HI Intensity Mapping cross-correlation with thermal SZ fluctuations: forecasted cosmological parameters estimation for FAST and Planck

TL;DR

This paper forecasts the potential of cross-correlating HI intensity mapping from FAST with thermal SZ data from Planck to improve cosmological parameter constraints and understand HI distribution in galaxy clusters.

Contribution

It introduces a forecast method for cross-correlation between HI intensity mapping and SZ fluctuations, estimating its effectiveness in constraining cosmological parameters and halo properties.

Findings

Potential to measure cosmic neutral hydrogen density with high precision.

Halo masses contributing to the cross-power spectrum are around 1.5×10^14 solar masses.

Cross-correlation can probe HI distribution within halos at low redshift.

Abstract

The 21 cm emission from neutral hydrogen surveys holds great potential as a valuable method for exploring the large-scale structure of the Universe. In this paper, we forecast for the cross-correlation between the Thermal Sunyaev-Zel'dovich (SZ) fluctuations as probed by the Planck satellite, and fluctuations in the HI brightness temperature as probed by the ground-based Five-hundred-meter Aperture Spherical Telescope (FAST), to trace the connection between galaxy clusters and the HI large-scale structure. Assuming that the measurement is limited by instrumental noise rather than by foreground, we estimate the potential detectability of the cross-correlation signal and their improvement in the measurement of the HI cosmic density, the hydrostatic mass bias parameter, and the universal pressure profile (UPP) parameters. We obtain a constraint on the cosmic neutral hydrogen density parameter significantly to $\sigma(\Omega_{\rm HI}) = 1.0 \times 10^{-6}$. We also find that the average halo masses contributing to the ${{\rm HI}-y}$ cross-power spectrum in the one-halo regime is $\sim 1.5\times 10^{14} M_{\odot}$. Our results also show that the HI-SZ cross-correlation has great potential to probe the distribution of neutral hydrogen (HI) within halos at low redshift.