Astronomy and Astrophysics – Astrophysics
Scientific paper
2008-04-03
Astrophys.J.690:1292-1302,2009
Astronomy and Astrophysics
Astrophysics
10 pages, 9 figures, 1 tables, submitted to ApJ
Scientific paper
10.1088/0004-637X/690/2/1292
We study the formation of fifty-three galaxy cluster-size dark matter halos formed within a pair of cosmological LCDM N-body simulations, and track the accretion histories of cluster subhalos with masses large enough to host 0.1L* galaxies. By associating subhalos with cluster galaxies, we find the majority of galaxies in clusters experience no pre-processing in the group environment prior to their accretion into the cluster. On average, ~70% of cluster galaxies fall into the cluster potential directly from the field, with no luminous companions in their host halos at the time of accretion; and less than ~12% are accreted as members of groups with five or more galaxies. Moreover, we find that cluster galaxies are significantly less likely to have experienced a merger in the recent past (~6 Gyr) than a field halo of the same mass. These results suggest that local, cluster processes like ram-pressure stripping, galaxy harassment, or strangulation play the dominant role in explaining the difference between cluster and field populations at a fixed stellar mass; and that pre-evolution or past merging in the group environment is of secondary importance for setting cluster galaxy properties for most clusters. The accretion times for z = 0 cluster members are quite extended, with ~20% incorporated into the cluster halo more than 7 Gyr ago and ~20% within the last 2 Gyr. By comparing the observed morphological fractions in cluster and field populations, we estimate an approximate timescale for late-type to early-type transformation within the cluster environment to be ~6 Gyr.
Barton Elizabeth J.
Berrier Joel C.
Bullock James S.
Purcell Chris W.
Stewart Kyle R.
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