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

• Published in: arXiv.org 2022-01
• Main Authors: Li, Ge, Shi, Xiheng, Tian, Qiguo, Sun, Luming, Shu, Xinwen, Chen, Xiangjun, Zhou, Hongyan
• Format: Article
• Language: English
• Subjects: Absorbers; Absorption; Accretion disks; Balmer series; Emission; Inflow; Quasars; Space telescopes; Supermassive black holes; Toruses
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2201.12495

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 \(v\sim0\) and extending to \(\sim1,000\ \mathrm{km~s}^{-1}\), and are clearly detected in hydrogen Balmer series up to H\(\iota\), in metastable neutral helium triplet, and in optical lines of excited states of single ionized iron. We estimated that the absorber has a density \(n_{\mathrm{H}}\approx10^{8.4}\ \mathrm{cm}^{-3}\) and an ionization parameter \(U\approx10^{-1.2}\), thereupon located it at \(r_{\mathrm{abs}}\approx1.5\) pc from the central supermassive black hole. The inferred distance is remarkably similar to the evaporation radius for dust grains \(r_{\mathrm{evap}}\approx1\) 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 \(E(B-V)\approx0.66\), 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 \ion{Ca}{2} and \ion{Na}{1} 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.