paper

Satellite Quenching, Galaxy Inner Density and the Halo Environment

arXiv:1607.06091 · doi:10.1093/mnras/stw2403

Abstract

Using the Sloan Digital Sky Survey, we adopt the sSFR- $I^£_{1 k p c}$ diagram as a diagnostic tool to understand quenching in different environments. sSFR is the specific star formation rate, and $I^£_{1 k p c}$ is the stellar surface density in the inner kpc. Although both the host halo mass and group-centric distance affect the satellite population, we find that these can be characterised by a single number, the quenched fraction, such that key features of the sSFR- $I^£_{1 k p c}$ diagram vary smoothly with this proxy for the "environment". Particularly, the sSFR of star-forming galaxies decreases smoothly with this quenched fraction, the sSFR of satellites being 0.1 dex lower than in the field. Furthermore, $I^£_{1 k p c}$ of the transition galaxies (i.e., the "green valley" or GV) decreases smoothly with the environment, by as much as 0.2 dex for $M_{*} = 1 0^{9.75 - 10} M_{⊙}$ from the field, and decreasing for satellites in larger halos and at smaller radial distances within same-mass halos. We interpret this shift as indicating the relative importance of today's field quenching track vs. the cluster quenching track. These environmental effects in the sSFR- $I^£_{1 k p c}$ diagram are most significant in our lowest mass range ( $9.75 < lo g M_{*} / M_{⊙} < 10$ ). One feature that is shared between all environments is that at a given $M_{*}$ quenched galaxies have about 0.2-0.3 dex higher $I^£_{1 k p c}$ than the star-forming population. These results indicate that either $I^£_{1 k p c}$ increases (subsequent to satellite quenching), or $I^£_{1 k p c}$ for individual galaxies remains unchanged, but the original $M_{*}$ or the time of quenching is significantly different from those now in the GV.

14 pages + Appendix, 12 figures, MNRAS accepted