Speaker
Description
Studies show that both radio jets from the active galactic nuclei (AGN) and the star formation (SF) activity in quasar host galaxies contribute to the quasar radio emission, yet their relative contributions across the population remain unclear. Here, I will present new constraints on the SF and AGN contribution to the quasar radio emission and their evolution with various physical processes, using an improved Bayesian parametric model that allows us to statistically separate the SF and AGN components in observed quasar radio flux density distributions. I will present new results based on the LOFAR Two-Metre Sky Survey Data Release 2, showing a quasar host galaxy SFR evolution that increases with bolometric luminosity and with redshift out to redshift ~4. The prevalence of radio AGN emissions increases with quasar luminosity, but has little dependence on redshift, indicating the AGN jet strength is mostly governed by local activities. Our new methodology and large sample size also allow us to investigate the role of parameters including quasar colour and black hole mass on quasar radio emission. I will show that the radio excess in red quasars is due to an enhancement in AGN-related emission, and that this radio enhancement occurs mostly in quasars with weak or intermediate radio power. I will also present a coherent picture of black hole mass impact on the quasar radio emission, where only the most massive black holes produce powerful jets that lead to excess in radio loudness.
