The Quasar Feedback Survey: Revealing the importance of sensitive radio imaging for AGN identification deeper into the radio-quiet regime

Abstract

We present new sub-arcsecond ($\sim$0.3-1 arcsec; $\sim$1--3\,kpc) VLA imaging at 1.4\,GHz and 6\,GHz of 29 optically-selected, [O~{\sc iii}] luminous ($L_{[\mathrm{OIII}]}$ > 10${}^{42.1}$\,erg\,s${}^{-1}$), $z<0.2$ quasars drawn from the expanded Quasar Feedback Survey (QFeedS; with $L_{1.4\mathrm{GHz}}=10^{22.6}$--10${}^{26.3}$\,W\,Hz${}^{-1}$). These 29 new objects occupy the low end of the radio-power distribution ($L_{1.4\mathrm{GHz}}$=$10^{22.63}$--10${}^{23.45}$\,W\,Hz${}^{-1}$) in the QFeedS sample and are nominally `radio quiet'. Despite this, we find widespread evidence of AGN-driven synchrotron activity. Nearly $\sim 31$per\,cent exhibit resolved radio structures on $\sim$0.1--20\,kpc scales consistent with compact jets or wind-driven outflows, and $\sim 90$per\,cent display steep spectra ($\alpha \lesssim -1$) indicative of optically thin synchrotron emission. Combining morphology, spectral index and brightness-temperature diagnostics, at least $\sim 38$per\,cent of the sample show clear AGN signatures that cannot be explained by star formation alone. These constitute the first results from the expanded QFeedS (now 71 quasars spanning $\approx 4$ dex in radio power) and demonstrate that compact, low-power jets and AGN shocks are common deep inside the radio-quiet regime. A thorough understanding of feedback processes from quasars, deep into the `radio-quiet' regime, will be obtained by connecting these high resolution radio observations with multi-wavelength observations.

17 pages, 7 figures