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February 1 (4:00PM) in the 2nd Floor Conference Room in Dearborn Speaker: Stelios Kazantzidis (Kavli Institute for Particle Astrophysics and Cosmology) “Infalling Satellites and Structure of Galactic Disks in CDM Models” The Cold Dark Matter (CDM) model of hierarchical structure formation has emerged as the dominant paradigm in galaxy formation theory owing to its remarkable ability to explain a plethora of observations on large scales. Yet, on galactic and sub-galactic scales the CDM model has been neither convincingly verified nor disproved, and several outstanding issues remain unresolved. Using a set of high-resolution numerical simulations I investigate whether the abundance of substructure predicted by CDM models is in conflict with the existence of thin, dynamically fragile galactic stellar disks. I show that encounters of massive subhalos with the center of the host potential where the disk resides at z < 1 are quite common and yield significant damage to the disk. However, these violent interactions are not absolutely ruinous to the survival of disks. I demonstrate that infalling satellites produce several distinct observational signatures including flaring, long-lived, low-surface, ring-like and filamentary structures, and a complex vertical morphology that resembles the commonly adopted thin-thick disk profiles used in the analysis of disk galaxies. These results imply that substructure plays a significant role in setting the structure of disks. Upcoming galactic surveys and astrometric satellites offer a unique opportunity to distinguish between competing cosmological models and constrain the nature of dark matter on non-linear scales through detailed observations of galactic structure. |