The impact of morphological quenching mechanisms on star formation activity at 0.2 <

The distribution of galaxies in the color-magnitude diagram (CMD) reveals two distinct groups: the red sequence and the blue cloud, along with an intermediate region known as the green valley (GV), which is considered an important transitional stage in galaxy evolution. Examining the difference in morphology and environment of GV galaxies with early-type disks (ETDs: bulge-dominated and with a disk) and late-type disks (LTDs: disk-dominated) could help improve our understanding of the corresponding quenching mechanisms. Based on the COSMOS2020 catalog, we selected a large sample of massive (M* ≥ 1010 M⊙) GV galaxies at 0.2 < z < 1.2 by using the extinction-corrected (U − V)rest colors. After excluding the possible active galactic nucleus candidates and applying the criterion of “mass-matching”, two subsamples of GV galaxies were ultimately constructed at 0.2 < z < 0.7 (457 ETDs and 457 LTDs) and 0.7 ≤ z < 1.2 (839 ETDs and 839 LTDs), respectively. Compared to LTDs, we find that ETDs present higher Gini coefficients and concentration C, more negative M20 values, and lower specific star formation rates (sSFRs); whereas ETDs possess more concentrated profiles, but there is no significant difference in terms of environment between ETDs and LTDs. These results indicate that the morphological effect could probably play an important role in quenching the star formation activity of massive GV galaxies instead of the environmental effect. Additionally, we employed a dimensionless parameter morphology quenching efficiency (Qmor) to quantify the connection between galaxy morphology and star formation activity. We find that Qmor is relatively sensitive to stellar mass than redshifts, especially for massive galaxies with M* > 1010.8 M⊙ at z < 1. The probability of Qmor ≥ 0.15 approaches ∼75% when the discrepancy of average star formation rates between ETDs and LTDs is approximately 0.3 M⊙ yr−1. The Qmor ≥ 0.15 could probably be used to characterize the level of morphological quenching in GV galaxies, which is more pronounced in massive (M* ≥ 1010.8 M⊙) galaxies.