Galaxy power spectrum in redshift space: Combining perturbation theory with the halo model

Teppei Okumura, Nick Hand, Uroš Seljak, Zvonimir Vlah, and Vincent Desjacques
Phys. Rev. D 92, 103516 – Published 19 November 2015

Abstract

Theoretical modeling of the redshift-space power spectrum of galaxies is crucially important to correctly extract cosmological information from galaxy redshift surveys. The task is complicated by the nonlinear biasing and redshift space distortion (RSD) 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 inside the halos and large virial velocities inside halos, a phenomenon known as the Finger-of-God (FoG) effect. We present a model for the redshift-space power spectrum of galaxies in which we decompose a given galaxy sample into central and satellite galaxies and relate different contributions to the power spectrum to 1-halo 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 lowest order 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 nonperturbative. 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 k2R2 term over the range of scales of interest, where R is related to the size of the halo given by its halo mass. We adopt a similar model for FoG in redshift space, ensuring that FoG velocity dispersion is related to the halo mass. For FoG k2 type expansions do not work over the range of scales of interest and FoG resummation must be used instead. We test several simple 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 k0.4hMpc1 within 1% if the halo power spectrum is measured using N-body simulations and within 3% if it is modeled using perturbation theory.

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  • Received 21 June 2015

DOI:https://doi.org/10.1103/PhysRevD.92.103516

© 2015 American Physical Society

Authors & Affiliations

Teppei Okumura1,*, Nick Hand2, Uroš Seljak2,3, Zvonimir Vlah4,5, and Vincent Desjacques6

  • 1Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes for Advanced Study, The University of Tokyo, Kashiwa, Chiba 277-8583, Japan
  • 2Astronomy Department, University of California, California 94720, USA
  • 3Lawrence Berkeley National Laboratory and Physics Department, University of California, California 94720, USA
  • 4Stanford Institute for Theoretical Physics and Department of Physics, Stanford University, Stanford, California 94306, USA
  • 5Kavli Institute for Particle Astrophysics and Cosmology, SLAC and Stanford University, Menlo Park, California 94025, USA
  • 6Département de Physique Théorique and Center for Astroparticle Physics (CAP), Université de Genève, 1211 Genève, Switzerland

  • *teppei.okumura@ipmu.jp

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Issue

Vol. 92, Iss. 10 — 15 November 2015

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