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Locating Star-Forming Regions in Quasar Host Galaxies

Description: This article presents a study of the morphology and intensity of star formation in the host galaxies of eight Palomar-Green quasars using observations with the Hubble Space Telescope.
Date: November 5, 2013
Creator: Young, Jason E.; Eracleous, Michael; Shemmer, Ohad; Netzer, Hagai; Gronwall, Caryl; Lutz, Dieter et al.
Partner: UNT College of Arts and Sciences

The Wolf effect and the redshift of quasars

Description: We consider a simple model, based on currently accepted models for active galactic nuclei, for a quasi-stellar object (QSO or "quasar") and examine the influence that correlation-induced spectral changes ("The Wolf Effect") may have upon the redshifts of the optical emission lines.
Date: January 23, 1998
Creator: James, Daniel F.V.
Partner: UNT Libraries Government Documents Department

QSO color selection in the SDSS

Description: The Sloan Digital Sky Survey (SDSS) will image 10,000 square degrees in the north galactic cap in five filters. We hope to identify and obtain spectra for about 100,000 quasars brighter than 20th magnitude in this area. The selection will be primarily on the basis of point spread function and colors, but we will also identify quasars from a catalog of FIRST radio sources. The selection areas in color space must be determined during the testing period prior to the official start of the survey. This task may determine the length of the test period. In anticipation of this becoming the critical path, we have written a body of software that will allow us to quickly analyze a set of multicolor data and make a first cut at the selection limits.
Date: January 1, 1998
Creator: Newberg, H.J. & Yanny, B.
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

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

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

A Statistical Relation Between the X-ray Spectral Index and Eddington Ratio of Active Galactic Nuclei in Deep Surveys

Description: This article presents an investigation into how well the properties of the accretion flow on to a supermassive black hole may be coupled to those of the overlying hot corona.
Date: May 22, 2013
Creator: Brightman, M.; Silverman, John David; Mainieri, Vincenzo; Ueda, Yoshihiro; Schramm, Malte; Matsuoka, Kenta et al.
Partner: UNT College of Arts and Sciences

High-Redshift SDSS Quasars With Weak Emission Lines

Description: This article identifies a sample of 74 high-redshift quasars with weak emission lines from the Fifth Data Release of the Sloan Digital Sky Survey and present infrared, optical, and radio observations of a subsample of four objects at z > 4.
Date: April 16, 2009
Creator: Diamond-Stanic, Aleksandar M.; Fan, Xiaohui; Brandt, William Nielsen; Shemmer, Ohad; Strauss, Michael A.; Anderson, Scott F. et al.
Partner: UNT College of Arts and Sciences

The Hard X-Ray Spectrum as a Probe for Black Hole Growth in Radio-Quiet Active Galactic Nuclei

Description: This article studies the hard X-ray spectral properties of 10 highly luminous radio-quiet active galactic nuclei at z = 1.3-3.2, including new XMM-Newton observations of four of these sources.
Date: April 3, 2008
Creator: Shemmer, Ohad; Brandt, William Nielsen; Netzer, Hagai; Maiolino, Roberto & Kaspi, Shai
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

PG 0946+301: the Rosetta Stone of BALQSOs?

Description: We describe the motivation and features of a multiwavelength spectroscopic campaign on broad absorption line (BAL) QSO PG 0946+301. The main goal of this project is to determine the ionization equilibrium and abundances (IEA) in BAL outflows. Previous studies of IEA in BALQSOs were based on the assumption that the BALs are not saturated so that the column densities inferred from the apparent optical depths are realistic. This critical assumption is at odds with several recent observations and with analysis of existing data which indicate that the absorption troughs are heavily saturated even when they are not black. In addition, X-ray observations, which are important for constraining the ionizing continuum, were not available for those objects that had UV spectral data. Quantifying the level of saturation in the BALs necessitates UV spectroscopy with much higher S/N and broader-spectral coverage than currently exist. After taking into account the capabilities of available observatories, our best hope for a substantial improvement in understanding the IEA in BALQSOs is to concentrate considerable observational resources on the most promising object. Our studies of available HST and ground-based spectra show that PG 0946+301 is by far the best candidate for such a program. This BALQSO is at least five times brighter, shortward of 1000 {Angstrom}, rest frame, than any other object, and due to its low redshift it has an especially sparse Ly{alpha} forest. At the same time PG 0946+301 is a typical BALQSO and therefore its IEA should be representative. To this effect we are developing a multiwavelength spectroscopic campaign (UV, FUV, X-ray and optical) on BALQSO PG 0946+301. We discuss the goals and feasibility of each observational component: HST, FUSE, ASCA and ground-based.
Date: June 1, 1998
Creator: Arav, N., LLNL
Partner: UNT Libraries Government Documents Department

On the speed of gravity and the nu/c corrections to the Shapirotime delay

Description: I compute the v/c correction to the gravitational time delayfor light passing by a massive object moving with speed v, and I finddisagreement with previously published results. It is also argued thatthe speed of gravity formula that was recently used in the conjunction ofJupiter and quasar J0842+1845 is frame dependent.
Date: March 26, 2003
Creator: Samuel, Stuart
Partner: UNT Libraries Government Documents Department