The quasar feedback survey: zooming into the origin of radio emission with e-MERLIN

We present 6 GHz e-MERLIN observations of 42 z < 0.2 type 1 and type 2 mostly radio-quiet quasars (L[OIII] ≳ 1042 erg s−1; LAGN ≳ 1045 erg s−1) from the Quasar Feedback Survey. The nature and origin of radio emission in these types of sources is typically ambiguous based on all-sky, low-resolution surveys. With e-MERLIN, we investigate radio emission on sub-kiloparsec scales (∼10s-100s pc). We find 37/42 quasars are detected, with a diversity of radio morphologies, including compact cores, knots and extended jet-like structures, with sizes of 30–540 pc. Based on morphology and brightness temperature, we classify 76 percnt of the quasars as radio-AGN, compared to the ∼57 percnt identified as radio-AGN at the ∼1–60 kpc scales probed in prior studies. Combining results from e-MERLIN and the Very Large Array, 86 percnt reveal a radio-AGN. On average, ∼60 percnt of the total radio flux is resolved away in the e-MERLIN maps, and is likely dominated by jet-driven lobes and outflow-driven shocks. We find no significant differences in measured radio properties between type 1 and type 2 quasars, and estimate sub-relativistic jet speeds of ∼0.2– 0.3c and modest jet powers of Pjet ≈ ×1043 erg s−1 for the few targets, where these measurements were possible. These quasars share characteristics with compact radio-selected populations, and the global radio emission likely traces strong interactions between the AGN (jets/outflows) and their host galaxy ISM from 10s parsec to 10s kiloparsec scales.