# The SUPERCOLD-CGM survey: \\ I. Probing the extended CO(4-3) Emission of the Circumglactic medium in a sample of 10 Enormous Ly$α$ Nebulae at $z\sim2$

**Authors:** Jianrui Li, Bjorn H. C. Emonts, Zheng Cai, Jianan Li, Fabrizio Arrigoni Battaia, Jason X Prochaska, Ilsang Yoon, Matthew D. Lehnert, Craig Sarazin, Yunjing Wu, Mark Lacy, Brian Mason, Kyle Massingill  
**arXiv:** [2304.02041](https://arxiv.org/abs/2304.02041)  
**Date:** 2023-04-04  
**Summary page:** https://www.summarizepaper.com/en/paper/2304.02041v1/

## Key points

- The study investigates the cold molecular gas on CGM scales at high redshifts.
- CO(4-3) is detected in all targets, with 60% exhibiting extended CO emission.
- Q1228+3128 stands out with the most extensive CO(4-3) reservoir spanning approximately 100 kiloparsecs.
- Radio-loud object Q1228+3128 shows a possible connection between inner radio-jets and cold halo gas.
- Four out of five radio-quiet ELANe exhibit predominantly extended CO(4-3) emission towards their companions.
- No evidence for diffuse molecular gas spread across the full extent of the Lyα nebulae based on CO(4-3) observations.
- Q0107 shows significant evidence for a massive CO disk associated with the QSO itself.
- 70% of the QSO fields contain at least one companion with detectable CO emission, two of which reveal extended CO outside of their respective ELANe.
- The findings provide insights into the roles of both the cold CGM and companions in driving early evolution of massive galaxies.

## Summary

The  investigates the  of  at high redshifts with their halo gas reservoirs. This study focuses on the coldest phase of the , which is directly related to stellar growth. It is the first statistical examination of cold molecular gas on CGM scales. The authors present  of CO(4-3) and continuum emission from 10 Enormous Ly$\alpha$ Nebulae (ELANe) surrounding ultraluminous type-I QSOs at a redshift of approximately 2. The results show that CO(4-3) is detected in all targets, with 60% exhibiting extended CO emission on scales ranging from 15 to 100 kiloparsecs. Among the observed ELANe, Q1228+3128 stands out as it reveals the most extensive CO(4-3) reservoir spanning approximately 100 kiloparsecs. Notably, this target is also the only radio-loud object in the sample. The location of the CO reservoir along the radio axis suggests a possible connection between inner radio-jets and cold halo gas. For five radio-quiet ELANe, four exhibit predominantly extended CO(4-3) emission towards their companions. These extended CO reservoirs indicate enrichment of the CGM and may potentially contribute to widespread star formation. However, there is no evidence for diffuse molecular gas spread across the full extent of the Ly$\alpha$ nebulae based on CO(4-3) observations. One target in the sample (Q0107) shows significant evidence for a massive CO disk associated with the QSO itself. Additionally, 70% of the QSO fields contain at least one companion with detectable CO emission, two of which reveal extended CO outside of their respective ELANe. Overall, the findings provide valuable insights into the roles of both the cold CGM and companions in driving the early evolution of massive galaxies. The detection and characterization of extended CO(4-3) reservoirs highlight the enrichment of the CGM, while the presence of CO companions suggests potential interactions and gas exchange between galaxies. These results contribute to our understanding of how massive galaxies at high redshifts co-evolve with their surrounding halo gas.