Abstract
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 S\'ersic 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.
Highlights
Ultra-diffuse galaxies (UDGs, van Dokkum et al 2015) are galaxies with effective radius similar to the Milky Way (Re 1.5 kpc) and extremely low surface brightness (μ(g, 0) 24 mag arcsec−2)
In the end we find 442 ultra-diffuse galaxies (UDGs) candidates in our eight field of view (FOV), with 247 of them lying at projected distances within 1R200
It is remarkable that we find different blue-to-red fractions and significant 1σ differences for the upper and lower limits of the colour distribution considering that (i) the analysis has not been done in bins of mass, so galaxies of different masses are all mixed in our groups, (ii) projection effects should be present when comparing the inner and outer UDGs, (iii) UDGs are likely to be a mixed group or bag of galaxies, and (iv) while expected to be low, we have some degree of background contamination
Summary
Ultra-diffuse galaxies (UDGs, van Dokkum et al 2015) are galaxies with effective radius similar to the Milky Way (Re 1.5 kpc) and extremely low surface brightness (μ(g, 0) 24 mag arcsec−2). Regarding UDGs in different environments, in Mancera Pina et al (2018, hereafter Paper I), we showed that clusters with different masses have their innermost UDGs at different projected distances, arguing in favour of a scenario where UDGs in the centres of highmass clusters are more efficiently destroyed With all this in mind, and with the aim of updating the census of UDGs in clusters, study their scaling relations and further investigate the influence of the environment on their properties, we present here our second paper in a series studying the UDG population in a set of nearby galaxy clusters.
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