Galaxy redshift surveys selected by neutral hydrogen using FAST

TL;DR

This paper explores the feasibility of conducting a large-scale galaxy redshift survey using 21cm neutral hydrogen emission with FAST, aiming to improve cosmological constraints beyond optical surveys.

Contribution

It presents a detailed feasibility analysis and estimates for a 21cm HI survey with FAST, highlighting its potential to complement optical surveys and refine cosmological parameters.

Findings

Survey could detect ~10^7 galaxies in two years

Constraints on Gamma and n_s could be significantly improved

Potential to measure w within 5% of -1 using combined data

Abstract

We discuss the possibility of performing a substantial spectroscopic galaxy redshift survey selected via the 21cm emission from neutral hydrogen using the Five-hundred metre Aperture Spherical Telescope (FAST) to be built in China. We consider issues related to the estimation of the source counts and optimizations of the survey, and discuss the constraints on cosmological models that such a survey could provide. We find that a survey taking around two years could detect ~10^7 galaxies with an average redshift of ~0.15 making the survey complementary to those already carried out at optical wavelengths. These conservative estimates have used the z=0 HI mass function and have ignored the possibility of evolution. The results could be used to constrain Gamma = (Omega_m h) to 5 per cent and the spectral index, n_s, to 7 per cent independent of cosmic microwave background data. If we also use simulated power spectra from the Planck satellite, we can constrain w to be within 5 per cent of -1.