Clustering in the simulated H α galaxy redshift survey from Nancy Grace Roman Space Telescope

Abstract

ABSTRACT We present a realistic 2000 deg2 H α galaxy mock catalogue with 1 < z < 2 for the Nancy Grace Roman Space Telescope (Roman) galaxy redshift survey, the High Latitude Spectroscopic Survey (HLSS), created using Galacticus, a semi-analytical galaxy formation model, and high-resolution cosmological N-body simulations. Galaxy clustering can probe dark energy and test gravity via baryon acoustic oscillation (BAO) and redshift space distortion (RSD) measurements. Using our realistic mock as the simulated Roman HLSS data, and a covariance matrix computed using a large set of approximate mocks created using ezmock, we investigate the expected precision and accuracy of the BAO and RSD measurements using the same analysis techniques used in analysing real data. We find that the Roman H α galaxy survey alone can measure the angular diameter distance with 2 per cent uncertainty, the Hubble parameter with 3–6 per cent uncertainty, and the linear growth parameter with 7 per cent uncertainty, in each of four redshift bins. Our realistic forecast illustrates the power of the Roman galaxy survey in probing the nature of dark energy and testing gravity.