Morphological Transformation and Star Formation Quenching of Massive Galaxies at 0.5 < z < 2.5 in 3D-HST/CANDELS

Abstract

To figure out the effect of stellar mass and local environment on morphological transformation and star formation quenching in galaxies, we use the massive (M * ≥ 10 10 M ) galaxies at 0.5 ≤ z ≤ 2.5 in five fields of 3D-HST/CANDELS. Based on the UVJ diagnosis and the possibility of possessing spheroid, our sample of massive galaxies are classified into four populations: quiescent early-type galaxies (qEs), quiescent late-type galaxies (qLs), star-forming early-type galaxies (sEs), and starforming late-type galaxies (sLs). It is found that the quiescent fraction is significantly elevated at the high ends of mass and local environmental overdensity, which suggests a clear dependence of quenching on both mass and local environment. Over cosmic time, the mass dependence of galaxy quiescence decreases while the local environment dependence increases. The early-type fraction is found to be larger only at high-mass end, indicating a evident mass dependence of morphological transformation. This mass dependence becomes more significant at lower redshifts. Among the four populations, the fraction of active galactic nucleus (AGN) in the qLs peaks at 2 < z ≤ 2.5, and rapidly declines with cosmic time. The sEs are found to have higher AGN fractions of 20 − 30% at 0.5 ≤ z < 2 . The redshift evolution of AGN fractions in the qLs and sEs suggests that the AGN feedback could have played important roles in the formation of the qLs and sEs.