Broad Balmer-line Absorption in SDSS J172341.10+555340.5
Abstract
I present the discovery of Balmer-line absorption from H alpha to H9 in iron low-ionizaton broad absorption line (FeLoBAL) quasar, SDSS~J172341.10+555340.5 by near-infrared spectroscopy with the Cooled Infrared Spectrograph and Camera for OHS (CISCO) attached to the Subaru telescope. The redshift of the Balmer-line absorption troughs is 2.0530 +/- 0.0003, and it is blueshifted by 5370 km s-1 from the Balmer emission lines. It is more than 4000 km s-1 blueshifted from the previously known UV absorption lines. I detect relatively strong (EWrest=20A) [O III] emission lines which are similar to those found in other broad absorption line quasars with Balmer-line absorption. I derived a column density of neutral hydrogen of 5.2x1017 cm-2 by using the curve of growth and taking account of Ly alpha trapping. I searched for UV absorption lines which have the same redshift with Balmer-line absorption. I found Al II and Fe III absorption lines at z=2.053 which correspond to previously unidentified absorption lines, and the presence of other blended troughs that were difficult to identify.