bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Application of Contrast Media for In Vivo Feature Enhancement in X-Ray Computed Tomography of Soil-Grown Plant Roots
Authors: Keyes Samuel D. , Gostling Neil J. , Cheung Jessica H. , Roose Tiina , Sinclair Ian , Marchant Alan 
Published: March 2017

AbstractThe use of in vivo X-ray microcomputed tomography (μCT) to study plant root systems has become routine, but is often hampered by poor contrast between roots, soil, soil water, and soil organic matter. In clinical radiology, imaging of poorly contrasting regions is frequently aided by the use of radio-opaque contrast media. In this study, we present evidence for the utility of iodinated contrast media (ICM) in the study of plant root systems using μCT. Different dilutions of an ionic and nonionic ICM (Gastrografin 370 and Niopam 300) were perfused into the aerial vasculature of juvenile pea plants via a leaf flap (Pisum sativum). The root systems were imaged via μCT, and a variety of image-processing approaches used to quantify and compare the magnitude of the contrast enhancement between different regions. Though the treatment did not appear to significantly aid extraction of full root system architectures from the surrounding soil, it did allow the xylem and phloem units of seminal roots and the vascular morphology within rhizobial nodules to be clearly visualized. The nonionic, low-osmolality contrast agent Niopam appeared to be well tolerated by the plant, whereas Gastrografin showed evidence of toxicity. In summary, the use of iodine-based contrast media allows usually poorly contrasting root structures to be visualized nondestructively using X-ray μCT. In particular, the vascular structures of roots and rhizobial nodules can be clearly visualized in situ.
Study of the growth of massive galaxies based on their outer stellar populations
Authors: Karabal Emin 
Published: March 2017

AbstractThe outskirts of early-type galaxies (ETGs) play a key role to shed light on the mass assembly of galaxies. Deep imaging has become one of the main tools to study these regions, however artificial halos caused by bright sources hampers the photometric analysis. To get around the problem, extended PSFs are built and deconvolution is performed on images.
Extended HI disks in nearby spiral galaxies
Authors: Bosma Albert 
Published: March 2017

AbstractIn this short write-up, I will concentrate on a few topics of interest. In the 1970s I found very extended HI disks in galaxies such as NGC 5055 and NGC 2841, out to 2 - 2.5 times the Holmberg radius. Since these galaxies are warped, a “tilted ring model” allows rotation curves to be derived, and evidence for dark matter to be found. The evaluation of the amount of dark matter is hampered by a disk-halo degeneracy, which can possibly be broken by observations of velocity dispersions in both the MgI region and the CaII region.
On the merger origin of nuclear star clusters
Authors: Tsatsi Athanasia , Mastrobuono-Battisti Alessandra 
Published: March 2017

AbstractNuclear Star Clusters (NSCs) are commonly observed in the centers of most galaxies, including our Milky Way (MW). While their study can reveal important information about the innermost regions of galaxies, the physical processes regulating their formation are still poorly understood. We explore a possible merger origin of NSCs by studying direct N-body simulations of globular clusters (GCs) that are initially randomly distributed in the outskirts and consecutively infall to the center of a MW-like nuclear bulge. We find that the NSC that forms through this process shows a significant amount of rotation, and both morphological and kinematic properties are comparable with observations of the MW NSC. We show that no fine-tuning of the orientation of the infalling GCs is necessary to result in a rotating NSC. This study shows the plausibility of the cluster infall scenario and can help towards setting better constraints to the formation history of NSCs.
Accretion phenomena in nearby star-forming dwarf galaxies
Authors: Annibali F. , Tosi M. , Aloisi A. , Bellazzini M. , Buzzoni A. , Cignoni M. , Ciotti L. , Cusano F. , Nipoti C. , Sacchi E. , Paris D. , Romano D. 
Published: March 2017

AbstractWe present two pilot studies for the search and characterization of accretion events in star-forming dwarf galaxies. Our strategy consists of two complementary approaches: i) the direct search for stellar substructures around dwarf galaxies through deep wide-field imaging, and ii) the characterization of the chemical properties in these systems up to large galacto-centric distances. We show our results for two star-forming dwarf galaxies, the starburst irregular NGC 4449, and the extremely metal-poor dwarf DDO 68.
Creating lenticular galaxies with mergers
Authors: Querejeta Miguel , Eliche-Moral M. Carmen , Tapia Trinidad , Borlaff Alejandro , van de Ven Glenn , Lyubenova Mariya , Martig Marie , Falcón-Barroso Jesús , Méndez-Abreu Jairo , Zamorano Jaime , Gallego Jesús 
Published: March 2017

AbstractLenticular galaxies (S0s) represent the majority of early-type galaxies in the local Universe, but their formation channels are still poorly understood. While galaxy mergers are obvious pathways to suppress star formation and increase bulge sizes, the marked parallelism between spiral and lenticular galaxies (e.g. photometric bulge–disc coupling) seemed to rule out a potential merger origin. Here, we summarise our recent work in which we have shown, throughN-body numerical simulations, that disc-dominated lenticulars can emerge from major mergers of spiral galaxies, in good agreement with observational photometric scaling relations. Moreover, we show that mergers simultaneously increase the light concentration and reduce the angular momentum relative to their spiral progenitors. This explains the mismatch in angular momentum and concentration between spirals and lenticulars recently revealed by CALIFA observations, which is hard to reconcile with simple fading mechanisms (e.g. ram-pressure stripping).
Redshift evolution of Tully-Fisher relation
Authors: Ferrero Ismael , Abadi Mario G. 
Published: March 2017

AbstractUsing the eagle cosmological simulation of galaxy formation we test the ability of the ΛCDM cosmological model to reproduce the Tully-Fisher relation (TFR) and its redshift evolution. We find that our simulated galaxies follow a TFR that is in good agreement with observed results up to z = 1, indicating no evolution in the slope and a weak decrease in the zero-point.
Spiral patterns beyond the optical radius: numerical simulations and synthetic HI observations
Authors: Khoperskov Sergey , Bertin Giuseppe 
Published: March 2017

AbstractThe outer parts of many galaxy disks exhibit extended spiral arms far beyond the optical radius. To understand the nature and the origin of such outer spiral structure, we investigate the propagation in the outer gaseous regions of large-scale spiral density waves excited in the bright optical disk. By means of 3D hydrodynamical simulations, we show that spiral density waves, penetrating in the gas through the outer Lindblad resonance, can indeed give rise to relatively regular patterns outside the bright optical stellar disk. The amplitude of spiral structure increases rapidly with radius. Beyond the optical radius, spirals become nonlinear and develop small-scale features related to shear-induced instabilities. We also construct the synthetic 21-cm data cubes extracted from simulated gaseous disks. Our synthetic HI observations point to the existence of specific kinematical features related to the presence of spiral pattern perturbations that should be found in deep HI observations.
Spatially-resolved stellar populations of nearby galaxies in multi-filter surveys
Authors: Roman Izaskun San , Cenarro A. Javier , Díaz-García Luis A. , López-Sanjuan Carlos , Varela Jesús ,   the J-PLUS Team
Published: March 2017

AbstractWe have developed a new technique using a novel approach to analyze unresolved stellar populations of spatially-resolved galaxies based on large sky multi-filter surveys. We have successfully applied this technique to 42 early-type galaxies in the ALHAMBRA survey. In agreement with some previous work, we find the gradients of early-type galaxies to be on average slightly positive in age and negative in metallicity at large radii (R > Reff). These mildly negative metallicity gradients support a merging scenario. The positive/flat age gradients could support a more uniformly distributed star formation or even secondary burst triggered by mergers.
Truncated disc surface brightness profiles produced by flares
Authors: Borlaff Alejandro , Eliche-Moral M. Carmen , Beckman John , Font Joan 
Published: March 2017

AbstractPrevious studies have discarded that flares in galactic discs may explain the truncation that are frequently observed in highly-inclined galaxies (Kregel et al. 2002). However, no study has systematically analysed this hypothesis using realistic models for the disc, the flare and the bulge. We derive edge-on and face-on surface brightness profiles for a series of realistic galaxy models with flared discs that sample a wide range of structural and photometric parameters across the Hubble Sequence, accordingly to observations. The surface brightness profile for each galaxy model has been simulated for edge-on and face-on views to find out whether the flared disc produces a significant truncation in the disc in the edge-on view compared to the face-on view or not. In order to simulate realistic images of disc galaxies, we have considered the observational distribution of the photometric parameters as a function of the morphological type for three mass bins (10 < log10(M/M⊙) < 10.7, 10.7 < log10(M/M⊙) < 11 and log10(M/M⊙) > 11), and four morphological type bins (S0–Sa, Sb–Sbc, Sc–Scd and Sd–Sdm). For each mass bin, we have restricted the photometric and structural parameters of each modelled galaxy to their characteristic observational ranges (μ0, disc, μeff, bulge, B/T, Mabs, reff, nbulge, hR, disc) and the flare in the disc (hz, disc/hR, disc, ∂hz, disc/∂R, see de Grijs & Peletier 1997, Graham 2001, López-Corredoira et al. 2002, Yoachim & Dalcanton 2006, Bizyaev et al. 2014, Mosenkov et al. 2015).Contrary to previous claims, the simulations show that realistic flared disks can be responsible for the truncations observed in many edge-on systems, preserving the profile of the non-flared analogous model in face-on view. These breaks reproduce the properties of the weak-to-intermediate breaks observed in many real Type-II galaxies in the diagram relating the radial location of the break (RbrkII) in units of the inner disk scale-length with the break strength S (Laine et al. 2014). Radial variation of the scale-height of the disc (flaring) can explain the existence of many breaks in edge-on galaxies, especially of those with low break strengths $S=\log _{10}\frac{h_{o}}{h_{i}} \sim \ [-0.3,-0.1]$.
Evolution of the anti-truncated stellar profiles of S0 galaxies since z=0.6 in the SHARDS survey
Authors: Borlaff Alejandro , Eliche-Moral M. Carmen , Beckman John , Pérez-González Pablo G. , Font Joan 
Published: March 2017

AbstractLenticular galaxies (S0s) are more likely to host anti-truncated (Type III) stellar discs than galaxies of later Hubble types. Previous work on Type-III S0s at z = 0 revealed that the characteristic parameters of the breaks obey tight scaling relations (Borlaff et al. 2014). These relation are similar in both S0’s and spirals, in optical and NIR, and for barred and non-barred galaxies (Eliche-Moral et al. 2015). We have analysed 3DHST images (Brammer et al. 2012) of S0 galaxies from the SHARDS survey (Pérez-González et al. 2013) in order to investigate if E/S0 and S0 galaxies with anti-truncated stellar profiles up to z ~ 0.6 follow similar scaling relations compared to the local sample. We find that the characteristic photometric parameters of Type-III S0s at 0.4 < z < 0.6 obey analogous scaling relations to those observed in their local counterparts, lying on top of the extrapolations of the local trends towards brighter magnitudes in several photometric diagrams and sharing similar trends and values in the hi – RbrkIII, ho – RbrkIII and hi – ho diagrams. We have measured the offsets in magnitudes between two subsets of the z ~ 0.5 and z = 0 samples with similar masses (log 10M/M⊙ ~ 10.7). The median offsets are: ΔμbrkIII = − 2.23+0.46−0.62, Δμ0, i = − 2.61+0.31−0.26 and Δμ0, o = − 2.31+0.57−0.78 mag arcsec-2. We find that PSF corrections in our images do not significantly affect the scaling relations obtained in our 0.2 < z < 0.6 sample. In conclusion, the existence of similar scaling relations in Type-III S0 discs since z ~ 0.6 implies that the structures of the inner and outer discs in anti-truncated S0s have been similarly linked in the last ~ 6 Gyr, posing strong constraints to the processes proposed to explain their formation.
Galaxies Unveiled: Rest-frame UV Clumps at 0.5 < z < 1.5
Authors: Soto Emmaris , de Mello Duilia F. , Rafelski Marc A. , Gardner Jonathan P. , Koekemoer Anton M. 
Published: March 2017

AbstractStudies of high redshift galaxies reveal compact sub-galactic regions of star formation, known as ‘clumps’. These ‘clumpy’ galaxies are useful for the study of galactic outskirts by enabling us to examine the radial progression of clumps over large time scales. We use the first deep high resolution NUV image from the Hubble Space Telescope covering intermediate redshifts to explore the implications this radial progression may have on galaxy evolution. From the analysis of 209 clumpy galaxies, we find that higher redshift clumps dominate the outer regions of galactic outskirts. This indicates that clumps may be migrating from the outskirts inward toward their galactic centers.
Local analogs of high-redshift galaxies: Interstellar medium conditions
Authors: Bian Fuyan , Kewley Lisa J. , Dopita Michael A. , Juneau Stephanie 
Published: March 2017

AbstractLocal analog galaxies play an important role in understanding the properties of high-redshift galaxies. We present a method to select a type of local analog that closely resembles the ionized interstellar medium conditions in high-redshift galaxies. These galaxies are selected based on their locations in the [O III]/Hβ versus [N II]/Hα nebular emission-line diagnostic diagram. The ionization parameters and electron densities in these analogs are comparable to those in z ≃ 2 − 3 galaxies, but higher than those in normal SDSS galaxies by ≃ 0.6 dex and ≃ 0.9 dex, respectively. We find that the high sSFR and SFR surface density can enhance the electron densities and the ionization parameters, but still cannot fully explain the difference in ISM condition between nearby galaxies and the local analogs/high-redshift galaxies.
SITELLE at the CFHT
Authors: Rousseau-Nepton Laurie , Robert Carmelle , Drissen Laurent , Martin R. Pierre , Martin Thomas ,   the SITELLE Collaboration
Published: March 2017

AbstractSITELLE is the new imaging Fourier transform spectrograph of the Canada-France-Hawaii Telescope. It produces an impressive 4 million spectra in a single datacube in selected bandpasses from 350 to 900 nm. Its large FOV (11′x11′) and its high spatial sampling (0.32′′/pixel, seeing limited) allow us to study extended objects with an unprecedented view (Drissen et al. 2014). SITELLE’s first observations of nearby galaxies revealed its capabilities to conduct detailed studies of emission line regions.
Hot gas in Milky Way size galaxies at z=0
Authors: Roca-Fàbrega Santi , Colin Pedro , Valenzuela Octavio , Figueras Francesca , Krongold Yair 
Published: March 2017

AbstractWe present a new set of cosmological Milky Way size galaxy simulations using ART. In our simulations the main system has been evolved inside a 28 Mpc cosmological box with a spatial resolution of 109 pc. At z=0 our systems have an Mvir = 6 − 8 × 1011 M⊙. In several of out models we have observed how a well defined disk is formed inside the dark matter halo and the overall amount of gas and stars is comparable with MW observations. Several non-axisymmetric structures arise out of the disk: spirals, bars and also a warp. We have also observed that a huge reservoir of hot gas is present at large distances from the disk, embedded in the dark matter halo region, accounting for only a fraction of the ”missing baryons”. Gas column density, emission (EM) and dispersion (DM) measure have been computed from inside the simulated disk at a position of 8 kpc from the center and in several directions. Our preliminary results reveal that the distribution of hot gas is non-isotropic according with observations (Gupta et al. 2012, Gupta et al. 2014). Also its metallic content presents a clear bimodality what is a consequence of a recent accretion of a satellite galaxy among others. After a careful analysis we confirm that due to the anisotropy in the gas distribution a new observational parameter needs to be defined to recover the real distribution of hot gas in the galactic halo (Roca-Fàbrega et al. 2016).
The MUSE QSO Blind Survey: A Census of Absorber Host Galaxies
Authors: Straka Lorrie A. ,   the MUSE GTO consortium
Published: March 2017

AbstractUnderstanding the distribution of gas in galaxies and its interaction with the IGM is crucial to complete the picture of galaxy evolution. At all redshifts, absorption features seen in QSO spectra serve as a unique probe of the gaseous content of foreground galaxies and the IGM, extending out to 200 kpc. Studies show that star formation history is intimately related to the co-evolution of galaxies and the IGM. In order to study the environments traced by absorption systems and the role of inflows and outflows, it is critical to measure the emission properties of host galaxies and their halos. We overcome the challenge of detecting absorption host galaxies with the MUSE integral field spectrograph on VLT. MUSE’s large field of view and sensitivity to emission lines has allowed a never-before seen match between the number density of absorbers along QSO sightlines and the number density of emission line galaxies within 200 kpc of the QSO. These galaxies represent a sample for which previously elusive connections can be made between mass, metallicity, SFR, and absorption.
Mapping the tidally disrupting Andromeda XXVII and its stellar stream
Authors: Preston Janet , Collins Michelle , Bonaca Ana , Ibata Rodrigo , Tollerud Erik , Geha Marla ,   the PAndAS collaboration
Published: March 2017

AbstractAndromeda XXVII is a dwarf spheroidal galaxy in the outskirts of the Andromeda galaxy (M31). It appears to be dissolving in to the Northern arc of M31, and could be the remnant of a strong tidal disruption. In the upcoming months, our spectroscopic program, which has measured velocities for multiple stars within both the dwarf galaxy progenitor and its stream (using the Keck II DEIMOS telescope, as part of the PAndAS survey), will determine velocity dispersions, scale radii and metallicities of both the dwarf and the stream. This in turn may enable us to ascertain the progenitor mass profile and determine whether it is cusped or cored.
A spatially-resolved study of initial mass function in the outer Galaxy
Authors: Yasui Chikako , Izumi Natsuko , Saito Masao , Kobayashi Naoto 
Published: March 2017

AbstractOutskirts of spiral galaxies, including our own, and dwarf irregular galaxies are known to have a different environment from the solar neighborhood, e.g., low metallicities ( ~ − 1 dex). Among them, the outer Galaxy is the closest and hence is so far the only site suitable for population studies of resolved stars on the same basis as solar neighborhood. We have obtained NIR images of young clusters in the outer Galaxy, using the Subaru 8.2-m telescope, and clearly resolved cluster members with mass detection limits of ~ 0.1 M⊙. Based on the fitting of K-band luminosity functions (KLFs) for four clusters, we found that the initial mass function (IMF) in the outer Galaxy is consistent with that in the solar neighborhood in terms of the high-mass slope and IMF peak. Upcoming observations with a higher spatial resolution and sensitivity, using JWST, TMT, etc., will allow us to extend spatially-resolved studies of the IMF to Local Group galaxies.
Probing the origin of thick disks using ultra-deep images
Authors: Martínez-Lombilla Cristina , Trujillo Ignacio , Knapen Johan H. 
Published: March 2017

AbstractThe origin of thick disks is still a matter of debate. To explore such structures in unprecedented detail, we have developed a technique to reach a surface brightness limit of 28.5-29 mag/arcsec2 with the combined g, r, i bands images from the IAC Stripe82 Legacy Project (Fliri & Trujillo, 2016). We present the characterisation of the thick disk in the edge-on galaxy UGC 01040. We carefully analyse the background subtraction and masking process. The effects of the PSF are considered through galaxy modelling. We present the study of radial and vertical surface brightness profiles, making a comparison between our data, the convolved and deconvolved models and its galactic components. We find that PSF effects are important, but can be accounted for. Our technique will allow us to model thick disks in external galaxies and elucidate their formation and evolutionary history.
Stellar populations in the outskirts of M31: the mid-infrared view
Authors: Barmby P. , Ravandi M. Rafiei 
Published: March 2017

AbstractThe mid-infrared provides a unique view of galaxy stellar populations, sensitive to both the integrated light of old, low-mass stars and to individual dusty mass-losing stars. We present results from an extended Spitzer/IRAC survey of M31 with total lengths of 6.6 and 4.4 degrees along the major and minor axes, respectively. The integrated surface brightness profile proves to be surprisingly difficult to trace in the outskirts of the galaxy, but we can also investigate the disk/halo transition via a star count profile, with careful correction for foreground and background contamination. Our point-source catalog allows us to report on mid-infrared properties of individual objects in the outskirts of M31, via cross-correlation with PAndAS, WISE, and other catalogs.
Outer spiral structure in disk galaxies
Authors: Patsis P.A. 
Published: March 2017

AbstractIn several grand design barred-spiral galaxies it is observed a second, fainter, outer set of spiral arms. Typical examples of objects of this morphology can be considered NGC 1566 and NGC 5248. I suggest that such an overall structure can be the result of two dynamical mechanisms acting in the disc. The bar and both spiral systems rotate with the same pattern speed. The inner spiral is reinforced by regular orbits trapped around the stable, elliptical, periodic orbits of the central family, while the outer system of spiral arms is supported by chaotic orbits. Chaotic orbits are also responsible for a rhomboidal area surrounding the inner barred-spiral region. In general there is a discontinuity between the two spiral structures at the corotation region.
The Vertical Displacement of the Milky Way Disk
Authors: Newberg Heidi Jo , Xu Yan 
Published: March 2017

AbstractAn oscillating vertical displacement of the Milky Way, with a wavelength of about 8 kpc and and amplitude of about 100 pc (increasing with distance from the Galactic center) is observed towards the Galactic anticenter. These oscillations are thought to be the result of disk perturbations from dwarf satellites of the Milky Way. They explain the Monoceros Ring and could be related to Milky Way spiral structure.