Quenching Low-mass Satellite Galaxies: Evidence for a Threshold ICM Density

Abstract

We compile a sample of Sloan Digital Sky Survey (SDSS) galaxy clusters with high-quality Chandra X-ray data to directly study the influence of the dense intracluster medium (ICM) on the quenching of satellite galaxies. We study the quenched fractions of satellite galaxies as a function of ICM density for low- (10 9  ≲  M ⋆  ≲ 10 10 M ⊙ ), intermediate- (10 10  ≲  M ⋆  ≲ 10 10.5 M ⊙ ), and high-mass ( M ⋆  ≳ 10 10.5 M ⊙ ) satellite galaxies with >3000 satellite galaxies across 24 low-redshift ( z  < 0.1) clusters. For low-mass galaxies we find evidence for a broken power-law trend between satellite quenched fraction and local ICM density. The quenched fraction increases modestly at ICM densities below a threshold before increasing sharply beyond this threshold toward the cluster center. We show that this increase in quenched fraction at high ICM density is well matched by a simple, analytic model of ram pressure stripping. These results are consistent with a picture where low-mass cluster galaxies experience an initial, slow-quenching mode driven by steady gas depletion, followed by rapid quenching associated with ram pressure of cold-gas stripping near (one-quarter of the virial radius, on average) the cluster center.