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 HδAvs.Dn4000,we can see that the control sample has higher HδAand 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 highmetallicity 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.
