2024ApJ...964..141Z

In this manuscript, clues are provided to support globally negative active galactic nuclei (AGN) feedback on star formation in the host galaxies of the local low-redshift Sloan Digital Sky Survey (SDSS) Type 2 AGN, based on the different dependence of narrow Hα line luminosity L_Hα on optical continuum luminosity λL_cont between star-forming galaxies and Type 2 AGN. Through the measured L_Hα and λL_cont in SDSS star-forming galaxies, there is a strong linear correlation between λL_cont and L_Hα, accepted as a standard correlation without the effects of AGN activity. Meanwhile, considering the apparent contribution of AGN activity to the narrow Hα line emissions in Type 2 AGN, the correlation between λL_cont and L_Hα in the SDSS Type 2 AGN leads to a statistically lower L_Hα in Type 2 AGN than in star-forming galaxies, with a significance level higher than 5σ, even after considering necessary effects (including effects of host galaxy properties), leading to the accepted conclusion on the globally negative AGN feedback in the local Type 2 AGN. Meanwhile, the properties of Dn(4000) and Hδ_A can provide indirect clues to support the globally negative AGN feedback in local Type 2 AGN, due to older stellar ages in Type 2 AGN. Moreover, it is interesting to expect more than 50% narrow Hα emissions globally suppressed in the host galaxies of Type 2 AGN relative to the star-forming galaxies. The results not only support globally negative AGN feedback in local Type 2 AGN, but also show further clues on the quantification of suppressions of star formation by the globally negative AGN feedback.