Clustering in the Simulated H$\alpha$ Galaxy Redshift Survey from Nancy Grace Roman Space Telescope

TL;DR

This paper creates a detailed mock catalog for the Nancy Grace Roman Space Telescope's H-alpha galaxy survey, assessing its potential to measure cosmological parameters related to dark energy and gravity with high precision.

Contribution

It introduces a realistic simulated galaxy catalog for the Roman HLSS and evaluates its expected cosmological measurement accuracy using advanced mock-based analysis.

Findings

Roman survey can measure angular diameter distance with 2% uncertainty

Hubble parameter can be measured with 3-6% uncertainty

Linear growth parameter can be constrained to 7% uncertainty

Abstract

We present a realistic 2000 deg$^{2}$ H$\alpha$ galaxy mock catalog with $1<z<2$ for the Nancy Grace Roman Space Telescope 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 analyzing real data. We find that the Roman H$\alpha$ galaxy survey alone can measure the angular diameter distance with 2\% uncertainty, the Hubble parameter with 3-6\% uncertainty, and the linear growth parameter with 7\% 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.