Empirical models for Dark Matter Halos. I. Nonparametric Construction of Density Profiles and comparison with Parametric Models

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Title: Empirical models for Dark Matter Halos. I. Nonparametric Construction of Density Profiles and comparison with Parametric Models
Author: Merritt, David; Graham, Alister; Moore, Ben; Diemand, Jurg; Terzic, Balsa
Abstract: We use techniques from nonparametric function estimation theory to extract the density pro- files, and their derivatives, from a set of N-body dark matter halos. We consider halos generated from ΛCDM simulations of gravitational clustering, as well as isolated, spherical collapses. The logarithmic density slopes d log /d log r of the ΛCDM halos are found to vary as power-laws in radius, reaching values of −1 at the innermost resolved radii, 10−2rvir. This behavior is significantly different from that of broken power-law models like the NFW profile, but similar to that of models like de Vaucouleurs’. Accordingly, we compare the N-body density profiles with various parametric models to find which provide the best fit. We consider an NFW-like model with arbitrary inner slope; Dehnen & McLaughlin’s anisotropic model; Einasto’s model (identi- cal in functional form to S´ersic’s model but fit to the space density); and the density model of Prugniel & Simien that was designed to match the deprojected form of S´ersic’s R1/n law. Over- all, the best-fitting model to the ΛCDM halos is Einasto’s, although the Prugniel-Simien and Dehnen-McLaughlin models also perform well. With regard to the spherical collapse halos, both the Prugniel-Simien and Einasto models describe the density profiles well, with an rms scatter some four times smaller than that obtained with either the NFW-like model or the 3-parameter Dehnen-McLaughlin model. Finally, we confirm recent claims of a systematic variation in profile shape with halo mass.
Description: RIT community members may access full-text via RIT Libraries licensed databases: http://library.rit.edu/databases/
Record URI: http://hdl.handle.net/1850/7506
Publishers URL: http://dx.doi.org/10.1086/508988
Date: 2006-12

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