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R.H. Wechsler (UC Santa Cruz, University of Michigan)
The mass assembly history of dark matter halos, and its effects on halo structural parameters and galaxy properties are studied, using a statistical sample of halos in a high-resolution N-body simulation of the Lambda-CDM cosmology. For each redshift zero halo, we identify its merger-history tree, and determine angular momentum properties and concentration parameters cvir for all progenitors, thus providing a structural merger tree for each halo. I demonstrate that halo mass accretion histories are well fit by a universal function with one parameter, the formation epoch ac, defined when the log mass accretion rate falls below a critical value. Halo density profiles measured at an epoch aobs can be characterized by a concentration parameter, cvir, which is strongly correlated with ac via cvir=cc aobs /ac. Scatter about this relation is mostly due to measurement errors in cvir and ac, implying that the actual spread in concentrations for halos of a given mass can be primarily attributed to scatter in formation time. This relation can also be used to predict the mass and redshift dependence of cvir, and the scatter about the median cvir(M,z), using accretion histories derived from the Extended Press-Schechter (EPS) formalism. Statistics of halo merging histories are investigated, and some discrepancies with EPS are noted. The relation between the build-up and evolution of a halo's angular momentum and its merging and accretion history is described. The correlations between halo structural parameters and their mass assembly histories have important implications for galaxy formation models and observable properties of galaxies.
The dissertation work presented here was supported by a GAANN Fellowship and a NASA ATP grant at UCSC.
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The author(s) of this abstract have provided an email address for comments about the abstract: wechsler@umich.edu