# Quenching of star formation from a lack of inflowing gas to galaxies

**Authors:** Katherine E. Whitaker, Christina C. Williams, Lamiya Mowla, Justin S. Spilker, Sune Toft, Desika Narayanan, Alexandra Pope, Georgios E. Magdis, Pieter G. van Dokkum, Mohammad Akhshik, Rachel Bezanson, Gabriel B. Brammer, Joel Leja, Allison Man, Erica J. Nelson, Johan Richard, Camilla Pacifici, Keren Sharon, Francesco Valentino  
**arXiv:** [2109.10384](https://arxiv.org/abs/2109.10384)  
**Date:** 2021-09-21  
**Summary page:** https://www.summarizepaper.com/en/paper/2109.10384v1/

## Key points

- Star formation in half of massive galaxies halted by the time the Universe was three billion years old
- Very low amounts of molecular gas responsible for quenching in some cases
- Other potential factors include morphological gas stabilization, shock heating, or activity associated with accretion onto a central supermassive black hole
- Previous studies limited by insufficiently sensitive upper limits or use of stacked emission
- Researchers conducted 1.3mm observations of dust emission from six strongly lensed galaxies where star formation had been quenched
- Four out of six galaxies undetected in dust emission
- Upper limit on dust mass estimated to be 0.0001 times the stellar mass, corresponding to 0.01 times the stellar mass in molecular gas (two orders of magnitude less than star-forming galaxies at similar redshifts)
- Gas depletion plays a role in halting star formation in a fraction of high-redshift galaxies
- Findings shed light on mechanisms behind galaxy evolution and star formation throughout cosmic history

## Summary

A recent study has found that star formation in half of massive galaxies was halted by the time the Universe was three billion years old. The researchers discovered that very low amounts of molecular gas were responsible for this quenching, at least in some cases. Other potential factors include morphological gas stabilization, shock heating, or activity associated with accretion onto a central supermassive black hole. Previous studies on quenching by gas depletion have been limited by insufficiently sensitive upper limits or the use of stacked emission, which can lead to issues with averaging. To address these limitations, the researchers conducted 1.3mm observations of dust emission from six strongly lensed galaxies where star formation had been quenched. These galaxies were magnified up to a factor of 30. Out of the six galaxies studied, four were undetected in dust emission. The researchers estimated an upper limit on the dust mass for these galaxies to be 0.0001 times the stellar mass. By proxy (assuming a Milky Way molecular gas-to-dust ratio), this corresponds to 0.01 times the stellar mass in molecular gas - two orders of magnitude less than what is seen in star-forming galaxies at similar redshifts. While it remains challenging to extrapolate from such small samples, these observations provide evidence that gas depletion plays a role in halting star formation in a fraction of high-redshift galaxies and shed light on the mechanisms behind galaxy evolution and star formation throughout cosmic history. The findings have been published online by Nature and offer valuable insights into how and why star formation ceases in certain galactic environments.