Probing the Wind Component of Radio Emission in Luminous High-Redshift Quasars

Abstract

We discuss a novel probe of the contribution of wind-related shocks to the radio emission in otherwise radio-quiet quasars. Given 1) the known non-linear correlation between UV and X-ray luminosity in quasars, 2) that such correlation leads to higher likelihood of radiation-line-driven winds in more luminous quasars, and 3) that luminous quasars are more abundant at high redshift, deep radio observations of high-redshift quasars are needed to probe potential contributions of accretion disk winds to radio emission from quasars. To this end, we target a sample of 50 z 1.65 color-selected quasars that span the range of expected accretion disk wind properties as traced by broad C IV emission. 3-GHz observations with the Very Large Array to an rms of ≈ 10µJy beam −1 probe to star formation rates of ∼ 400 M yr −1 , leading to 22 detections. Supplementing these pointed observations are survey data of 388 sources from the LOFAR Two-metre Sky Survey Data Release 1 that reach comparable depth (for a typical radio spectral index), where 123 sources are detected. These combined observations reveal a radio detection fraction that is a non-linear function of C IV emission line properties and suggest that the data may require multiple origins of radio emission in radio-quiet quasars. Specifically, in radio-quiet quasars we find evidence for radio emission from weak jets or coronae in quasars with low Eddingtion ratios, with either (or both) star formation and accretion disk winds playing an important role in luminous quasars and correlated with increasing Eddington ratio. Additional pointed radio observations will be needed to fully establish the nature of radio emission in radio-quiet quasars.

Optical and UV properties of a radio-loud and a radio-quiet Population A quasar at high redshift

“…Q1410+096 (radio-quiet) shows a C IV 1549 BLUE with a FWHM = 10882 km s −1 , while PKS2000-330 (radio-loud) have a C IV BLUE that is somewhat narrower (∼ 7300 km s −1 ). The fact that radio-quiet sources show a preference of having wider FWHM(C IV BLUE ) than the radio-loud ones is already known by the recent literature and seems to be the normal behaviour in this type of sources (Richards et al, 2021). Apart from that, these results also may indicate that there is an important contribution of outflowing gas in the nuclear activity in the two sources, in agreement with previous results in other quasar samples (Marziani et al, 2017;Sulentic et al, 2017).…”