The Study Of The Galaxy Quenching Mode At 0.5<Z<1 In CANDELS

Studying the spatial distribution of specific star formation rate(s SFR = SFR / M *)is helpful to understand how stellar mass(M *)is built up in galaxies as they evolve along the star formation main sequence(SFMS),and how and where the star formation shuts down as galaxies move off the SFMS to become fully quiescent.Broadly speaking,there are two types of processes responsible for cessation of star formation in galaxies: the internal and the external processes.The two types of processes are expected to change the radial s SFR profile of a galaxy in a different way during its quenching process.In this thesis,we investigate the galaxy quenching process at intermediate redshift using a sample of ～ 4400 galaxies with M*>109M⊙ between redshift 0.5 and 1.0 in all five CANDELS fields.We divide this sample,using the integrated specific star formation rate(s SFR),into four sub-groups: star-forming galaxies(SFGs)above and below the ridge of the star-forming main sequence(SFMS),transition galaxies and quiescent galaxies.We study their UV I(U-V versus V-I)color gradients to infer their s SFR gradients out to twice effective radii.We show that on average both star-forming and transition galaxies at all masses are not fully quenched at any radii,whereas quiescent galaxies are fully quenched at all radii.We find that at low masses(M*= 109-1010M⊙)SFGs both above and below the SFMS ridge generally have flat s SFR profiles,whereas the transition galaxies at the same masses generally have s SFRs that are more suppressed in their outskirts.In contrast,at high masses(M*> 1010.5M⊙),SFGs above and below the SFMS ridge and transition galaxies generally have varying degrees of more centrally-suppressed s SFRs relative to their outskirts.These findings indicate that at z ～ 0.5-1.0 the main galaxy quenching mode depends on its already formed stellar mass,exhibiting a transition from “the outside-in” at M*≤ 1010M⊙ to “the inside-out” at M*> 1010.5M⊙.In other words,our findings support that internal processes dominate the quenching of massive galaxies,whereas external processes dominate the quenching of low-mass galaxies.