Oral Presentation

The origin of post-starburst galaxies probed with HSC imaging at z ∼ 0.2–1.0

Author(s): Arina Saito, Yoshiki Matsuoka, Masaru Kajisawa, Yuta Suzuki, Kohei Shibata(Ehime University)

Presenter: Arina Saito (Ehime University)

Galaxies are generally classified into two major categories, i.e., blue star-forming galaxies (SFGs) and red quiescent galaxies (QGs). The standard evolutionary scenario of galaxies suggests that galaxies migrate from SFGs to QGs over time. It is therefore important to understand what processes are responsible for the quenching of star formation.
Post-starburst galaxies (PSBs), which have experienced rapid quenching following starburst in the recent past, are thought to represent the transitional stage between the two classes of galaxies. It has been suggested that this rapid quenching mechanism could manifest itself in the morphology of PSBs. However, previous studies have not reached firm conclusions due to insufficient image quality or small sample size.
We present a statistical analysis of PSBs using a large sample drawn from the HSC-SSP S21a wide layer. The HSC-SSP detected 894 objects listed in a SDSS PSBs catalog (Pattarakijwanich et al. 2016) at redshift between z = 0.2 and 1.0. We measure non-parametric morphological metrics such as concentration (C), shape asymmetry(As), Gini, M20, and compared them to those of control SFGs.
As a result, we found that PSBs tend to have higher values of C and Gini, and lower values of M20 compared to control SFGs, regardless of redshift. These findings suggest that PSBs generally have more prominent bulge components than control SFGs, and are similar to the state of QGs whose star formation has already been quenched.
On the other hand, we found that the merger fraction of PSBs inferred from the As, Gini, and M20 values higher than those of control SFGs. This indicates that the origin of PSBs is related to past galaxy mergers.