Abstract

We show that the presence of a r−3/2 dark matter overdensity can be robustly predicted at the center of any galaxy old enough to have grown a power-law density cusp in the stars via the Bahcall-Wolf mechanism. Using both Fokker-Planck and direct N-body integrations, we demonstrate collisional generation of these dark matter “crests” (Collisionally REgenerated STtructures) even in the extreme case that the density of both stars and dark matter were previously lowered by slingshot ejection from a binary supermassive black hole. The time scale for collisional growth of the crest is approximately the two-body relaxation time as defined by the stars, which is . 10 Gyr at the centers of stellar spheroids with luminosities L . 109.5L⊙, including the bulge of the Milky Way. The presence of crests can robustly be predicted in such galaxies, unlike the steeper enhancements, called “spikes”, produced by the adiabatic growth of black holes. We discuss special cases where the prospects for detecting dark matter annihilations from the centers of galaxy haloes are significantly affected by the formation of crests.

Publication Date

2-22-2007

Comments

Also archived in: v1 Oct 16 2006Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works in February 2014.

Document Type

Article

Department, Program, or Center

School of Physics and Astronomy (COS)

Campus

RIT – Main Campus

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