PAC. V. The Roles of Mass and Environment in the Quenching of Galaxies

Abstract The roles that mass and environment play in galaxy quenching are still under debate. Leveraging the Photometric objects Around Cosmic webs method, we analyze the excess surface distribution n ¯ 2 w p ( r p ) of photometric galaxies in different colors (rest-frame u − r ) within the stellar mass range of 10 9.0 ∼ 10 11.0 M ⊙ around spectroscopic massive central galaxies (10 10.9 ∼ 10 11.7 M ⊙ ) at the redshift interval of 0 < z s < 0.7, utilizing data from the Hyper Suprime-Cam Subaru Strategic Program and the spectroscopic samples of Slogan Digital Sky Survey (i.e., Main, LOWZ, and CMASS samples). We find that both mass and environmental quenching contribute to the evolution of companion galaxies. To isolate the environmental effect, we quantify the quenched fraction excess (QFE) of companion galaxies encircling massive central galaxies within 0.01 h −1 Mpc < r p < 20 h −1 Mpc, representing the surplus quenched fraction relative to the average. We find that the high-density halo environment affects star formation quenching up to about three times the virial radius, and this effect becomes stronger at lower redshift. We also find that even after being scaled by the virial radius, the environmental quenching efficiency is higher for more massive halos or for companion galaxies of higher stellar mass, though the trends are quite weak. We present a fitting formula that comprehensively captures the QFE across central and companion stellar mass bins, halo-centric distance bins, and redshift bins, offering a valuable tool for constraining galaxy formation models. Furthermore, we have made a quantitative comparison with IllustrisTNG that underscores some important differences, particularly in the excessive quenching of low-mass companion galaxies (<10 9.5 M ⊙ ) in the simulation.