Craig D. Harrison, Christopher J. Miller, Joseph W. Richards, E. J. Lloyd-Davies, Ben Hoyle, A. Kathy Romer, Nicola Mehrtens, Matt Hilton, John P. Stott, Diego Capozzi, Chris A. Collins, Paul-James Deadman, Andrew R. Liddle, Martin Sahlén, S. Adam Stanford, Pedro T. P. Viana
This paper presents both the result of a search for fossil systems within the
XMM Cluster Survey and the Sloan Digital Sky Survey and the results of a study
of the stellar mass assembly and stellar populations of their fossil galaxies.
In total, 17 groups and clusters are identified at z < 0.25 with large
magnitude gaps between the first and fourth brightest galaxies. All the
information necessary to classify these systems as fossils is provided. For
both groups and clusters, the total and fractional luminosity of the brightest
galaxy are positively correlated with the magnitude gap. The brightest galaxies
in fossil systems (called fossil galaxies) have stellar populations and
star-formation histories which are similar to normal brightest cluster
galaxies. However, at fixed group/cluster mass, the stellar masses of the
fossil galaxies are larger compared to normal brightest cluster galaxies, a
fact that holds true over a wide range of group/cluster masses. Moreover, the
fossil galaxies are found to contain a significant fraction of the the total
optical luminosity of the group/cluster within 0.5R200, as much as 85%,
compared to the non-fossils, which can have as little as 10%. Our results
suggest that fossil systems formed early and in the highest density regions of
the Universe and that fossil galaxies represent the end products of galaxy
mergers in groups and clusters.
View original:
http://arxiv.org/abs/1202.4450
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