The Relationship Between Star-formation Activity and Galaxy Structural Properties in CANDELS and a Semi-analytic Model

TL;DR

This study investigates how galaxy structural properties correlate with their position relative to the star formation main sequence, using observational data and a semi-analytic model to understand galaxy evolution mechanisms.

Contribution

It provides a comprehensive analysis of structural property trends around the SFMS and tests a semi-analytic model that links bulge growth, black holes, and star formation quenching.

Findings

Strong correlation between structural properties and distance from SFMS

Model reproduces observed trends supporting co-evolution of black holes and bulges

AGN feedback is crucial for moving galaxies off the SFMS

Abstract

We study the correlation of galaxy structural properties with their location relative to the SFR-M* correlation, also known as the star formation "main sequence" (SFMS), in the CANDELS and GAMA surveys and in a semi-analytic model (SAM) of galaxy formation. We first study the distribution of median Sersic index, effective radius, star formation rate (SFR) density and stellar mass density in the SFR-M* plane. We then define a redshift dependent main sequence and examine the medians of these quantities as a function of distance from this main sequence, both above (higher SFRs) and below (lower SFRs). Finally, we examine the distributions of distance from the main sequence in bins of these quantities. We find strong correlations between all of these galaxy structural properties and the distance from the SFMS, such that as we move from galaxies above the SFMS to those below it, we see a nearly monotonic trend towards higher median Sersic index, smaller radius, lower SFR density, and higher stellar density. In the semi-analytic model, bulge growth is driven by mergers and disk instabilities, and is accompanied by the growth of a supermassive black hole which can regulate or quench star formation via Active Galactic Nucleus (AGN) feedback. We find that our model qualitatively reproduces the trends described above, supporting a picture in which black holes and bulges co-evolve, and AGN feedback plays a critical role in moving galaxies off of the SFMS.