Speaker
Description
A density field mapped from a galaxy redshift survey can be used to predict the peculiar velocity field, up to normalisation and any external tidal field. Fitting such a model for the predicted peculiar velocities to those measured using a distance estimator such as the Tully-Fisher relation provides a test for theories of gravity via a measurement of the growth factor. We present a Bayesian forward-modelling method that simultaneously determines the parameters of both the Tully-Fisher relation and the peculiar velocity field, while incorporating a selection function and an intrinsic Tully-Fisher scatter model. We also show how this methodology can be applied to improve upon Tully-Fisher measurements of the Hubble constant and directly measure possible variations of H_0 on the sky. The former is currently limited by uncertainties in the absolute calibration, but the latter is only limited by sample size and sky/redshift coverage. These methods were applied to the Cosmiclfows-4 Tully-Fisher dataset to obtain measurements on the growth rate, H_0, and a possible dipole in H_0. Using Tully-Fisher mocks of the ongoing WALLABY survey, we show the extent to which each of these constraints will be improved.
