Volume 607, November 2017
|Number of page(s)||13|
|Published online||17 November 2017|
The abundance of ultra-diffuse galaxies from groups to clusters
UDGs are relatively more common in more massive haloes
1 IRFU, CEA, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
2 Université Paris Diderot, AIM, Sorbonne Paris Cité, CEA, CNRS, 91191 Gif-sur-Yvette, France
3 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
4 Department of Physics and Astronomy, York University, 4700 Keele St., Toronto, Ontario MJ3 1P3, Canada
5 Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544, USA
6 Astrophysics Group, School of Physics, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, UK
7 School of Physics, University of New South Wales, NSW 2052, Australia
8 International Centre for Radio Astronomy Research (ICRAR), The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia
9 School of Physics & Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS, UK
10 Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany
11 Scottish Universities Physics Alliance, Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
12 Department of Physics and Astronomy, University of Louisville, Louisville, KY 40292, USA
13 School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
14 INAF–Osservatorio Astronomico di Capodimonte, via Moiariello 16, 80131 Napoli, Italy
15 ICC & CEA, Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
16 Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn 3122, Australia
17 Kapteyn Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands
Received: 8 June 2017
Accepted: 7 August 2017
In recent years, many studies have reported substantial populations of large galaxies with low surface brightness in local galaxy clusters. Various theories that aim to explain the presence of such ultra-diffuse galaxies (UDGs) have since been proposed. A key question that will help to distinguish between models is whether UDGs have counterparts in host haloes with lower masses, and if so, what their abundance as a function of halo mass is. We here extend our previous study of UDGs in galaxy clusters to galaxy groups. We measure the abundance of UDGs in 325 spectroscopically selected groups from the Galaxy And Mass Assembly (GAMA) survey. We make use of the overlapping imaging from the ESO Kilo-Degree Survey (KiDS), from which we can identify galaxies with mean surface brightnesses within their effective radii down to ~25.5 mag arcsec-2 in the r band. We are able to measure a significant overdensity of UDGs (with sizes reff ≥ 1.5 kpc) in galaxy groups down to M200 = 1012 M⊙, a regime where approximately only one in ten groups contains a UDG that we can detect. We combine measurements of the abundance of UDGs in haloes that cover three orders of magnitude in halo mass, finding that their numbers scale quite steeply with halo mass: NUDG(R < R200) ∝ M2001.11±0.07. To better interpret this, we also measure the mass-richness relation for brighter galaxies down to Mr* + 2.5 in the same GAMA groups, and find a much shallower relation of NBright(R < R200) ∝ M2000.78±0.05. This shows that compared to bright galaxies, UDGs are relatively more abundant in massive clusters than in groups. We discuss the implications, but it is still unclear whether this difference is related to a higher destruction rate of UDGs in groups or if massive haloes have a positive effect on UDG formation.
Key words: galaxies: dwarf / galaxies: formation / galaxies: evolution / galaxies: structure / galaxies: groups: general / galaxies: clusters: general
© ESO, 2017
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