Conditions for galaxy quenching at 0.5 < z < 2.5 from CANDELS: compact cores and environment

We investigate two classes of conditions for galaxy quenching at 0.5 < z < 2.5 based on the structural scaling relations of galaxies in the five Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) fields: the formation of a compact core and the environment. We confirm that in the entire redshift range, massive quiescent galaxies (M * > 1010 M ⊙) have much higher stellar mass surface densities within the central 1 kpc (Σ1) and smaller sizes than star-forming galaxies in the same stellar mass range. In addition, the quiescent fractions significantly increase with the increase of Σ1 regardless of whether galaxies are centrals or satellites. In contrast, we find that the overall lower-mass quiescent galaxies (M * 10 M ⊙) have slightly higher Σ1 and comparable sizes compared to star-forming galaxies of the same mass and at the same redshift. At z < 1.5, satellites have higher halo masses and larger quiescent fractions than those of centrals at a given Σ1 (stellar mass). Our findings indicate that the significant growth of the galaxy cores is closely related to the quenching of massive galaxies since z ∼ 2.5, while the environmental effect plays an important role in the quenching of low-mass galaxies at z ≲ 1.5.