Mon. Not. R. Astron. Soc., 454, 876-888 (2015/November-3)
A coronagraphic absorbing cloud reveals the narrow-line region and extended Lyman α emission of QSO J0823+0529.
FATHIVAVSARI H., PETITJEAN P., NOTERDAEME P., PARIS I., FINLEY H., LOPEZ S., SRIANAND R. and SANCHEZ P.
Abstract (from CDS):
We report long-slit spectroscopic observations of the quasar SDSS J082303.22+052907.6 (z_C IV ∼ 3.1875), whose broad-line region (BLR) is partly eclipsed by a strong damped Lyman α (DLA; logN(Hi) = 21.7) cloud. This allows us to study the narrow-line region (NLR) of the quasar and the Lyman α emission from the host galaxy. Using cloudy models that explain the presence of strong Nv and Pv absorption together with the detection of Siii* and Oi** absorption in the DLA, we show that the density and the distance of the cloud to the quasar are in the ranges 180 < nH < 710/ cm3 and 580 > r0 > 230 pc, respectively. Sizes of the neutral ( ∼ 2-9pc) and highly ionized phases ( ∼ 3-80pc) are consistent with the partial coverage of the Civ BLR by the Civ absorption from the DLA (covering factor of ∼ 0.85). We show that the residuals are consistent with emission from the NLR with Civ/Lyman α ratios varying from 0 to 0.29 through the profile. Remarkably, we detect extended Lyman α emission up to 25 kpc to the north and west directions and 15 kpc to the south and east. We interpret the emission as the superposition of strong emission in the plane of the galaxy up to 10 kpc with emission in a wind of projected velocity ∼ 500 km/s which is seen up to 25 kpc. The low metallicity of the DLA (0.27 solar) argues for at least part of this gas being infalling towards the active galactic nucleus and possibly being located where accretion from cold streams ends up.