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Register a new userReviewing the frequency and central depletion of Ultra-Diffuse Galaxies in galaxy clusters from the KIWICS survey
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Added by
Pavel Mancera Pi\\~na
Publication date
2018
fields
Physics
and research's language is
English
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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.
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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.
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.
Using deep g,r,i imaging from the VEGAS survey, we have searched for ultra diffuse galaxies (UDGs) in the IC 1459 group. Assuming they are group members, we identify 9 galaxies with physical sizes and surface brightnesses that match the UDG criteria within our measurement uncertainties. They have mean colours of g--i = 0.6 and stellar masses of $sim$10$^8$ M$_{odot}$. Several galaxies appear to have associated systems of compact objects, e.g. globular clusters. Two UDGs contain a central bright nucleus, with a third UDG revealing a remarkable double nucleus. This appears to be the first reported detection of a double nucleus in a UDG - its origin is currently unclear.
Many ultra diffuse galaxies (UDGs) have now been identified in clusters of galaxies. However, the number of nearby UDGs suitable for detailed follow-up remain rare. Our aim is to begin to identify UDGs in the environments of nearby bright early-type galaxies from the VEGAS survey. Here we use a deep g band image of the NGC 5846 group, taken as part of the VEGAS survey, to search for UDGs. We found one object with properties of a UDG if it associated with the NGC 5846 group, which seems likely. The galaxy, we name NGC 5846$_$UDG1, has an absolute magnitude of M$_g$ = -14.2, corresponding to a stellar mass of $sim$10$^8$ M$_{odot}$. It also reveals a system of compact sources which are likely globular clusters. Based on the number of globular clusters detected we estimate a halo mass that is greater than 8$times$10$^{10}$ M$_{odot}$ for UDG1.
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