Empirical models for Dark Matter Halos. I. Nonparametric Construction of Density Profiles and comparison with Parametric Models
Date
2006-12Author
Merritt, David
Graham, Alister
Moore, Ben
Diemand, Jurg
Terzic, Balsa
Metadata
Show full item recordAbstract
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.