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$1–3 kpc) Very Large Array imaging at 1.4 and 6 GHz of 29 optically selected [O iii] luminous ($L_{\rm [O III]}$ > 10$^{42.1}$ erg s$^{-1}$) $z\lt 0.2$ quasars drawn from the expanded Quasar Feedback Survey (QFeedS; with $L_\mathrm{1.4\, GHz} = 10^{22.6}$–10$^{26.3}$ W Hz$^{-1}$). These 29 new objects occupy the low end of the radio-power distribution ($L_\mathrm{1.4\, GHz}$=$10^{22.63}$–10$^{23.45}$ W Hz$^{-1}$) in the QFeedS sample and are nominally ‘radio quiet’. Despite this, we find widespread evidence of active galactic nucleus (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 multiwavelength observations.