2018ApJ...853..167S

We present the discovery of strong Balmer line absorption in Hα to Hγ in two luminous low-ionization broad absorption line quasars at z∼1.5, with black hole masses around 10¹⁰ M_☉ from near-IR spectroscopy. There are only two previously known quasars at z 1.0 showing Balmer line absorption. SDSS J1019+0225 shows blueshifted absorption by ∼1400 km s^–1 with an Hα rest-frame equivalent width of 13 Å. In SDSS J0859+4239, we find redshifted absorption by ∼500 km s^–1 with an Hα rest-frame equivalent width of 7 Å. The redshifted absorption could indicate an inflow of high-density gas onto the black hole, though we cannot rule out alternative interpretations. The Balmer line absorption in both objects appears to be saturated, indicating partial coverage of the background source by the absorber. We estimate the covering fractions and optical depth of the absorber and derive neutral hydrogen column densities, N_H I_ ∼ 1.3 x 10¹⁸ cm^–2 for SDSS J1019+0225 and N_H I_ ∼ 9 x 10¹⁷ cm^–2 for SDSS J0859+4239. In addition, the optical spectra reveal also absorption troughs in He I* λ3889 and λ3189 in both objects.