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

We investigate the environmental quenching of galaxies, especially those with stellar masses (M _∗) < 10^9.5 M _o, 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 whether or not such a dwarf QG-massive central galaxy connection exists beyond the local universe. For this purpose, we only need a statistically representative, rather than complete, sample of low-mass galaxies, which enables our study to z 1.5. For each low-mass galaxy, we measure the projected distance (d _proj) to its nearest massive neighbor (M _∗ > 10^10.5 M _o) within a redshift range. At a given z and M _∗, the environmental quenching effect is considered to be observed if the d _proj distribution of QGs () is significantly skewed toward lower values than that of star-forming galaxies (). For galaxies with 10⁸ M _o < M _∗ < 10¹⁰ M _o, such a difference between and is detected up to z ∼ 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, , decreases with satellite M _∗ at M _∗ ≲ 10^9.5 M _o, but increases with satellite M _∗ at M _∗ 10^9.5 M _o. This trend suggests a smooth, if any, transition of the quenching timescale around M _∗ ∼ 10^9.5 M _o at 0.5 < z < 1.0.