Galaxy assembly bias of central galaxies in the Illustris simulation. (arXiv:1812.11210v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Xu_X/0/1/0/all/0/1">Xiaoju Xu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zheng_Z/0/1/0/all/0/1">Zheng Zheng</a>
Galaxy assembly bias, the correlation between galaxy properties and halo
properties at fixed halo mass, could be an important ingredient in halo-based
modelling of galaxy clustering. We investigate the central galaxy assembly bias
by studying the relation between various galaxy and halo properties in the
Illustris hydrodynamic galaxy formation simulation. Galaxy stellar mass
$M_{star}$ is found to have a tighter correlation with peak maximum halo
circular velocity $V_{peak}$ than with halo mass $M_h$. Once the correlation
with $V_{peak}$ is accounted for, $M_{star}$ has nearly no dependence on any
other halo assembly variables. The correlations between galaxy properties
related to star formation history and halo assembly properties also show a
cleaner form as a function of $V_{peak}$ than as a function of $M_h$, with the
main correlation being with halo formation time and to a less extent halo
concentration. Based on the galaxy-halo relation, we present a simple model to
relate the bias factors of a central galaxy sample and the corresponding halo
sample, both selected based on assembly-related properties. It is found that
they are connected by the correlation coefficient of the galaxy and halo
properties used to define the two samples, which provides a reasonable
description for the samples in the simulation and suggests a simple
prescription to incorporate galaxy assembly bias into the halo model. By
applying the model to the local galaxy clustering measurements in Lin et
al.(2016), we infer that the correlation between star formation history or
specific star formation rate and halo formation time is consistent with being
weak.
Galaxy assembly bias, the correlation between galaxy properties and halo
properties at fixed halo mass, could be an important ingredient in halo-based
modelling of galaxy clustering. We investigate the central galaxy assembly bias
by studying the relation between various galaxy and halo properties in the
Illustris hydrodynamic galaxy formation simulation. Galaxy stellar mass
$M_{star}$ is found to have a tighter correlation with peak maximum halo
circular velocity $V_{peak}$ than with halo mass $M_h$. Once the correlation
with $V_{peak}$ is accounted for, $M_{star}$ has nearly no dependence on any
other halo assembly variables. The correlations between galaxy properties
related to star formation history and halo assembly properties also show a
cleaner form as a function of $V_{peak}$ than as a function of $M_h$, with the
main correlation being with halo formation time and to a less extent halo
concentration. Based on the galaxy-halo relation, we present a simple model to
relate the bias factors of a central galaxy sample and the corresponding halo
sample, both selected based on assembly-related properties. It is found that
they are connected by the correlation coefficient of the galaxy and halo
properties used to define the two samples, which provides a reasonable
description for the samples in the simulation and suggests a simple
prescription to incorporate galaxy assembly bias into the halo model. By
applying the model to the local galaxy clustering measurements in Lin et
al.(2016), we infer that the correlation between star formation history or
specific star formation rate and halo formation time is consistent with being
weak.
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