Giant scattering cones in obscured quasars

Abstract

We analyze Hubble Space Telescope observations of scattering regions in 20\nluminous obscured quasars at $0.24<z<0.65$ (11 new observations and 9 archival\nones) observed at rest-frame $\\sim 3000$\\AA. We find spectacular $5-10$\nkpc-scale scattering regions in almost all cases. The median scattering\nefficiency at this wavelength (the ratio of observed to estimated intrinsic\nflux) is 2.3\\%, and 73\\% of the observed flux at this wavelength is due to\nscattered light, which if unaccounted for may strongly bias estimates of quasar\nhosts' star formation rates. Modeling these regions as illuminated dusty cones,\nwe estimate the radial density distributions of the interstellar medium as well\nas the geometric properties of circumnuclear quasar obscuration -- inclinations\nand covering factors. Small derived opening angles (median half-angle and\nstandard deviation 27\\dg$\\pm$9\\dg) are inconsistent with a 1:1 type 1 / type 2\nratio. We suggest that quasar obscuration is patchy and that the observer has a\n$\\sim 40\\%$ chance of seeing a type 1 source even through the obscuration. We\nestimate median density profile of the scattering medium to be $n_{\\rm\nH}=0.04-0.5$ $(1{\\rm kpc}/r)^2$ cm$^{-3}$, depending on the method. Quasars in\nour sample likely exhibit galaxy-wide winds, but if these consist of optically\nthick clouds then only a small fraction of the wind mass ($\\la 10\\%$)\ncontributes to scattering.\n