Contributed Papers

Cold Dark Matter Substructure and Galactic Disks

Stelios Kazantzidis^a1, Andrew R. Zentner^a2 and James S. Bullock^a3

^a1 Center for Cosmology and Astro-Particle Physics, The Ohio State University, 191 West Woodruff Avenue, Columbus, OH 43210, USA email: stelios@mps.ohio-state.edu

^a2 Department of Physics & Astronomy, University of Pittsburgh, 100 Allen Hall, 3941 O'Hara Street, Pittsburgh, PA 15260, USA email: zentner@pitt.edu

^a3 Center for Cosmology, Department of Physics & Astronomy, The University of California at Irvine, 4168 Reines Hall, Irvine, CA 92697, USA email: bullock@uci.edu

Abstract

We perform a set of high-resolution, fully self-consistent dissipationless N-body simulations to investigate the influence of cold dark matter (CDM) substructure on the dynamical evolution of thin galactic disks. Our method combines cosmological simulations of galaxy-sized CDM halos to derive the properties of substructure populations and controlled numerical experiments of consecutive subhalo impacts onto initially-thin, fully-formed disk galaxies. We demonstrate that close encounters between massive subhalos and galactic disks since z ~ 1 should be common occurrences in ΛCDM models. In contrast, extremely few satellites in present-day CDM halos are likely to have a significant impact on the disk structure. One typical host halo merger history is used to seed controlled N-body experiments of subhalo-disk encounters. As a result of these accretion events, the disk thickens considerably at all radii with the disk scale height increasing in excess of a factor of 2 in the solar neighborhood. We show that interactions with the subhalo population produce a wealth of distinctive morphological signatures in the disk stars, many of which resemble those being discovered in the Milky Way (MW), M31, and in other disk galaxies, including: conspicuous flares; bars; low-lived, ring-like features in the outskirts; and low-density, filamentary structures above the disk plane. These findings highlight the significant role of CDM substructure in setting the structure of disk galaxies and driving galaxy evolution.

Keywords

• cosmology: theory;
• dark matter;
• galaxies: formation;
• galaxies: dynamics;
• galaxies: structure;
• methods: numerical