Oral Presentation

The stellar mass growth of brightest cluster galaxies

Author(s): Yen-Ting Lin et al

Presenter: Yen-Ting Lin (ASIAA)

The details of the stellar mass assembly of brightest cluster galaxies (BCGs)
remain an unresolved problem in galaxy formation. We have developed a novel
approach that allows us to construct a sample of clusters that form an
evolutionary sequence (that is, the clusters on the sequence are expected to
evolve into each other), and have applied it to the Spitzer IRAC Shallow
Cluster Survey (ISCS) to examine the stellar mass evolution of BCGs in
progenitors of present-day clusters with mass of 3x10^14 Msun. We follow the
cluster mass growth history extracted from a high resolution cosmological
simulation, and then use an empirical method that infers the cluster mass based
on the ranking of cluster luminosity to select high-z clusters of appropriate
mass from ISCS to be progenitors of the given set of z=0 clusters. We find
that, between z=1.5 and 0.5, the BCGs have grown by a factor of 2.3, which is
well-matched by the predictions from a state-of-the-art semi-analytic model
(Guo et al. 2011). Below z=0.5 we see hints of differences in behavior between
the model and observation. While the observed BCGs show only a small increase
in stellar mass content down to z~0 (<10%), the model BCGs appear to exhibit an
accelerated growth below z=0.5; that is, ~50% of the final mass of the model
BCGs is acquired between z=0.5 and 0. Such a contrast suggests the period of
z=0-0.5 is potentially key in differentiating models of BCG assembly history.