Correlation of bulge transformation in disc galaxies with the gradual decrease in their stellar activity

The speaker will present their latest results which demonstrate that as disc galaxies accumulate more mass, their central stellar mass density increases, bulge type transforms, stellar population ages and stellar activity recedes. These results have been derived after performing careful 2D mass-based structural (bulge + disc) decomposition of all disc galaxies (1263) in the Herschel imaging area of the Stripe82 region using Ks-band images from the latest 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 (CBD) and pseudo bulge hosting disc galaxies (PBD). The rest of the galaxies (<20%) whose bulges could not be stringently classified are marked as discs with ambiguous bulges (ABD). PBDs and CBDs exhibit clearly distinct peaks in terms of all structural and stellar parameters. All PBDs are blue and star-forming and all CBDs are red and quiescent with less than 5% transgressions. ABDs are intermittent to PBDs and CBDs in all cases suggesting that disc galaxies in transition from pseudo (star forming) to classical (quiescent) stage host ambiguous bulges. Although ABDs are redder than PBDs, their SFR and sSFR is similar, suggesting that either they are dust reddened or have composite populations. All scenarios lend credence to the argument that bulge transformation and recession of stellar activity occur smoothly and simultaneously in disc galaxies with time.

Speaker: 
Dr. Sonali SACHDEVA @ KIAA
Location: 
Meeting ID: 731 2099 7847, Password: astroPKU
Time: 
Thu, 2020-06-11 14:00 to 14:30