Constraining the optical depth of galaxies and velocity bias with crosscorrelation between the kinetic SunyaevZeldovich effect and the peculiar velocity field
Abstract
We calculate the crosscorrelation function < (Δ T/T)({v}\cdot \hat{n}/σ _v) > between the kinetic SunyaevZeldovich (kSZ) effect and the reconstructed peculiar velocity field using linear perturbation theory, with the aim of constraining the optical depth τ and peculiar velocity bias of central galaxies with Planck data. We vary the optical depth τ and the velocity bias function b_{v}(k) = 1 + b(k/k_{0})^{n}, and fit the model to the data, with and without varying the calibration parameter y_{0} that controls the vertical shift of the correlation function. By constructing a likelihood function and constraining the τ, b and n parameters, we find that the quadratic powerlaw model of velocity bias, b_{v}(k) = 1 + b(k/k_{0})^{2}, provides the best fit to the data. The bestfit values are τ = (1.18 ± 0.24) × 10^{4}, b=0.84^{+0.16}_{0.20} and y_{0}=(12.39^{+3.65}_{3.66})× 10^{9} (68 per cent confidence level). The probability of b > 0 is only 3.12 × 10^{8} for the parameter b, which clearly suggests a detection of scaledependent velocity bias. The fitting results indicate that the largescale (k ≤ 0.1 h Mpc^{1}) velocity bias is unity, while on small scales the bias tends to become negative. The value of τ is consistent with the stellar masshalo mass and optical depth relationship proposed in the literature, and the negative velocity bias on small scales is consistent with the peak background split theory. Our method provides a direct tool for studying the gaseous and kinematic properties of galaxies.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 March 2018
 DOI:
 10.1093/mnras/stx3063
 arXiv:
 arXiv:1711.08756
 Bibcode:
 2018MNRAS.475..379M
 Keywords:

 methods: statistical;
 galaxies: kinematics and dynamics;
 largescale structure of Universe;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 13 pages, 13 figures, 3 tables