Simulating the Anisotropic Clustering of Luminous Red Galaxies with Subhalos: A Direct Confrontation with Observation and Cosmological Implications

We examine how well we can explain the large-scale anisotropic clustering of Luminous Red Galaxies (LRGs) in the Sloan Digital Sky Survey with mock galaxies assigned to subhalos identified in a large suite of high-resolution cosmological simulations. Instead of relying on an analytical model, we vary the parameters that characterize the condition of subhalos to host LRGs and search for the best-fit parameters to the observed multipole moments of the power spectrum using the Markov-chain Monte Carlo method. After demonstrating that we cannot find a reasonable fit to the observation when we assign mock LRGs only to the central population of subhalos sitting at the center of their host halos, we show that simple models using both centrals and satellites can simultaneously fit the multipole moments up to hexadecapole at large scale ($k\lesssim0.3\,h\mathrm{Mpc}^{-1}$). The multiplicity function measured from the best-fit mock catalogs shows good agreement with the observation, when the mean spacial number density is adjusted by random sampling. We finally demonstrate the possibility of a simultaneous determination of the nature of LRGs and cosmological parameters by deforming the simulation box (the Alcock-Paczynski distortion) and changing by hand the velocities of mock LRGs (the amplitude of the redshift-space distortions). We derive constraints on the Hubble parameter $H(z)$, the angular diameter distance $D_\mathrm{A}(z)$ and the amplitude of the velocity perturbations $f\sigma_8(z)$ by utilizing a clear acoustic feature in the observed spectrum. We argue the robustness of these constraints against the range of the wavenumber used in the fit, and conclude that the underlying cosmological model assumed in the simulations as well as in the redshift-distance conversion has a significant discrepancy with the true one. (Abridged)

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Date added: Fri, 11 Oct 13