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

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.
This work is supported by the National Key Research and Development Program of China (No. 2017YFA0402703) and by the National Natural Science Foundation of China (No. 11733002). In addition, we acknowledge the support of the staff from CAHA and NOEMA. Ruben Garcia-Benito acknowledges financial support from the Spanish Ministry of Economy and Competitiveness through grant 205 AYA2016-77846-P. Ruben Garcia-Benito acknowledges support from the State Agency for 206 Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award to 207 the Instituto de Astrofisica de Andalucia (SEV-2017-0709).