 for active galaxies in the cluster.</figcaption></figure>

<figure><img src="image_12.png" /><figcaption>**Figure 10.** Colour–magnitude diagram for AC114 galaxies with photometry in superCOSMOS database (Maddox et al. 1990b). The solid line is the red sequence as defined in Paper I, and the horizontal dotted line represents the separation between red and blue galaxies as in CS87.</figcaption></figure>

10 Gyr, and a metallicity $Z=0.02$. Galaxies cannot be older than the universe, so it is re-assuring to see that the age of the universe at the redshift of AC114 is indeed no less than 10 Gyr (see Figs 15 and 16). The best-fitting models are shown overlaid to the co-added spectra in Figs 8 and 9. Figs 6 and 7 show that adopting model ages
and metallicities closest to the best fits, would also give good results: this uncertainty is included in the calculation of mass-to-light (M/L) values in Section 3.3.

This exercise reveals that passive galaxies must have formed the bulk of their population early on, in a strong burst that quickly enriched their ISM to solar metallicities: indeed, the remarkably good fit of a simple stellar population (SSP) model indicates that those stars were formed in a relatively short time span. On the contrary, the low stellar metallicity of active galaxies is an indication that star formation (SF) proceeded at a low pace in these systems, which are indeed still forming stars. Still, the good fit of an SSP to the observed spectrum is telling us that most stars in active galaxies were also formed rapidly, although later than those in passive galaxies.

Passive galaxies are in general more massive than active ones (see below), but physical sizes do not vary too much between the two classes; therefore one expects a higher gas density in passive galaxies, which would explain their higher SFR, according to the Schmidt-Kennicutt law (Kennicutt 1998). Figs 2 and 3 show that passive galaxies are concentrated near the cluster centre, where mass must have been accumulating in the early formation epochs, thus easing the formation of the largest objects (see also fig. 6 in Proust et al. 2015). In addition, SF in the densest regions of galaxy clusters is quenched more effectively than in their outskirts (see, e.g. Deshev et al. 2017): therefore the active/passive dichotomy can also be explained, at least partially, by an effect of the environment.

## 3.2 Comparison with Couch & Sharples (1987)

To confirm the results above, it is instructive to compare them to Couch & Sharples (1987, hereafter CS87). They classify their galaxy sample into 'red' and 'blue' objects, based on their position in the colour-magnitude plot, which is shown in Fig. 10 for the subset of galaxies having published colours in superCOSMOS. In CS87, blue galaxies are defined having colours smaller than $B_J - R_F = 2$, which is represented by the dotted line in the figure; the solid line represents the 'red sequence' as defined in Paper I, which is similar to the one found by CS87. Passive and active galaxies are plotted with red or blue symbols, so the figure demonstrates that most active galaxies would be classified as 'blue' by CS87, while passive galaxies gather around the red sequence.

Most red galaxies in CS87 have spectra comparable to nearby E/SO galaxies, and indeed their comparison to models of population synthesis yields a typical age of 10 Gyr. They also find 15 per cent of red galaxies having strong Hδ absorption, which are interpreted as hosting a short 0.5 Gyr burst with an age of 1.5 Gyr. These results are consistent with our findings above, where the typical age of passive galaxies was indeed found to be 10 Gyr, with a few exceptions identified in Section 3.5.3. This age is used in Section 3.3 to compute M/L ratios, therefore we can expect that masses of passive galaxies are on the average correct: indeed the tight sequence found in Section 3.5.2 and Fig. 17 validate this conclusion.

As expected from their spread in colour, blue galaxies in CS87 have a more diverse SF history and interestingly, almost half of them are pure absorption-line objects. By comparison to local galaxies and models, their emission-line objects are split between having spectra comparable to nearby spiral galaxies (their type 2) and hosting a current SF burst (their type 1). Finally, blue galaxies with no emission lines are interpreted as having experienced an SF burst of varying strength, up to 1.5 Gyr prior to the epoch of observation. The stacked spectrum of our active galaxies, which by definition are emission-line objects, must be a mix of type 1 and type 2 of CS87, therefore the age of 2 Gyr found above is a reasonable

guess. Once more, this is reinforced by Fig. 17, which shows a well-defined trend of metallicity index versus masses. Note also that some objects do require a small correction to their ages, as discussed in Section 3.5.3.

Only four galaxies are in common between this work and CS87, and they all belong to the red sequence, with normal Hδ absorption. A larger overlap in the two sets would be needed for a thorough comparison, nevertheless in Appendix C we show that our spectra match the classification of CS87.

In the context of this discussion, it is also interesting to examine 'postage stamps' of our targets as shown in Figs B1 and B2, for passive and active galaxies, respectively. As expected for an E/SO type, most passive galaxies have regular shapes, but there are some galaxies that appear to be interacting (at least in projection) with nearby smaller objects (see image caption). It is interesting to note that two of these potentially interacting galaxies (44 and 49) present an anomalous $D_n(4000)$ index, as discussed in Section 3.5.3, which means that their ages deviate from the typical one of their class. Conversely, galaxies 64 and 21 also have a deviant $D_n(4000)$ index, but they appear to be isolated in Fig. B1. Active galaxies appear more diffuse than passive ones, and contrary to passive ones, objects with anomalous $D_n(4000)$ index do not have close companions but rather appear irregular in shape (numbers 36, 56, 48, 40, and 26). The implications of galaxy morphology will be examined in more detail in a forthcoming paper where nebular abundances will be obtained (Andrade et al., in preparation), and contrasted with the stellar abundances obtained in this work.

## 3.3 Mass-to-light ratios

Having in hand the age of the stellar populations, the next step is the computation of their M/L ratios. From the plots in BC03, we obtained Fig. 11, which shows $M/L_V$ versus age: as discussed in BC03, the M/L ratio is affected by the choice of the initial mass function (IMF), spectral library, theoretical evolutionary tracks, and metallicity, so the shaded band in the figure represents those uncertainties, estimated as 1/4 of the full variation interval.

As shown in Table 2, the most complete photometric catalogue for our galaxies is in the R band, therefore M/L ratios were converted from V-to-R band using the expression: $M/L_R = M/L_V \times 10^{-0.4(V-R)}$, where the V-R colour of an old population was taken as the average of globular clusters in the Harris (1996) catalogue: $V - R = 0.64 \pm 0.17$. The resulting ratios are then $M/L_R = 0.64 \pm 0.26$ and $2.41 \pm 1.12$ for active and passive galaxies, respectively.

## 3.4 Galaxy distances, luminosities and masses

To compute galaxy luminosities, apparent magnitudes were converted to absolute ones with the usual $M_R = R - \mu$, where the distance modulus is $\mu = 5 \log D_L - 5$. The luminosity distance $D_L$ is a function of redshift, and it was evaluated following Wright (2006), with input parameters $H_0 = 69.6$, $\Omega_{\text{matter}} = 0.286$, and $\Omega_{\text{vac}} = 0.714$ (flat universe). After computing the relation for a few selected values, it was interpolated by a quadratic function, as shown in Fig. 12. We find:

$$D_L = 2245.7 z^2 + 4628.4 z - 20.838,$$

which is valid for $0.05 \le z \le 0.7$. At the mean redshift quoted in Section 1.1, the distance is $D_L = 1670 \pm 17$ Mpc.

Absolute luminosities were then computed as $L_R = 10^{-0.4(M_R - M_{R\odot})}$, with $M_{R\odot} = 4.5$. Finally, luminosities were converted into masses with the M/L ratios computed in Section
<figure><img src="image_13.png" /></figure>

**Figure 11.** V-band *M/L* ratio as a function of the age of the population, from BC2003: the band represents uncertainties introduced by the choice of different initial IMF, spectral library, theoretical evolutionary tracks and metallicities. Based on the age returned by the best-fitting models, representative *M/L* ratios can be estimated for passive and active galaxies, which are shown by the dots and error bars. Arrows in the lower right corner show that, for ages greater than ~0.1 Gyr, a change in age of 0.5 dex translates into a similar 0.5 dex change in *M/L* ratio.

<figure><img src="image_14.png" /></figure>

**Figure 12.** Luminosity distance, expressed in Mpc, versus redshift: the curve is a quadratic interpolation of selected values calculated using the cosmology calculator of Wright (2006).

### 3.3. Uncertainties on mass values were computed by adding in quadrature uncertainties from photometry and from *M/L* ratios.

As a consistency check between photometric and spectral properties, the integrated spectral flux is compared to absolute *R* magnitudes in Figs 13 and 14 for the two classes of galaxies. It is reassuring to see that there is a good correlation between the two quantities: the correlation coefficient is -0.94, with a dispersion of ~0.24 mag for passive galaxies, and the same quantities are -0.85 and ~0.4 mag for active ones. However-, the correlation breaks down for galaxies at the faint end of the luminosity range: therefore for the next analysis we retained only objects with $\Sigma(\text{flux}) > 10^{-15} \text{ erg cm}^{-2} \text{s}^{-1}$.

Fig. 15 shows that passive galaxies in AC114 span an order of magnitude in mass; interestingly, looser cluster members at higher and lower redshift tends to define a mild tendency of having masses increasing while moving to more recent times: from 9.8 to 10.3 Gyr ago, their mass increases from $0.4 \times 10^{11}$ to $10^{11} M_{\odot}$. It could be inferred that some galaxies continued forming stars both before and after a cluster-wide main SF episode.

<figure><img src="image_15.png" /></figure>

**Figure 13.** Comparing absolute *R* magnitudes *M/L* integrated flux, for passive galaxies in AC114 redshift range. As expected, the two quantities are proportional to each other, but the correlation breaks down at the lower end of total fluxes. An uncertainty of 0.5 mag has been assumed both for the total flux and the *R*-band photometry.

<figure><img src="image_16.png" /></figure>

**Figure 14.** Same as Fig. 13, for active galaxies in AC114 redshift range.

<figure><img src="image_17.png" /></figure>

**Figure 15.** Mass of passive galaxies as a function of redshift and age of the universe. The dotted line represents a linear fit through the data. Errors in mass are taken from Table 3, while errors in redshift are smaller than the symbols.
<figure><img src="image_18.png" /><figcaption>**Figure 16.** Mass of active galaxies as a function of redshift. The dotted line represents a linear fit through the data, while the contours represent the general distribution of passive galaxies in the same plot of Fig. 15. Errors in mass are taken from Table 3, while errors in redshift are smaller than the symbols.</figcaption></figure>

<figure><img src="image_19.png" /><figcaption>**Figure 17.** Relationship between $D_n(4000)$ and galaxy mass, for passive (red dots) and active (blue dots) galaxies. The straight lines and shaded areas represent weighted linear fits to the data, and the dispersion around the fit. The top panel shows the original measurements, with the most evident outliers marked with large circles. To these objects, a correction in mass has been applied, as explained in the text, and their new position can be seen in the bottom panel. Their spectra are plotted in Fig. 18.</figcaption></figure>

On the contrary, Fig. 16 shows that active galaxies closer to us have lower masses than objects located in the main body of the cluster, which also span a smaller mass range of ~0.5 dex, and are generally less massive than passive galaxies in the same region. This confirms the idea that active galaxies formed later than passive ones, and did not participate to the initial strong galaxy formation epoch.

## 3.5 Metallicities

### 3.5.1 Introduction of the D4000 index

Having measured the masses of AC114 galaxies in the previous sections, metallicities were then estimated using the $D_n(4000)$ index, which measures the ratio of spectral continuum at the red and blue sides of the 4000 Å discontinuity. As in Balogh et al. (1999), the average of the continuum and its dispersion were calculated within the bands 3850–3950 and 4000–4100 Å, both for the galaxy sample and the models. If we call $\bar{F}_{\text{red}}$ and $\bar{F}_{\text{blue}}$ the average continuum level in the two bands computed over $n_{\text{pix}}$ spectral elements, and $\sigma_{\text{red}}$ and $\sigma_{\text{blue}}$ their dispersion, then $D_n(4000)$ and its uncertainty are computed as $D_n(4000) = \bar{F}_{\text{red}}/\bar{F}_{\text{blue}}$ and $\sigma_{D_n(4000)} = D_n(4000) \times (\sigma_{\text{F,blue}}/\bar{F}_{\text{blue}} + \sigma_{\text{F,red}}/\bar{F}_{\text{red}})$, where $\sigma_{\text{F}} = \sigma_{\text{px}}/\sqrt{n_{\text{px}}}$.

### 3.5.2 $D_n(4000)$ versus mass for galaxy spectra

Fig. 17 shows the results of our measurements, with $D_n(4000)$ plotted as a function of galaxy mass. It appears that passive and active galaxies occupy distinct places in such diagram, with active galaxies generally with lower masses and smaller $D_n(4000)$ values, compared with passive galaxies. In the hypotheses that galaxies within a class have a common age (Section 3.1), the variation of the index must be mainly due to metallicity differences, thus the graph can be interpreted as passive galaxies having higher metallicities than active ones.

Fig. 17 also shows that some objects lay outside the general trend defined by galaxies of comparable mass, which can be interpreted by using Fig. 19: it is likely that galaxies with larger/smaller values of $D_n(4000)$ have typical ages that are larger/smaller than the typical age inferred in Section 3.1.

### 3.5.3 Special cases of $D_n(4000)$

An inspection of Fig. 18 shows that such interpretation must be correct: active galaxies with large $D_n(4000)$ values have red SEDs which resemble those of passive galaxies of similar index values, thus having ages greater than the typical 2 Gyr. Furthermore, their spectra have very weak [O II] $\lambda3727$ and $H\alpha$ emission lines, which indicates a low SFR. At the opposite side, active galaxies with relatively low index values, have blue SEDs and very prominent emission lines, indicative of an age younger than 2 Gyr. For these galaxies, a second possibility is a metallicity which is intrinsically lower than galaxies of comparable mass, for example due to accretion of fresh gas: indeed the same, Fig. 18 shows a low-luminosity tail emerging from object Q4/26, so this option cannot be excluded.

As Fig. 11 demonstrates, an age increase/decrease translates into a larger/smaller M/L ratio, with a change of 0.1 dex in M/L for every change of 0.1 dex in age. Thus, if galaxies with large $D_n(4000)$ are older than the others, their luminosities must be converted into larger masses: from Fig. 17, it can be evinced that corrections of ~±0.3 dex in mass, that is, in M/L, would bring deviant galaxies back into the general trend. Such corrections are within the uncertainties of the measurements.

Such a change would bring the age of active galaxies with large $D_n(4000)$ close to that of passive galaxies, in agreement with the conclusion inferred from their spectra. At the other side, active galaxies with a low discontinuity index would re-enter the general trend, if their ages were ~1 Gyr.
<figure><img src="image_20.png" /></figure>

**Figure 18.** In the left two panels, spectra of passive galaxies having $D_n(4000)$ values that are larger or smaller than those of galaxies of comparable mass, are plotted in the left-hand panels, with index values increasing from bottom to top. The right-hand panels plot spectra of 'deviant' active galaxies. Within each panel, the $D_n(4000)$ value is printed in the top left corner, following the galaxy identification. In each spectrum, the blue and red bands highlight the wavelength range that is used to compute the ratio of continuum near the 4000 Å break. In the right two panels, images of the same galaxies, extracted from the VIMOS pre-imaging are displayed.

<figure><img src="image_21.png" /></figure>

**Figure 19.** Relationship between $D_n(4000)$ and [m/H] from the BC03 model spectra, for ages 1, 2, 5, 10, and 20 Gyr, going from left to right. The shaded areas represent linear (for ages $\le 2$ Gyr) and quadratic fits to the points, and the dispersion around the fits. The vertical blue dotted segment marks the smaller value of $D_n(4000)$ for active galaxies, while the vertical red dotted segments mark the range of $D_n(4000)$ for passive galaxies.

<figure><img src="image_22.png" /></figure>

**Figure 20.** Illustration of different ways to obtain an MZR, with boxes representing two galaxies of different mass, and arrows connecting the start and end points of their evolution, assumed to happen in the same time interval. Light blue is pristine gas, darker blue is enriched gas, and red represents metals. In case (a), two galaxies of different mass produce the same fraction of metals over pristine gas, so no MZR is generated. In case (b), the more massive galaxy generates a higher fraction of metals. In case (c), both galaxies produce the same fraction of metals, but the low-mass objects ejects more of them into the Inter-Galactic Medium (IGM). Finally in case (d), gas is lost before chemical evolution is complete, in such a way that the less massive galaxy will have generated a smaller fraction of metals, compared with the more massive one.

Looking at passive galaxies, object Q4/49 has a $D_n(4000)$ value and SED close to that of objects Q4/44 and Q4/64: again, a correction of $\sim+0.3$ dex in $M/L$, corresponding to a correction of $\sim+0.3$ dex in age, would bring its mass in agreement with the general trend. Conversely, galaxies with relatively low index values have bluer SEDs than galaxies with masses initially estimated to be the same: a reduction in age of a few Gyr would thus move them to the left in the figure, and reconcile $D_n(4000)$ measurements with estimated masses.

The lower panel of Fig. 17 shows how the mass and hence age corrections proposed above improve the definition of the loci occupied by the two classes of galaxies.

### 3.5.4 $D_n(4000)$ for model spectra

To convert $D_n(4000)$ values to metallicities, a calibration of the index was obtained from BC03 models, as shown in Fig. 19. It can be seen that a given value of $D_n(4000)$ can correspond to a range of metallicities, depending on the age of the population: for most active and passive galaxies, the calibration for ages 2 and 10 Gyr were used. Calibrations for 5 and 20 Gyr (in a relative extrapolation) were used
<table><caption>**Table 3.** Main characteristics of passive galaxies entering the MZR. Luminosities and masses are given in $10^{10}$ solar units. Galaxies are sorted by luminosity, from fainter to brighter. Typical error on *R* magnitudes is 0.5, which yields ~50 per cent errors on luminosities and masses, after accounting for the uncertainty in *M/L* ratios.</caption><thead><tr><th>Q no.-sl no.</th><th>RA</th><th>Dec.</th><th>z</th><th>R</th><th>M<sub>R</sub></th><th>L<sub>R</sub></th><th>M/M<sub>☉</sub> ±</th><th>D<sub>n</sub>(4000) ±</th><th>[m/H] ±</th></tr></thead><tbody><tr><td>Q4-45</td><td>344.652</td><td>-34.781</td><td>0.31390</td><td>20.600</td><td>-20.490</td><td>0.990</td><td>2.390</td><td>1.110</td><td>1.589 0.099</td><td>-0.668 0.308</td></tr><tr><td>Q4-23</td><td>344.646</td><td>-34.743</td><td>0.32270</td><td>20.600</td><td>-20.560</td><td>1.060</td><td>2.550</td><td>1.180</td><td>1.387 0.095</td><td>-1.355 0.402</td></tr><tr><td>Q4-24</td><td>344.638</td><td>-34.744</td><td>0.31450</td><td>20.500</td><td>-20.600</td><td>1.090</td><td>2.630</td><td>1.220</td><td>1.438 0.076</td><td>-1.160 0.296</td></tr><tr><td>Q4-16</td><td>344.623</td><td>-34.732</td><td>0.31850</td><td>20.400</td><td>-20.730</td><td>1.230</td><td>2.970</td><td>1.380</td><td>1.660 0.121</td><td>-0.481 0.336</td></tr><tr><td>Q4-21</td><td>344.711</td><td>-34.738</td><td>0.30610</td><td>19.500</td><td>-21.530</td><td>2.580</td><td>3.117</td><td>1.448</td><td>1.402 0.086</td><td>-1.022 0.445</td></tr><tr><td>Q3-26</td><td>344.618</td><td>-34.614</td><td>0.31480</td><td>20.200</td><td>-20.900</td><td>1.440</td><td>3.480</td><td>1.620</td><td>1.494 0.096</td><td>-0.962 0.349</td></tr><tr><td>Q4-43</td><td>344.620</td><td>-34.778</td><td>0.31720</td><td>20.200</td><td>-20.920</td><td>1.470</td><td>3.540</td><td>1.650</td><td>1.394 0.084</td><td>-1.327 0.350</td></tr><tr><td>Q4-63</td><td>344.719</td><td>-34.811</td><td>0.31870</td><td>20.200</td><td>-20.930</td><td>1.490</td><td>3.580</td><td>1.660</td><td>1.386 0.082</td><td>-1.359 0.345</td></tr><tr><td>Q4-28</td><td>344.612</td><td>-34.751</td><td>0.31470</td><td>20.000</td><td>-21.100</td><td>1.730</td><td>4.180</td><td>1.940</td><td>1.592 0.090</td><td>-0.659 0.276</td></tr><tr><td>Q2-35</td><td>344.919</td><td>-34.651</td><td>0.31290</td><td>19.700</td><td>-21.380</td><td>2.260</td><td>5.440</td><td>2.530</td><td>1.642 0.092</td><td>-0.525 0.257</td></tr><tr><td>Q4-41</td><td>344.616</td><td>-34.774</td><td>0.31820</td><td>19.700</td><td>-21.430</td><td>2.350</td><td>5.650</td><td>2.630</td><td>1.626 0.081</td><td>-0.567 0.231</td></tr><tr><td>Q4-20</td><td>344.664</td><td>-34.739</td><td>0.30860</td><td>19.600</td><td>-21.450</td><td>2.400</td><td>5.780</td><td>2.690</td><td>1.704 0.099</td><td>-0.379 0.244</td></tr><tr><td>Q4-2</td><td>344.646</td><td>-34.707</td><td>0.31980</td><td>19.500</td><td>-21.640</td><td>2.850</td><td>6.880</td><td>3.200</td><td>1.581 0.074</td><td>-0.690 0.228</td></tr><tr><td>Q4-38</td><td>344.618</td><td>-34.767</td><td>0.30100</td><td>19.200</td><td>-21.790</td><td>3.270</td><td>7.890</td><td>3.670</td><td>1.576 0.136</td><td>-0.705 0.447</td></tr><tr><td>Q4-47</td><td>344.645</td><td>-34.785</td><td>0.31670</td><td>19.300</td><td>-21.810</td><td>3.350</td><td>8.080</td><td>3.760</td><td>1.624 0.092</td><td>-0.572 0.266</td></tr><tr><td>Q3-40</td><td>344.642</td><td>-34.648</td><td>0.31830</td><td>19.300</td><td>-21.830</td><td>3.390</td><td>8.180</td><td>3.800</td><td>1.753 0.090</td><td>-0.278 0.195</td></tr><tr><td>Q4-58</td><td>344.674</td><td>-34.802</td><td>0.31080</td><td>19.200</td><td>-21.870</td><td>3.520</td><td>8.490</td><td>3.940</td><td>1.694 0.096</td><td>-0.401 0.241</td></tr><tr><td>Q4-49</td><td>344.665</td><td>-34.788</td><td>0.31820</td><td>20.000</td><td>-21.130</td><td>1.780</td><td>8.560</td><td>3.971</td><td>1.895 0.164</td><td>-0.185 0.255</td></tr><tr><td>Q4-51</td><td>344.693</td><td>-34.792</td><td>0.30950</td><td>19.100</td><td>-21.960</td><td>3.830</td><td>9.220</td><td>4.280</td><td>1.748 0.151</td><td>-0.288 0.357</td></tr><tr><td>Q4-31</td><td>344.652</td><td>-34.755</td><td>0.31780</td><td>19.100</td><td>-22.020</td><td>4.060</td><td>9.800</td><td>4.550</td><td>1.825 0.094</td><td>-0.155 0.166</td></tr><tr><td>Q4-32</td><td>344.658</td><td>-34.757</td><td>0.31710</td><td>18.200</td><td>-22.920</td><td>9.260</td><td>22.330</td><td>10.380</td><td>1.947 0.103</td><td>-0.014 0.114</td></tr><tr><td>Q4-52</td><td>344.609</td><td>-34.794</td><td>0.31790</td><td>18.200</td><td>-22.920</td><td>9.320</td><td>22.460</td><td>10.440</td><td>1.925 0.104</td><td>-0.033 0.129</td></tr><tr><td>Q4-64</td><td>344.631</td><td>-34.815</td><td>0.31450</td><td>18.300</td><td>-22.800</td><td>8.290</td><td>39.865</td><td>18.536</td><td>2.077 0.136</td><td>-0.072 0.067</td></tr><tr><td>Q4-44</td><td>344.671</td><td>-34.779</td><td>0.31520</td><td>18.300</td><td>-22.800</td><td>8.330</td><td>40.065</td><td>18.616</td><td>2.063 0.133</td><td>-0.075 0.075</td></tr></tbody></table>

<table><caption>**Table 4.** Main characteristics of active galaxies entering the MZR. Luminosities and masses are given in $10^{10}$ solar units. Galaxies are sorted by luminosity, from fainter to brighter. Typical error on *R* magnitudes is 0.5, which yields ~50 per cent errors on luminosities and masses, after accounting for the uncertainty in *M/L* ratios.</caption><thead><tr><th>Q no.-sl no.</th><th>RA</th><th>Dec.</th><th>z</th><th>R</th><th>M<sub>R</sub></th><th>L<sub>R</sub></th><th>M/M<sub>☉</sub> ±</th><th>D<sub>n</sub>(4000) ±</th><th>[m/H] ±</th></tr></thead><tbody><tr><td>Q4-15</td><td>344.608</td><td>-34.731</td><td>0.30800</td><td>20.900</td><td>-20.140</td><td>0.720</td><td>0.460</td><td>0.190</td><td>1.117 0.063</td><td>-2.497 0.399</td></tr><tr><td>Q4-14</td><td>344.673</td><td>-34.730</td><td>0.30460</td><td>20.700</td><td>-20.320</td><td>0.840</td><td>0.540</td><td>0.220</td><td>0.931 0.071</td><td>-3.674 0.449</td></tr><tr><td>Q2-38</td><td>344.846</td><td>-34.663</td><td>0.29870</td><td>20.100</td><td>-20.870</td><td>1.400</td><td>0.900</td><td>0.370</td><td>1.013 0.053</td><td>-3.155 0.335</td></tr><tr><td>Q4-19</td><td>344.609</td><td>-34.737</td><td>0.31070</td><td>20.200</td><td>-20.870</td><td>1.400</td><td>0.900</td><td>0.360</td><td>0.996 0.048</td><td>-3.262 0.304</td></tr><tr><td>Q4-46</td><td>344.712</td><td>-34.784</td><td>0.32950</td><td>20.100</td><td>-21.110</td><td>1.760</td><td>1.130</td><td>0.460</td><td>1.155 0.056</td><td>-2.256 0.354</td></tr><tr><td>Q1-18</td><td>344.846</td><td>-34.751</td><td>0.31300</td><td>19.700</td><td>-21.380</td><td>2.260</td><td>1.450</td><td>0.590</td><td>1.137 0.073</td><td>-2.370 0.462</td></tr><tr><td>Q3-1</td><td>344.673</td><td>-34.555</td><td>0.32950</td><td>19.800</td><td>-21.410</td><td>2.320</td><td>1.480</td><td>0.600</td><td>1.175 0.063</td><td>-2.129 0.399</td></tr><tr><td>Q1-37</td><td>344.849</td><td>-34.791</td><td>0.31600</td><td>19.600</td><td>-21.510</td><td>2.530</td><td>1.620</td><td>0.660</td><td>1.290 0.056</td><td>-1.402 0.354</td></tr><tr><td>Q4-26</td><td>344.675</td><td>-34.748</td><td>0.32460</td><td>18.900</td><td>-22.280</td><td>5.130</td><td>1.644</td><td>1.330</td><td>1.071 0.031</td><td>-2.410 0.230</td></tr><tr><td>Q1-30</td><td>344.901</td><td>-34.779</td><td>0.31860</td><td>19.600</td><td>-21.530</td><td>2.580</td><td>1.650</td><td>0.670</td><td>1.251 0.066</td><td>-1.648 0.418</td></tr><tr><td>Q2-32</td><td>344.854</td><td>-34.643</td><td>0.30910</td><td>19.500</td><td>-21.550</td><td>2.640</td><td>1.690</td><td>0.690</td><td>1.174 0.055</td><td>-2.136 0.348</td></tr><tr><td>Q4-22</td><td>344.666</td><td>-34.741</td><td>0.31450</td><td>19.400</td><td>-21.700</td><td>3.010</td><td>1.930</td><td>0.780</td><td>1.137 0.059</td><td>-2.370 0.373</td></tr><tr><td>Q4-48</td><td>344.621</td><td>-34.787</td><td>0.31460</td><td>20.000</td><td>-21.100</td><td>1.730</td><td>2.215</td><td>0.450</td><td>1.470 0.088</td><td>-0.726 0.392</td></tr><tr><td>Q3-12</td><td>344.654</td><td>-34.583</td><td>0.30940</td><td>19.000</td><td>-22.060</td><td>4.190</td><td>2.680</td><td>1.090</td><td>1.227 0.051</td><td>-1.800 0.323</td></tr><tr><td>Q4-40</td><td>344.604</td><td>-34.772</td><td>0.31780</td><td>19.000</td><td>-22.120</td><td>4.460</td><td>2.850</td><td>1.160</td><td>1.225 0.037</td><td>-1.813 0.234</td></tr><tr><td>Q4-60</td><td>344.685</td><td>-34.806</td><td>0.31830</td><td>19.000</td><td>-22.130</td><td>4.470</td><td>2.860</td><td>1.160</td><td>1.224 0.039</td><td>-1.819 0.247</td></tr><tr><td>Q1-40</td><td>344.848</td><td>-34.799</td><td>0.32280</td><td>18.100</td><td>-23.060</td><td>10.580</td><td>3.393</td><td>2.750</td><td>1.081 0.047</td><td>-2.335 0.348</td></tr><tr><td>Q4-36</td><td>344.650</td><td>-34.764</td><td>0.31310</td><td>18.400</td><td>-22.690</td><td>7.480</td><td>9.557</td><td>1.950</td><td>1.757 0.094</td><td>-0.025 0.132</td></tr><tr><td>Q4-56</td><td>344.684</td><td>-34.800</td><td>0.31380</td><td>18.400</td><td>-22.690</td><td>7.520</td><td>9.597</td><td>1.960</td><td>1.743 0.095</td><td>-0.039 0.149</td></tr></tbody></table>

for passive galaxies needing correction to their masses as explained in Section 3.5.3, while for active galaxies calibrations for 1 and 5 Gyr were used.

The figure also shows that $D_n(4000)$ measured for active galaxies reaches values lower than those spanned by theoretical models. Although the linear extrapolation looks relatively safe, metallicities lower than [m/H] ~ -2.5 must be regarded as uncertain.

Metallicities can now be added to the main parameters of passive and active galaxies in AC114, which are summarized in Tables 3

and 4. It is also useful to be able to inspect the morphology of each object, therefore Figs B1 and B2 in Appendix B show images of the same galaxies, extracted from the VIMOS pre-imaging.

## 4 DISCUSSION

Taking the key quantities from the aforementioned tables, we can now use them to define the evolutionary status of galaxies in AC114.
<figure><img src="image_23.png" /></figure>

**Figure 21.** The top panel shows the location of passive galaxies (red symbols) and active galaxies (blue symbols) in the [m/H] versus stellar mass plane. The tracks are close-box models as explained in the text: for passive galaxies, the tracks just reach their representative point, while for active galaxies, we also plot the expected evolution until close to terminal gas fraction $\mu = 0.001$. Tracks are not plotted for active galaxies located in the passive galaxy region, which are identified by their quadrant-slit combination. The magenta points on active tracks represent the expected evolution until the present time for a linear $\mu(t)$ function set by past evolution. The lower panel shows the calculated $\mu$ as a function of the galaxy mass and metallicity, assuming the yield values displayed in the plot. The grey area shows the typical value of $\mu$ for local galaxies, taken from Fig. 22. Magenta segments represent the expected evolution until the present time.

<figure><img src="image_24.png" /></figure>

**Figure 22.** Gas mass fraction distribution for local spiral galaxies, with data from McGaugh & de Blok (1997). The curve is a Gaussian with average and dispersion as displayed in the plot.

In particular, we can construct the MZR, and interpret it by way of a simple model of chemical evolution: it will tell us that both the mass of a galaxy, and its location within the cluster, are key drivers of evolution.

## 4.1 Mass-metallicity relation

As subsequent stellar generations are created within a galaxy, they enrich the ISM and build the stellar mass at the expense of gas mass. It is therefore expected that mass and metallicity grow in time, and if galaxies were able to perform the gas conversion at the same rate, isolated galaxies of the same age would have converted the same fraction of gas into stars, and thus would have the same metallicity, irrespective of mass. But galaxies show an ubiquitous MZR, as testified by a vast literature on the subject (see e.g. Maiolino & Mannucci 2019, for a review). This fact can have several explanations, which are illustrated in Fig. 20: galaxies of larger mass might be able to convert larger fractions of gas into stars, in the
<figure><img src="image_25.png" /><figcaption>**Figure 23.** The upper panel shows the location of active and passive galaxies in the [m/H] versus mass plane, with the two classes identified by blue and red colour, respectively. A general trend of metallicity increasing with mass can be seen. In the lower panel, symbols are inversely proportional to the measurement errors: the red and blue solid curves are weighted linear fit to points representing passive and active galaxies. The blue dashed curve is the relation obtained after excluding galaxies with metallicities lower than −3. The red and blue shaded areas mark the location of the tracks taken from Fig. 21. The dashed curves on top of the panel represent MZRs from Peng et al. (2015), with red and blue colour distinguishing passive and active galaxies.</figcaption></figure>

same amount of time (higher SF efficiency); their stellar generations might be able to produce more metals than those in low-mass galaxies (higher yield); metals produced by low-mass galaxies might be more easily lost into the IGM; or finally, low-mass galaxies might have been originally higher mass objects, whose SF was truncated due to loss of residual gas into the IGM. It is then interesting to investigate the existence of an MZR of AC114 galaxies, and see what it can tell us about the evolutionary history of the cluster.

### 4.1.1 The MZR and its interpretation

When $D_n(4000)$ is converted into a metallicity, Fig. 17 is converted into Fig. 21, which shows the location of AC114 galaxies in the [m/H] versus mass plane. As expected, the trend of $D_n(4000)$ with mass converts into an MZR, for the two galaxy classes. To interpret the MZR, we make use of the so-called closed-box model (Searle & Sargent 1972), which, despite its simplicity, allows to draw interesting conclusions on the evolutionary status of the galaxy cluster.

In the close-box approximation, the evolution of a galaxy is parametrized by the gas mass fraction $\mu = m_{gas}/m_{tot} = m_{gas}/(m_{gas} + m_{stars})$: a galaxy starts as a mass of pristine gas ($\mu = 1$), which is converted into stars thereby producing metals, until $\mu = 0$. All along, the total mass remains constant. In the same framework, according to Pagel (1997), the average abundance of a stellar population starts at zero and it evolves with $\mu$ according to the equation:

$$<z> = 1 + \frac{\mu \ln \mu}{1 - \mu}, \qquad (1)$$

where the metallicity is expressed as $z = Z/p$, and $p$ is the metal yield of a stellar generation:<fnref n="1" /> therefore $<Z> \rightarrow p$ when $\mu \rightarrow 0$. At the end of its SF history, a galaxy will then have an average metallicity similar to the yield, which can then be estimated in this way. Thus, if passive galaxies have reached the end of their SF history, then Fig. 21 is telling us that their yield depends on galaxy mass. And because the stellar yield only depends on the IMF, what must be changing is the ability of a galaxy to return its metals to the ISM: indeed a common explanation for the MZR is that a less massive object has a shallower gravitational potential from which metals can escape more easily (e.g. Dekel & Silk 1986).

If instead the yield is constant, then $\mu$ must depend on the galaxy mass: this is shown in the lower panel of Fig. 21, where $\mu$ has been calculated assuming that the constant yield is close to that of the most metal-rich galaxies, that is, equal to $Z_{\odot}$. The plot shows that larger galaxies would have been able to convert a higher fraction of their initial mass into stars. Because passive galaxies do not have associated large gas masses, the unprocessed gas must have been lost into the IGM, thus truncating their SF: again, the gas dispersal would be easier for less massive objects. Of course this would be a stochastic process which could be also influenced by the galaxy location in a cluster and an MZR might be not expected, but the close-box tracks of Fig. 21 run almost parallel to the MZR, so even a random truncation of the SF would naturally lead to a relationship. Therefore, this is our preferred explanation for the distribution of passive galaxies in Fig. 21.

If active galaxies had the same yield as passive ones, their low metallicity would be explained by a very slow chemical evolution: the close-box model predicts that only 2 per cent of the initial gas mass needs to be processed ($\mu = 0.98$), to reach a metallicity [m/H] = −2. The age of the cluster is ~10 Gyr, so if active galaxies continued their evolution at the same pace, today (~3.7 Gyr later) they would have reached [m/H] = −1.86, and consumed only an additional 1 per cent of gas mass.

This means that we should observe a mass of gas associated to active galaxies ~50 times the mass of stars, and that their total masses would be more than an order of magnitude larger than those of passive galaxies. Both deductions are not in agreement with observations, so we must conclude that active galaxies have a lower yield compared to passive ones. Indeed this is also the conclusion of Köppen et al. (2007), based on the idea that stars in less massive galaxies are generated in less massive stellar clusters: these are not able to form massive stars, thereby skewing the IMF to lower masses and reducing yields. More massive galaxies can produce more massive clusters because they compress their gas more efficiently, as predicted by the Schmidt-Kennicutt law (Schmidt 1959; Kennicutt 1998).

To put some constraints to low-mass galaxy yields, we imposed that the total masses of active galaxies should not be larger than those of passive ones: thus we plotted the track that reaches the higher mass at end of evolution, and changed the yield until its total mass was similar to that of the most massive passive galaxy. The result is $p = 0.03 Z_{\odot}$, which we adopted for all active galaxies: this value is well within the yield reduction computed by Köppen et al. (2007).

As for passive galaxies, the location of active ones along their tracks constrains their mass fractions, which are plotted in the lower

<footnote n="1">¹The yield of metal i is given by $p_i = [\int_{m_{(i)}}^{m_{\odot}} m q_i(m) \phi(m) dm]/S$, where $q_i(m)$ is the yield per stellar mass, and $\phi(m)$ is the initial mass function; the global yield is then $p = \Sigma p_i$. S is the mass in stars and remnants of each generation, such that $p \times S$ is the mass of metals returned to the ISM.</footnote>
<table><caption>**Table 5.** Positions, photometric data, and velocities for galaxies of AC114. The *R* column is the correlation peak height to the amplitude of the asymmetric noise (see the text for explanation).</caption><thead><tr><th>Gal.</th><th>RA<br>(J2000)</th><th>Dec.<br>(J2000)</th><th>B<sub>j</sub><br>(mag)</th><th>R<sub>f</sub><br>(mag)</th><th>R<sub>comp</sub><br>(mag)</th><th>Redshift</th><th>Error</th><th>R</th><th>Notes</th></tr></thead><tbody><tr><td colspan="10"><strong>Quadrant 1</strong></td></tr><tr><td>1</td><td>22 59 20.70</td><td>-34 42 24.6</td><td></td><td></td><td>20.0</td><td>0.39852</td><td>0.00030</td><td>3.50</td><td>em:Hα, S1</td></tr><tr><td>2</td><td>22 59 31.37</td><td>-34 42 28.4</td><td></td><td></td><td>20.5</td><td>0.35306</td><td>0.00018</td><td></td><td>em:O II, Hβ, 2O III, Hα, S1</td></tr><tr><td>3</td><td>22 59 33.46</td><td>-34 42 39.8</td><td></td><td></td><td>18.0</td><td>0.05717</td><td>0.00011</td><td></td><td>em:Hβ, 2O III, Hα, S1</td></tr><tr><td>5</td><td>22 59 32.31</td><td>-34 42 58.2</td><td>20.2</td><td></td><td>20.1</td><td>0.05842</td><td>0.00009</td><td></td><td>em:Hβ, 2O III, Hα, S1</td></tr><tr><td>8</td><td>22 59 36.51</td><td>-34 43 25.4</td><td>20.2</td><td></td><td>20.3</td><td>0.38058</td><td>0.00022</td><td></td><td>em:Hα, S1</td></tr><tr><td>9</td><td>22 59 25.99</td><td>-34 43 31.9</td><td></td><td></td><td></td><td>0.21032?</td><td></td><td></td><td>Very uncertain</td></tr><tr><td>10</td><td>22 59 18.60</td><td>-34 43 43.6</td><td>20.5</td><td>18.8</td><td>18.9</td><td>0.21940</td><td>0.00024</td><td>4.76</td><td>em: Hα, S1 65840 km s<sup>-1</sup></td></tr><tr><td>11</td><td>22 59 17.61</td><td>-34 43 57.1</td><td></td><td></td><td>19.3</td><td>0.62605</td><td>0.00031</td><td></td><td>Measured on O II, H,K (Ca I)</td></tr><tr><td>12</td><td>22 59 20.05</td><td>-34 44 09.4</td><td>20.8</td><td>19.5</td><td>18.2</td><td>0.22127</td><td>0.00012</td><td>3.56</td><td>em:Hβ, Hα 66509 km s<sup>-1</sup></td></tr><tr><td>13</td><td>22 59 20.00</td><td>-34 44 20.3</td><td></td><td></td><td>20.0</td><td>0.40975</td><td>0.00022</td><td>4.79</td><td></td></tr><tr><td>15</td><td>22 59 28.09</td><td>-34 44 29.0</td><td></td><td></td><td>19.4</td><td>0.07309</td><td>0.00045</td><td></td><td>em:Hβ, 2O III, Hα</td></tr><tr><td>16</td><td>22 59 28.82</td><td>-34 44 44.1</td><td></td><td></td><td>18.6</td><td>0.40819</td><td>0.00039</td><td>3.57</td><td></td></tr><tr><td>17</td><td>22 59 38.42</td><td>-34 44 52.4</td><td></td><td></td><td>20.5</td><td>0.63163</td><td>0.00045</td><td>3.09</td><td>Very weak</td></tr><tr><td>18</td><td>22 59 23.15</td><td>-34 45 03.0</td><td></td><td></td><td>19.7</td><td>0.31301</td><td>0.00007</td><td></td><td>em:Hα, S1</td></tr><tr><td>19</td><td>22 59 18.51</td><td>-34 45 13.1</td><td>21.2</td><td>20.3</td><td>19.6</td><td>0.40876</td><td>0.00022</td><td></td><td>em:O II, Hβ, 2O III, Hα, S1</td></tr><tr><td>20</td><td>22 59 40.37</td><td>-34 45 21.8</td><td></td><td></td><td>18.1</td><td>0.23192</td><td>0.00018</td><td>5.23</td><td></td></tr><tr><td>22</td><td>22 59 24.80</td><td>-34 45 36.6</td><td>22.3</td><td>19.6</td><td>18.8</td><td>0.41015</td><td>0.00025</td><td>5.19</td><td>em:Hβ, Hα</td></tr><tr><td>24</td><td>22 59 28.59</td><td>-34 45 49.8</td><td>21.6</td><td>19.6</td><td>18.9</td><td>0.33369</td><td>0.00018</td><td>4.84</td><td>em:O II</td></tr><tr><td>25</td><td>22 59 35.08</td><td>-34 45 57.0</td><td>22.4</td><td></td><td>20.9</td><td>0.48600</td><td>0.00055</td><td></td><td>Measured on H,K (Ca I)</td></tr><tr><td>26</td><td>22 59 32.09</td><td>-34 46 13.6</td><td></td><td></td><td>19.6</td><td>0.53351</td><td>0.00056</td><td></td><td>Measured on O II, H,K (Ca I)</td></tr><tr><td>27</td><td>22 59 32.34</td><td>-34 46 23.3</td><td></td><td></td><td>19.9</td><td>0.46615</td><td>0.00022</td><td>3.22</td><td></td></tr><tr><td>28</td><td>22 59 26.16</td><td>-34 46 32.5</td><td>20.2</td><td>19.2</td><td>19.0</td><td>0.35118</td><td>0.00028</td><td>3.11</td><td>Weak confirmed on H,K (Ca I)</td></tr><tr><td>30</td><td>22 59 36.18</td><td>-34 46 43.1</td><td>20.8</td><td>18.8</td><td>19.6</td><td>0.31860</td><td>0.00033</td><td>3.15</td><td></td></tr><tr><td>31</td><td>22 59 33.65</td><td>-34 46 49.2</td><td></td><td></td><td>19.9</td><td>0.33342</td><td></td><td></td><td>Measured on Hα</td></tr><tr><td>34</td><td>22 59 25.25</td><td>-34 47 05.9</td><td></td><td></td><td>20.0</td><td>0.63182</td><td>0.00068</td><td></td><td>Measured on H,K (Ca I)</td></tr><tr><td>36</td><td>22 59 34.22</td><td>-34 47 19.9</td><td></td><td></td><td>19.6</td><td>0.49978</td><td></td><td></td><td>Measured on O II</td></tr><tr><td>37</td><td>22 59 23.76</td><td>-34 47 27.4</td><td>21.0</td><td>19.8</td><td>19.6</td><td>0.31604</td><td>0.00004</td><td></td><td>em:Hβ, 2O III, Hα, S1</td></tr><tr><td>38</td><td>22 59 18.07</td><td>-34 47 39.8</td><td></td><td></td><td>19.9</td><td>0.49805</td><td>0.00064</td><td>3.04</td><td>Very weak</td></tr><tr><td>40</td><td>22 59 23.41</td><td>-34 47 57.6</td><td>20.6</td><td>18.9</td><td>18.1</td><td>0.32283</td><td>0.00027</td><td>3.37</td><td>em:Hβ, 2O III, Hα, S1: 96857 km s<sup>-1</sup></td></tr><tr><td>41</td><td>22 59 16.77</td><td>-34 48 06.8</td><td></td><td></td><td>20.0</td><td>0.47645</td><td>0.00054</td><td></td><td>Measured on H,K (Ca I)</td></tr><tr><td>44</td><td>22 59 15.92</td><td>-34 48 43.8</td><td>22.2</td><td>21.1</td><td>19.1</td><td>0.57779</td><td>0.00066</td><td></td><td>Measured on O II, H,K (Ca I)</td></tr><tr><td>45a</td><td>22 59 31.40</td><td>-34 48 50.3</td><td></td><td></td><td></td><td>0.35159</td><td></td><td></td><td>Measured on Hα, S1</td></tr><tr><td>45b</td><td>22 59 31.40</td><td>-34 48 50.4</td><td></td><td></td><td></td><td>0.34461</td><td></td><td></td><td>Measured on Hα, S1</td></tr><tr><td colspan="10"><strong>Quadrant 2</strong></td></tr><tr><td>1a</td><td>22 59 16.30</td><td>-34 33 40.6</td><td>20.8</td><td>19.0</td><td>19.6</td><td>0.25782</td><td>0.00023</td><td>3.43</td><td>em:Hβ, 2O III, Hα</td></tr><tr><td>1b</td><td>22 59 16.30</td><td>-34 33 40.6</td><td></td><td></td><td></td><td>0.33069</td><td>0.00024</td><td>3.18</td><td>em:Hα, two galaxies</td></tr><tr><td>2</td><td>22 59 18.23</td><td>-34 33 50.7</td><td></td><td></td><td>18.2</td><td>0.49578</td><td>0.00029</td><td></td><td>em:O II, Hβ, 2O III, Hα, S1</td></tr><tr><td>3</td><td>22 59 18.00</td><td>-34 33 58.5</td><td></td><td></td><td>20.5</td><td>0.41000</td><td>0.00033</td><td></td><td>em:O II, Hβ, 2O III, Hα</td></tr><tr><td>4</td><td>22 59 13.67</td><td>-34 34 11.1</td><td></td><td></td><td>19.3</td><td>0.40846</td><td>0.00033</td><td></td><td>em:Hβ, 2O III</td></tr><tr><td>5</td><td>22 59 15.03</td><td>-34 34 23.5</td><td>22.5</td><td>20.1</td><td>18.8</td><td>0.41440</td><td>0.00034</td><td>3.01</td><td>Very uncertain</td></tr><tr><td>6</td><td>22 59 23.91</td><td>-34 34 32.7</td><td>21.3</td><td>19.2</td><td>18.9</td><td>0.42284</td><td>0.00021</td><td>6.45</td><td></td></tr><tr><td>7</td><td>22 59 21.45</td><td>-34 34 41.8</td><td></td><td></td><td>18.6</td><td>0.56176</td><td>0.00052</td><td></td><td>Measured on H,K (Ca I)</td></tr><tr><td>8</td><td>22 59 12.89</td><td>-34 34 48.4</td><td></td><td></td><td>21.2</td><td>0.25744</td><td>0.00018</td><td></td><td>Measured on 2O III</td></tr><tr><td>9</td><td>22 59 17.73</td><td>-34 34 54.1</td><td></td><td></td><td>20.9</td><td>0.37079</td><td>0.00063</td><td></td><td>Measured on 2O III</td></tr><tr><td>10</td><td>22 59 18.77</td><td>-34 35 02.2</td><td>21.5</td><td>19.9</td><td>19.5</td><td>0.40848</td><td>0.00023</td><td>3.36</td><td></td></tr><tr><td>11</td><td>22 59 16.88</td><td>-34 35 08.5</td><td></td><td></td><td>17.6</td><td>0.34546</td><td></td><td></td><td>Measured on Hα</td></tr><tr><td>12</td><td>22 59 32.84</td><td>-34 35 24.7</td><td>21.9</td><td></td><td>19.2</td><td>0.59523</td><td></td><td></td><td>Measured on O II</td></tr><tr><td>13</td><td>22 59 26.31</td><td>-34 35 32.2</td><td></td><td></td><td>17.8</td><td>0.27013</td><td>0.00038</td><td>3.52</td><td>Very weak</td></tr><tr><td>14</td><td>22 59 20.21</td><td>-34 35 43.7</td><td></td><td></td><td>18.7</td><td>0.37370</td><td>0.00009</td><td></td><td>em:O II, Hα, S1</td></tr><tr><td>15</td><td>22 59 15.61</td><td>-34 35 51.1</td><td></td><td></td><td>20.7</td><td>0.41045</td><td>0.00026</td><td>4.01</td><td></td></tr><tr><td>16</td><td>22 59 19.18</td><td>-34 35 59.7</td><td>21.4</td><td>20.4</td><td>19.7</td><td>0.56822</td><td>0.00074</td><td></td><td>Measured on O II, H,K (Ca I)</td></tr><tr><td>18</td><td>22 59 12.16</td><td>-34 36 28.0</td><td>21.0</td><td></td><td>19.4</td><td>0.38110</td><td>0.00042</td><td>4.03</td><td></td></tr><tr><td>19</td><td>22 59 19.31</td><td>-34 36 38.6</td><td>22.00</td><td>20.1</td><td>18.8</td><td>0.37706</td><td>0.00021</td><td>6.71</td><td></td></tr><tr><td>21</td><td>22 59 21.69</td><td>-34 36 53.5</td><td></td><td></td><td>19.2</td><td>0.41304</td><td>0.00020</td><td>6.52</td><td></td></tr><tr><td>22</td><td>22 59 36.79</td><td>-34 36 53.5</td><td></td><td></td><td>21.3</td><td>0.39104</td><td></td><td></td><td>em:Hα</td></tr><tr><td>23</td><td>22 59 21.57</td><td>-34 37 07.8</td><td>19.3</td><td>18.4</td><td>18.3</td><td>0.41310</td><td>0.00022</td><td>6.81</td><td></td></tr><tr><td>24</td><td>22 59 36.81</td><td>-34 37 21.2</td><td></td><td></td><td>19.2</td><td>0.37972</td><td>0.00052</td><td></td><td>em:O II, Hβ, 2O III</td></tr><tr><td>26</td><td>22 59 12.34</td><td>-34 37 37.5</td><td>22.3</td><td>20.2</td><td>19.4</td><td>0.48676</td><td>0.00018</td><td></td><td>em:O II, Hβ, 2O III</td></tr><tr><td>27</td><td>22 59 21.00</td><td>-34 37 46.0</td><td>20.6</td><td>20.0</td><td>19.9</td><td>0.49642</td><td>0.00024</td><td>4.53</td><td></td></tr><tr><td>28</td><td>22 59 15.56</td><td>-34 37 57.2</td><td>20.8</td><td>19.4</td><td>19.7</td><td>0.61361</td><td>0.00047</td><td></td><td>Measured on O II, Hβ</td></tr><tr><td>29</td><td>22 59 17.62</td><td>-34 38 03.8</td><td></td><td></td><td>20.9</td><td>0.52230</td><td></td><td></td><td>Measured on O II</td></tr></tbody></table>
<table><caption>**Table 5 – continued**</caption><thead><tr><th>Gal.</th><th>RA<br>(J2000)</th><th>Dec.<br>(J2000)</th><th>B<sub>j</sub><br>(mag)</th><th>R<sub>f</sub><br>(mag)</th><th>R<sub>comp</sub><br>(mag)</th><th>Redshift</th><th>Error</th><th>R</th><th>Notes</th></tr></thead><tbody><tr><td>31</td><td>22 59 24.67</td><td>-34 38 18.4</td><td>21.4</td><td>20.6</td><td>18.5</td><td>0.49717</td><td>0.00016</td><td></td><td>em:O II, Hβ, 2O III, Hα</td></tr><tr><td>32</td><td>22 59 25.00</td><td>-34 38 35.6</td><td>20.8</td><td>19.5</td><td>19.5</td><td>0.30913</td><td>0.00028</td><td></td><td>em:Hβ, 2O III, Hα</td></tr><tr><td>33</td><td>22 59 16.65</td><td>-34 38 43.7</td><td>20.1</td><td>18.1</td><td>20.4</td><td>0.46922</td><td>0.00051</td><td>3.17</td><td>em:Hβ 140472 km s<sup>-1</sup></td></tr><tr><td>35</td><td>22 59 40.57</td><td>-34 39 05.1</td><td></td><td></td><td>19.7</td><td>0.31290</td><td>0.00016</td><td>7.72</td><td></td></tr><tr><td>36</td><td>22 59 25.79</td><td>-34 39 11.8</td><td>21.4</td><td>20.0</td><td>19.8</td><td>0.46367</td><td>0.00020</td><td>6.71</td><td></td></tr><tr><td>37</td><td>22 59 13.94</td><td>-34 39 33.0</td><td>21.8</td><td>20.7</td><td>18.7</td><td>0.13963</td><td>0.00063</td><td></td><td>Measured on Hβ, 2O III</td></tr><tr><td>38</td><td>22 59 23.08</td><td>-34 39 47.1</td><td></td><td></td><td>20.1</td><td>0.29869</td><td>0.00017</td><td></td><td>em:Hβ, 2O III, Hα, S1</td></tr><tr><td>39</td><td>22 59 39.01</td><td>-34 39 53.1</td><td></td><td></td><td>20.6</td><td>0.37203</td><td>0.00012</td><td></td><td>em:O II, Hβ, 2O III, Hα</td></tr><tr><td>40</td><td>22 59 36.39</td><td>-34 39 58.4</td><td></td><td></td><td>20.3</td><td>0.41913</td><td>0.00023</td><td>4.96</td><td></td></tr><tr><td>41</td><td>22 59 43.80</td><td>-34 40 06.7</td><td></td><td></td><td>20.5</td><td>0.54027</td><td></td><td></td><td>Measured on O II</td></tr><tr><td colspan="10">Quadrant 3</td></tr><tr><td>1</td><td>22 58 41.57</td><td>-34 33 18.1</td><td>20.3</td><td>18.8</td><td>19.8</td><td>0.32951</td><td>0.00015</td><td></td><td>em:Hβ, 2O III, Hα, S1</td></tr><tr><td>2</td><td>22 58 41.21</td><td>-34 33 27.8</td><td>20.5</td><td>18.8</td><td>18.7</td><td>0.33307</td><td>0.00011</td><td></td><td>em:Hβ, 2O III, Hα, S1</td></tr><tr><td>3</td><td>22 58 40.11</td><td>-34 33 34.6</td><td>21.9</td><td>19.2</td><td>19.4</td><td>0.33127</td><td>0.00024</td><td>5.48</td><td></td></tr><tr><td>4</td><td>22 58 40.08</td><td>-34 33 42.2</td><td>21.3</td><td>19.9</td><td>20.0</td><td>0.21259</td><td>0.00019</td><td></td><td>em:Hβ, 2O III, Hα, S1</td></tr><tr><td>5</td><td>22 58 41.10</td><td>-34 33 49.0</td><td></td><td></td><td>20.5</td><td>0.33189</td><td>0.00020</td><td></td><td>em:Hβ, 2O III, Hα, S1</td></tr><tr><td>7</td><td>22 58 48.40</td><td>-34 34 01.6</td><td></td><td></td><td></td><td>0.31092</td><td>0.00054</td><td></td><td>Measured on H,K (Ca1)</td></tr><tr><td>8</td><td>22 58 42.73</td><td>-34 34 23.0</td><td>22.0</td><td></td><td>19.7</td><td>0.39969</td><td>0.00028</td><td>3.48</td><td>em:Hα: 119724 km s<sup>-1</sup></td></tr><tr><td>10</td><td>22 58 22.64</td><td>-34 34 33.3</td><td>19.8</td><td>18.7</td><td>18.8</td><td>0.31365</td><td>0.00012</td><td>4.63</td><td></td></tr><tr><td>11</td><td>22 58 35.95</td><td>-34 34 45.6</td><td>22.4</td><td>20.6</td><td>20.1</td><td>0.21245</td><td>0.00026</td><td></td><td>em:Hβ, 2O III, Hα, S1</td></tr><tr><td>12</td><td>22 58 36.88</td><td>-34 34 58.2</td><td>21.5</td><td>19.6</td><td>19.0</td><td>0.30939</td><td>0.00009</td><td></td><td>em:Hβ, 2O III, Hα, S1</td></tr><tr><td>13</td><td>22 58 51.29</td><td>-34 35 07.6</td><td></td><td></td><td>19.3</td><td>0.65153</td><td>0.00048</td><td>3.03</td><td>Very weak</td></tr><tr><td>15</td><td>22 58 41.00</td><td>-34 35 21.4</td><td></td><td></td><td>20.3</td><td>0.47562</td><td>0.00038</td><td>3.01</td><td>Very weak</td></tr><tr><td>16</td><td>22 58 45.84</td><td>-34 35 30.4</td><td>20.9</td><td>20.4</td><td>20.0</td><td>0.17739</td><td>0.00012</td><td></td><td>em:Hβ, 2O III, Hα, S1</td></tr><tr><td>18</td><td>22 58 56.50</td><td>-34 35 48.2</td><td>20.8</td><td>19.3</td><td>19.5</td><td>0.22176</td><td>0.00009</td><td></td><td>em:Hβ, 2O III, Hα, S1</td></tr><tr><td>19</td><td>22 58 23.26</td><td>-34 35 57.0</td><td>20.0</td><td>18.6</td><td>18.9</td><td>0.15860</td><td>0.00015</td><td>4.84</td><td></td></tr><tr><td>20</td><td>22 58 32.46</td><td>-34 36 07.9</td><td></td><td></td><td>19.2</td><td>0.35487</td><td>0.00038</td><td>3.07</td><td>Confirmed on O II</td></tr><tr><td>21</td><td>22 58 32.39</td><td>-34 36 15.5</td><td>21.1</td><td>19.2</td><td>20.8</td><td>0.35231</td><td>0.00021</td><td></td><td>em:Hβ, Hα, S1, S2</td></tr><tr><td>23</td><td>22 58 22.99</td><td>-34 36 26.7</td><td>22.1</td><td>20.5</td><td>20.5</td><td>0.35371</td><td>0.00035</td><td></td><td>Measured on H,K (Ca1)</td></tr><tr><td>24</td><td>22 58 28.94</td><td>-34 36 34.7</td><td></td><td></td><td>18.2</td><td>0.30386</td><td>0.00045</td><td>3.01</td><td>Very weak</td></tr><tr><td>25</td><td>22 58 40.69</td><td>-34 36 41.1</td><td></td><td></td><td>20.1</td><td>0.59540</td><td>0.00068</td><td></td><td>Measured on H,K (Ca1)</td></tr><tr><td>26</td><td>22 58 28.24</td><td>-34 36 48.7</td><td></td><td></td><td>20.2</td><td>0.31477</td><td>0.00024</td><td>4.07</td><td></td></tr><tr><td>28</td><td>22 58 24.28</td><td>-34 37 02.1</td><td></td><td></td><td>18.4</td><td>0.25761</td><td>0.00018</td><td>5.51</td><td></td></tr><tr><td>29</td><td>22 58 32.32</td><td>-34 37 07.5</td><td>21.6</td><td>20.1</td><td>20.6</td><td>0.47283</td><td>0.00038</td><td>3.15</td><td></td></tr><tr><td>30</td><td>22 58 27.93</td><td>-34 37 16.9</td><td>21.2</td><td>20.1</td><td>21.1</td><td>0.40221</td><td>0.00023</td><td></td><td>em:O II, Hβ, 2O III, Hα</td></tr><tr><td>31</td><td>22 58 44.38</td><td>-34 37 24.2</td><td>22.2</td><td>20.2</td><td>20.1</td><td>0.39764</td><td>0.00040</td><td>3.04</td><td>em:Hβ, Hα</td></tr><tr><td>33</td><td>22 58 39.09</td><td>-34 37 52.3</td><td></td><td></td><td>18.8</td><td>0.34480</td><td></td><td></td><td>Measured on Hα</td></tr><tr><td>34</td><td>22 58 39.66</td><td>-34 38 03.8</td><td></td><td></td><td>20.1</td><td>0.35179</td><td>0.00011</td><td></td><td>em:O II, Hβ, 2O III, Hα, S1</td></tr><tr><td>35</td><td>22 58 33.67</td><td>-34 38 18.9</td><td>21.4</td><td>20.1</td><td>18.9</td><td>0.43091</td><td>0.00014</td><td></td><td>em:Hβ, 2O III, Hα, S1</td></tr><tr><td>36</td><td>22 58 31.51</td><td>-34 38 24.2</td><td>22.3</td><td>20.7</td><td>20.5</td><td>0.20326</td><td>0.00031</td><td></td><td>em:Hα, S1</td></tr><tr><td>38</td><td>22 58 41.21</td><td>-34 38 40.5</td><td></td><td></td><td>19.3</td><td>0.43205</td><td>0.00029</td><td>3.58</td><td>em: O II</td></tr><tr><td>39</td><td>22 58 46.63</td><td>-34 38 45.7</td><td>21.9</td><td>20.6</td><td>20.2</td><td>0.39935</td><td>0.00011</td><td></td><td>em:O II, Hβ, 2O III, Hα, S1</td></tr><tr><td>40</td><td>22 58 34.07</td><td>-34 38 53.1</td><td>21.9</td><td>19.9</td><td>19.3</td><td>0.31828</td><td>0.00031</td><td>4.12</td><td></td></tr><tr><td>43</td><td>22 58 39.42</td><td>-34 39 13.5</td><td></td><td></td><td>20.2</td><td>0.51016</td><td>0.00028</td><td>3.32</td><td></td></tr><tr><td>44</td><td>22 58 39.45</td><td>-34 39 24.1</td><td>22.2</td><td>19.4</td><td>19.5</td><td>0.22464</td><td>0.00017</td><td>3.34</td><td>em: Hα, S1 67344 km s<sup>-1</sup></td></tr><tr><td>45</td><td>22 58 43.50</td><td>-34 39 32.3</td><td>21.6</td><td>20.6</td><td>20.1</td><td>0.62790</td><td>0.00061</td><td></td><td>Measured on O II, H,K (Ca1)</td></tr><tr><td>46</td><td>22 58 42.70</td><td>-34 39 40.6</td><td></td><td></td><td>20.4</td><td>0.52153</td><td>0.00028</td><td>3.21</td><td></td></tr><tr><td>49</td><td>22 58 37.09</td><td>-34 40 06.8</td><td>19.4</td><td>18.2</td><td>18.9</td><td>0.20657</td><td>0.00019</td><td>4.82</td><td>em:Hα, S1 61753 km s<sup>-1</sup></td></tr><tr><td colspan="10">Quadrant 4</td></tr><tr><td>2</td><td>22 58 34.99</td><td>-34 42 24.0</td><td></td><td></td><td>19.5</td><td>0.31982</td><td>0.00035</td><td>5.82</td><td>em:Hα weak</td></tr><tr><td>3</td><td>22 58 45.17</td><td>-34 42 28.9</td><td>22.6</td><td>19.1</td><td>20.1</td><td>0.41385</td><td>0.00042</td><td></td><td>Measured on O II, H,K (Ca1)</td></tr><tr><td>4</td><td>22 58 35.53</td><td>-34 42 35.8</td><td></td><td></td><td>19.7</td><td>0.31108</td><td>0.00014</td><td>3.42</td><td></td></tr><tr><td>5</td><td>22 58 42.57</td><td>-34 42 42.5</td><td></td><td></td><td>20.6</td><td>0.42558</td><td>0.00012</td><td></td><td>em:Hβ, 2O III, Hα, S1</td></tr><tr><td>7</td><td>22 58 32.37</td><td>-34 42 55.1</td><td>20.4</td><td>19.7</td><td>20.0</td><td>0.16952</td><td>0.00009</td><td></td><td>em:Hβ, 2O III, Hα, S1</td></tr><tr><td>8</td><td>22 58 32.75</td><td>-34 43 02.0</td><td></td><td></td><td>19.5</td><td>0.17061</td><td>0.00022</td><td></td><td>em:Hβ, 2O III, Hα, S1</td></tr><tr><td>9a</td><td>22 58 31.70</td><td>-34 43 18.8</td><td>21.0</td><td>18.9</td><td>18.4</td><td>0.29095</td><td>0.00009</td><td>10.95</td><td></td></tr><tr><td>9b</td><td>22 58 31.70</td><td>-34 43 18.8</td><td></td><td></td><td></td><td>0.25836</td><td>0.00035</td><td></td><td>Measured on H,K (Ca1)</td></tr><tr><td>10</td><td>22 58 25.31</td><td>-34 43 25.5</td><td>20.5</td><td>18.8</td><td>19.5</td><td>0.31228</td><td></td><td></td><td>em:Hα very weak</td></tr><tr><td>11</td><td>22 58 32.43</td><td>-34 43 30.3</td><td>19.0</td><td>17.4</td><td>20.0</td><td>0.30473</td><td>0.00008</td><td>3.02</td><td>em:Hα</td></tr><tr><td>12</td><td>22 58 26.84</td><td>-34 43 34.1</td><td>22.1</td><td>21.0</td><td>19.7</td><td>0.31166</td><td>0.00026</td><td>3.05</td><td></td></tr><tr><td>13</td><td>22 58 26.64</td><td>-34 43 44.0</td><td>22.4</td><td>20.5</td><td>20.9</td><td>0.47564</td><td>0.00016</td><td>3.40</td><td></td></tr><tr><td>14</td><td>22 58 41.60</td><td>-34 43 46.5</td><td>20.5</td><td>18.9</td><td>20.7</td><td>0.30460</td><td>0.00007</td><td></td><td>em:O II, Hβ, 2O III, Hα, S1</td></tr><tr><td>15</td><td>22 58 25.91</td><td>-34 43 52.0</td><td>21.2</td><td>19.8</td><td>20.9</td><td>0.30799</td><td>0.00030</td><td></td><td>em:Hβ, 2O III</td></tr></tbody></table>
<table><caption>**Table 5** – continued</caption><thead><tr><th>Gal.</th><th>RA<br>(J2000)</th><th>Dec.<br>(J2000)</th><th>B<sub>j</sub><br>(mag)</th><th>R<sub>f</sub><br>(mag)</th><th>R<sub>comp</sub><br>(mag)</th><th>Redshift</th><th>Error</th><th>R</th><th>Notes</th></tr></thead><tbody><tr><td>16</td><td>22 58 29.50</td><td>-34 43 55.5</td><td>22.2</td><td>19.8</td><td>20.4</td><td>0.31854</td><td>0.00035</td><td>3.52</td><td></td></tr><tr><td>18</td><td>22 58 25.81</td><td>-34 44 06.4</td><td></td><td></td><td>20.6</td><td>0.32247</td><td>0.00029</td><td>3.19</td><td></td></tr><tr><td>19</td><td>22 58 26.24</td><td>-34 44 12.1</td><td></td><td></td><td>20.2</td><td>0.31070</td><td>0.00011</td><td></td><td>em:Hβ, 2O III, Hα, S1</td></tr><tr><td>20</td><td>22 58 39.44</td><td>-34 44 18.6</td><td></td><td></td><td>19.6</td><td>0.30863</td><td>0.00011</td><td></td><td>em:Hβ, 2O III, Hα, S1</td></tr><tr><td>21</td><td>22 58 50.72</td><td>-34 44 16.7</td><td></td><td></td><td>19.5</td><td>0.30605</td><td>0.00024</td><td>4.32</td><td></td></tr><tr><td>22</td><td>22 58 39.87</td><td>-34 44 28.0</td><td></td><td></td><td>19.4</td><td>0.31445</td><td>0.00022</td><td>5.69</td><td></td></tr><tr><td>23</td><td>22 58 35.11</td><td>-34 44 34.8</td><td>21.9</td><td></td><td>20.6</td><td>0.32268</td><td>0.00030</td><td>3.09</td><td></td></tr><tr><td>24</td><td>22 58 33.19</td><td>-34 44 39.7</td><td></td><td></td><td>20.5</td><td>0.31448</td><td>0.00028</td><td>3.12</td><td></td></tr><tr><td>25</td><td>22 58 30.22</td><td>-34 44 42.4</td><td></td><td></td><td>19.4</td><td>0.30132</td><td>0.00035</td><td>3.20</td><td></td></tr><tr><td>26</td><td>22 58 42.00</td><td>-34 44 51.2</td><td>20.6</td><td>18.9</td><td>18.9</td><td>0.32462</td><td>0.00012</td><td></td><td>em:O II, Hβ, 2O III, Hα, S1</td></tr><tr><td>27</td><td>22 58 29.86</td><td>-34 44 55.5</td><td></td><td></td><td>21.4</td><td>0.31265</td><td>0.00023</td><td>3.08</td><td></td></tr><tr><td>28</td><td>22 58 26.83</td><td>-34 45 02.6</td><td></td><td></td><td>20.0</td><td>0.31467</td><td>0.00032</td><td>3.53</td><td></td></tr><tr><td>31</td><td>22 58 36.47</td><td>-34 45 17.4</td><td>21.0</td><td>19.3</td><td>19.1</td><td>0.31779</td><td>0.00024</td><td>5.33</td><td></td></tr><tr><td>32</td><td>22 58 38.00</td><td>-34 45 24.1</td><td>20.2</td><td>17.7</td><td>18.2</td><td>0.31708</td><td>0.00024</td><td>5.65</td><td></td></tr><tr><td>33</td><td>22 58 41.30</td><td>-34 45 30.6</td><td>21.1</td><td>19.6</td><td>19.8</td><td>0.10193</td><td>0.00029</td><td></td><td>em:O II, Hβ, 2O III, Hα, S1</td></tr><tr><td>35</td><td>22 58 47.92</td><td>-34 45 45.0</td><td>21.7</td><td>19.5</td><td>20.2</td><td>0.17040</td><td>0.00011</td><td></td><td>em:Hβ, 2O III, Hα, S1</td></tr><tr><td>36</td><td>22 58 35.91</td><td>-34 45 50.1</td><td>19.8</td><td>17.7</td><td>18.4</td><td>0.31307</td><td>0.00019</td><td>5.65</td><td></td></tr><tr><td>37</td><td>22 58 29.65</td><td>-34 45 57.5</td><td></td><td></td><td>19.1</td><td>0.17051</td><td>0.00018</td><td>3.01</td><td>Uncertain</td></tr><tr><td>38</td><td>22 58 28.42</td><td>-34 46 02.3</td><td>22.0</td><td>19.8</td><td>19.2</td><td>0.30100</td><td>0.00026</td><td>5.63</td><td></td></tr><tr><td>40</td><td>22 58 24.92</td><td>-34 46 18.7</td><td>20.8</td><td>19.0</td><td>19.0</td><td>0.31779</td><td>0.00004</td><td></td><td>em:Hα</td></tr><tr><td>41</td><td>22 58 27.85</td><td>-34 46 26.3</td><td></td><td></td><td>19.7</td><td>0.31816</td><td>0.00033</td><td>4.55</td><td></td></tr><tr><td>42</td><td>22 58 29.75</td><td>-34 46 32.1</td><td>22.2</td><td>20.5</td><td>19.9</td><td>0.50228</td><td>0.00035</td><td>3.04</td><td></td></tr><tr><td>43</td><td>22 58 28.88</td><td>-34 46 40.3</td><td></td><td></td><td>20.2</td><td>0.31717</td><td>0.00033</td><td>3.68</td><td></td></tr><tr><td>44</td><td>22 58 40.93</td><td>-34 46 45.7</td><td>20.6</td><td>18.6</td><td>18.3</td><td>0.31523</td><td>0.00030</td><td>4.73</td><td></td></tr><tr><td>45</td><td>22 58 36.47</td><td>-34 46 51.2</td><td></td><td></td><td>20.6</td><td>0.31389</td><td>0.00019</td><td>4.66</td><td></td></tr><tr><td>46</td><td>22 58 51.00</td><td>-34 47 00.6</td><td>20.8</td><td>19.5</td><td>20.1</td><td>0.32953</td><td>0.00028</td><td>3.10</td><td></td></tr><tr><td>47</td><td>22 58 34.80</td><td>-34 47 07.1</td><td>22.2</td><td></td><td>19.3</td><td>0.31674</td><td>0.00019</td><td>6.24</td><td></td></tr><tr><td>48</td><td>22 58 29.14</td><td>-34 47 13.1</td><td>21.6</td><td>20.0</td><td>20.0</td><td>0.31462</td><td>0.00022</td><td>5.29</td><td></td></tr><tr><td>49</td><td>22 58 39.56</td><td>-34 47 17.4</td><td>21.8</td><td>19.1</td><td>20.0</td><td>0.31818</td><td>0.00024</td><td>4.89</td><td></td></tr><tr><td>50</td><td>22 58 48.11</td><td>-34 47 21.3</td><td></td><td></td><td>20.2</td><td>0.33032</td><td>0.00039</td><td>3.02</td><td>Very weak</td></tr><tr><td>51</td><td>22 58 46.31</td><td>-34 47 31.5</td><td>20.8</td><td>18.8</td><td>19.1</td><td>0.30954</td><td>0.00019</td><td>6.32</td><td></td></tr><tr><td>52</td><td>22 58 26.11</td><td>-34 47 37.5</td><td>22.6</td><td>20.9</td><td>18.2</td><td>0.31789</td><td>0.00042</td><td>3.04</td><td>Confirmed on H,K (Ca I)</td></tr><tr><td>54</td><td>22 58 33.80</td><td>-34 47 46.6</td><td>22.3</td><td>19.5</td><td>18.9</td><td>0.34779</td><td>0.00030</td><td>3.06</td><td>Weak</td></tr><tr><td>55a</td><td>22 58 33.96</td><td>-34 47 53.3</td><td></td><td></td><td>20.2</td><td>0.31776</td><td>0.00031</td><td>3.26</td><td></td></tr><tr><td>55b</td><td>22 58 33.96</td><td>-34 47 53.3</td><td></td><td></td><td></td><td>0.17199</td><td></td><td></td><td>em:Hβ, 2O III, Hα, S1</td></tr><tr><td>56</td><td>22 58 44.05</td><td>-34 47 59.4</td><td></td><td></td><td>18.4</td><td>0.31380</td><td>0.00015</td><td></td><td>Measured on H,K (Ca I)</td></tr><tr><td>57</td><td>22 58 49.74</td><td>-34 48 01.9</td><td>21.6</td><td>19.7</td><td>19.1</td><td>0.31451</td><td>0.00028</td><td>3.35</td><td></td></tr><tr><td>58</td><td>22 58 41.65</td><td>-34 48 06.7</td><td>21.9</td><td>19.2</td><td>19.2</td><td>0.31082</td><td>0.00028</td><td>6.10</td><td></td></tr><tr><td>60</td><td>22 58 44.45</td><td>-34 48 21.3</td><td></td><td></td><td>19.0</td><td>0.32473</td><td>0.00031</td><td>4.42</td><td></td></tr><tr><td>61</td><td>22 58 38.22</td><td>-34 48 27.8</td><td>20.7</td><td>18.6</td><td>19.7</td><td>0.72072</td><td>0.00014</td><td>3.05</td><td></td></tr><tr><td>62</td><td>22 58 42.81</td><td>-34 48 33.4</td><td>21.0</td><td>18.9</td><td>29.9</td><td>0.31090</td><td>0.00047</td><td>5.43</td><td></td></tr><tr><td>63</td><td>22 58 52.67</td><td>-34 48 39.1</td><td></td><td></td><td>20.2</td><td>0.31874</td><td>0.00024</td><td>4.98</td><td></td></tr><tr><td>64</td><td>22 58 31.46</td><td>-34 48 53.3</td><td></td><td></td><td>18.3</td><td>0.31447</td><td>0.00030</td><td>5.28</td><td></td></tr><tr><td>65</td><td>22 58 34.69</td><td>-34 49 01.3</td><td></td><td></td><td>20.6</td><td>0.47788</td><td>0.00023</td><td>5.33</td><td></td></tr></tbody></table>

panel of Fig. 21. But because these objects are still evolving, we can expect that nowadays they will have reached higher masses and metallicities and lower $\mu$ values: therefore we also computed the expected evolution from an age of the universe $t_{10} \simeq 10$ Gyr to the present time, assuming a linear dependence of $\mu(t) = 1 - (1 - \mu_{10})/t_{10} \times t$. This evolution is shown by the magenta symbols and magenta segments in the upper and lower panels of Fig. 21, respectively.

The lower panel of the figure also shows the $\pm 1 \sigma$ range of gas fractions in local spiral galaxies, taken from McGaugh & de Blok (1997, see Fig. 22). The comparison tells us that, at the current pace of evolution, most active galaxies in AC114 will not be able to reach the same level of gas processing as galaxies in the local universe.

Some active galaxies in the upper panel of Fig. 21 are located in the region of passive galaxies, so a comparable yield was adopted to compute their evolutionary tracks. These are galaxies Q1-30, Q1-37,

Q4-36, Q4-48, and Q4-56: from Fig. B2, it appears that the first three objects are relatively large galaxies with a disc/bulge morphology, therefore their high $D_h(4000)$ values might be due to the fact that our VIMOS slits include a large fraction of the central, older, and more metal-rich regions. To some extent this also applies to Q4-48, while the case of Q4-36 requires more investigation, because its classification as a high luminosity galaxy does not seem granted by its appearance.

### 4.1.2 Relationships for passive and active galaxies

To compare the MZR of AC114 galaxies with other relations from the literature, they are plotted again in Fig. 23, without model tracks. Weighted linear fits to the data run nearly parallel to the model tracks discussed in the previous section, both for passive and active
galaxies. Therefore in our scenario, MZRs for AC114 objects are naturally generated by galaxy evolution.

In the lower panel of the figure, dashed blue and red lines are the relationships for active and passive galaxies found by Peng et al. (2015), who analysed the Sloan Digital Sky Survey (SDSS) spectra of local galaxies ($z \approx 0.05$). Clearly, galaxies in the AC114 cluster have much lower metallicities than field ones, and for the case of passive galaxies, we must conclude that the dense cluster environment curtailed star formation of its more massive members in a short time after their formation.

Active galaxies are evolving along different tracks than passive ones, probably because of lower metal yields. And they are also evolving slower, as it can be inferred from their younger ages and larger mass fractions. We also expect that, even if allowed to reach the end of their chemical evolution, they would still be ~1 dex more metal poor than local active galaxies. The likely explanation is that the cluster environment facilitates the loss of metals from these lower mass objects, thus reducing their effective yields even further.

An evolutionary scenario would then be that the first objects to form got the largest masses, formed significant amounts of metals in SF bursts that lasted only a few Gyr, cut short through their mutual interactions. The stripped gas stayed in the cluster potential and is now facilitating the loss of metals from less massive galaxies that formed later via ram pressure stripping.

## 5 SUMMARY

In this paper, we investigate the MZR for galaxies in the AC114 from 7 h of VIMOS/MR data collected at the European Southern Observatory-VLT telescope in 2009. The dynamical analysis of Proust et al. (2015) allowed us to select cluster members, whose spectra are here analysed with models from Bruzual & Charlot (2003).

Active and passive galaxies are identified based on the presence/absence of the [O II] λ3727, and/or [O III] λλ4959, 5007 and/or Hβ emission lines, depending on the galaxy redshift, and we conclude that active galaxies have lower average masses and metallicities than passive ones.

We establish that the MZR of the cluster is found to be steeper than that for galaxies in the local universe. In a forthcoming paper, the MZR of active galaxies, based on the oxygen abundance of their gaseous component, will be presented and discussed in light of the present results. Fig. 2 showed that passive and active galaxies tend to occupy central and external regions, respectively. Therefore the results above show the well-known fact that galaxy evolution in the centre of galaxy clusters is faster than that in their periphery. In the central regions of AC114, and in the course of the last 9.8 Gyr, galaxies reached masses and metallicities that are comparable to present-day galaxies, while in the outskirts galaxies are still forming stars, and in their past they have built substantially less mass than central objects.

The case of large active galaxies highlights the fact that conclusions about their global properties are influenced by population gradients within their bodies. Therefore a conclusive study could only be realized by a 2D mapping of their SEDs, such as can be afforded by IFU instruments: in this respect, MUSE at the VLT would be an obvious choice.

## ACKNOWLEDGEMENTS

DP thanks ESO in the context of the *Visiting Scientists* program for its hospitality at Santiago (Chile). We thank the anonymous referee

for a careful reading of the manuscript, which greatly improved the presentation of our work. Alain Andrade is also thanked for helping in the revision of the paper.

## DATA AVAILABILITY

The complete redshift values of the 163 galaxies of this work are listed in Table 5 and the description of each column can be found in Section 2.1.

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## APPENDIX A: SPECTRA OF GALAXIES
IDENTIFIED AS ACTIVE BASED ON [O II] λ3727
<figure><img src="image_26.png" /><figcaption>**Figure A1.** Spectra of galaxies identified as active based on [O II] λ3727. bottom</figcaption></figure>

APPENDIX B: POSTAGE STAMPS
<figure><img src="image_27.png" /><figcaption>**Figure B1.** Images of galaxies classified as passive, from the VIMOS pre-imaging, sorted in luminosity from top to bottom. The number identifies the slit, while the quadrant can be evinced from Table 3. Each frame is 10.5 arcsec × 10.5 arcsec, and the image quality is ~1 arcsec FWHM. Most galaxies have regular shapes, as expected from E/SO types, but notable exceptions are galaxies 44, 51, 49, 53, and 58, which appear to be interacting with smaller neighbours.</figcaption></figure>
<figure><img src="image_28.png" /><figcaption>**Figure B2.** Same as Fig. B1 for galaxies classified as active.</figcaption></figure>

## APPENDIX C: GALAXIES IN COMMON WITH CS87

After transforming from the B1950.0 to the J2000.0² system, coordinates were used together with a matching radius of 10 arcsec, to find common objects between this work and Couch & Sharples (1987). The result is shown in Fig. C1 and is summarized in Table C1, where galaxies are listed from top to bottom in order of increasing separation on sky. There are only a few galaxies in common, and in particular only three have null separation on sky; galaxy Q4-47

might also be a possible match, because the difference in redshift is comparable to the first three. The other three galaxies are likely not the same object in the two works, because of the large difference in redshift. Besides, [O II] λ3727 is detected in galaxy C243 but it is absent in our Q4-44; and conversely, it is not present in C134 but we detect it in Q4-56, as Fig. C2 shows. Indeed, Q4-56 is classified as ‘active’ as we have shown above.

Based on their colours, all four common galaxies belong to the ‘red sequence’ in CS87 and have normal Hδ absorption, with the exception of C832 which has a marginally stronger absorption. Fig. C2 shows the spectra of the seven galaxies, and it confirms the absence of emission lines in the four best matches.

<footnote n="2">²Using the NED coordinate calculator https://ned.ipac.caltech.edu/</footnote>
<table><caption>**Table C1.** Parameters of galaxies in common between this work and Couch & Sharples (1987). Columns 1 and 2 are the identifications in the respective works; columns 3–5, are coordinates in this work and the separation in arcseconds; columns 6 and 7 are the redshift measured in this work and the difference with CS87; columns 8–10 are the colours and magnitude from CS87 and the difference in magnitude with the present work; column 11 is the cross-correlation quality from CS87; columns 12 and 13 are the [O II] λ3727 and Hδ lines measurements from CS87; columns 14 and 15 are the metallicity and error from this work; and finally, the last column is our galaxy classification, as(p)assive or (a)ctive. An empty line separates possible matches from unlikely ones.</caption><thead><tr><th>S23<br>1</th><th>CS87<br>2</th><th>RA[2000]<br>3</th><th>Dec.EC[2000]<br>d (arcsec)<br>4</th><th>z<br>5</th><th>Δz<br>6</th><th>Δz<br>7</th><th>B<sub>1</sub> - R<sub>F</sub><br>8</th><th>R<sub>F</sub><br>9</th><th>ΔR<br>10</th><th>r<br>11</th><th>[O II]<br>12</th><th>Hδ<br>13</th><th>[m/H]<br>14</th><th>ε[m/H]<br>15</th><th>Flag<br>16</th></tr></thead><tbody><tr><td>Q4-51</td><td>C5</td><td>344.693</td><td>-34.792</td><td>0.0</td><td>0.310</td><td>-0.0011</td><td>2.20</td><td>19.19</td><td>-0.09</td><td>6.0</td><td></td><td></td><td>-0.29</td><td>0.36</td><td>p</td></tr><tr><td>Q4-58</td><td>C145</td><td>344.674</td><td>-34.802</td><td>0.0</td><td>0.311</td><td>-0.0015</td><td>2.37</td><td>19.18</td><td>0.02</td><td>7.1</td><td></td><td>1.3</td><td>-0.40</td><td>0.24</td><td>p</td></tr><tr><td>Q4-49</td><td>C247</td><td>344.665</td><td>-34.788</td><td>0.0</td><td>0.318</td><td>-0.0015</td><td>2.46</td><td>19.12</td><td>0.88</td><td>7.6</td><td></td><td></td><td>-0.18</td><td>0.26</td><td>p</td></tr><tr><td>Q4-47</td><td>C832</td><td>344.645</td><td>-34.784</td><td>3.6</td><td>0.317</td><td>-0.0011</td><td>2.25</td><td>19.98</td><td>-0.68</td><td>5.3</td><td></td><td>3.6</td><td>-0.57</td><td>0.27</td><td>p</td></tr><tr><td>Q4-44</td><td>C243</td><td>344.670</td><td>-34.779</td><td>2.9</td><td>0.315</td><td>-0.0100</td><td>1.58</td><td>19.57</td><td>-1.27</td><td>2.2</td><td>19.4</td><td>5.2</td><td>-0.08</td><td>0.08</td><td>p</td></tr><tr><td>Q4-63</td><td>C191</td><td>344.720</td><td>-34.813</td><td>7.8</td><td>0.319</td><td>0.0144</td><td>1.63</td><td>19.69</td><td>0.51</td><td>4.7</td><td></td><td>5.6</td><td>-1.36</td><td>0.35</td><td>p</td></tr><tr><td>Q4-56</td><td>C134</td><td>344.681</td><td>-34.801</td><td>9.5</td><td>0.314</td><td>0.2172</td><td>0.86</td><td>19.66</td><td>-1.26</td><td></td><td></td><td></td><td>-0.04</td><td>0.15</td><td>a</td></tr></tbody></table>

<figure><img src="image_29.png" /><figcaption>**Figure C1.** Representation on sky of galaxies from this work (black symbols), and from Couch and Sharples (1987, open circles). After transforming coordinates from B1950.0 to J2000.0, objects were matched with a radius of 10 arcsec. Matching galaxies are marked with a double circle.</figcaption></figure>

## APPENDIX D: SUMMARY OF CLASSIFICATION OF ALL GALAXIES

The results of Section 2.2 are summarized in Table D1. In the table, and from left to right, columns contain an ordinal number, the VIMOS quadrant and slit, the redshift, the classification flag

<figure><img src="image_30.png" /><figcaption>**Figure C2.** Spectra of galaxies in common with CS87. The separation on sky is displayed in each panel, with separation increasing from top to bottom. Vertical dotted lines mark the position of [O II] λ3727 and Hδ.</figcaption></figure>

(a)ctive or (p)assive, and notes: this scheme is repeated in three blocks. Notes are the following: [O II] = galaxy identified by the presence of [O II] λ3727; OI = bad sky subtraction of [O I] λ5579 oxygen line, which creates a spurious [O II] λ3727 emission line for objects at redshift ≃ 0.4967; M-dwarf = object is actually a local star; :: = spectrum is uncertain and is not used in this paper.
<table><caption>**Table D1.** Classification of galaxies as described in Section 2.2.</caption><thead><tr><th>n</th><th>q</th><th>sl</th><th>z</th><th>a/p</th><th>Notes</th><th>n</th><th>q</th><th>sl</th><th>z</th><th>a/p</th><th>Notes</th><th>n</th><th>q</th><th>sl</th><th>z</th><th>a/p</th><th>Notes</th></tr></thead><tbody><tr><td>1</td><td>1</td><td>1</td><td>0.3985</td><td>a</td><td>[O II]</td><td>56</td><td>2</td><td>29</td><td>0.523</td><td>a</td><td></td><td>110</td><td>4</td><td>7</td><td>0.1695</td><td>a</td><td></td></tr><tr><td>2</td><td>1</td><td>2</td><td>0.3531</td><td>a</td><td></td><td>57</td><td>2</td><td>31</td><td>0.4972</td><td>a</td><td></td><td>111</td><td>4</td><td>8</td><td>0.1706</td><td>a</td><td></td></tr><tr><td>3</td><td>1</td><td>3</td><td>0.05717</td><td>a</td><td></td><td>58</td><td>2</td><td>32</td><td>0.3091</td><td>a</td><td></td><td>112</td><td>4</td><td>9</td><td>0.2584</td><td>p</td><td></td></tr><tr><td>4</td><td>1</td><td>5</td><td>0.05842</td><td>a</td><td></td><td>59</td><td>2</td><td>33</td><td>0.5797</td><td>a</td><td></td><td>113</td><td>4</td><td>10</td><td>0.3123</td><td>p</td><td></td></tr><tr><td>5</td><td>1</td><td>8</td><td>0.3806</td><td>a</td><td></td><td>60</td><td>2</td><td>35</td><td>0.3129</td><td>p</td><td></td><td>114</td><td>4</td><td>11</td><td>0.3047</td><td>p</td><td></td></tr><tr><td>6</td><td>1</td><td>10</td><td>0.2194</td><td>p</td><td></td><td>61</td><td>2</td><td>36</td><td>0.4637</td><td>a</td><td></td><td>115</td><td>4</td><td>12</td><td>0.3117</td><td>p</td><td></td></tr><tr><td>7</td><td>1</td><td>11</td><td>0.626</td><td>a</td><td>[O II]</td><td>62</td><td>2</td><td>37</td><td>0.1396</td><td>a</td><td></td><td>116</td><td>4</td><td>13</td><td>0.4756</td><td>p</td><td></td></tr><tr><td>8</td><td>1</td><td>12</td><td>0.2213</td><td>a</td><td></td><td>63</td><td>2</td><td>38</td><td>0.2987</td><td>a</td><td></td><td>117</td><td>4</td><td>14</td><td>0.3046</td><td>a</td><td></td></tr><tr><td>9</td><td>1</td><td>13</td><td>0.4098</td><td>p</td><td></td><td>64</td><td>2</td><td>39</td><td>0.372</td><td>a</td><td></td><td>118</td><td>4</td><td>15</td><td>0.308</td><td>a</td><td></td></tr><tr><td>10</td><td>1</td><td>15</td><td>0.07309</td><td>a</td><td></td><td>65</td><td>2</td><td>40</td><td>0.4191</td><td>p</td><td></td><td>119</td><td>4</td><td>16</td><td>0.3185</td><td>a</td><td>::</td></tr><tr><td>11</td><td>1</td><td>16</td><td>0.4082</td><td>a</td><td>[O II]</td><td>66</td><td>2</td><td>41</td><td>0.5403</td><td>a</td><td>[O II]</td><td>120</td><td>4</td><td>18</td><td>0.527</td><td>p</td><td></td></tr><tr><td>12</td><td>1</td><td>17</td><td>0.6316</td><td>p</td><td></td><td>67</td><td>3</td><td>1</td><td>0.3295</td><td>a</td><td></td><td>121</td><td>4</td><td>19</td><td>0.3107</td><td>a</td><td></td></tr><tr><td>13</td><td>1</td><td>18</td><td>0.313</td><td>a</td><td></td><td>68</td><td>3</td><td>2</td><td>0.3331</td><td>a</td><td></td><td>122</td><td>4</td><td>20</td><td>0.3086</td><td>p</td><td></td></tr><tr><td>14</td><td>1</td><td>19</td><td>0.4088</td><td>a</td><td></td><td>69</td><td>3</td><td>3</td><td>0.3313</td><td>p</td><td></td><td>123</td><td>4</td><td>21</td><td>0.3061</td><td>p</td><td></td></tr><tr><td>15</td><td>1</td><td>20</td><td>0.2319</td><td>p</td><td></td><td>70</td><td>3</td><td>4</td><td>0.2126</td><td>a</td><td></td><td>124</td><td>4</td><td>22</td><td>0.3145</td><td>a</td><td></td></tr><tr><td>16</td><td>1</td><td>22</td><td>0.4102</td><td>a</td><td></td><td>71</td><td>3</td><td>5</td><td>0.3319</td><td>a</td><td></td><td>125</td><td>4</td><td>23</td><td>0.3227</td><td>p</td><td></td></tr><tr><td>17</td><td>1</td><td>24</td><td>0.3337</td><td>p</td><td></td><td>72</td><td>3</td><td>6</td><td>0.4968</td><td>p</td><td>OI</td><td>126</td><td>4</td><td>24</td><td>0.3145</td><td>p</td><td></td></tr><tr><td>18</td><td>1</td><td>25</td><td>0.486</td><td>p</td><td></td><td>73</td><td>3</td><td>8</td><td>0.3997</td><td>p</td><td>::</td><td>127</td><td>4</td><td>25</td><td>0.3013</td><td>p</td><td></td></tr><tr><td>19</td><td>1</td><td>26</td><td>0.5335</td><td>a</td><td>[O II]</td><td>74</td><td>3</td><td>10</td><td>0.3137</td><td>p</td><td>::</td><td>128</td><td>4</td><td>26</td><td>0.3246</td><td>a</td><td></td></tr><tr><td>20</td><td>1</td><td>27</td><td>0.4662</td><td>p</td><td></td><td>75</td><td>3</td><td>11</td><td>0.2125</td><td>a</td><td></td><td>129</td><td>4</td><td>27</td><td>0.3127</td><td>p</td><td></td></tr><tr><td>21</td><td>1</td><td>28</td><td>0.3512</td><td>p</td><td></td><td>76</td><td>3</td><td>12</td><td>0.3094</td><td>a</td><td></td><td>130</td><td>4</td><td>28</td><td>0.3147</td><td>p</td><td></td></tr><tr><td>22</td><td>1</td><td>30</td><td>0.3186</td><td>a</td><td>[O II]</td><td>77</td><td>3</td><td>13</td><td>0.6515</td><td>a</td><td></td><td>131</td><td>4</td><td>31</td><td>0.3178</td><td>p</td><td></td></tr><tr><td>23</td><td>1</td><td>31</td><td>0.3334</td><td>p</td><td></td><td>78</td><td>3</td><td>15</td><td>0.4756</td><td>p</td><td></td><td>132</td><td>4</td><td>32</td><td>0.3171</td><td>p</td><td></td></tr><tr><td>24</td><td>1</td><td>34</td><td>0.6319</td><td>p</td><td></td><td>79</td><td>3</td><td>16</td><td>0.1774</td><td>a</td><td></td><td>133</td><td>4</td><td>33</td><td>0.1019</td><td>a</td><td></td></tr><tr><td>25</td><td>1</td><td>36</td><td>0.4998</td><td>a</td><td>[O II]</td><td>80</td><td>3</td><td>17</td><td>0.4967</td><td>p</td><td>OI</td><td>134</td><td>4</td><td>35</td><td>0.1704</td><td>a</td><td></td></tr><tr><td>26</td><td>1</td><td>37</td><td>0.316</td><td>a</td><td></td><td>81</td><td>3</td><td>18</td><td>0.2218</td><td>p</td><td></td><td>135</td><td>4</td><td>36</td><td>0.3131</td><td>a</td><td>[O II]</td></tr><tr><td>27</td><td>1</td><td>38</td><td>0.498</td><td>p</td><td></td><td>82</td><td>3</td><td>19</td><td>0.1586</td><td>p</td><td></td><td>136</td><td>4</td><td>37</td><td>0.1705</td><td>p</td><td></td></tr><tr><td>28</td><td>1</td><td>40</td><td>0.3228</td><td>a</td><td></td><td>83</td><td>3</td><td>20</td><td>0.3549</td><td>a</td><td></td><td>137</td><td>4</td><td>38</td><td>0.301</td><td>p</td><td></td></tr><tr><td>29</td><td>1</td><td>41</td><td>0.4764</td><td>p</td><td></td><td>84</td><td>3</td><td>21</td><td>0.3523</td><td>p</td><td>::</td><td>138</td><td>4</td><td>39</td><td>0.3259</td><td>p</td><td>M-dwarf</td></tr><tr><td>30</td><td>1</td><td>44</td><td>0.5778</td><td>a</td><td></td><td>85</td><td>3</td><td>23</td><td>0.3537</td><td>p</td><td>::</td><td>139</td><td>4</td><td>40</td><td>0.3178</td><td>a</td><td></td></tr><tr><td>31</td><td>2</td><td>1</td><td>0.2578</td><td>a</td><td></td><td>86</td><td>3</td><td>24</td><td>0.3039</td><td>p</td><td>::</td><td>140</td><td>4</td><td>41</td><td>0.3182</td><td>p</td><td></td></tr><tr><td>32</td><td>2</td><td>2</td><td>0.4958</td><td>a</td><td></td><td>87</td><td>3</td><td>25</td><td>0.5954</td><td>p</td><td></td><td>141</td><td>4</td><td>42</td><td>0.5023</td><td>p</td><td></td></tr><tr><td>33</td><td>2</td><td>3</td><td>0.41</td><td>a</td><td></td><td>88</td><td>3</td><td>26</td><td>0.3148</td><td>p</td><td></td><td>142</td><td>4</td><td>43</td><td>0.3172</td><td>p</td><td></td></tr><tr><td>34</td><td>2</td><td>4</td><td>0.4085</td><td>a</td><td></td><td>89</td><td>3</td><td>27</td><td>0.4969</td><td>p</td><td>OI</td><td>143</td><td>4</td><td>44</td><td>0.3152</td><td>p</td><td></td></tr><tr><td>35</td><td>2</td><td>5</td><td>0.4144</td><td>p</td><td></td><td>90</td><td>3</td><td>28</td><td>0.2576</td><td>p</td><td></td><td>144</td><td>4</td><td>45</td><td>0.3139</td><td>p</td><td></td></tr><tr><td>36</td><td>2</td><td>6</td><td>0.4228</td><td>p</td><td></td><td>91</td><td>3</td><td>29</td><td>0.4728</td><td>a</td><td>::</td><td>145</td><td>4</td><td>46</td><td>0.3295</td><td>a</td><td>[O II]</td></tr><tr><td>37</td><td>2</td><td>7</td><td>0.5618</td><td>p</td><td></td><td>92</td><td>3</td><td>30</td><td>0.4022</td><td>a</td><td></td><td>146</td><td>4</td><td>47</td><td>0.3167</td><td>p</td><td></td></tr><tr><td>38</td><td>2</td><td>8</td><td>0.2574</td><td>a</td><td></td><td>93</td><td>3</td><td>31</td><td>0.332</td><td>a</td><td></td><td>147</td><td>4</td><td>48</td><td>0.3146</td><td>a</td><td>[O II]</td></tr><tr><td>39</td><td>2</td><td>9</td><td>0.3708</td><td>a</td><td></td><td>94</td><td>3</td><td>33</td><td>0.3448</td><td>p</td><td></td><td>148</td><td>4</td><td>49</td><td>0.3182</td><td>p</td><td></td></tr><tr><td>40</td><td>2</td><td>10</td><td>0.4085</td><td>p</td><td>::</td><td>95</td><td>3</td><td>34</td><td>0.3518</td><td>a</td><td></td><td>149</td><td>4</td><td>50</td><td>0.3303</td><td>p</td><td></td></tr><tr><td>41</td><td>2</td><td>11</td><td>0.3455</td><td>p</td><td>::</td><td>96</td><td>3</td><td>35</td><td>0.4309</td><td>a</td><td></td><td>150</td><td>4</td><td>51</td><td>0.3095</td><td>p</td><td></td></tr><tr><td>42</td><td>2</td><td>12</td><td>0.5952</td><td>p</td><td></td><td>97</td><td>3</td><td>36</td><td>0.2033</td><td>a</td><td></td><td>151</td><td>4</td><td>52</td><td>0.3179</td><td>p</td><td></td></tr><tr><td>43</td><td>2</td><td>13</td><td>0.2701</td><td>p</td><td></td><td>98</td><td>3</td><td>38</td><td>0.4321</td><td>p</td><td>::</td><td>152</td><td>4</td><td>54</td><td>0.3478</td><td>p</td><td></td></tr><tr><td>44</td><td>2</td><td>14</td><td>0.3737</td><td>a</td><td>[O II]</td><td>99</td><td>3</td><td>39</td><td>0.3994</td><td>a</td><td></td><td>153</td><td>4</td><td>55</td><td>0.172</td><td>a</td><td></td></tr><tr><td>45</td><td>2</td><td>15</td><td>0.4105</td><td>p</td><td></td><td>100</td><td>3</td><td>40</td><td>0.3183</td><td>p</td><td></td><td>154</td><td>4</td><td>56</td><td>0.3138</td><td>a</td><td>[O II]</td></tr><tr><td>46</td><td>2</td><td>16</td><td>0.5682</td><td>a</td><td>[O II]</td><td>101</td><td>3</td><td>43</td><td>0.5101</td><td>p</td><td>::</td><td>155</td><td>4</td><td>57</td><td>0.3145</td><td>a</td><td>::</td></tr><tr><td>47</td><td>2</td><td>18</td><td>0.6152</td><td>a</td><td>[O II]</td><td>102</td><td>3</td><td>44</td><td>0.2246</td><td>p</td><td>::</td><td>156</td><td>4</td><td>58</td><td>0.3108</td><td>p</td><td></td></tr><tr><td>48</td><td>2</td><td>19</td><td>0.3771</td><td>a</td><td>[O II]</td><td>103</td><td>3</td><td>45</td><td>0.6279</td><td>p</td><td></td><td>157</td><td>4</td><td>59</td><td>0.3183</td><td>p</td><td>M-dwarf</td></tr><tr><td>49</td><td>2</td><td>21</td><td>0.413</td><td>a</td><td>[O II]</td><td>104</td><td>3</td><td>46</td><td>0.5215</td><td>a</td><td>[O II]</td><td>158</td><td>4</td><td>60</td><td>0.3183</td><td>a</td><td></td></tr><tr><td>50</td><td>2</td><td>22</td><td>0.391</td><td>a</td><td></td><td>105</td><td>3</td><td>49</td><td>0.2066</td><td>p</td><td></td><td>159</td><td>4</td><td>61</td><td>0.7207</td><td>p</td><td></td></tr><tr><td>51</td><td>2</td><td>23</td><td>0.4131</td><td>p</td><td></td><td>106</td><td>4</td><td>2</td><td>0.3198</td><td>p</td><td></td><td>160</td><td>4</td><td>62</td><td>0.2838</td><td>p</td><td></td></tr><tr><td>52</td><td>2</td><td>24</td><td>0.3797</td><td>a</td><td></td><td>107</td><td>4</td><td>3</td><td>0.4139</td><td>a</td><td>[O II]</td><td>161</td><td>4</td><td>63</td><td>0.3187</td><td>p</td><td></td></tr><tr><td>53</td><td>2</td><td>26</td><td>0.4868</td><td>a</td><td></td><td>108</td><td>4</td><td>4</td><td>0.3111</td><td>p</td><td></td><td>162</td><td>4</td><td>64</td><td>0.3145</td><td>p</td><td></td></tr><tr><td>54</td><td>2</td><td>27</td><td>0.4964</td><td>a</td><td>[O II]</td><td>109</td><td>4</td><td>5</td><td>0.4135</td><td>a</td><td></td><td>163</td><td>4</td><td>65</td><td>0.4779</td><td>p</td><td></td></tr><tr><td>55</td><td>2</td><td>28</td><td>0.6136</td><td>p</td><td>::</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr></tbody></table>

This paper has been typeset from a *TEX/LATEX* file prepared by the author.