Optically selected fossil groups; X-ray observations and galaxy properties

Abstract

We report on the X-ray and optical observations of galaxy groups selected from the 2dfGRS group catalog, to explore the possibility that galaxy groups hosting a giant elliptical galaxy and a large optical luminosity gap present between the two brightest group galaxies, can be associated with an extended X-ray emission, similar to that observed in fossil galaxy groups. The X-ray observations of 4 galaxy groups were carried out with Chandra telescope with 10-20 ksec exposure time. Combining the X-ray and the optical observations we find evidences for the presence of a diffuse extended X-ray emission beyond the optical size of the brightest group galaxy. Taking both the X-ray and the optical criteria, one of the groups is identified as a fossil group and one is ruled out because of the contamination in the earlier optical selection. For the two remaining systems, the X-ay luminosity threshold is close to the convention know for fossil groups. In all cases the X-ray luminosity is below the expected value from the X-ray selected fossils for a given optical luminosity of the group. A rough estimation for the comoving number density of fossil groups is obtained and found to be in broad agreement with the estimations from observations of X-ray selected fossils and predictions of cosmological simulations.

arXiv commentAccepted for publication in MNRAS

References in corpus (22)

• Simulating the joint evolution of quasars, galaxies and their large-scale distribution
• The Leiden/Argentine/Bonn (LAB) Survey of Galactic HI: Final data release of the combined LDS and IAR surveys with improved stray-radiation corrections
• Galaxy groups in the 2dFGRS: the group-finding algorithm and the 2PIGG catalogue
• The GEMS project: X-ray analysis and statistical properties of the group sample
• The nature and space density of fossil groups of galaxies
• The Lx-T and Lx-sigma Relationships for Galaxy Clusters Revisited
• The WARPS X-ray survey of galaxies, groups and clusters I: Method and first results
• Scaling relations in fossil galaxy groups
• X-ray groups and clusters of galaxies in the Subaru-XMM Deep Field
• An old galaxy group: Chandra X-ray observations of the nearby fossil group NGC 6482
• The Mass Assembly of Fossil Groups of Galaxies in the Millennium Simulation
• The mass assembly of galaxy groups and the evolution of the magnitude gap
• LoCuSS: Connecting the Dominance and Shape of Brightest Cluster Galaxies with the Assembly History of Massive Clusters
• ESO 3060170 -- a massive fossil galaxy group with a heated gas core?
• Fossil Groups in the Sloan Digital Sky Survey
• A fossil galaxy cluster; an X-ray and optical study of RX J1416.4+2315
• Correlations of near-infrared, optical and X-ray luminosity for early-type galaxies
• The central elliptical galaxy in fossil groups and formation of BCGs
• First results of the XI Groups Project: Studying an unbiased sample of galaxy groups
• Cl 1205+44, a fossil group at z = 0.59
• X-ray bright groups and their galaxies
• A statistical study of the luminosity gap in galaxy groups

Cited by in corpus (13)

• Chandra centres for COSMOS X-ray galaxy groups: Differences in stellar properties between central dominant and offset brightest group galaxies
• Evolution of galaxy groups in the Illustris simulation
• Fossil group origins V. The dependence of the luminosity function on the magnitude gap
• Are fossil groups early-forming galaxy systems?
• Fossil Group Origins VII. Galaxy substructures in fossil systems
• Evolution of the galaxy luminosity function in progenitors of fossil groups
• Fossil group origins - VI. Global X-ray scaling relations of fossil galaxy clusters
• Galaxy And Mass Assembly (GAMA): 'No Smoking' zone for giant elliptical galaxies?
• Fossil group origins IX. Probing the formation of fossil galaxy groups with stellar population gradients of their central galaxies
• Merger history of central galaxies in Semi-Analytic Models of galaxy formation
• Fossil group origins: VIII RXJ075243.6+455653 a transitionary fossil group
• Assembly Conformity of Structure Growth: Fossil versus Normal Groups of Galaxies
• The Complex Structure of the Abell 548 - Abell 3367 Region