Massive Star-Forming Galaxies Have Converted Most of Their Halo Gas into Stars

TL;DR

This study finds that massive star-forming galaxies in the local universe have converted over 60% of their halo gas into stars, challenging current galaxy formation models and suggesting a need to revise our understanding of galaxy evolution.

Contribution

The paper reveals that a significant fraction of halo gas in massive star-forming galaxies is converted into stars, which is higher than predicted by existing models, indicating incomplete understanding of galaxy formation processes.

Findings

Massive star-forming galaxies have >60% efficiency in converting halo gas into stars.

Current galaxy formation models do not reproduce this high efficiency.

Implications for circumgalactic media and star formation quenching are discussed.

Abstract

In the local Universe, the efficiency for converting baryonic gas into stars is very low. In dark matter halos where galaxies form and evolve, the average efficiency varies with galaxy stellar mass and has a maximum of about twenty percent for Milky-Way-like galaxies. The low efficiency at higher mass is believed to be produced by some quenching processes, such as the feedback from active galactic nuclei. We perform an analysis of weak lensing and satellite kinematics for SDSS central galaxies. Our results reveal that the efficiency is much higher, more than sixty percent, for a large population of massive star-forming galaxies around $10^{11}M_{\odot}$. This suggests that these galaxies acquired most of the gas in their halos and converted it into stars without being affected significantly by quenching processes. This population of galaxies is not reproduced in current galaxy formation models, indicating that our understanding of galaxy formation is incomplete. The implications of our results on circumgalactic media, star formation quenching and disc galaxy rotation curves are discussed. We also examine systematic uncertainties in halo-mass and stellar-mass measurements that might influence our results.