# Massive and Multiphase Gas Outflow in a Quenching Galaxy at z=2.445

**Authors:** Sirio Belli, Minjung Park, Rebecca L. Davies, J. Trevor Mendel, Benjamin D. Johnson, Charlie Conroy, Chloë Benton, Letizia Bugiani, Razieh Emami, Joel Leja, Yijia Li, Gabriel Maheson, Elijah P. Mathews, Rohan P. Naidu, Erica J. Nelson, Sandro Tacchella, Bryan A. Terrazas, Rainer Weinberger  
**arXiv:** [2308.05795](https://arxiv.org/abs/2308.05795)  
**Date:** 2023-08-10  
**Summary page:** https://www.summarizepaper.com/en/paper/2308.05795v1/

## Key points

- Large-scale outflows driven by supermassive black holes suppress star formation in massive galaxies
- Lack of direct observational evidence for this hypothesis, especially in the young universe
- Outflows of ionized gas commonly detected in distant massive galaxies, but not enough to suppress star formation effectively
- Gas ejection expected to be more efficient in neutral and molecular phases
- Deep spectroscopy from JWST identifies outflow of both neutral and ionized gas in a rapidly quenching galaxy at redshift z=2.445
- Majority of outflowing mass is in the neutral phase, with expulsion rate exceeding residual star formation rate
- Possible presence of a supermassive black hole indicated by properties of ionized gas emission lines
- Supermassive black holes can rapidly suppress star formation by efficiently ejecting neutral gas
- Research provides important observational evidence supporting role of supermassive black hole-driven outflows in regulating star formation during early stages of galaxy evolution

## Summary

Large-scale outflows driven by supermassive black holes are believed to play a crucial role in suppressing star formation in massive galaxies. However, there has been a lack of direct observational evidence for this hypothesis, especially in the young universe where star formation quenching occurs rapidly and requires efficient removal of gas. While outflows of ionized gas have been commonly detected in distant massive galaxies, the amount of ejected mass has been too small to effectively suppress star formation. It is expected that gas ejection would be more efficient in the neutral and molecular phases, but observations at high redshifts have only shown these phases in starbursts and quasars. In this study, using deep spectroscopy from the James Webb Space Telescope (JWST), researchers have identified the presence of an outflow of both neutral and ionized gas in a massive galaxy undergoing rapid quenching of its star formation at a redshift of z=2.445. The majority of the outflowing mass is found to be in the neutral phase, and the rate at which mass is being expelled exceeds the residual star formation rate. This suggests that the ejection of gas is likely to have a significant impact on the evolution of the galaxy. Although X-ray or radio activity was not detected, properties of the ionized gas emission lines indicate the possible presence of a supermassive black hole. As a result, it can be concluded that supermassive black holes are capable of rapidly suppressing star formation in massive galaxies by efficiently ejecting neutral gas. This research provides important observational evidence supporting the role of supermassive black hole-driven outflows in regulating star formation in galaxies during their early stages. By better understanding these processes, scientists can gain insights into how galaxies evolve over time and how black holes influence their growth and development.