|Speaker:||Benedikt Diemer (Harvard U)|
|Title:||The edge of darkness, and other halo surprises|
|Date (JST):||Thu, Apr 07, 2016, 13:30 - 14:30|
|Place:||Seminar Room A|
The density profiles of dark matter halos are an essential input for models of galaxy formation, as well as for the interpretation of numerous observations such as weak and strong lensing signals. These profiles are commonly thought to be universal and modeled using the NFW form, assuming that they depend on only two parameters: mass and concentration. In this talk, I will show that the outer density profiles depend on an additional parameter, the mass accretion rate, and present an accurate new fitting formula that takes this dependence into account. Similarly, I will present a universal model for halo concentrations that is based on a previously unknown dependence of concentration on the local slope of the matter power spectrum.
Finally, I will introduce a novel feature in the density profiles, the splashback radius. Contrary to the common belief that halos have no well-defined edge, this radius provides a physically motivated definition of the halo boundary.