Redshift-space distortions with split densities
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Date
2021
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Abstract
Accurate modelling of redshift-space distortions (RSD) is challenging in the nonlinear regime for two-point statistics e.g. the two-point correlation function (2PCF). We take a different perspective to split the galaxy density field according to the local density, and cross-correlate those densities with the entire galaxy field. We demonstrate that combining a series of cross-correlation functions (CCFs) offers improvements over the 2PCF as follows: 1. The distribution of peculiar velocities in each split density is nearly Gaussian. This allows the Gaussian streaming model for RSD to perform accurately for a wide range of scales. 2. The probability distribution function of the density field at small scales is non-Gaussian, but the CCFs of split densities capture the non-Gaussianity, leading to improved cosmological constraints over the 2PCF. We can obtain unbiased constraints on the growth parameter fσ12 at the per-cent level, and Alcock-Paczynski (AP) parameters at the sub-per-cent level with the minimal scale of 15 Mpc/h. This is a ~30 per cent and ~6 times improvement over the 2PCF, respectively. 3. Baryon acoustic oscillations (BAO) are contained in all CCFs of split densities. Including BAO scales helps to break the degeneracy between the line-of-sight and transverse AP parameters, allowing independent constraints on them. We test our methodology on N-body simulations and apply it to the BOSS DR12 galaxy samples, obtaining constraints for the growth rate of structure at different redshifts.
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Tesis (Ph.D. in Astrophysics)--Pontificia Universidad Católica de Chile, 2021