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 ⊙ yr −1 ) and molecular gas mass ( ) of PGC 26218 based on the extinction-corrected H α emission line and the CO–H 2 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 H α , we find that the rotational axis of CO( J  = 1–0) is 45° different from that of H α . 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.