Correlation of Structure and Stellar Properties of Galaxies in Stripe 82

Abstract

Abstract Establishing a correlation (or lack thereof) between the bimodal color distribution of galaxies and their structural parameters is crucial to understand the origin of bimodality. To achieve that, we have performed a 2D mass-based structural decomposition (bulge+disk) of all disk galaxies (total = 1263) in the Herschel imaging area of the Stripe 82 region using Ks-band images from the VICS82 survey. The scaling relations thus derived are found to reflect the internal kinematics and are employed in combination to select an indubitable set of classical- and pseudo-bulge-hosting disk galaxies. The rest of the galaxies (<20%) are marked as disks with “ambiguous” bulges. Pseudo- and classical bulge–disk galaxies exhibit clear bimodality in terms of all stellar parameters (M *, specific star formation rate, r − K s ). All pseudo-bulge–disk galaxies are blue and star forming, and all classical bulge–disk galaxies are red and quiescent with less than 5% digressions. Ambiguous bulge–disk galaxies are intermediate to pseudo- and classical bulge–disk galaxies in the distribution of all structural and stellar parameters. —based on the placement of bulges on the Kormendy relation—is found to be the most efficient single structural indicator of both bulge type and stellar activity. The placement of ambiguous bulge–disk galaxies on scaling relations and the fundamental plane, in addition to their peculiar stellar properties, suggests that they are dominantly part of the green valley.