Ultra-dense Broad-line Region Scale Outflow in Highly Reddened Quasar SDSS J145057.28+530007.6

Abstract

Abstract We report the discovery of highly reddening and hydrogen Balmer and metastable helium broad absorption lines in the quasar SDSS J145057.28+530007.6, based on the optical and near-infrared spectra taken from the SDSS-III/BOSS and the TripleSpec observations. The nuclear continuum, Balmer decrement, and absorption-line depth analyses suggest that (1) the accretion disk is completely obscured and the covering factor of the broad-line region (BLR) is only 0.39 ± 0.03, (2) the power-law continuum is reddened by the SMC extinction law of E(B – V) =0.72 ± 0.01 mag and the dusty materials are mainly associated with Ca ii H and K rather than the Balmer and He i* absorption-line system, (3) the unsaturated Balmer (Hβ, Hγ, and Hδ) and He i* λ3889 absorption lines have the same two-Gaussian profiles as the shifts of −931 ± 33 and −499 ± 39 km s−1 and the widths of 121 ± 28 and 196 ± 37 km s−1, respectively. Constrained mutually by the Balmer, He i* absorption lines and undetected Fe ii* λ5169 in the photoionization simulations, the physical properties of the outflow gases are derived as follows: ionization parameter 10−1.4 ≲ U ≲ 10−0.8, density 108.2±0.4 ≲ n H ≲ 109.0±0.4 cm−3, and column density 1022.0±0.2 ≲ N H ≲ 1022.2–22.3 cm−2. We propose that the ultra-dense outflow gases appear in the vicinity of the surface of the BLR or are located at most 3.12 pc away from the engine. That probably implies that the outflow originates from the BLR, and this kind of ultra-dense BLR scale outflow gases can effectively test the physical properties of the outer gases of the BLR.