Search

This study compiles stellar populations and internal properties of ultra-diffuse galaxies (UDGs) to highlight correlations with their local environment, globular cluster (GC) richness, and star formation histories. Complementing our sample of 88 UDGs, we include 36 low-surface brightness dwarf galaxies with UDG-like properties, referred to as NUDGes (nearly-UDGs). All galaxies were studied using the same spectral energy distribution fitting methodology to explore what sets UDGs apart from other galaxies. We show that NUDGes are similar to UDGs in all properties except for being, by definition, smaller and having higher surface brightness. We find that UDGs and NUDGes show similar behaviours in their GC populations, with the most metal-poor galaxies hosting consistently more GCs on average. This suggests that GC content may provide an effective way to distinguish extreme galaxies within the low surface brightness regime alongside traditional parameters like size and surface brightness. We confirm previous results using clustering algorithms that UDGs split into two main classes, which might be associated with the formation pathways of a puffy dwarf and a failed galaxy. The clustering applied to the UDGs+NUDGes dataset yields an equivalent result. The difference in mass contained in the GC system suggests that galaxies in different environments have not simply evolved from one another but may have formed through distinct processes., Comment: Accepted for publication in MNRAS. 12 pages, 7 figures

We present an analysis of the spatial distribution of globular cluster (GC) systems of 118 nearby early-type galaxies in the Next Generation Virgo Cluster Survey (NGVS) and Mass Assembly of early-Type GaLAxies with their fine Structures (MATLAS) survey programs, which both used MegaCam on the Canada-France-Hawaii Telescope. We describe the procedure used to select GC candidates and fit the spatial distributions of GCs to a two-dimensional S\'ersic function, which provides effective radii (half number radii) and S\'ersic indices, and estimate background contamination by adding a constant term to the S'ersic function. In cases where a neighboring galaxy affects the estimation of the GC spatial distribution in the target galaxy, we fit two 2D S\'ersic functions, simultaneously. We also investigate the color distributions of GCs in our sample by using Gaussian Mixture Modeling. For GC systems with bimodal color distributions, we divide the GCs into blue and red subgroups and fit their respective spatial distributions with S\'ersic functions. Finally, we measure the total number of GCs based on our fitted S\'ersic function, and calculate the GC specific frequency., Comment: 31 pages, 10 Figures (115 additional figures are available in the ApJS online Journal), 2 Tables, accepted for publication in ApJS

A recent study of the distribution of dwarf galaxies in the MATLAS sample in galaxy groups revealed an excess of flattened satellite structures, reminiscent of the co-rotating planes of dwarf galaxies discovered in the local Universe. If confirmed, this lends credence to the plane-of-satellite problem and further challenges the standard model of hierarchical structure formation. However, with only photometric data and no confirmation of the satellite membership, the study could not address the plane-of-satellite problem in full detail. Here we present spectroscopic follow-up observations of one of the most promising planes-of-satellites candidates in the MATLAS survey, the satellite system of NGC 474. Employing MUSE at the VLT and full spectrum fitting, we studied 13 dwarf galaxy candidates and confirmed nine to be members of the field around NGC 474. Measuring the stellar populations of all observed galaxies, we find that the MATLAS dwarfs have lower metallicities than the Local Group dwarfs at given luminosity. Two dwarf galaxies may form a pair of satellites based on their close projection and common velocity. Within the virial radius, we do not find a significant plane-of-satellites, however, there is a sub-population of six dwarf galaxies which seem to be anti-correlated in phase-space. Due to the low number of dwarf galaxies, this signal may arise by chance. With over 2000 dwarf galaxy candidates found in the MATLAS survey, this remains an intriguing data set to study the plane-of-satellites problem in a statistical fashion once more follow-up observations have been conducted., Comment: 9 pages, 8 figures, 2 tables. Accepted for publication in Astronomy & Astrophysics (A&A)

Ultra diffuse galaxies, characterized by their low surface brightness and large physical size, constitute a subclass of dwarf galaxies that challenge our current understanding of galaxy formation and evolution. In this paper, we probe the properties of 74 UDGs, identified in the MATLAS survey, based on a comprehensive study of their globular cluster (GC) populations. We obtained high resolution HST imaging of these galaxies using the ACS F606W and F814W filters, allowing us to select GCs based on color and concentration index. After background subtraction and completeness correction, we calculate an overall total of 387 GCs. The number of GCs per galaxy ranges from 0 to 38, with the majority (64%) having low counts (0-2 GCs). On average, the more massive UDGs host a larger number of GCs. We find that our UDGs have specific frequencies (S_N) ranging from 0 to 91, with a small population (9%) with S_N > 30. The median S_N of our sample is similar to the one for the Perseus cluster UDGs, despite the fact that our UDGs are found in lower density environments. The S_N measurements for individual galaxies can extend beyond those found in Perseus, but remain below the values found for UDGs in the Virgo and Coma cluster. Based on a trending analysis of the S_N values with the host galaxy properties, we find trends with host galaxy size, roundness, color, and local density. For the UDGs with sufficiently high statistics, we study 2D density maps of the GC distributions, which show a variety of appearances: symmetric, asymmetric, off-center, and elongated. The UDGs with disturbed density maps also show disturbed stellar light morphologies. We further quantify the distribution by modeling it with a Sersic profile, finding R_{e,GC}/R_{e,gal} ~ 1.0, which indicates that the GCs follow the stellar light of the host galaxy., Comment: 20 pages, 17 figures, 2 tables, accepted for publication in A&A

We study the size and structure of globular clusters (GC) systems of 118 early-type galaxies from the NGVS, MATLAS, and ACSVCS surveys. Fitting S\'ersic profiles, we investigate the relationship between effective radii of GC systems ($R_{e, \rm gc}$) and galaxy properties. GC systems are 2--4 times more extended than host galaxies across the entire stellar mass range of our sample ($10^{8.3} < M_* < 10^{11.6}~M_{\odot}$). The relationship between $R_{e, \rm gc}$ and galaxy stellar mass exhibits a characteristic "knee" at a stellar mass of $M_p \simeq 10^{10.8}$, similar to galaxy $R_e$--stellar mass relationship. We present a new characterization of the traditional blue and red GC color sub-populations, describing them with respect to host galaxy $(g'-i')$ color ($\Delta_{gi}$): GCs with similar colors to their hosts have a "red" $\Delta_{gi}$, and those significantly bluer GCs have a "blue" $\Delta_{gi}$. The GC populations with red $\Delta_{gi}$, even in dwarf galaxies, are twice as extended as the stars, suggesting that formation or survival mechanisms favor the outer regions. We find a tight correlation between $R_{e, \rm gc}$ and the total number of GCs, with intrinsic scatter $\lesssim 0.1$ dex spanning two and three orders of magnitude in size and number, respectively. This holds for both red and blue subpopulations, albeit with different slopes. Assuming that $N_{GC, Total}$ correlates with $M_{200}$, we find that the red GC systems have effective radii of roughly 1-5\% $R_{\rm 200}$, while the blue GC systems in massive galaxies can have sizes as large as $\sim$10\% $R_{\rm 200}$. Environmental dependence on $R_{e, \rm gc}$ is also found, with lower density environments exhibiting more extended GC systems at fixed mass., Comment: 28 pages, 18 Figures, 3 tables, accepted for publication in ApJ

We use spectral energy distribution (SED) fitting to place constraints on the stellar populations of 59 ultra-diffuse galaxies (UDGs) in the low-to-moderate density fields of the MATLAS survey. We use the routine PROSPECTOR, coupled with archival data in the optical from DECaLS, and near- and mid-infrared imaging from WISE, to recover the stellar masses, ages, metallicities and star formation timescales of the UDGs. We find that a subsample of the UDGs lies within the scatter of the mass-metallicity relation (MZR) for local classical dwarfs. However, another subsample is more metal-poor, being consistent with the evolving MZR at high-redshift. We investigate UDG positioning trends in the mass-metallicity plane as a function of surface brightness, effective radius, axis ratio, local volume density, mass-weighted age, star formation timescale, globular cluster (GC) counts and GC specific frequency. We find that our sample of UDGs can be separated into two main classes. Class A: Comprised of UDGs with lower stellar masses, prolonged star formation histories (SFHs), more elongated, inhabiting less dense environments, hosting fewer GCs, younger, consistent with the classical dwarf MZR, and fainter. Class B: UDGs with higher stellar masses, rapid SFHs, rounder, inhabiting the densest of our probed environments, hosting on average the most numerous GC systems, older, consistent with the high-redshift MZR (i.e., consistent with early-quenching), and brighter. The combination of these properties suggests that UDGs of Class A are consistent with a `puffed-up dwarf' formation scenario, while UDGs of Class B seem to be better explained by `failed galaxy' scenarios., Comment: Accepted for publication in MNRAS. 19 pages (+6 of appendices), 10 figures, 5 tables

We study a compact nucleus embedded in an early-type dwarf galaxy, MATLAS-167, which is in the process of disruption by the tidal force of the neighboring giant S0 galaxy, NGC 936, in a group environment. Using the imaging data of the MATLAS survey, we analyze the stellar tidal tail of MATLAS-167 and its central compact nucleus, designated as NGC 936_UCD. We find that NGC 936_UCD has a luminosity of M$_{g}$ = $-$11.43$\pm$0.01 mag and a size of 66.5$\pm$17 pc, sharing the global properties of Ultra Compact Dwarf galaxies (UCDs) but significantly larger and brighter compared to the typical UCD populations observed in the Virgo cluster. By integrating the total luminosity of both the tidal stream and MATLAS-167, we estimate that the disrupted dwarf progenitor possesses a luminosity of M$_{g}$ = $-$15.92$\pm$0.06 mag, a typical bright dE luminosity. With the help of the optical spectrum observed by the SDSS survey, we derive the simple stellar population properties of NGC 936_UCD: a light-weighted age of 5.6$\pm$0.7 Gyr and metallicity of [Z/H] = $-$0.83$\pm$0.3 dex. Our findings suggest that tidal threshing is a possible formation mechanism of bright UCD populations in close proximity to giant galaxies., Comment: Accepted for publication in MNRAS

Dwarf galaxies have been extensively studied in the Local Group, in nearby groups, and selected clusters, giving us a robust picture of their global stellar and dynamical properties in particular locations in the Universe. Intense study of these properties has revealed correlations between them, including the well known universal stellar mass-metallicity relation. However, since dwarfs play a role in a vast range of different environments, much can be learned about galaxy formation and evolution through extending the study of these objects to various locations. We present MUSE spectroscopy of a sample of 56 dwarf galaxies as a follow-up to the MATLAS survey in low-to-moderate density environments beyond the Local Volume. The dwarfs have stellar masses in the range of $M_{*}/M_{\odot}$ = 10$^{6.1}$-10$^{9.4}$ and show a distance range of D = 14-148 Mpc, the majority (75%) of which are located in the range targeted by the MATLAS survey (10-45 Mpc). We thus report a 75% (79% for dwarf ellipticals) success rate for the semi-automatic identification of dwarf galaxies in the MATLAS survey on the here presented subsample. Using pPXF full spectrum fitting, we determine their line-of-sight velocity and can match the majority of them with their massive host galaxy. Close inspection of their spectra reveals that ~30% show clear emission lines and thus star formation activity. We estimate their stellar population properties (age and metallicity) and compare our results with other works investigating Local Volume and cluster dwarf galaxies. We find that the dwarf galaxies presented in this work show a systematic offset from the stellar mass-metallicity relation towards lower metallicities at the same stellar mass. A similar deviation is present in other works in the stellar mass range probed in this work and might be attributed to the use of different methodologies for deriving the metallicity., Comment: 19 pages, 15 figures, 1 table. Accepted for publication in Astronomy & Astrophysics, Abstract shortened due to arxiv abstract length requirements