The morphological evolution, AGN fractions, dust content, environments, and downsizing of massive green valley galaxies at 0.5<z<2.5 in 3D-HST/CANDELS

TL;DR

This study investigates the properties and evolutionary pathways of massive green valley galaxies at 0.5<z<2.5, highlighting their transitional nature, AGN activity, and environmental influences in galaxy quenching.

Contribution

It provides new insights into the morphological, dust, and AGN characteristics of green valley galaxies, supporting their transitional role and the downsizing quenching scenario.

Findings

Green galaxies have intermediate dust and morphology.

Green galaxies exhibit the highest AGN fraction at z<2.

Environmental effects are less significant for star formation cessation at z>0.5.

Abstract

To explore the evolutionary connection among red, green, and blue galaxy populations, based on a sample of massive ($M_* > 10^{10} M_{\odot} $) galaxies at 0.5<z<2.5 in five 3D-HST/CANDELS fields, we investigate the dust content, morphologies, structures, AGN fractions, and environments of these three galaxy populations. Green valley galaxies are found to have intermediate dust attenuation, and reside in the middle of the regions occupied by quiescent and star-forming galaxies in the UVJ diagram. Compared with blue and red galaxy populations at z<2, green galaxies have intermediate compactness and morphological parameters such as Sersic index, concentration, Gini coefficient, and the second order moment of the 20% brightest pixels of a galaxy. Above findings seem to favor the scenario that green galaxies are at transitional phase when star-forming galaxies are being quenched into quiescent status. The green galaxies at z<2 show the highest AGN fraction, suggesting that AGN feedback may have played an important role in star formation quenching. For the massive galaxies at 2<z<2.5, both red and green galaxies are found to have a similarly higher AGN fraction than the blue ones, which implies that AGN feedback may help to keep quiescence of red galaxies at z>2. A significant environmental difference is found between green and red galaxies at z<1.5. Green and blue galaxies at z>0.5 seem to have similar local density distributions, suggesting that environment quenching is not the major mechanism to cease star formation at z>0.5. The fractions of three populations as functions of mass support a "downsizing" quenching picture that the bulk of star formation in more massive galaxies is completed earlier than that of lower mass galaxies.