New constraints on the evolution of the MHI-M* scaling relation combining CHILES and MIGHTEE-HI data

TL;DR

This study uses combined HI data from two surveys at z=0.36 to refine the galaxy HI-stellar mass relation, revealing evolutionary trends and gas accretion insights relevant for future SKA research.

Contribution

It presents the first robust HI-stellar mass relation at z=0.36 by stacking data from MIGHTEE and CHILES, highlighting the evolution of atomic gas in galaxies.

Findings

Galaxies at z=0.36 are HI richer than local galaxies but poorer than at z=1.

The HI-stellar mass relation slope remains consistent across redshift.

Cold gas accretion is slower than molecular gas consumption in star formation.

Abstract

The improved sensitivity of interferometric facilities to the 21-cm line of atomic hydrogen (HI) enables studies of its properties in galaxies beyond the local Universe. In this work, we perform a 21 cm line spectral stacking analysis combining the MIGHTEE and CHILES surveys in the COSMOS field to derive a robust HI-stellar mass relation at z=0.36. In particular, by stacking thousands of star-forming galaxies subdivided into stellar mass bins, we optimize the signal-to-noise ratio of targets and derive mean HI masses in the different stellar mass intervals for the investigated galaxy population. We combine spectra from the two surveys, estimate HI masses, and derive the scaling relation log10(MHI) = (0.32 +- 0.04)log10(M*) + (6.65 +- 0.36). Our findings indicate that galaxies at z=0.36 are HI richer than those at z=0, but HI poorer than those at z=1, with a slope consistent across redshift, suggesting that stellar mass does not significantly affect HI exchange mechanisms. We also observe a slower growth rate HI relative to the molecular gas, supporting the idea that the accretion of cold gas is slower than the rate of consumption of molecular gas to form stars. This study contributes to understanding the role of atomic gas in galaxy evolution and sets the stage for future development of the field in the upcoming SKA era.