The SAMI Galaxy Survey: Observing the environmental quenching of star formation in GAMA groups

Abstract

We explore the radial distribution of star formation in galaxies in the SAMI Galaxy Survey as a function of their local group environment. Using a sample of galaxies in groups (with halo masses less than $\simeq 10^{14}{\mathrm{M}}_{\odot }$) from the Galaxy And Mass Assembly Survey, we find signatures of environmental quenching in high-mass groups ($M_G>10^{12.5}{\mathrm{M}}_{\odot }$). The mean integrated specific star formation rate of star-forming galaxies in high-mass groups is lower than for galaxies in low-mass groups or that are ungrouped, with $\hat{I}”\log (sSFR/\mathrm{y}{\mathrm{r}}^{-1})=0.45\pm 0.07$. This difference is seen at all galaxy stellar masses. In high-mass groups, star-forming galaxies more massive than $M_{\ast }\sim 10^{10}{\mathrm{M}}_{\odot }$ have centrally-concentrated star formation. These galaxies also lie below the star-formation main sequence, suggesting they may be undergoing outside-in quenching. Lower mass galaxies in high-mass groups do not show evidence of concentrated star formation. In groups less massive than $M_G=10^{12.5}{\mathrm{M}}_{\odot }$ we do not observe these trends. In this regime we find a modest correlation between centrally-concentrated star formation and an enhancement in total star formation rate, consistent with triggered star formation in these galaxies.

22 Pages, 11 Figures, accepted for publication in MNRAS