# z-GAL -- A NOEMA spectroscopic redshift survey of bright Herschel galaxies: [II] Dust properties

**Authors:** D. Ismail, A. Beelen, V. Buat, S. Berta, P. Cox, F. Stanley, A. Young, S. Jin, R. Neri, T. Bakx, H. Dannerbauer, K. Butler, A. Cooray, A. Nanni, A. Omont, S. Serjeant, P. van der Werf, C. Vlahakis, A. Weiss, C. Yang  
**arXiv:** [2307.15747](https://arxiv.org/abs/2307.15747)  
**Date:** 2023-07-28  
**Summary page:** https://www.summarizepaper.com/en/paper/2307.15747v1/

## Key points

- Study analyzes dust properties of 125 bright Herschel galaxies
- NOEMA used to sample dust continuum emission at 2 and 3 mm
- Spectral energy distribution (SED) analyzed using NOEMA data and other flux densities
- Dust emissivity index (beta) estimated between 1.5 and 3 with high precision
- Dust temperatures range from 20 K to 50 K
- Inverse correlation between dust temperature and beta observed
- Increasing dust temperature as a function of redshift for the sample
- Rate of increase estimated to be 6.5 +/- 0.5 K per unit redshift

## Summary

In the study titled "z-GAL -- A NOEMA spectroscopic redshift survey of bright Herschel galaxies: [II] Dust properties," Ismail et al. present a comprehensive analysis of the dust properties of 125 bright Herschel galaxies selected from the z-GAL survey. The authors utilize the large instantaneous bandwidth of NOEMA to sample the dust continuum emission at 2 and 3 mm in the observed frame, with flux densities measured in at least four side bands for each source. To analyze the spectral energy distribution (SED) of each galaxy, Ismail et al. combine the NOEMA data with available flux densities at Herschel wavelengths (250, 350, and 500 microns) and SCUBA-2 wavelength (850 microns). This extensive dataset allows for a detailed examination of the SED from far-infrared to millimeter wavelengths, providing a fine sampling of the Rayleigh-Jeans tail. The wealth of data enables the derivation of robust dust properties, particularly focusing on two key parameters: the dust emissivity index (beta) and the dust temperature (T(dust)). To demonstrate their ability to constrain these parameters accurately, the authors employ a flux-generated mock catalog and analyze it under assumptions of both optically thin and optically thick modified black body emission. For the z-GAL sources studied, Ismail et al. report a range of dust emissivities with beta estimated between 1.5 and 3. These estimates are determined with high precision, accompanied by relative uncertainties ranging from 7% to 15%, with an average value of 2.2 +/- 0.3. Additionally, they find that dust temperatures vary between 20 K and 50 K, with an average temperature around T(dust) ~30 K for optically thin cases and approximately T(dust) ~38 K for optically thick cases. The authors also estimate the dust masses and apparent infrared luminosities for all sources based on an optically thin approach. They observe an inverse correlation between T(dust) and beta which is consistent with similar findings in local Universe studies. Furthermore, Ismail et al report an intriguing trend of increasing dust temperature as a function redshift for this 500 micron-selected sample; they estimate this rate to be 6.5 +/- 0.5 K per unit redshift which opens up possibilities for further exploration into evolution across cosmic time scales .