Radio Active Galactic Nuclei Activity in Low Redshift Galaxies Is Not Directly Related to Star Formation Rates

Abstract

We examine the demographics of radio-emitting active galactic nuclei (AGN) in the local Universe as a function of host galaxy properties, most notably both stellar mass ( M _⋆ ) and star formation rate (SFR). Radio AGN activity is theoretically implicated in helping reduce the SFR of galaxies, and therefore it is natural to investigate the relationship between these two galaxy properties. We use the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) optical IFU catalog in conjunction with the NVSS and Faint Images of the Radio Sky at Twenty radio catalogs. MaNGA's high precision determinations of SFR allow us to impose a clean cut to reliably identify radio AGN from star formers. Using this sample of AGN, the well-measured stellar velocity dispersions from MaNGA, and the black hole M – σ relationship, we examine the Eddington ratio distribution (ERD) and its dependence on M _⋆ and SFR. We find that the ERD depends strongly on M _⋆ , with more massive galaxies having larger Eddington ratios ( λ ). Interpreting our model fit to the data leads to a completeness-corrected estimate of F _AGN ( λ > 0.001), the fraction of galaxies with radio AGN with λ > 0.001. At $\mathrm{log}\left({M}_{\star }/{M}_{\odot }\right)\sim 11$ , we estimate F _AGN = 0.02. The AGN fraction increases rapidly with M _⋆ , and at $\mathrm{log}\left({M}_{\star }/{M}_{\odot }\right)\sim 12$ , we estimate F _AGN ∼ 0.24. We do not find any dependence on SFR, specific star formation rate, or velocity dispersion when controlling for stellar mass. We conclude that galaxy SFRs appear to be unrelated to the presence or absence of a radio AGN, which may be useful in constraining theoretical models of AGN feedback.

Keywords

• Radio active galactic nuclei
• AGN host galaxies
• Star formation
• Stellar masses