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 ⊙ , 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 ⊙ ) 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 10 8 M ⊙  <  M *  < 10 10 M ⊙ , 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 ⊙ , but increases with satellite M * at M *  ≳ 10 9.5 M ⊙ . This trend suggests a smooth, if any, transition of the quenching timescale around M *  ∼ 10 9.5 M ⊙ at 0.5 <  z  < 1.0.