Galaxy power spectrum in redshift space: combining perturbation theory
  with the halo model
  Theoretical modeling of the redshift-space power spectrum of galaxies is
crucially important to correctly extract cosmological information from redshift
surveys. The task is complicated by the nonlinear biasing and redshift space
distortion effects, which change with halo mass, and by the wide distribution
of halo masses and their occupations by galaxies. One of the main modeling
challenges is the existence of satellite galaxies that have both radial
distribution and large virial velocities inside halos, a phenomenon known as
the Finger-of-God effect. We present a model for the galaxy power spectrum of
in which we decompose a given galaxy sample into central and satellite galaxies
and relate different contributions to 1- and 2-halo terms in a halo model. Our
primary goal is to ensure that any parameters that we introduce have physically
meaningful values, and are not just fitting parameters. For the 2-halo terms we
use the previously developed RSD modeling of halos in the context of
distribution function and perturbation theory approach. This term needs to be
multiplied by the effect of radial distances and velocities of satellites
inside the halo. To this one needs to add the 1-halo terms, which are
non-perturbative. We show that the real space 1-halo terms can be modeled as
almost constant, with the finite extent of the satellites inside the halo
inducing a small k^2R^2 term, where R is related to the size of the halo. We
adopt a similar model for FoG in redshift space, ensuring that FoG velocity
dispersion is related to the halo mass. For FoG k^2 type expansions do not work
and FoG resummation must be used instead. We test several damping functions to
model the velocity dispersion FoG effect. Applying the formalism to mock
galaxies modeled after the "CMASS" sample of the BOSS survey, we find that our
predictions for the redshift-space power spectra are accurate up to k~0.4Mpc/h.
