2021/09/20 by Lalitwadee Kawinwanichakij, John D. Silverman, Xuheng Ding +11
Physics and Astronomy · #astro-ph.GA
paper · pdf · doi:10.3847/1538-4357/ac1f21
Accepted for publication in ApJ. 45 pages, 17 figures
arxiv created 2021/09/20 · arxiv updated 2021/11/24
We present the galaxy size-mass (Re-M∗) distributions using a stellar-mass complete sample of ∼1.5 million galaxies, covering ∼100 deg2, with log(M∗/M\odot)>10.2~(9.2) over the redshift range 0.2<z<1.0 (z<0.6) from the second public data release of the Hyper Suprime-Cam Subaru Strategic Program. We confirm that, at fixed redshift and stellar mass over the range of log(M∗/M\odot)<11, star-forming galaxies are on average larger than quiescent galaxies. The large sample of galaxies with accurate size measurements, thanks to the excellent imaging quality, also enables us to demonstrate that the Re-M∗ relations of both populations have a form of broken power-law, with a clear change of slopes at a pivot stellar mass Mp. For quiescent galaxies, below an (evolving) pivot mass of log(Mp/M\odot)=10.2-10.6 the relation follows Re∝ M∗0.1; above Mp the relation is steeper and follows Re∝ M∗0.6-0.7. For star-forming galaxies, below log(Mp/M\odot)∼10.7 the relation follows Re∝ M∗0.2; above Mp the relation evolves with redshift and follows Re∝ M∗0.3-0.6. The shallow power-law slope for quiescent galaxies below Mp indicates that large low-mass quiescent galaxies have sizes similar to those of their counterpart star-forming galaxies. We take this as evidence that large low-mass quiescent galaxies have been recently quenched (presumably through environment-specific process) without significant structural transformation. Interestingly, the pivot stellar mass of the Re-M∗ relations coincides with mass at which half of the galaxy population is quiescent, implied that the pivot mass represents the transition of galaxy growth from being dominated by in-situ star formation to being dominated by (dry) mergers.