# z-GAL -- A NOEMA spectroscopic redshift survey of bright Herschel galaxies: [I] Overview

**Authors:** P. Cox, R. Neri, S. Berta, D. Ismail, F. Stanley, A. Young, S. Jin, T. Bakx, A. Beelen, H. Dannerbauer, M. Krips, M. Lehnert, A. Omont, D. A. Riechers, A. J. Baker, G. Bendo, E. Borsato, V. Buat, K. Butler, N. Chartab  
**arXiv:** [2307.15732](https://arxiv.org/abs/2307.15732)  
**Date:** 2023-07-28  
**Summary page:** https://www.summarizepaper.com/en/paper/2307.15732v1/

## Key points

- The z-GAL survey used the IRAM NOEMA interferometer to measure redshifts of 126 bright galaxies detected in Herschel surveys
- 124 of these galaxies have reliable spectroscopic redshifts estimated from scans of the 3 and 2-mm bands
- Together with the Pilot Programme, a total of 135 bright Herschel-selected galaxies have precise redshifts
- Majority of emission lines detected are from 12CO, with some sources also showing [CI] and H2O emission lines
- Spectroscopic redshifts range from 0.8 < z < 6.55, with a median value of z=2.56 +/- 0.10
- Line widths generally large, with mean full width at half maximum Delta(V) of 590 +/-25 km/s
- Most sources appear unresolved or barely resolved on scales of 2 to 3 arcsec
- Some fields reveal double or multiple sources and even sources at different redshifts, resulting in a total count of 165 individual sources with robust spectroscopic redshifts
- The z-GAL survey provides an overview of observed properties such as emission lines and derived spectroscopic redshifts

## Summary

The z-GAL survey has used the IRAM NOEMA interferometer to measure the redshifts of 126 bright galaxies detected in the Herschel H-ATLAS, HeLMS, and HerS surveys. Out of these galaxies, 124 have reliable spectroscopic redshifts estimated from scans of the 3 and 2-mm bands (and in one case, the 1-mm band) based on the detection of at least two emission lines. Together with the Pilot Programme which included 11 sources, a total of 135 bright Herschel-selected galaxies have precise redshifts. This is currently the largest sample of high-z galaxies with robust redshifts. The majority of emission lines detected are from 12CO (mainly from J=2-1 to 5-4), although some sources also show [CI] and H2O emission lines. The spectroscopic redshifts range from 0.8 < z < 6.55 with a median value of z=2.56 +/- 0.10 and line widths generally large with a mean value for full width at half maximum Delta(V) of 590 +/-25 km/s; about 35% having line widths between 700 km/s < Delta(V) <1800 km/s. Most sources appear unresolved or barely resolved on scales of 2 to 3 arcsec (or linear sizes of approximately15-25 kpc). However, some fields reveal double or multiple sources and even sources at different redshifts resulting in a total count of 165 individual sources with robust spectroscopic redshifts including lensed galaxies, binary systems, and over-densities. The z-GAL survey provides an overview of observed properties such as emission lines and derived spectroscopic redshifts along with an atlas for the entire sample which will serve as foundation for further papers reporting on dust emission, molecular and atomic gas properties as well as detailed analysis on nature of these sources.