The existence of intermediate-width emission line regions (IELRs) in active galactic nuclei has been discussed for over two decades. A consensus, however, is yet to be arrived at due to the lack of convincing evidence for their detection. We present a detailed analysis of the broadband spectrophotometry of the partially obscured quasar OI 287. The ultraviolet intermediate-width emission lines (IELs) are very prominent, in high contrast to the corresponding broad emission lines (BELs) which are heavily suppressed by dust reddening. Assuming that the IELR is virialized, we estimated its distance to the central black hole to be ∼2.9 pc, similar to the dust sublimation radius of ∼1.3 pc. Photo-ionization calculations suggest that the IELR has a hydrogen density of ∼10 8.8 -10 9.4 cm −3 , within the range of values quoted for the dusty torus near the sublimation radius. Both its inferred location and physical conditions suggest that the IELR originates from the inner surface of the dusty torus. In the spectrum of this quasar, we identified only one narrow absorption-line system associated with the dusty material. With the aid of photo-ionization model calculations, we found that the obscuring material might originate from an outer region of the dusty torus. We speculate that the dusty torus, which is exposed to the central ionizing source, may produce IELs through photo-ionization processes, as well as obscure BELs as a natural "coronagraph." Such a "coronagraph" could be found in a large number of partially obscured quasars and may be a useful tool to study IELRs.

SDSS J095253.83+011422.0 (J0952+0114) was reported by Hall et al. (2004) as an exotic quasar at z em = 3.020. In contrast to prominent broad metal-line emissions with FWHM∼ 9000 km s −1 , only a narrow Lyα emission line is present with FWHM∼1000 km s −1 . The absence of broad Lyα emission line has been a mystery for more than a decade. In this paper, we demonstrate that this is due to dark Proximate Damped Lyα Absorption (PDLA) at z abs = 3.010 by identifying associated Lyman absorption line series from the damped Lyβ up to Ly9, as well as the Lyman limit absorption edge. The PDLA cloud has a column density of log N H I (cm −2 ) = 21.8 ± 0.2 , a metallicity of [Zn/H]> −1.0, and a spatial extent exceeding the Narrow Emission Line Region (NELR) of the quasar. With a luminosity of L Lyα ∼ 10 45 erg s −1 , the residual Lyα emission superposed on the PDLA trough is of two orders of magnitude stronger than previous reports. This is best explained as re-radiated photons arising from the quasar outflowing gas at a scale larger than the NELR. The PDLA here, acting like a natural coronagraph, provides us with a good insight into the illuminated gas in the vicinity of the quasar, which are usually hard to resolve due to their small size and "seeing fuzz" of bright quasars. Notably, J0952+0114 analogies might be easily omitted in the spectroscopic surveys of DLAs and PDLAs, as -2their damped Lyα troughs can be fully filled by additional strong Lyα emissions. Our preliminary survey shows that such systems are not very rare. They are potentially a unique sample for probing strong quasar feedback phenomenon in the early universe.