Dissecting the Main Sequence: AGN Activity and Bulge Growth in the Local Universe

Conor McPartland, David B. Sanders, Lisa J. Kewley, Sarah K. Leslie

Published 2018-10-23Version 1

Local galaxies from the Sloan Digital Sky Survey are used to provide additional support for an evolutionary pathway in which AGN activity is associated with star-formation quenching. Composite, Seyfert 2 and LINER galaxies account for $\sim$60\% of all star-formation in massive galaxies ($M_\star > 10^{10.5} M_\odot$). Inclusion of these galaxies results in a "turnover" in the $SFR - M_\star$ relation for massive galaxies. Our analysis shows that bulge growth has already occurred in the most massive galaxies ($M_\star > 10^{10.5}$ $M_\odot$), and bulges continue to grow as galaxies quench and redden, $(g-r)$ = 0.5 $\rightarrow$ 0.75. Significant bulge growth is also occurring in low mass starburst galaxies ($M_\star < 10^{10.5} M_\odot$) at 0.5 dex above the "main sequence" (MS), where we find an increase in $B/T$ from 0.1 $\rightarrow$ 0.3 and bluer colours, $(g-r) < 0.25$ compared to low-mass galaxies on the MS.