# The Dust Attenuation of Star-forming Galaxies at $z\sim3$ and Beyond: New Insights from ALMA Observations

## TL;DR

This study investigates dust attenuation in high-redshift star-forming galaxies using ALMA data, revealing that dust correction methods valid at z~3 may not apply at higher redshifts, indicating evolution in dust properties.

## Contribution

The paper provides new observational evidence of redshift evolution in the IRX-$eta_{
m UV}$ relation beyond z~3 using ALMA data, challenging the universality of local dust correction calibrations.

## Key findings

- IRX-$eta_{
m UV}$ relation at z~3 aligns with local starburst galaxies
- Large dispersion observed around the IRX-$eta_{
m UV}$ relation
- Evidence for evolution of IRX-$eta_{
m UV}$ at z>3 towards lower IRX values

## Abstract

We present results on the dust attenuation of galaxies at redshift $\sim3-6$ by studying the relationship between the UV spectral slope ($\beta_{\rm UV}$) and the infrared excess (IRX; $L_{\rm IR}$/$L_{\rm UV}$) using ALMA far-infrared continuum observations. Our study is based on a sample of 67 massive, star-forming galaxies with a median mass of $M_{\ast}\sim 10^{10.7}\,M_{\rm \odot}$ spanning a redshift range $z=2.6-3.7$ (median $z=3.2$) that were observed with ALMA at $\lambda_{rest}=300\,{\rm \mu m}$. Both the individual ALMA detections (41 sources) and stacks including all galaxies show the IRX-$\beta_{\rm UV}$ relationship at $z\sim3$ is mostly consistent with that of local starburst galaxies on average. However, we find evidence for a large dispersion around the mean relationship by up to $\pm0.5$ dex. Nevertheless, the locally calibrated dust correction factors based on the IRX-$\beta_{\rm UV}$ relation are on average applicable to main-sequence $z\sim3$ galaxies. This does not appear to be the case at even higher redshifts, however. Using public ALMA observations of $z\sim4-6$ galaxies we find evidence for a significant evolution in the IRX-$\beta_{\rm UV}$ and the IRX-$M_{\ast}$ relations beyond $z\sim3$ toward lower IRX values. We discuss several caveats that could affect these results, including the assumed dust temperature. ALMA observations of larger $z>3$ galaxy samples will be required to confirm this intriguing redshift evolution.