Discovery of Balmer broad absorption lines in the quasar LBQS 1206+1052

作     者：Tuo Ji Ting-Gui Wang Hong-Yan Zhou Hui-Yuan Wang 

作者机构：Key Laboratory for Research in Galaxies and Cosmology University of Science and Technology of China （USTC） Hefei 230026 China Center for Astrophysics USTC Hefei 230026 China Polar Research Institute of China Shanghai 200136 China 

出 版 物：《Research in Astronomy and Astrophysics》 (天文和天体物理学研究（英文版）)

年 卷 期：2012年第12卷第4期

页      面：369-382页

核心收录：

学科分类：07[理学] 070401[理学-天体物理] 0704[理学-天文学] 

基　　金：supported by the National Natural Science Foundation of China(Grants Nos.10973013 and 11033007) the Fundamental Research Funds for the Central Universities through grant WK 2030220006 the SOA project CHINARE2012-02-03 Funding for the SDSS and SDSS-Ⅱ has been provided by the Alfred P.Sloan Foundation the Participating Institutions the National Science Foundation the U.S. Department of Energy the National Aeronautics and Space Administration the Japanese Monbukagakusho the Max Planck Society the Higher Education Funding Council for England 

主　　题：galaxies active -- quasar absorption lines -- quasar individual (LBQS1206+1052) 

摘      要：We report the discovery of Balmer broad absorption lines （BALs） in the quasar LBQS 1206＋1052 and present a detailed analysis of the peculiar absorption line spectrum. Besides the Mg II λλ2796, 2803 doublet, BALs are also detected in the He I＊ multiplet at λλ2946, 3189, 3889 A arising from the metastable helium 2 3 S level, and in Hα and Hβ from the excited hydrogen H I＊ n = 2 level, which are rarely seen in quasar spectra. We identify two components in the BAL troughs of v ～ 2000 km s 1 width： One component shows an identical profile in H I＊, He I＊ and Mg II with its centroid blueshifted by v c ≈ 726 km s-1 . The other component is detected in He I＊ and Mg II with v c ≈ 1412 km s-1 . We estimate the column densities of H I＊, He I＊, and Mg II, and compare them with possible level population mechanisms. Our results favor the scenario that the Balmer BALs originate in a partially ionized region with a column density of N H ～ 10 21 10 22 cm-2 for an electron density of n e ～ 10 6 10 8 cm-3 via Lyα resonant scattering pumping. The harsh conditions needed may help to explain the rarity of Balmer absorption line systems in quasar spectra. With an i-band PSF magnitude of 16.50, LBQS 1206＋1052 is the brightest Balmer-BAL quasar ever reported. Its high brightness and unique spectral properties make LBQS 1206＋1052 a promising candidate for followup high-resolution spectroscopy, multi-band observations, and long-term monitoring.