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Register a new userThe dwarf galaxy population in nearby clusters from the KIWICS survey
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Added by
Nelvy Choque Challapa
Publication date
2021
fields
Physics
and research's language is
English
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We analyse a sample of twelve galaxy clusters, from the Kapteyn IAC WEAVE INT Cluster Survey (KIWICS) looking for dwarf galaxy candidates. By using photometric data in the $r$ and $g$ bands from the Wide Field Camera (WFC) at the 2.5-m Isaac Newton telescope (INT), we select a sample of bright dwarf galaxies (M$_r$ $leq$ -15.5 mag) in each cluster and analyse their spatial distribution, stellar colour, and as well as their Sersic index and effective radius. We quantify the dwarf fraction inside the $R_{200}$ radius of each cluster, which ranges from $sim$ 0.7 to $sim$ 0.9. Additionally, when comparing the fraction in the inner region with the outermost region of the clusters, we find that the fraction of dwarfs tends to increase going to the outer regions. We also study the clustercentric distance distribution of dwarf and giant galaxies (M$_r$ $<$ -19.0 mag), and in half of the clusters of our sample, the dwarfs are distributed in a statistically different way as the giants, with the giant galaxies being closer to the cluster centre. We analyse the stellar colour of the dwarf candidates and quantify the fraction of blue dwarfs inside the $R_{200}$ radius, which is found to be less than $sim$ 0.4, but increases with distance from the cluster centre. Regarding the structural parameters, the Sersic index for the dwarfs we visually classify as early type dwarfs tends to be higher in the inner region of the cluster. These results indicate the role that the cluster environment plays in shaping the observational properties of low-mass halos.
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We study the population of ultra-diffuse galaxies (UDGs) in a set of eight nearby ($z <$ 0.035) galaxy clusters, from the Kapteyn IAC WEAVE INT Clusters Survey ($texttt{KIWICS}$). We report the discovery of 442 UDG candidates in our eight field of views, with 247 of these galaxies lying at projected distances < 1 R$_{200}$ from their host cluster. With the aim of testing theories about their formation, we study the scaling relations of UDGs comparing with different types of galaxies, finding that in the full parameter space they behave as dwarf galaxies and their colors do not seem to correlate with their effective radii. To investigate the influence of the environment on the evolution of UDGs we analyze their structural properties as functions of the projected clustercentric distance and the mass of their host cluster. We find no systematic trends for the stellar mass nor effective radius as function of the projected distance. However, the fraction of blue UDGs seems to be lower towards the center of clusters, and UDGs in the inner and outer regions of clusters have different Sersic index and axis ratio distributions. Specifically, the axis ratio distributions of the outer and inner UDGs resemble the axis ratio distributions of, respectively, late-type dwarfs and dwarf ellipticals in the Fornax Cluster suggesting an environmentally-driven evolution and another link between UDGs and dwarf galaxies. In general our results suggest strong similarities between UDGs and smaller dwarf galaxies in their structural parameters and their transformation within clusters.
The number of Ultra-Diffuse Galaxies (UDGs) in clusters is of significant importance to constrain models of their formation and evolution. Furthermore, their distribution inside clusters may tell us something about their interactions with their environments. In this work we revisit the abundance of UDGs in a more consistent way than in previous studies. We add new data of UDGs in eight clusters from the Kapteyn IAC WEAVE INT Clusters Survey (KIWICS), covering a mass range in which only a few clusters have been studied before, and complement these with a compilation of works in the literature to homogeneously study the relation between the number of UDGs and the mass of their host cluster. Overall, we find that the slope of the number of UDGs$-$cluster mass relation is consistent with being sublinear when considering galaxy groups or linear if they are excluded, but we argue that most likely the behavior is sublinear. When systematically studying the relation between the projected distance to the innermost UDG and M$_{200}$ for each cluster, we find hints that favor a picture in which massive clusters destroy UDGs in their centres.
We present a photometric study of the dwarf galaxy population in the core region ($< r_{rm vir}/4$) of the Fornax galaxy cluster based on deep $ugi$ photometry from the Next Generation Fornax Cluster Survey. All imaging data were obtained with the Dark Energy Camera mounted on the 4-meter Blanco telescope at the Cerro-Tololo Interamerican Observatory. We identify 258 dwarf galaxy candidates with luminosities $-17 < M_{g} < -8$ mag, corresponding to typical stellar masses of $9.5gtrsim log{cal M}_{star}/M_odot gtrsim 5.5$, reaching $sim!3$ mag deeper in point-source luminosity and $sim!4$ mag deeper in surface-brightness sensitivity compared to the classic Fornax Cluster Catalog. Morphological analysis shows that surface-brightness profiles are well represented by single-component Sersic models with average Sersic indices of $langle nrangle_{u,g,i}=(0.78-0.83) pm 0.02$, and average effective radii of $langle r_erangle_{u,g,i}!=(0.67-0.70) pm 0.02$ kpc. Color-magnitude relations indicate a flattening of the galaxy red sequence at faint galaxy luminosities, similar to the one recently discovered in the Virgo cluster. A comparison with population synthesis models and the galaxy mass-metallicity relation reveals that the average faint dwarf galaxy is likely older than ~5 Gyr. We study galaxy scaling relations between stellar mass, effective radius, and stellar mass surface density over a stellar mass range covering six orders of magnitude. We find that over the sampled stellar mass range several distinct mechanisms of galaxy mass assembly can be identified: i) dwarf galaxies assemble mass inside the half-mass radius up to $log{cal M}_{star}$ ~8.0, ii) isometric mass assembly in the range $8.0 < log{cal M}_{star}/M_odot < 10.5$, and iii) massive galaxies assemble stellar mass predominantly in their halos at $log{cal M}_{star}$ ~10.5 and above.
While studies of gas-phase metallicity gradients in disc galaxies are common, very little has been done in the acquisition of stellar abundance gradients in the same regions. We present here a comparative study of the stellar metallicity and age distributions in a sample of 62 nearly face-on, spiral galaxies with and without bars, using data from the CALIFA survey. We measure the slopes of the gradients and study their relation with other properties of the galaxies. We find that the mean stellar age and metallicity gradients in the disc are shallow and negative. Furthermore, when normalized to the effective radius of the disc, the slope of the stellar population gradients does not correlate with the mass or with the morphological type of the galaxies. Contrary to this, the values of both age and metallicity at $sim$2.5 scale-lengths correlate with the central velocity dispersion in a similar manner to the central values of the bulges, although bulges show, on average, older ages and higher metallicities than the discs. One of the goals of the present paper is to test the theoretical prediction that non-linear coupling between the bar and the spiral arms is an efficient mechanism for producing radial migrations across significant distances within discs. The process of radial migration should flatten the stellar metallicity gradient with time and, therefore, we would expect flatter stellar metallicity gradients in barred galaxies. However, we do not find any difference in the metallicity or age gradients in galaxies with without bars. We discuss possible scenarios that can lead to this absence of difference.
We study the relationship between the field star formation and cluster formation properties in a large sample of nearby dwarf galaxies. We use optical data from the Hubble Space Telescope and from ground-based telescopes to derive the ages and masses of the young (t_age < 100Myr) cluster sample. Our data provides the first constraints on two proposed relationships between the star formation rate of galaxies and the properties of their cluster systems in the low star formation rate regime. The data show broad agreement with these relationships, but significant galaxy-to-galaxy scatter exists. In part, this scatter can be accounted for by simulating the small number of clusters detected from stochastically sampling the cluster mass function. However, this stochasticity does not fully account for the observed scatter in our data suggesting there may be true variations in the fraction of stars formed in clusters in dwarf galaxies. Comparison of the cluster formation and the brightest cluster in our sample galaxies also provide constraints on cluster destruction models.
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