CANDELS Sheds Light on the Environmental Quenching of Low-mass Galaxies

Abstract

We investigate the environmental quenching of galaxies, especially those with stellar masses (M*)$<10^{9.5}{M}_{\odot }$, beyond the local universe. Essentially all local low-mass quenched galaxies (QGs) are believed to live close to massive central galaxies, which is a demonstration of environmental quenching. We use CANDELS data to test {\it whether or not} such a dwarf QG--massive central galaxy connection exists beyond the local universe. To this purpose, we only need a statistically representative, rather than a complete, sample of low-mass galaxies, which enables our study to $z\gtrsim 1.5$. For each low-mass galaxy, we measure the projected distance ($d_{proj}$) to its nearest massive neighbor (M*$>10^{10.5}{M}_{\odot }$) within a redshift range. At a given redshift and M*, the environmental quenching effect is considered to be observed if the $d_{proj}$ distribution of QGs ($d_{proj}^Q$) is significantly skewed toward lower values than that of star-forming galaxies ($d_{proj}^{SF}$). For galaxies with $10^8{M}_{\odot }<M\ast <10^{10}{M}_{\odot }$, such a difference between $d_{proj}^Q$ and $d_{proj}^{SF}$ is detected up to $z\sim 1$. Also, about 10\% of the quenched galaxies in our sample are located between two and four virial radii ($R_{Vir}$) of the massive halos. The median projected distance from low-mass QGs to their massive neighbors, $d_{proj}^Q/R_{Vir}$, decreases with satellite M* at $M\ast \lesssim 10^{9.5}{M}_{\odot }$, but increases with satellite M* at $M\ast \gtrsim 10^{9.5}{M}_{\odot }$. This trend suggests a smooth, if any, transition of the quenching timescale around $M\ast \sim 10^{9.5}{M}_{\odot }$ at $0.5<z<1.0$.

8 pages, 5 figures. ApJL accepted. Typos corrected