Cosmology with peculiar velocity surveys

Speaker

Fei Qin
Korea Astronomy and Space Science Institute (Republic of Korea)

Abstract

In the local Universe, the gravitational effects of mass density fluctuations exert perturbations on galaxies’ redshifts on top of Hubble’s Law, called ‘peculiar velocities’. These peculiar velocities provide an excellent way to test the cosmological model in the nearby Universe. In this talk, we present new cosmological constraints using peculiar velocities measured with the Cosmicflows-4TF compilation (CF4TF) and the Fundamental Plane Catalogue of Sloan Digital Sky Survey Data Release-14 (SDSSv). Firstly, the dipole and the quadrupole of the peculiar velocity field, commonly named ‘bulk flow’ and ‘shear’ respectively, enable us to test whether our cosmological model accurately describes the motion of galaxies in the nearby Universe. We use an estimator that accurately preserves the error distribution of the measurements to measure these moments. In all cases, our results are consistent with the predictions of the Λ cold dark matter model. Additionally, measurements of the growth rate of structure, fσ₈ in the low-redshift Universe allow us to test different gravitational models. We use joint measurements of the galaxy two point correlation function and velocity correlation functions as well as velocity-galaxy cross correlation function to place new constraints on the growth rate of structure from the SDSSv data. Finally, we introduce the new halo occupation distribution (HOD) model of HI galaxies. It will be used to generate mocks for the future HI galaxy surveys, for example the WALLABY and DESI HI galaxies surveys. These mocks will be the key to estimate the covariance matrix and errors of correlation functions and power spectrum. They can also be used to test the methods of these measurements and density field reconstruction algorithm to identify any possible biases.

Date and Time

November 25 2021
4pm KST (= 7am UTC)

Recording

Link to the recording on Youtube