The Physical Properties of S0 Galaxy PGC 26218: The Origin of Starburst and Star Formation

Abstract

We present 2D-spectroscopic observations from the Centro Astronómico Hispano Alemán 3.5 m telescope and millimeter observations from the NOrthern Extended Millimeter Array of the nearby S0 galaxy PGC 26218, which shows central star formation activity and post-starburst features in the disk. We estimate the star formation rate (SFR = 0.28 ± 0.01 M o˙ yr-1) and molecular gas mass (log M H-2=7.60± 0.15 M⊙ ) of PGC 26218 based on the extinction-corrected Hα emission line and the CO-H2 conversion factor (α CO) of the Milky Way, respectively. We find that PGC 26218 follows the star-forming main sequence (SFMS) and the Kennicutt-Schmidt law. Comparing the kinematics of CO(J = 1-0), stars, and Hα, we find that the rotational axis of CO(J = 1-0) is 45° different from that of Hα. In addition, the profile of the CO(J = 1-0) emission line shows asymmetry and has an inflow component of ∼46 km s-1. With the decomposition of the optical image, we confirm that PGC 26218 shows multiple nuclear structures. The projected offset between the most luminous optical center and the center of CO(J = 1-0) is 5.″2 (∼0.6 kpc) and the latter overlaps with one of the optical cores. These results indicate that PGC 26218 may have experienced a gas-rich minor merger, extending its star formation and locating it in the SFMS. © 2020. The American Astronomical Society. All rights reserved.