2021RAA....21...65L

We report on the discovery of unusual broad absorption lines (BALs) in the bright quasar SDSS J075133.35+134548.3 at z ∼ 1, using archival and newly obtained optical and NIR spectroscopic data. The BALs are detected reliably in He I* λ3889, He I* λ10830 and tentatively in Al III , Mg II . These BALs show complex velocity structures consisting of two major components: a high-velocity component (HV), with a blueshifted velocity range of [?]v_HV ∼ -9300 - -3500 km s^–1, which can be reliably detected in He I* λ10830, and tentatively in Al III and Mg II , whereas it is undetectable in He I* λ3889; and a low-velocity component (LV), with [?]v_LV ∼ -3500 - -1800 km s^–1, is only detected in He I* λ3889 and He I* λ10830. With the BALs from different ions, the HV outflowing gas can be constrained to have a density of n_H ∼10 10.3 -10 11.4 cm -3 , a column density of N_H ∼ 10 21 cm^–2 and an ionization parameter of U ∼10^–1.83 -10^–1.72 ; inferring a distance of R_HV ∼0.5 pc from the central continuum source with a monochromatic luminosity λL_λ (5100)=7.0x10 45 erg s^–1 at 5100 Å. This distance is remarkably similar to that of the normal broad line region (BLR) estimated from reverberation experiments, suggesting association of the BLR and the HV BAL outflowing gas. Interestingly, a blueshifted component is also detected in Al III and Mg II broad emission lines (BELs), and the Al III/Mg II of such a BEL component can be reproduced by the physical parameters inferred from the HV BAL gas. The LV BAL gas likely has a larger column density, a higher ionization level and hence a smaller distance than the HV BAL gas. Further spectroscopy with a high S/N ratio and broader wavelength coverage is needed to confirm this to shed new light on the possible connection between BALs and BELs.