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 _* <∼ 10¹⁰ 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. (paper)