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Abstract
In recent years, multiple studies have reported substantial populations
of large, low-surface-brightness galaxies 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 differentiate between models is whether UDGs have counterparts in
lower-mass host haloes, and what their abundance as a function of halo
mass is. In this study we 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 r_eff > 1.5 kpc) in galaxy groups
down to M200=10^12 Msun, a regime where approximately only 1 in 10
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;
N_UDG (R<R200) $\propto$ M200^(1.11+/-0.07). To better interpret
this, we also measure the mass-richness relation for brighter galaxies
down to $M^*_r$+2.5 in the same GAMA groups, and find a much shallower
relation of N_Bright (R<R200) $\propto$ M200^(0.78+/-0.05). This
shows that UDGs are relatively more abundant, compared to bright
galaxies, in massive clusters than in groups. We discuss implications,
but whether this difference is related to a higher destruction rate of
UDGs in groups, or whether massive haloes have a positive effect on
their formation, is not yet clear.
Original language | English |
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Article number | A79 |
Number of pages | 13 |
Journal | Astronomy and Astrophysics |
Volume | 607 |
Early online date | 17 Nov 2017 |
DOIs | |
Publication status | Published - Nov 2017 |
Keywords
- Galaxies: dwarf
- Galaxies: formation
- Galaxies: evolution
- Galaxies: structure
- Galaxies: groups: general
- Galaxies: clusters: general
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Dive into the research topics of 'The abundance of ultra-diffuse galaxies from groups to clusters: UDGs are relatively more common in more massive haloes'. Together they form a unique fingerprint.Projects
- 1 Finished
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Research in planetary formation, astrophysics, and cosmology at Bristol
1/04/15 → 31/03/18
Project: Research