Generating Log-Normal Mock Catalog of Galaxies in Redshift Space
We present a public code to generate a mock galaxy catalog in redshift space assuming a log-normal probability density function (PDF) of galaxy and matter density fields. We draw galaxies by Poisson-sampling the log-normal field, and calculate the velocity field from the linearised continuity equation of matter fields, assuming zero vorticity. This procedure yields a PDF of the pairwise velocity fields that is qualitatively similar to that of N-body simulations. We check fidelity of the catalog, showing that the measured two-point correlation function and power spectrum in real space agree with the input precisely. We find that a linear bias relation in the power spectrum does not guarantee a linear bias relation in the density contrasts, leading to a cross-correlation coefficient of matter and galaxies deviating from unity on small scales. We also find that linearising the Jacobian of the real-to-redshift space mapping provides a poor model for the two-point statistics in redshift space. That is, non-linear redshift-space distortion is dominated by non-linearity in the Jacobian. The power spectrum in redshift space shows a damping on small scales that is qualitatively similar to that of the well-known Fingers-of-God (FoG) effect due to random velocities, except that the log-normal mock does not include random velocities. This damping is a consequence of non-linearity in the Jacobian, and thus attributing the damping of the power spectrum solely to FoG, as commonly done in the literature, is misleading.
A. Agrawal et al., "Generating Log-Normal Mock Catalog of Galaxies in Redshift Space," Journal of Cosmology and Astroparticle Physics, vol. 2017, no. 10, Institute of Physics - IOP Publishing, Oct 2017.
The definitive version is available at https://doi.org/10.1088/1475-7516/2017/10/003
Keywords and Phrases
cosmological simulations; dark matter simulations; power spectrum; redshift surveys
International Standard Serial Number (ISSN)
Article - Journal
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01 Oct 2017