2021ApJ...916...86L

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 Hι, 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.