# SUNRISE: The rich molecular inventory of high-redshift dusty galaxies revealed by broadband spectral line surveys

**Authors:** Chentao Yang, Alain Omont, Sergio Martín, Thomas G. Bisbas, Pierre Cox, Alexandre Beelen, Eduardo González-Alfonso, Raphaël Gavazzi, Susanne Aalto, Paola Andreani, Cecilia Ceccarelli, Yu Gao, Mark Gorski, Michel Guélin, Hai Fu, Rob J. Ivison, Kirsten K. Knudsen, Matthew Lehnert, Hugo Messias, Sebastien Muller  
**arXiv:** [2308.07368](https://arxiv.org/abs/2308.07368)  
**Date:** 2023-08-14  
**Summary page:** https://www.summarizepaper.com/en/paper/2308.07368v1/

## Key points

- Understanding the nature of high-redshift (high-$z$) dusty galaxies and their interstellar medium (ISM) is crucial for unraveling the early Universe's evolution.
- Current knowledge of the molecular ISM in these objects is limited, commonly studied using only a few species beyond carbon monoxide (CO).
- Deep 3 mm spectral line surveys using NOEMA were conducted on two lensed dusty galaxies: APM 08279+5255 (APM) and NCv1.143 (NC).
- The surveys covered rest-frame frequencies ranging from about 330-550 GHz.
- The authors detected 38 emission lines in APM and 25 in NC, revealing the chemical richness and complexity of the ISM in these high-$z$ galaxies.
- Comparing the spectra and conducting gas excitation analysis, significant differences were found in physical properties and chemical imprints between APM and NC.
- Molecular gas in APM is more excited than in NC, exhibiting higher temperatures and densities.
- Chemical abundances in APM resemble those found in local active galactic nuclei (AGN), showing boosted relative abundances of dense gas tracers possibly linked to high-temperature chemistry and/or X-ray Dominated Regions (XDRs).
- NC more closely resembles local starburst galaxies.
- Water vapor (H2O) is significantly brighter at the 448 GHz H2O line in APM, likely associated with intense far-infrared radiation from dust powered by AGN activity.
- Astrochemical modeling suggests that at high column densities, ultraviolet (UV) radiation plays a less significant role while cosmic rays (CRs), X-rays, and shocks become key players in shaping molecule abundance.
- The deep spectral line surveys provide a new window for studying physical properties and chemical composition of interstellar medium within distant galaxies located at early stages of Universe's evolution process.

## Summary

Understanding the nature of high-redshift (high-$z$) dusty galaxies and their interstellar medium (ISM) is crucial for unraveling the early Universe's evolution. However, our current knowledge of the molecular ISM in these objects is limited, as it is commonly studied using only a few species beyond carbon monoxide (CO). In this paper, the authors present the results of deep 3 mm spectral line surveys using NOEMA, targeting two lensed dusty galaxies: APM 08279+5255 (APM), a quasar at redshift $z=3.911$, and NCv1.143 (NC), a starburst galaxy at $z=3.565$. The surveys cover rest-frame frequencies ranging from about 330-550 GHz. The authors report the detection of 38 and 25 emission lines in APM and NC, respectively. These spectra reveal the chemical richness and complexity of the physical properties of the ISM in these high-$z$ galaxies. By comparing the spectra of APM and NC and conducting gas excitation analysis, they find significant differences in both physical properties and chemical imprints between the two sources. In particular, they observe that molecular gas in APM is more excited than in NC, exhibiting higher temperatures and densities. The chemical abundances in APM resemble those found in local active galactic nuclei (AGN), showing boosted relative abundances of dense gas tracers that may be linked to high-temperature chemistry and/or X-ray Dominated Regions (XDRs). On the other hand, NC more closely resembles local starburst galaxies. One notable difference between APM and NC is found in water vapor (H2O), where the 448 GHz H2O line is significantly brighter in APM. This brightness is likely associated with intense far-infrared radiation from dust powered by AGN activity. The authors' astrochemical model suggests that at such high column densities, ultraviolet (UV) radiation plays a less significant role in regulating the ISM while cosmic rays (CRs), X-rays, and shocks become key players in shaping molecules' abundance. The deep spectral line surveys conducted in this study provide a new window for studying physical properties as well as chemical composition of interstellar medium within distant galaxies located at early stages of Universe's evolution process. By expanding our understanding of high-$z$ dusty galaxies' molecular complexity we can gain valuable insights into their formation and evolution processes.