MIGHTEE-HI: The star-forming properties of HI selected galaxies

TL;DR

This study analyzes 187 HI-selected galaxies to understand how atomic gas influences star formation and galaxy evolution, revealing correlations between gas content, formation time, and environment, with no strong link to filament proximity.

Contribution

It provides new insights into the relationship between HI properties, star formation histories, and large-scale structure in a sample of HI-selected galaxies.

Findings

HI-to-stellar mass ratio correlates with galaxy formation time.

Lower mass, gas-rich galaxies have longer gas depletion times.

No significant correlation between star formation activity and filament proximity.

Abstract

The interplay between atomic gas, the star-formation history of a galaxy and its environment are intrinsically linked, and we need to decouple these dependencies to understand their role in galaxy formation and evolution. In this paper, we analyse the star formation histories (SFHs) of 187 galaxies from the MIGHTEE-HI Survey Early Science Release data, focusing on the relationships between HI properties and star formation. A strong correlation emerges between a galaxy's HI-to-stellar mass ratio and the time of formation, alongside an inverse correlation between stellar mass and time of formation, regardless of the inferred SFH. Additionally, galaxies with lower stellar masses and higher HI-to-stellar mass ratios exhibit longer gas depletion times compared to more massive galaxies, which appear to have depleted their gas and formed stars more efficiently. This suggests that smaller, gas-rich galaxies have higher depletion times due to shallower potential wells and less efficient star formation. Furthermore, we explore the connection between spin-filament alignment and HI content. We find no significant correlation between peak star formation activity and proximity to filaments. However, we do find that the two galaxies in our sample within 1 Mpc of a filament have very low gas-depletion timescales and have their spin axis misaligned with the filament, suggestive of a link between the galaxy properties and proximity to a filament.