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Reverberation Mapping of High-Luminosity Quasars

Description: This article presents the CIV BLR size and luminosity relation over eight orders of magnitude in luminosity, pushing the luminosity limit to its highest point so far.
Date: August 31, 2017
Creator: Kaspi, Shai; Brandt, William Nielsen; Maoz, Dan; Netzer, Hagai; Schneider, Donald P. & Shemmer, Ohad
Partner: UNT College of Arts and Sciences

The X-Ray Properties of the Most Luminous Quasars From the Sloan Digital Sky Survey

Description: This article studies the X-ray properties of a representative sample of 59 of the most optically luminous quasars in the universe spanning a redshift range of z ≈ 1.5-4.5.
Date: May 18, 2007
Creator: Just, Dennis W.; Brandt, William Nielsen; Shemmer, Ohad; Steffen, Aaron; Schneider, Donald P.; Chartas, George et al.
Partner: UNT College of Arts and Sciences

The X-Ray Properties of the Optically Brightest Mini-Bal Quasars from the Sloan Digital Sky Survey

Description: This article compiles a sample of 14 of the optically brightest radio-quiet quasars in the Sloan Digital Sky Survey Data Release 5 quasar catalog that have mini-broad absorption lines present in their spectra.
Date: September 12, 2010
Creator: Wu, Jianfeng; Brandt, William Nielsen; Comins, M.L.; Gibson, Robert R.; Shemmer, Ohad; Garmire, Gordon P. et al.
Partner: UNT College of Arts and Sciences

The X-ray Spectral Properties and Variability of Luminous High-Redshift Active Galactic Nuclei

Description: This article contains a detailed investigation of moderate- to high-quality X-ray spectra of 10 of the most luminous active galactic nuclei known at z > 4.
Date: May 20, 2005
Creator: Shemmer, Ohad; Brandt, William Nielsen; Vignali, Christian; Schneider, Donald P.; Fan, Xiaohui; Richards, Gordon T. et al.
Partner: UNT College of Arts and Sciences

A Population of X-Ray Weak Quasars: PHL 1811 Analogs at High Redshift

Description: This article reports the results from Chandra and XMM-Newton observations of a sample of 10 type 1 quasars selected to have unusual UV emission-line properties similar to those of PHL 1811.
Date: April 15, 2011
Creator: Wu, Jianfeng; Brandt, William Nielsen; Hall, Patrick B.; Gibson, Robert R.; Richards, Gordon T.; Schneider, Donald P. et al.
Partner: UNT College of Arts and Sciences

Variability-Selected Low-Luminosity Active Galactic Nuclei in the 4 Ms Chandra Deep Field-South

Description: This article demonstrates that the observed variability cannot be explained by X-ray Binary populations or ultraluminous X-ray sources, so the variability is most likely caused by accretion onto a supermassive black hole.
Date: January 18, 2012
Creator: Young, Monica; Brandt, William Nielsen; Xue, Yongquan; Alexander, David M.; Bauer, Franz E.; Lehmer, Bret et al.
Partner: UNT College of Arts and Sciences

X-Ray and Multiwavelength Insights into the Nature of Weak Emission-Line Quasars at Low Redshift

Description: This article reports on the X-ray and multiwavelength properties of 11 radio-quiet quasars with weak or no emission lines identified by the Sloan Digital Sky Survey with redshift.
Date: December 9, 2011
Creator: Wu, Jianfeng; Brandt, William Nielsen; Anderson, Scott F.; Diamond-Stanic, Aleksandar M.; Hall, Patrick B.; Plotkin, Richard M. et al.
Partner: UNT College of Arts and Sciences

X-Ray Insights Into the Nature of Weak Emission-Line Quasars at High Redshift

Description: This article presents Chandra observations of nine high-redshift quasars discovered by the Sloan Digital Sky Survey with weak or undetectable high-ionization emission lines in their UV spectra.
Date: February 8, 2009
Creator: Shemmer, Ohad; Brandt, William Nielsen; Anderson, Scott F.; Diamond-Stanic, Aleksandar M.; Fan, Xiaohui; Richards, Gordon T. et al.
Partner: UNT College of Arts and Sciences

Multiwavelength Observations of Radio-Quiet Quasars with Weak Emission Lines

Description: This article presents radio and X-ray observations, as well as optical light curves, for a subset of 26 BL Lac candidates from the Sloan Digital Sky Survey lacking strong radio emission and with z < 2.2.
Date: July 26, 2010
Creator: Plotkin, Richard M.; Anderson, Scott F.; Brandt, William Nielsen; Diamond-Stanic, Aleksandar M.; Fan, Xiaohui; MacLeod, Chelsea L. et al.
Partner: UNT College of Arts and Sciences

Mass Models and Environment of the New Quadruply Lensed Quasar SDSS J1330+1810

Description: We present the discovery of a new quadruply lensed quasar. The lens system, SDSS J1330+1810 at z{sub s} = 1.393, was identified as a lens candidate from the spectroscopic sample of the Sloan Digital Sky Survey. Optical and near-infrared images clearly show four quasar images with a maximum image separation of 1.76 inch, as well as a bright lensing galaxy. We measure a redshift of the lensing galaxy of z{sub 1} = 0.373 from absorption features in the spectrum. We find a foreground group of galaxies at z = 0.31 centred {approx} 120 inch southwest of the lens system. Simple mass models fit the data quite well, including the flux ratios between images, although the lens galaxy appears to be {approx} 1 mag brighter than expected by the Faber-Jackson relation. Our mass modeling suggests that shear from nearby structure is affecting the lens potential.
Date: September 9, 2008
Creator: Oguri, Masamune; Inada, Naohisa; Blackburne, Jeffrey A.; Shin, Min-Su; Kayo, Issha; Strauss, Michael A. et al.
Partner: UNT Libraries Government Documents Department

Candidate isolated neutron stars and other optically blank x-ray fields identified from the rosat all-sky and sloan digital sky surveys

Description: Only seven radio-quiet isolated neutron stars (INSs) emitting thermal X rays are known, a sample that has yet to definitively address such fundamental issues as the equation of state of degenerate neutron matter. We describe a selection algorithm based on a cross-correlation of the ROSAT All-Sky Survey (RASS) and the Sloan Digital Sky Survey (SDSS) that identifies X-ray error circles devoid of plausible optical counterparts to the SDSS g {approx} 22 magnitudes limit. We quantitatively characterize these error circles as optically blank; they may host INSs or other similarly exotic X-ray sources such as radio-quiet BL Lacs, obscured AGN, etc. Our search is an order of magnitude more selective than previous searches for optically blank RASS error circles, and excludes the 99.9% of error circles that contain more common X-ray-emitting subclasses. We find 11 candidates, nine of which are new. While our search is designed to find the best INS candidates and not to produce a complete list of INSs in the RASS, it is reassuring that our number of candidates is consistent with predictions from INS population models. Further X-ray observations will obtain pinpoint positions and determine whether these sources are entirely optically blank at g {approx} 22, supporting the presence of likely isolated neutron stars and perhaps enabling detailed follow-up studies of neutron star physics.
Date: November 1, 2005
Creator: Agueros, Marcel A.; Anderson, Scott F.; Margon, Bruce; Haberl, Frank; Voges, Wolfgang; Annis, James et al.
Partner: UNT Libraries Government Documents Department

Weak Line Quasars at High Redshift: Extremely High Accretion Rates or Anemic Broad-Line Regions?

Description: This article presents Gemini-North K-band spectra of two representative members of the class of high-redshift quasars with exceptionally weak rest-frame ultraviolet emission lines.
Date: September 8, 2010
Creator: Shemmer, Ohad; Trakhtenbrot, Benny; Anderson, Scott F.; Brandt, William Nielsen; Diamond-Stanic, Aleksandar M.; Fan, Xiaohui et al.
Partner: UNT College of Arts and Sciences

The Ultraviolet-To-Mid-Infrared Spectral Energy Distribution of Weak Emission Line Quasars

Description: This article presents Spitzer Space Telescope photometry of 18 Sloan Digital Sky Survey quasars which have weak or undetectable high-ionization emission lines in their rest-frame ultraviolet spectra.
Date: September 23, 2011
Creator: Lane, Ryan A.; Shemmer, Ohad; Diamond-Stanic, Aleksandar M.; Fan, Xiaohui; Anderson, Scott F.; Brandt, William Nielsen et al.
Partner: UNT College of Arts and Sciences

The 4Ms Chandra Deep Field-South Number Counts Apportioned By Source Class: Pervasive Active Galactic Nuclei and the Ascent of Normal Galaxies

Description: This article presents cumulative and differential number-count measurements for the recently completed 4 Ms Chandra Deep Field-South survey.
Date: April 9, 2012
Creator: Lehmer, Bret; Xue, Yongquan; Brandt, William Nielsen; Alexander, David M.; Bauer, Franz E.; Brusa, Marcella et al.
Partner: UNT College of Arts and Sciences

A New Survey for Giant Arcs

Description: We report on the first results of an imaging survey to detect strong gravitational lensing targeting the richest clusters selected from the photometric data of the Sloan Digital Sky Survey (SDSS) with follow-up deep imaging observations from the Wisconsin Indiana Yale NOAO (WIYN) 3.5m telescope and the University of Hawaii 88-inch telescope (UH88). The clusters are selected from an area of 8000 deg{sup 2} using the Red Cluster Sequence technique and span the redshift range 0.1 {approx}&lt; z {approx}&lt; 0.6, corresponding to a comoving cosmological volume of {approx} 2Gpc{sup 3}. Our imaging survey thus targets a volume more than an order of magnitude larger than any previous search. A total of 240 clusters were imaged of which 141 had sub-arcsecond image quality. Our survey has uncovered 16 new lensing clusters with definite giant arcs, an additional 12 systems for which the lensing interpretation is very likely, and 9 possible lenses which contain shorter arclets or candidate arcs which are less certain and will require further observations to confirm their lensing origin. The number of new cluster lenses detected in this survey is likely &gt; 30. Among these new systems are several of the most dramatic examples of strong gravitational lensing ever discovered with multiple bright arcs at large angular separation. These will likely become 'poster-child' gravitational lenses similar to Abell 1689 and CL0024+1654. The new lenses discovered in this survey will enable future systematic studies of the statistics of strong lensing and its implications for cosmology and our structure formation paradigm.
Date: November 15, 2006
Creator: Hennawi, Joseph F.; Gladders, Michael D.; Oguri, Masamune; Dalal, Neal; Koester, Benjamin; Natarajan, Priyamvada et al.
Partner: UNT Libraries Government Documents Department

Five New High-Redshift Quasar Lenses from the Sloan Digital Sky Survey

Description: We report the discovery of five gravitationally lensed quasars from the Sloan Digital Sky Survey (SDSS). All five systems are selected as two-image lensed quasar candidates from a sample of high-redshift (z &gt; 2.2) SDSS quasars. We confirmed their lensing nature with additional imaging and spectroscopic observations. The new systems are SDSS J0819+5356 (source redshift z{sub s} = 2.237, lens redshift z{sub l} = 0.294, and image separation {theta} = 4.04 inch), SDSS J1254+2235 (z{sub s} = 3.626, {theta} = 1.56 inch), SDSS J1258+1657 (z{sub s} = 2.702, {theta} = 1.28 inch), SDSS J1339+1310 (z{sub s} = 2.243, {theta} = 1.69 cin), and SDSS J1400+3134 (z{sub s} = 3.317, {theta} = 1.74 inch). We estimate the lens redshifts of the latter four systems to be z{sub l} = 0.4-0.6 from the colors and magnitudes of the lensing galaxies. We find that the image configurations of all systems are well reproduced by standard mass models. Although these lenses will not be included in our statistical sample of z{sub s} &lt; 2.2 lenses, they expand the number of lensed quasars which can be used for high-redshift galaxy and quasar studies.
Date: September 8, 2008
Creator: Inada, Naohisa; Oguri, Masamune; Shin, Min-Su; Kayo, Issha; Strauss, Michael A.; Morokuma, Tomoki et al.
Partner: UNT Libraries Government Documents Department

Long-Term X-Ray Variability of Typical Active Galactic Nuclei in the Distant Universe

Description: This article discusses the long-term (≈15 years, observed frame) X-ray variability analyses of the 68 brightest radio-quiet active galactic nuclei (AGNs) in the 6 Ms Chandra Deep Field-South survey.
Date: November 3, 2016
Creator: Yang, G.; Brandt, William Nielsen; Luo, Bin; Xue, Yongquan; Bauer, Franz E.; Sun, M. et al.
Partner: UNT College of Arts and Sciences

Optically Selected BL Lacertae Candidates from the Sloan Digital Sky Survey Data Release Seven

Description: This article presents a sample of 723 optically selected BL Lac candidates from the Sloan Digital Sky Survey Data Release 7 spectroscopic database.
Date: October 30, 2009
Creator: Plotkin, Richard M.; Anderson, Scott F.; Brandt, William Nielsen; Diamond-Stanic, Aleksandar M.; Fan, Xiaohui; Hall, Patrick B. et al.
Partner: UNT College of Arts and Sciences

X-Ray Spectral Constraints for z ≈ 2 Massive Galaxies: The Identification of Reflection-Dominated Active Galactic Nuclei

Description: This article uses the 4 Ms Chandra Deep Field-South survey to place direct constraints on the ubiquity of z ≈ 2 heavily obscured active galactic nuclei.
Date: June 6, 2011
Creator: Alexander, David M.; Bauer, Franz E.; Brandt, William Nielsen; Daddi, Emanuele; Hickox, Ryan; Lehmer, Bret et al.
Partner: UNT College of Arts and Sciences