Investigating central star formation in local AGN host galaxies: is there tension between coeval growth and AGN feedback?

TL;DR

This study investigates the relationship between central star formation and AGN activity in local galaxies, finding evidence supporting coeval growth but also acknowledging the modest impact of AGN feedback.

Contribution

It provides observational analysis of the connection between star formation rates and X-ray AGN activity in a large galaxy sample, highlighting selection effects.

Findings

X-ray AGN fraction increases with central star formation rate density.

AGN host galaxies show elevated central star formation compared to normal galaxies.

Optically-selected AGN hosts also have high central star formation, but with different trends.

Abstract

It has been argued that supermassive black holes (BHs) coevolve with the central parts of galaxies, as a result of the common fuel for both the BH and star formation in the galaxy central region, as supported by the particularly significant relation between BH growth and the central mass density within 1 kpc found among star-forming galaxies. In the context of this scenario, one would naturally expect a close observational link between AGN activity and star formation activity in the central regions, e.g., the surface star formation rate density in the central 1 kpc region ($\Sigma_{\rm SFR, 1~kpc}$), as the manifestation of coeval growth. With ~3000 galaxies in the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey that have X-ray coverage from SRG/eROSITA, XMM-Newton, or Chandra, we studied how the X-ray AGN fraction varies with $\Sigma_{\rm SFR, 1~kpc}$. We found that the fraction of X-ray AGNs with relatively higher specific BH accretion rates increases with $\Sigma_{\rm SFR, 1~kpc}$, consistent with the expectation. Comparison of the mean star formation rate surface density ($\Sigma_{\rm SFR}$) profiles of the host galaxies of these AGNs and normal galaxies sharing similar properties reveals elevated $\Sigma_{\rm SFR}$ in AGN hosts across the entire central region. As for optically-selected AGNs, their hosts also tend to show high $\Sigma_{\rm SFR}$ in the central regions on average compared to normal galaxies, but are discrepant with X-ray AGNs in terms of the trend of AGN fraction vs. $\Sigma_{\rm SFR, 1~kpc}$, which can be explained by selection effects. While these general trends all support the coeval growth scenario, they do not contradict observational evidence for AGN feedback, as the time-averaged effects from local AGN feedback are modest in star-forming regions.