Constraints on the merging timescale of luminous red galaxies, or, where do all the halos go?

Abstract

In the LCDM cosmology dark matter halos grow primarily through the accretion of smaller halos. Much of the mass in a halo of 10^14Msun comes in through accretion of ~10^13Msun halos. If each such halo hosted one luminous red galaxy (LRG) then the accretion of so many halos is at odds with the observed number of LRGs in clusters unless these accreted LRGs merge or disrupt on relatively short timescales (~2Gyr). These timescales are consistent with classical dynamical friction arguments, and imply that 2-3 LRGs have merged or disrupted within each halo more massive than 10^14Msun by z=0. The total amount of stellar mass brought into these massive halos by z=0 is consistent with observations once the intracluster light (ICL) is included. If disrupted LRGs build up the ICL, then the hierarchical growth of massive halos implies that a substantial amount of ICL should also surround satellite LRGs, as suggested by recent observations of the Virgo cluster. Finally, we point out that these results are entirely consistent with a non-evolving clustering strength and halo occupation distribution, and note that observations of the latter in fact support the hypothesis that merging/disruption of massive galaxies does indeed take place at late times.

8 pages, 4 figures, final version, to appear in MNRAS

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Cited by in corpus (14)

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• The 2dF-SDSS LRG and QSO survey: evolution of the clustering of luminous red galaxies since z = 0.6
• Mapping the Dark Matter From UV Light at High Redshift: An Empirical Approach to Understand Galaxy Statistics
• Luminosity Function Constraints on the Evolution of Massive Red Galaxies Since z~0.9
• Simulating Subhalos at High Redshift: Merger Rates, Counts, and Types
• The growth of luminous red galaxies by merging
• Mining the gap: evolution of the magnitude gap in X-ray galaxy groups from the 3 square degree XMM coverage of CFHTLS
• The Late Stellar Assembly of Massive Cluster Galaxies Via Major Merging
• Luminous Red Galaxies in hierarchical cosmologies
• Luminous Red Galaxy Population in Clusters at $0.2\le z\le 0.6$
• Mass segregation trends in SDSS galaxy groups
• On the Fe abundance peak formation in cool-core clusters of galaxies: hints from cluster WARPJ1415.1+3612 at z=1.03
• Merger history trees of dark matter haloes in moving barrier models
• Rapidly spinning massive black holes in active galactic nuclei: evidence from the black hole mass function