The physical properties of galaxies with unusually high gas-phase metallicity

Abstract

We use 1221 galaxies with unusually high gas-phase metallicity to study their physical properties. The scope of redshift is 0.02 < z < 0.25 for these galaxies with unusually high gas-phase metallicity. Our goal is to understand the physical origins of the high gas-phase metallicity. To address this study, we select a control sample matching similar redshift and stellar mass. Our main results are as follows. (i) Compared with the control sample, the high-metallicity sample shows lower ionization parameter, higher electron density and more dust content. (ii) We also find that the high-metallicity sample has older stellar age and higher [Mgb/<Fe>] ratio, which indicates that the high-metallicity sample has shorter timescale of star formation. (iii) According to the plane of HδA vs. Dn4000, we can see that the control sample has higher HδA and lower Dn4000 than the high-metallicity sample, which may imply that the control sample experiences recent star formation. (iv) There is a significant difference in gas distribution between the high-metallicity and control samples. The high-metallicity sample has lower gas fraction than control sample, which indicates that galaxies have high gas-phase metallicity probably due to their low HI gas fraction. (v) There is no significant difference between the high-metallicity and control samples in environment, which may suggest that the environment has no effect on gas-phase metallicity.