The Wavelength Dependence of High-Redshift Galaxy Structure in the Rest-Frame Ultraviolet

TL;DR

This study examines how the UV light distribution in high-redshift star-forming galaxies varies with wavelength, revealing insights into galaxy structure, star formation, and dust content over cosmic time.

Contribution

It provides the first detailed analysis of the wavelength dependence of galaxy size and concentration at 0.5 < z < 1.5, highlighting structural differences related to bulges and dust.

Findings

Size decreases by ~5% from 1500 Å to 3000 Å.

Concentration decreases more sharply in the far-UV for large galaxies at z ~ 1.

Inner light profile flattening suggests older stellar populations or dust in bulges.

Abstract

We present the rest-frame UV wavelength dependence of the Petrosian-like half-light radius ($r_{50}$), and the concentration parameter for a sample of 198 star-forming galaxies at 0.5 < z < 1.5. We find a ~5% decrease in $r_{50}$ from 1500 \AA\ to 3000 \AA, with half-light radii at 3000 \AA\ ranging from 0.6 kpc to 6 kpc. We also find a decrease in concentration of ~0.07 (1.9 < $C_{3000}$ < 3.9). The lack of a strong relationship between $r_{50}$ and wavelength is consistent with a model in which clumpy star formation is distributed over length scales comparable to the galaxy's rest-frame optical light. While the wavelength dependence of $r_{50}$ is independent of size at all redshifts, concentration decreases more sharply in the far-UV (~1500 \AA) for large galaxies at z ~ 1. This decrease in concentration is caused by a flattening of the inner ~20% of the light profile in disk-like galaxies, indicating that the central regions have different UV colors than the rest of the galaxy. We interpret this as a bulge component with older stellar populations and/or more dust. The size-dependent decrease in concentration is less dramatic at z ~ 2, suggesting that bulges are less dusty, younger, and/or less massive than the rest of the galaxy at higher redshifts.