The radio loudness of SDSS quasars from the LOFAR Two-metre Sky Survey: ubiquitous jet activity and constraints on star formation

Abstract

We examine the distribution of radio emission from ∼42, 000 quasars from the Sloan Digital Sky Survey, as measured in the LOFAR Two-Metre Sky Survey (LoTSS). We present a model of the radio luminosity distribution of the quasars that assumes that every quasar displays a superposition of two sources of radio emission: active galactic nuclei (jets) and star-formation. Our two-component model provides an excellent match to the observed radio flux density distributions across a wide range of redshifts and quasar optical luminosities; this suggests that the jet-launching mechanism operates in all quasars but with different powering efficiency. The wide distribution of jet powers allows for a smooth transition between the ‘radio-quiet’ and ‘radio-loud’ quasar regimes, without need for any explicit bimodality. The best-fit model parameters indicate that the star-formation rate of quasar host galaxies correlates strongly with quasar luminosity and also increases with redshift at least out to z ∼ 2. For a model where star-formation rate scales as $L_{\rm bol}^{\alpha } (1+z)^{\beta }$, we find α = 0.47 ± 0.01 and β = 1.61 ± 0.05, in agreement with far-infrared studies. Quasars contribute ≈0.15 per cent of the cosmic star-formation rate density at z = 0.5, rising to 0.4 per cent by z ∼ 2. The typical radio jet power is seen to increase with both increasing optical luminosity and black hole mass independently, but does not vary with redshift, suggesting intrinsic properties govern the production of the radio jets. We discuss the implications of these results for the triggering of quasar activity and the launching of jets.

How Are Red and Blue Quasars Different? The Radio Properties

“…It has been shown in previous studies that SF dominates the radio emission in the majority of classically radio-quiet quasars, although many can still be AGN/jet-powered [33][34][35]. In our previous study, we analyzed the spectral energy distributions (SEDs) for a sample of rQSOs and cQSOs and found no differences in the average star-formation rate properties [12]; this will be robustly tested in our future ALMA study.…”

“…It has been shown in previous studies that SF dominates the radio emission in the majority of classically radio-quiet quasars, although many can still be AGN/jet-powered [33][34][35].…”

Quasar Feedback Survey: Multi-phase outflows, turbulence and evidence for feedback caused by low power radio jets inclined into the galaxy disk

“…We plan such a study across the wider QFeedS sample, where it will become possible to investigate trends with jet power and jet inclination angle, which are two crucial parameters according to simulations (Mukherjee et al 2018b). Further careful studies of the role of low power jets for AGN feedback is important because lower power jets are very common, compared to their more powerful counterparts, in high mass galaxies (including quasars) even if it is harder to decouple their radio emission from that produced by starformation (Gürkan et al 2019;Sabater et al 2019;Macfarlane et al 2021).…”

LeMMINGs III. The e-MERLIN legacy survey of the Palomar sample: exploring the origin of nuclear radio emission in active and inactive galaxies through the [O iii] – radio connection

“…Kukula et al 1999;Nagar et al 2000;Mezcua & Prieto 2014;Padovani 2016), although a few studies have found contradictory results (e.g. Jiang et al 2007;Macfarlane et al 2021). This result can be generalized by the fact that the radio loudness, i.e.…”