Effect of Bars on Evolution of SDSS Spiral Galaxies

We explore the significance of bars in triggering central star formation (SF) and active galactic nucleus (AGN) activity for spiral galaxy evolution using a volume-limited sample with 0.020 < z < 0.055, M-r < -19.5, and sigma > 70 km s(-1) selected from Sloan Digital Sky Survey Data Release 7. On a central SF rate-sigma plane, we measure the fraction of galaxies with strong bars in our sample and also the AGN fractions for barred and non-barred galaxies, respectively. The comparison between the bar and AGN fractions reveals a causal connection between the two phenomena of SF quenching and AGN activity. A massive black hole and abundant gas fuels are sufficient conditions to trigger AGNs. We infer that the AGNs triggered by satisfying the two conditions drive the strong AGN feedback, suddenly suppressing the central SF and leaving the SF sequence. We find that in galaxies where either of the two conditions is not sufficient, bars are a great help for the AGN triggering, accelerating the entire process of evolution, which is particularly evident in pseudo-bulge galaxies. All of our findings are obtained only when plotted in terms of their central velocity dispersion and central SFR (not galactic scale SFR), indicating that the AGN-driven SF quenching is confined in the central kpc region.