Feeding the Accretion Disk from the Dusty Torus in a Reddened Quasar

Abstract

We present here a detailed analysis of an unusual absorption line system in the quasar SDSS J122826.79+100532.2. The absorption lines in the system have a common redshifted velocity structure starting from v ∼ 0 and extending to ∼1000 km s −1 , and are clearly detected in the hydrogen Balmer series up to H ι , in the metastable neutral helium triplet, and in optical lines of excited states of single ionized iron. We estimated that the absorber has a density n H ≈ 10 8.4 cm −3 and an ionization parameter U ≈ 10 −1.2 , thereupon we located it at r abs ≈ 1.5 pc from the central supermassive black hole. The inferred distance is remarkably similar to the evaporation radius for dust grains r evap ≈ 1 pc in the quasar. Thus the absorber may be a probe of an inflow starting from the dusty torus and feeding the accretion disk. Both the featureless continuum and the broad emission lines are heavily reddened with E ( B − V ) ≈ 0.66, in contrast to the narrow emission lines whose reddening is negligible. The dusty medium could be located in between the broad and narrow emission line regions, and possibly be associated with a “cold” narrow absorption line system detected in Ca ii and Na i doublets nearly unshifted from the quasar systemic velocity. SDSS J122826.79+100532.2 might represent such a rare case that both the inflow and the torus could be tracked by absorption lines.