LOW-z Mg II BROAD ABSORPTION-LINE QUASARS FROM THE SLOAN DIGITAL SKY SURVEY

	LOW-z Mg II BROAD ABSORPTION-LINE QUASARS FROM THE SLOAN DIGITAL SKY SURVEY
	Zhang, SH 1,2; Wang, TG 1,2; Wang, HY 1,2; Zhou, HY 1,2; Dong, XB1,2 ; Wang JG(王建国)3,4,5
	2010-05-01
关键词	galaxies: active quasars: absorption lines quasars: emission lines quasars: general
卷号	714
期号	1
页码	367-383
通讯作者	Zhang, SH (reprint author), Chinese Acad Sci, Univ Sci & Technol China, Key Lab Res Galaxies & Cosmol, Hefei 230026, Anhui, Peoples R China.
英文摘要	We present a sample of 68 low-z Mg II low-ionization broad absorption-line (loBAL) quasars. The sample is uniformly selected from the Sloan Digital Sky Survey Data Release 5 according to the following criteria: (1) redshift 0.4 < z less than or similar to 0.8, (2) median spectral S/N > 7 pixel(-1), and (3) Mg II absorption-line width Delta upsilon(c) >= 1600 km s(-1). The last criterion is a trade-off between the completeness and consistency with respect to the canonical definition of BAL quasars that have the " balnicity index" BI > 0 in C IV BAL. We adopted such a criterion to ensure that similar to 90% of our sample are classical BAL quasars and the completeness is similar to 80%, based on extensive tests using high-z quasar samples with measurements of both C IV and Mg II BALs. We found (1) Mg II BAL is more frequently detected in quasars with narrower H beta emission line, weaker [O III] emission line, stronger optical Fe II multiplets, and higher luminosity. In term of fundamental physical parameters of a black hole accretion system, loBAL fraction is significantly higher in quasars with a higher Eddington ratio than those with a lower Eddington ratio. The fraction is not dependent on the black hole mass in the range concerned. The overall fraction distribution is broad, suggesting a large range of covering factor of the absorption material. (2) [O III]-weak loBAL quasars averagely show undetected [Ne v] emission line and a very small line ratio of [Ne v] to [O III]. However, the line ratio in non-BAL quasars, which is much larger than that in [O III]-weak loBAL quasars, is independent of the strength of the [O III] line. (3) loBAL and non-loBAL quasars have similar colors in near-infrared to optical band but different colors in ultraviolet. (4) Quasars with Mgii absorption lines of intermediate width are indistinguishable from the non-loBAL quasars in optical emission line properties but their colors are similar to loBAL quasars, redder than non-BAL quasars. We also discuss the implication of these results.
收录类别	SCI
产权排序	第三完成单位
会议网址	http://iopscience.iop.org/0004-637X/714/1/367/
会议录	ASTROPHYSICAL JOURNAL
学科主题	Astronomy & Astrophysics
语种	英语
ISSN号	0004-637X
WOS记录号	WOS:000276701000030
研究领域[WOS]	Astronomy & Astrophysics
WOS标题词	Science & Technology ; Physical Sciences
内容类型	会议论文
源URL	[http://ir.ynao.ac.cn/handle/114a53/5393]
专题	云南天文台_高能天体物理研究组云南天文台_中国科学院天体结构与演化重点实验室
作者单位	1.Key Laboratory for Research in Galaxies and Cosmology, The University of Sciences and Technology of China, Chinese Academy of Sciences, Hefei, Anhui 230026, China 2.Center for Astrophysics, University of Science and Technology of China, Hefei, Anhui 230026, China 3.National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, P.O. Box 110, Kunming, Yunnan 650011, China 4.Graduate School of the Chinese Academy of Sciences, 19A Yuquan Road, P.O. Box 3908, Beijing 100039, China 5.Laboratory for the Structure and Evolution of Celestial Bodies, Chinese Academy of Sciences, P.O. Box 110, 650011 Kunming, China
推荐引用方式 GB/T 7714	Zhang, SH,Wang, TG,Wang, HY,et al. LOW-z Mg II BROAD ABSORPTION-LINE QUASARS FROM THE SLOAN DIGITAL SKY SURVEY[C]. 见:.http://iopscience.iop.org/0004-637X/714/1/367/.