# Revealing the Stellar Mass and Dust Distributions of Submillimeter Galaxies at Redshift 2

## TL;DR

This study combines ALMA and HST observations to analyze the detailed dust and stellar mass distributions in 20 submillimeter galaxies at redshift 2, revealing compact dust regions and insights into galaxy evolution.

## Contribution

It provides the first resolved structural analysis of dust and stellar components in high-redshift SMGs using combined ALMA and HST data, highlighting their compact dust configurations.

## Key findings

- Dust regions are more compact than stellar components (median ratio 0.6).
- Centroid positions of dust and stars agree within 1.1 kpc.
- SMGs show centrally enhanced star formation, unlike local spirals.

## Abstract

We combine high-resolution ALMA and HST/CANDELS observations of 20 submillimeter galaxies (SMGs) predominantly from the AS2UDS survey at z~2 with bright rest-frame optical counterparts (Ks < 22.9) to investigate the resolved structural properties of their dust and stellar components. We derive two-dimensional stellar-mass distributions that are inferred from spatial mass-to-light ratio (M/L) corrections based on rest-frame optical colors. Due to the high central column densities of dust in our SMGs, our mass distributions likely represent a lower limit to the true central mass density. The centroid positions between the inferred stellar-mass and the dust distributions agree within 1.1 kpc, indicating an overall good spatial agreement between the two components. The majority of our sources exhibit compact dust configurations relative to the stellar component (with a median ratio of effective radii Re,dust/Re,Mstar = 0.6). This ratio does not change with specific star-formation rate (sSFR) over the factor of 30 spanned by our targets, sampling the locus of "normal" main sequence galaxies up to the starburst regime, log(sSFR/sSFRMS) > 0.5. Our results imply that massive SMGs are experiencing centrally enhanced star formation unlike typical spiral galaxies in the local Universe. The sizes and stellar densities of our SMGs are in agreement with those of the passive population at z=1.5, consistent with these systems being the descendants of z~2 SMGs.