A novel Bayesian approach for decomposing the radio emission of quasars: II. Link between quasar radio emission and black hole mass

TL;DR

This study uses a Bayesian model to analyze SDSS quasars and finds that supermassive black hole mass is linked to the likelihood of hosting strong radio jets, especially in the most massive black holes, but not directly to star formation or overall radio luminosity.

Contribution

Introduces a Bayesian approach to disentangle radio emission sources in quasars, revealing the specific link between black hole mass and radio jet presence in the most massive SMBHs.

Findings

No correlation between SMBH mass and star formation rate.

Most massive SMBHs are 2-3 times more likely to host strong radio jets.

Radio enhancement affects only the top 5% most radio-bright quasars.

Abstract

Whether the mass of supermassive black hole ($M_\mathrm{BH}$) is directly linked to the quasar radio luminosity remains a long-debated issue, and understanding the role of $M_\mathrm{BH}$ in the evolution of quasars is pivotal to unveiling the mechanism of AGN feedback. In this work, based on a two-component Bayesian model, we examine how $M_\mathrm{BH}$ affects the radio emission from quasars, separating the contributions from host galaxy star formation (SF) and AGN activity. By modelling the radio flux density distribution of Sloan Digital Sky Survey (SDSS) quasars from the LOFAR Two-metre Sky Survey Data Release 2, we find no correlation between $M_\mathrm{BH}$ and SF rate (SFR) at any mass for quasars at a given redshift and bolometric luminosity. The same holds for AGN activity across most $M_\mathrm{BH}$ values; however, quasars with the top 20\% most massive SMBHs are 2 to 3 times more likely to host strong radio jets than those with lower-mass SMBHs at similar redshift and luminosity. We suggest defining radio quasar populations by their AGN and SF contributions instead of radio loudness; our new definition unifies previously divergent observational results on the role of $M_\mathrm{BH}$ in quasar radio emissions. We further demonstrate that this radio enhancement in quasars with the 20\% most massive SMBHs affects only the $\sim5\%$ most radio bright quasars at a given redshift and bolometric luminosity. We discuss possible physical origins of this radio excess in the most massive and radio-bright quasar population, which remains an interest for future study.