The Star Formation and Extinction Co-Evolution of UV-Selected Galaxies over 0.05<z<1.2

TL;DR

This study investigates how star formation and dust extinction co-evolve in UV-selected galaxies from redshift 0.05 to 1.2, revealing systematic trends with galaxy mass and age using a novel stacking technique.

Contribution

It introduces a new stacking method to analyze IR and UV flux ratios across a broad redshift range, providing insights into galaxy evolution and gas exhaustion processes.

Findings

IRX increases with mass up to a characteristic mass M_0

Above M_0, IRX decreases, indicating gas exhaustion

SSFR and IRX evolve systematically with galaxy age and mass

Abstract

We use a new stacking technique to obtain mean mid IR and far IR to far UV flux ratios over the rest near-UV/near-IR color-magnitude diagram. We employ COMBO-17 redshifts and COMBO-17 optical, GALEX far and near UV, Spitzer IRAC and MIPS Mid IR photometry. This technique permits us to probe infrared excess (IRX), the ratio of far IR to far UV luminosity, and specific star formation rate (SSFR) and their co-evolution over two orders of magnitude of stellar mass and redshift 0.1<z<1.2. We find that the SSFR and the characteristic mass (M_0) above which the SSFR drops increase with redshift (downsizing). At any given epoch, IRX is an increasing function of mass up to M_0. Above this mass IRX falls, suggesting gas exhaustion. In a given mass bin below M_0 IRX increases with time in a fashion consistent with enrichment. We interpret these trends using a simple model with a Schmidt-Kennicutt law and extinction that tracks gas density and enrichment. We find that the average IRX and SSFR follows a galaxy age parameter which is determined mainly by the galaxy mass and time since formation. We conclude that blue sequence galaxies have properties which show simple, systematic trends with mass and time such as the steady build-up of heavy elements in the interstellar media of evolving galaxies and the exhaustion of gas in galaxies that are evolving off the blue sequence. The IRX represents a tool for selecting galaxies at various stages of evolution.