Gabriella De Lucia, Simone Weinmann, Bianca Poggianti, Alfonso Aragon-Salamanca, Dennis Zaritsky
We use publicly available galaxy merger trees, obtained applying
semi-analytic techniques to a large high resolution cosmological simulation, to
study the environmental history of group and cluster galaxies. Our results
highlight the existence of an intrinsic history bias which makes the nature
versus nurture (as well as the mass versus environment) debate inherently ill
posed. In particular we show that: (i) surviving massive satellites within
clusters were accreted later than their less massive counterparts, from more
massive haloes; (ii) the mixing of galaxy populations is incomplete during
cluster assembly, which creates a correlation between the time a galaxy becomes
satellite and its present distance from the cluster centre. The weakest trends
are found for the most massive satellites as a result of efficient dynamical
friction and late formation times of massive haloes. A large fraction of the
most massive cluster members are accreted onto the main progenitor of the final
group/cluster as central galaxies, while about half of all cluster galaxies
with low and intermediate stellar mass are accreted as satellites. Large
fractions of group and cluster galaxies (in particular those of low stellar
mass) have therefore been `pre-processed' as satellites of groups with mass
~10^{13} Msun. To quantify the relevance of hierarchical structure growth on
the observed environmental trends, we have considered observational estimates
of the passive galaxy fractions, and their variation as a function of halo mass
and cluster-centric distance. Comparisons with our theoretical predictions
require relatively long times (~5-7 Gyr) for the suppression of star formation
in group and cluster satellites. [abridged]
View original:
http://arxiv.org/abs/1111.6590
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