The inner structure of ACDM halos

Abstract

We have used high resolution N-body simulations to investigate the internal properties of Cold Dark Matter (CDM) halos with virial masses of M(_200) ~ 10(^10) M(_o) at z = 0, comparable to those of dwarf galaxy halos, forming in the ACDM cosmology. In particular, we have focused on providing accurate constraints on the mass distribution in these objects at ~ 1% of the virial radius, r(_200)-. After a brief introduction (chapter 1), the first part of this thesis is concerned with establishing the conditions under which the distribution of mass in simulated CDM halos is unaffected by finite numerical resolution. In chapter 2, we present results from a comprehensive set of simulations of a single galaxy mass halo in which numerical parameters have been varied systematically in order to determine their impact on the spherically averaged mass profile. Based on these results, we have defined a set of convergence criteria that allow us to identify the radial extent over which the spherically averaged circular velocity profile can be considered reliably resolved to better than 10%. In chapter 3, we have examined the abundance of substructure found in three sets of "converged" simulations, and quantified the effect of increasing mass resolution on the number of resolved subhalos of a given mass. The second part of this thesis is concerned with the detailed analysis of the internal structure and kinematics of the simulated dwarf galaxy halos in our sample. In chapter 4, we analyse the structure and kinematics of the dwarfs for possible redshift dependence, and investigate whether these halos could sustain a gaseous disk. In chapter 5, we concentrate on mass dependent trends by performing a detailed comparison with galaxy and cluster mass halos. Finally, chapter 6 provides a summary of the main findings of this work and highlights aspects that may prove rewarding for further study.