The Opacity of Galactic Disks at z~0.7

TL;DR

This study compares the opacity of galactic disks at z~0.7 with local universe disks, finding that high-redshift disks are more opaque, indicating evolution in dust content or distribution over cosmic time.

Contribution

It provides the first comparison of surface brightness-inclination relations for disks at z~0.7 with local disks, revealing increased opacity at higher redshift.

Findings

High-redshift disks are more opaque than local disks.

Surface brightness-inclination relation is flatter at z~0.7.

Opacity increase could be due to more dust or different dust distribution.

Abstract

We compare the surface brightness-inclination relation for a sample of COSMOS pure disk galaxies at z~0.7 with an artificially redshifted sample of SDSS disks well matched to the COSMOS sample in terms of rest-frame photometry and morphology, as well as their selection and analysis. The offset between the average surface brightness of face-on and edge-on disks in the redshifted SDSS sample matches that predicted by measurements of the optical depth of galactic disks in the nearby universe. In contrast, large disks at z~0.7 have a virtually flat surface brightness-inclination relation, suggesting that they are more opaque than their local counterparts. This could be explained by either an increased amount of optically thick material in disks at higher redshift, or a different spatial distribution of the dust.