Leaked Lyα Emission: An Indicator of the Size of Quasar Absorption Outflows

Abstract

Abstract The galactocentric distance of quasar absorption outflows are conventionally determined using absorption troughs from excited states, a method hindered by severely saturated or self-blended absorption troughs. We propose a novel method to estimate the size of a broad absorption line (BAL) region, which partly obscures an emission line region by assuming virialized gas in the emission region surrounding a supermassive black hole with known mass. When a spiky Lyα line emission is present at the flat bottom of the deep N v absorption trough, the size of the BAL region can be estimated. We have found three BAL quasars in the SDSS database showing such Lyα lines. The scale of their BAL outflows are found to be 3–26 pc, moderately larger than the theoretical scale (0.01–0.1 pc) of trough forming regions for winds originating from accretion disks, but significantly smaller than most outflow sizes derived using the absorption troughs of the excited states of ions. For these three outflows, the lower limits of the ratio of kinetic luminosity to Eddington luminosity are 0.02%–0.07%. These lower limits are substantially smaller than that required to have a significant feedback effect on their host galaxies.