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

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 $0.39\pm0.03$, (2) the power-law continuum is reddened by the SMC extinction law of $E(B-V )=0.72\pm 0.01$ mag and the dusty materials are mainly associated with \ion{Ca}{2} H and K rather than the Balmer and \ion{He}{1}* absorption-line system, (3) the unsaturated Balmer (H$\beta$, H$\gamma$, and H$\delta$) and \ion{He}{1}* $\lambda3889$ absorption lines have same two-Gaussian profiles with the shifts of $-931\pm33$ and $-499\pm39$ km s$^{-1}$ and the widths of $121\pm28$ and $196\pm37$ km s$^{-1}$, respectively. Constrained mutually by the Balmer, \ion{He}{1}* absorption lines and undetected \ion{Fe}{2}* $\lambda5169$ in the photoionization simulations, the physical properties of the outflow gases are derived as follows: ionization parameter $10^{-1.4} \lesssim U \lesssim 10^{-0.8}$, density $10^{8.2\pm0.4} \lesssim n_{\rm H} \lesssim 10^{9.0\pm0.4}$ cm$^{-3}$, and column density $10^{22.0\pm0.2} \lesssim N_{\rm H} \lesssim 10^{22.2-22.3}$ 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.