Effect of Bars on Evolution of SDSS Spiral Galaxies

TL;DR

This study investigates how bars influence central star formation and AGN activity in spiral galaxies, revealing a causal link and the role of bars in accelerating galaxy evolution through AGN feedback.

Contribution

It demonstrates the connection between bars, AGN activity, and star formation quenching, emphasizing the importance of central properties in galaxy evolution.

Findings

Bars are associated with increased AGN activity in spiral galaxies.

AGN feedback driven by bars suppresses central star formation.

Bars help trigger AGNs, especially in pseudo-bulge galaxies.

Abstract

We explore the significance of bars in triggering central star formation (SF) and AGN activity for spiral galaxy evolution using a volume-limited sample with $0.020<z<0.055$, $M_{\rm r}<-19.5$, and $\sigma>70\rm km s^{-1}$ selected from SDSS DR7. 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 BH 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.