The nature and space density of fossil groups of galaxies

By L. Jones, Trevor J. Ponman, Anthony D Horton, Arif Babul, H. Ebeling, D. Burke. 2003

255 citations recorded by the source corpus.

We describe the properties of a sample of galaxy groups with very unusual distributions of galaxy luminosities. The most extreme example has an X-ray luminosity similar to that of the Virgo cluster but has a very low richness, with only one galaxy brighter than L*, compared with six in Virgo. That one galaxy, however, is optically more luminous than any galaxy in Virgo and has an optical luminosity as bright as many of the central cD galaxies in rich Abell clusters. The characteristic feature of the fossil groups we study is that most of the light arises from one dominant, central galaxy. We define a fossil system and, based on this definition, construct a small X-ray-selected, flux-limited sample of fossil groups with well-known selection criteria. We confirm that these systems are indeed groups of galaxies, but dominated by one central luminous giant elliptical galaxy and with few, or no, L* galaxies. We find that fossil systems represent 8–20 per cent of all systems of the same X-ray luminosity. Fossil groups are at least as numerous as all poor and rich clusters combined, and are thus a possible site for the formation of luminous central cluster galaxies before infall into clusters occurs. The fossil systems in our sample have significantly higher X-ray luminosities than normal groups of similar total optical luminosities (or similar X-ray temperature, where the latter can be measured). These enhanced X-ray luminosities may be due to relatively cool gas in the innermost regions or due to a low central gas entropy. We interpret fossil groups as old, undisturbed systems which have avoided infall into clusters, but where galaxy merging of most of the L* galaxies has occurred. An early formation epoch, before that of most groups, could explain low central gas entropies and high X-ray luminosities.

Subfields: Astronomy and Astrophysics, Computer Vision and Pattern Recognition

View Paper: https://www.semanticscholar.org/paper/a1e73a2cade20ce5ab4b9485ab526e759e45a5d1

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Citations in the corpus

CHANDRA STUDIES OF THE X-RAY GAS PROPERTIES OF GALAXY GROUPS (2008, methodology): “Jones et al. (2003) used r200 as the virial radius, while we use the exact definition of the virial radius for our cosmology, rvir = r∆ (∆ ∼ 101).”
The 400 Square Degree ROSAT PSPC Galaxy Cluster Survey: Catalog and Statistical Calibration (2006, background): “…cluster if 1) there was an obvious associated excess in the galaxy number density, or 2) there was a bright elliptical galaxy at the X-ray centroid, even if it was seemingly isolated (this is a signature of so-called fossil groups, see Ponman et al. 1994; Vikhlinin et al. 1999b; Jones et al. 2003).”
Galaxy Groups in the SDSS DR4. II. Halo Occupation Statistics (2007, methodology): “…have merged, are often termed ‘‘fossil groups’’ and have received a significant amount of attention in the recent literature (see Vikhlinin et al. 1999; Jones et al. 2003; D’Onghia et al. 2005; Milosavljević et al. 2006; Sommer-Larsen 2006; van den Bosch et al. 2007; Sales et al. 2007; von…”
The GEMS project: X-ray analysis and statistical properties of the group sample (2004, background): “Only one of the GEMS systems qualifies as a fossil group, according to the definition of Jones et al. (2003), which requires LX > 10 42 h50 −2 erg s−1 (h50 = H0/50) and L12 > 6.3 (2 magnitudes).”
Galaxy groups and clouds in the local (z∼ 0.01) Universe (2010, background): “Some authors (Jones et al. 2003; Dı́az-Giménez et al. 2008; von Benda-Beckmann et al. 2008) propose to distinguish a special category of ‘fossil’ groups, where the main galaxy significantly surpasses all the other members on the luminosity scale.”
Theoretical Models of the Halo Occupation Distribution: Separating Central and Satellite Galaxies (2004, background): “The isolated, luminous, X-ray bright ellipticals known as “fossil groups” (Vikhlinin et al. 1999; Jones et al. 2003) may represent an extreme example of the central galaxy bump in intermediate mass halos.”
The Physics of Galaxy Clustering. I. A Model for Subhalo Populations (2004, background): “The fossil groups are systems that are characterized by Xray luminosities comparable to those of poor galaxy clusters, while their optical luminosities are dominated by a single, bright, central galaxy (e.g., Vikhlinin et al. 1999; Jones et al. 2003).”
Towards a concordant model of halo occupation statistics (2006, background): “…to the fact that the brightest galaxies in the halo have merged, are often termed as ‘fossil groups’ and have received a significant amount of attention in the recent literature (see Vikhilin et al. 1999; Jones et al. 2003; D’Onghia et al. 2005; Milosavljević et al. 2006, and references therein).”
K-band Properties of Galaxy Clusters and Groups: Brightest Cluster Galaxies and Intracluster Light (2004, background): “Fossil Groups There exists a class of galactic systems with masses comparable to groups of galaxies, with diffuse X-ray emission from hot gas, but where the optical light is totally dominated by one single galaxy (the so-called fossil groups; e.g., Jones et al. 2003 and references therein).”
Measurement of Galaxy Cluster Sizes, Radial Profiles, and Luminosity Functions from SDSS Photometric Data (2004, background): “This scenario is supported by the observations that the central galaxies emit a very high fraction of the total optical light of the group, and that there is a dearth of L∗ galaxies in the central region of these systems (Jones et al. 2003).”
Galaxy Zoo: the dependence of morphology and colour on environment (2008, background): “Some of these galaxies may be fossil groups (Jones et al. 2003), and hence only appear to be in lowdensity environments.”
Galaxy ecology: groups and low-density environments in the SDSS and 2dFGRS (2003, background): “could have neighbours that are just below our luminosity limit. c© 0000 RAS, MNRAS 000, 000–000 star formation are fossil groups (Ponman & Bertram 1993; Mulchaey & Zabludoff 1999; Smith et al. 2003; Jones et al. 2003).”