Observations of feedback from radio-quiet quasars – I. Extents and morphologies of ionized gas nebulae

Abstract

Black hole feedback -- the strong interaction between the energy output of\nsupermassive black holes and their surrounding environments -- is routinely\ninvoked to explain the absence of overly luminous galaxies, the black hole vs.\nbulge correlations and the similarity of black hole accretion and star\nformation histories. Yet direct probes of this process in action are scarce and\nlimited to small samples of active nuclei. We present Gemini IFU observations\nof the distribution of ionized gas around luminous, obscured, radio-quiet (RQ)\nquasars at z~0.5. We detect extended ionized gas nebulae via [O III]5007\nemission in every case, with a mean diameter of 28 kpc. These nebulae are\nnearly perfectly round. The regular morphologies of nebulae around RQ quasars\nare in striking contrast with lumpy or elongated nebulae seen around radio\ngalaxies at low and high redshifts. We present the uniformly measured\nsize-luminosity relationship of [O III] nebulae around Seyfert 2 galaxies and\ntype 2 quasars spanning 6 orders of magnitude in luminosity and confirm the\nflat slope of the correlation (R ~ L^{0.25+/-0.02}). We find a universal\nbehavior of the [O III]/H-beta ratio in our entire RQ quasar sample: it\npersists at a constant value (~10) in the central regions, until reaching a\n"break" isophotal radius ranging from 4 to 11 kpc where it starts to decrease.\nWe propose a model of clumpy nebulae in which clouds that produce line emission\ntransition from being ionization-bounded at small distances from the quasar to\nbeing matter-bounded in the outer parts of the nebula, which qualitatively\nexplains the observed line ratio and surface brightness profiles. It is\nstriking that we see such smooth and round large-scale gas nebulosities in this\nsample, which are inconsistent with illuminated merger debris and which we\nsuggest may be the signature of accretion energy from the nucleus reaching gas\nat large scales.\n