Results 131 to 140 of about 94,086 (264)

The LAMOST Survey of Background Quasars in the Vicinity of the Andromeda and Triangulum Galaxies -- II. Results from the Commissioning Observations and the Pilot Surveys

, 2013
We present new quasars discovered in the vicinity of the Andromeda and Triangulum galaxies with the LAMOST during the 2010 and 2011 observational seasons.
Bai, Zhong-Rui, Chen, Jian-Jun, Chen, Xiao-Yan, Chu, Jia-Ru, Chu, Yao-Quan, Cui, Xiang-Qun, Du, Bing, Hou, Yong-Hui, Hu, Hong-Zhuan, Hu, Zhong-Wen, Huang, Yang, Huo, Zhi-Ying, Jia, Lei, Jiang, Fang-Hua, Lei, Ya-Juan, Li, Ai-Hua, Li, Guang-Wei, Li, Guo-Ping, Li, Jian, Li, Xin-Nan, Li, Yan, Li, Ye-Ping, Liu, Gen-Rong, Liu, Xiao-Wei, Liu, Zhi-Gang, Lu, Qi-Shuai, Luo, A-Li, Luo, Yu, Men, Li, Ni, Ji-Jun, Qi, Yong-Jun, Qi, Zhao-Xiang, Shi, Huo-Ming, Shi, Jian-Rong, Sun, Shi-Wei, Tang, Zheng-Hong, Tian, Yuan, Tu, Liang-Ping, Wang, Dan, Wang, Feng-Fei, Wang, Gang, Wang, Jia-Ning, Wang, Lei, Wang, Shu-Qing, Wang, You, Wang, Yue-Fei, Wei, Ming-Zhi, Wu, Yue, Xiang, Mao-Sheng, Xue, Xiang-Xiang, Yan, Lin, Yao, Zheng-Qiu, Yu, Yong, Yuan, Hai-Bo, Yuan, Hui, Zhai, Chao, Zhang, En-Peng, Zhang, Hao-Tong, Zhang, Hui-Hua, Zhang, Jian-Nan, Zhang, Wei, Zhang, Yan-Xia, Zhang, Yong, Zhang, Zhen-Chao, Zhao, Gang, Zhao, Ming, Zhao, Yong-Heng, Zhou, Fang, Zhou, Xin-Lin, Zhu, Yong-Tian, Zou, Si-Cheng   +70 more
core   +1 more source

Quasar viscosity crisis [PDF]

Nature Astronomy, 2018
For consistency with Nature policy, the version posted here is the text as submitted to Nature Astronomy in November 2017. The final version is available at the DOI below, and differs slightly in wording.
openaire   +3 more sources

Machine Learning–based Search of High-redshift Quasars

The Astrophysical Journal Supplement Series
We present a machine learning search for high-redshift (5.0 < z < 6.5) quasars using the combined photometric data from the Dark Energy Spectroscopic Instrument (DESI) Imaging Legacy Surveys and the Wide-field Infrared Survey Explorer survey.
Guangping Ye, Huanian Zhang, Qingwen Wu
doaj   +1 more source

The Race Between Stars and Quasars in Reionizing Cosmic Hydrogen

, 2009
The cosmological background of ionizing radiation has been dominated by quasars once the Universe aged by ~2 billion years. At earlier times (redshifts z>3), the observed abundance of bright quasars declined sharply, implying that cosmic hydrogen was ...
A. Loeb, A. Loeb, A. Soltan, A.S. Eddington, Abraham Loeb, C.-L. Jiao, C.A. Faucher-Giguère, C.W. Morgan, F. Shankar, F. Shankar, I.D. Novikov, J. Magorrian ., J. Silk, J.A. Kollmeier ., J.L. Tinker ., J.S.B. Wyithe, J.S.B. Wyithe, J.S.B. Wyithe, J.S.B. Wyithe, K. Gebhardt ., L. Ferrarese, M. Dijkstra, M. Dijkstra, M.S. Warren, N. Haring, N.I. Shakura, P.F. Hopkins, R. Shafee, R. Shafee ., R.C. Kennicutt, R.C. Telfer, R.L. White, R.M. O'Leary, R.M. O'Leary, S. Poindexter, S. Tremaine ., S. Tremaine ., S. Wyithe, T. Tanaka, T.R. Lauer ., V. Bromm, WMAP collaboration, Y. Li ., Z. Haiman, Z. Haiman   +44 more
core   +1 more source

SDSS quasars in the WISE preliminary data release and quasar candidate selection with optical/infrared colors

, 2012
We present a catalog of 37,842 quasars in the SDSS Data Release 7, which have counterparts within 6" in the WISE Preliminary Data Release. The overall WISE detection rate of the SDSS quasars is 86.7%, and it decreases to less than 50.0% when the quasar ...
Arnaboldi, Barkhouse, Eisenstein, Fan, Fan, Fan, Fazio, Glikman, Guoqiang Hao, Lacy, Lupton, Nanbo Peng, Polletta, Reyes, Richards, Richards, Richards, Richards, Ross, Schlegel, Schneider, Schneider, Skrutskie, Stern, The Dark Energy Survey Collaboration, Weinstein, Wright, Wu, Wu, Wu, Wu, Wu, Xue-Bing Wu, Yanxia Zhang, York, Zhendong Jia   +35 more
core   +1 more source

The X-ray Properties of the Most-Luminous Quasars from the Sloan Digital Sky Survey

, 2007
Utilizing 21 new Chandra observations as well as archival Chandra, ROSAT, and XMM-Newton data, we study the X-ray properties of a representative sample of 59 of the most optically luminous quasars in the Universe (M_i~~-29.3 to -30.2) spanning a redshift
Brandt, W. N., Chartas, G., Garmire, G. P., Just, D. W., Schneider, D. P., Shemmer, O., Steffen, A. T.   +6 more
core   +2 more sources

Quest for a Coherent Definition of Weak-line Quasars and Its Physical Implications

The Astrophysical Journal
Weak-line quasars (WLQs) represent a subset of type 1 quasars distinguished by remarkably weak high-ionization broad emission lines, yet exhibiting normal optical/UV continua. This study establishes a physically motivated definition of WLQs using 371,091
Xiaoqiang Cheng, Jianfeng Wu, Qiaoya Wu
doaj   +1 more source

A Comprehensive Study of Broad Absorption Line Quasars: I. Prevalence of HeI* Absorption Line Multiplets in Low-Ionization Objects

, 2015
Neutral Helium multiplets, HeI*3189,3889,10830 are very useful diagnostics to the geometry and physical conditions of the absorbing gas in quasars. So far only a handful of HeI* detections have been reported.
Ji, Tuo, Jian, Ge, Jiang, Peng, Liu, Bo, Liu, Wen-Juan, Shi, Xiheng, Shu, Xinwen, Sun, Luming, Wang, Huiyuan, Wang, Shu-Fen, Wang, Ting-Gui, Yang, Chenwei, Yuan, Weimin, Zhang, Shaohua, Zhao, Wen, Zhou, Hongyan   +15 more
core   +1 more source

Some Constraints on Quasar Progenitors and Quasar Evolution [PDF]

Symposium - International Astronomical Union, 1986
There is strong evidence that quasars are powered by the gravitational energy released by in fall of matter into a compact supermassive object which is most likely a black hole with mass M>106 to 109MO. The question then arises as to how such massive black holes came to be formed. What sort of objects were the progenitors?
openaire   +1 more source

Star formation rate and dynamical mass of 10^8 solar mass black hole host galaxies at redshift 6

, 2015
We present ALMA observations of two moderate luminosity quasars at redshift 6. These quasars from the Canada-France High-z Quasar Survey (CFHQS) have black hole masses of ~10^8 M_solar.
Bergeron, Jacqueline, Omont, Alain, Willott, Chris J.   +2 more
core   +2 more sources