A comprehensive study of broad absorption line quasars. i. Prevalence of He i* absorption line multiplets in low-ionization objects

Journal Article · Sun Mar 01 04:00:00 EST 2015 · Astrophysical Journal, Supplement Series

DOI:https://doi.org/10.1088/0067-0049/217/1/11· OSTI ID:22872404

Liu, Wen-Juan; Zhou, Hongyan; Ji, Tuo; Wang, Ting-Gui; Jiang, Peng; Wang, Huiyuan; Wang, Shu-Fen; Sun, Luming; Yang, Chenwei; Liu, Bo; Zhao, Wen ^[1]; Yuan, Weimin ^[2]; Jian, Ge ^[3]; Shi, Xiheng; Zhang, Shaohua ^[4]; Shu, Xinwen ^[5]

---

1. Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Sciences and Technology of China, Chinese Academy of Sciences, Hefei, Anhui 230026 (China)
2. National Astronomical Observatories, Chinese Academy of Sciences, 20 A Datun Road, Beijing 100012 (China)
3. Astronomy Department, University of Florida, 211 Bryant Space Science Center, P.O. Box 112055, Gainesville, FL 32611 (United States)
4. Polar Research Institute of China, 451 Jinqiao Rd, Shanghai 200136 (China)
5. CEA Saclay, DSM/Irfu/Service d’Astrophysique, Orme des Merisiers, F-91191 Gif-sur-Yvette Cedex (France)

Neutral helium multiplets, He i* λλ3189,3889,10830, are very useful diagnostics for the geometry and physical conditions of the absorbing gas in quasars. So far only a handful of He i* detections have been reported. Using a newly developed method, we detected the He i*λ3889 absorption line in 101 sources of a well-defined sample of 285 Mg ii broad absorption line (BAL) quasars selected from SDSS DR5. This has increased the number of He i* BAL quasars by more than one order of magnitude. We further detected He i*λ3189 in 50% (52/101) of the quasars in the sample. The detection fraction of He i* BALs in Mg ii BAL quasars is ∼35% as a whole, and it increases dramatically with increasing spectral signal-to-noise ratio (S/N), from ∼18% at S/N ⩽ 10 to ∼93% at S/N ⩾ 35. This suggests that He i* BALs could be detected in most Mg ii LoBAL quasars, provided the spectra S/N is high enough. Such a surprisingly high He i* BAL fraction is actually predicted from photoionization calculations based on a simple BAL model. The result indicates that He i* absorption lines can be used to search for BAL quasars at low z, which cannot be identified by ground-based optical spectroscopic surveys with commonly seen UV absorption lines. Using He i* λ3889, we discovered 19 BAL quasars at z<0.3 from the available SDSS spectral database. The fraction of He i* BAL quasars is similar to that of LoBAL objects.

• OSTI ID: 22872404
• Journal Information: Astrophysical Journal, Supplement Series, Journal Name: Astrophysical Journal, Supplement Series Journal Issue: 1 Vol. 217; ISSN 0067-0049; ISSN APJSA2
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABSORPTION
DETECTION
GALAXIES
GEOMETRY
HELIUM
MULTIPLETS
PHOTOIONIZATION
QUASARS
SIGNAL-TO-NOISE RATIO
SPECTRA