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Xiaoju Xu (University of Utah)

Date: Tue. October 16th, 2018, 11:30 am-12:30 pm
Location: foldy room (Rock 221)

Multivariate Dependent Halo and Galaxy Assembly Bias

Galaxies form in dark matter halos, and their properties and
distributions are connected to the host halos. With a prescription of
the galaxy-halo relation and the theoretically known halo clustering
(e.g., from N-body simulations), galaxy clustering data from large
galaxy surveys can be modeled to learn about galaxy formation and
cosmology. In the above halo-based model, it is usually assumed that
the statistical distribution of galaxies inside halos only depends on
halo mass. However, it is found that in addition to mass halo
clustering also depends on the formation history and environment of
halos, which is named halo assembly bias. The formation history and
environment of halos may also affect galaxy properties, leading to the
so-called galaxy assembly bias. Both halo and galaxy assembly bias
effects need to be accounted for to improve the halo-based model of
galaxy clustering. In this talk, I will first review the halo assembly
bias. Then I will present our investigation of the joint dependence of
halo bias on halo mass and assembly variables based on large N-body
simulations. We find that it is unlikely to have a combination of
halo variables to absorb all assembly bias effects and that there
exists a correlation between halo assembly bias and halo kinematics.
Finally, I will talk about a study of galaxy assembly bias based on
the Illustris hydrodynamic galaxy formation simulation, presenting the
relation between galaxy properties and halo properties and discussing
the implications.

Host: Idit Zehavi

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