Patrick Hall - York University

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Name
Patrick Hall
Affiliation
York University
City
Toronto
Country
Canada

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Cosmology and Nongalactic Astrophysics (33)
 
Astrophysics of Galaxies (14)
 
Astrophysics (6)
 
High Energy Astrophysical Phenomena (5)
 
Instrumentation and Methods for Astrophysics (3)
 
Earth and Planetary Astrophysics (2)
 
Physics - Physics Education (2)
 
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Publications Authored By Patrick Hall

2017May

If the atmospheric density $\rho_{atm}$ in the accretion disk of an active galactic nucleus (AGN) is sufficiently low, scattering in the atmosphere can produce a non-blackbody emergent spectrum. For the same bolometric luminosity, at ultraviolet and optical wavelengths such disks have lower fluxes and apparently larger sizes as compared to disks that emit as blackbodies. Using unified equations for the interior $\rho$ and $T$ in gas pressure dominated regions of a thin accretion disk, we show that models with $\rho_{atm}$ a sufficiently low fixed fraction of $\rho$ can match the AGN STORM observations of NGC 5548 but produce disk spectral energy distributions (SEDs) that peak at shorter wavelengths than observed. Read More

2016Oct
Authors: Demitri Muna, Michael Alexander, Alice Allen, Richard Ashley, Daniel Asmus, Ruyman Azzollini, Michele Bannister, Rachael Beaton, Andrew Benson, G. Bruce Berriman, Maciej Bilicki, Peter Boyce, Joanna Bridge, Jan Cami, Eryn Cangi, Xian Chen, Nicholas Christiny, Christopher Clark, Michelle Collins, Johan Comparat, Neil Cook, Darren Croton, Isak Delberth Davids, Éric Depagne, John Donor, Leonardo A. dos Santos, Stephanie Douglas, Alan Du, Meredith Durbin, Dawn Erb, Daniel Faes, J. G. Fernández-Trincado, Anthony Foley, Sotiria Fotopoulou, Søren Frimann, Peter Frinchaboy, Rafael Garcia-Dias, Artur Gawryszczak, Elizabeth George, Sebastian Gonzalez, Karl Gordon, Nicholas Gorgone, Catherine Gosmeyer, Katie Grasha, Perry Greenfield, Rebekka Grellmann, James Guillochon, Mark Gurwell, Marcel Haas, Alex Hagen, Daryl Haggard, Tim Haines, Patrick Hall, Wojciech Hellwing, Edmund Christian Herenz, Samuel Hinton, Renee Hlozek, John Hoffman, Derek Holman, Benne Willem Holwerda, Anthony Horton, Cameron Hummels, Daniel Jacobs, Jens Juel Jensen, David Jones, Arna Karick, Luke Kelley, Matthew Kenworthy, Ben Kitchener, Dominik Klaes, Saul Kohn, Piotr Konorski, Coleman Krawczyk, Kyler Kuehn, Teet Kuutma, Michael T. Lam, Richard Lane, Jochen Liske, Diego Lopez-Camara, Katherine Mack, Sam Mangham, Qingqing Mao, David J. E. Marsh, Cecilia Mateu, Loïc Maurin, James McCormac, Ivelina Momcheva, Hektor Monteiro, Michael Mueller, Roberto Munoz, Rohan Naidu, Nicholas Nelson, Christian Nitschelm, Chris North, Juan Nunez-Iglesias, Sara Ogaz, Russell Owen, John Parejko, Vera Patrício, Joshua Pepper, Marshall Perrin, Timothy Pickering, Jennifer Piscionere, Richard Pogge, Radek Poleski, Alkistis Pourtsidou, Adrian M. Price-Whelan, Meredith L. Rawls, Shaun Read, Glen Rees, Hanno Rein, Thomas Rice, Signe Riemer-Sørensen, Naum Rusomarov, Sebastian F. Sanchez, Miguel Santander-García, Gal Sarid, William Schoenell, Aleks Scholz, Robert L. Schuhmann, William Schuster, Peter Scicluna, Marja Seidel, Lijing Shao, Pranav Sharma, Aleksandar Shulevski, David Shupe, Cristóbal Sifón, Brooke Simmons, Manodeep Sinha, Ian Skillen, Bjoern Soergel, Thomas Spriggs, Sundar Srinivasan, Abigail Stevens, Ole Streicher, Eric Suchyta, Joshua Tan, O. Grace Telford, Romain Thomas, Chiara Tonini, Grant Tremblay, Sarah Tuttle, Tanya Urrutia, Sam Vaughan, Miguel Verdugo, Alexander Wagner, Josh Walawender, Andrew Wetzel, Kyle Willett, Peter K. G. Williams, Guang Yang, Guangtun Zhu, Andrea Zonca

The Astropy Project (http://astropy.org) is, in its own words, "a community effort to develop a single core package for Astronomy in Python and foster interoperability between Python astronomy packages." For five years this project has been managed, written, and operated as a grassroots, self-organized, almost entirely volunteer effort while the software is used by the majority of the astronomical community. Read More

2016May
Authors: Alan McConnachie, Carine Babusiaux, Michael Balogh, Simon Driver, Pat Côté, Helene Courtois, Luke Davies, Laura Ferrarese, Sarah Gallagher, Rodrigo Ibata, Nicolas Martin, Aaron Robotham, Kim Venn, Eva Villaver, Jo Bovy, Alessandro Boselli, Matthew Colless, Johan Comparat, Kelly Denny, Pierre-Alain Duc, Sara Ellison, Richard de Grijs, Mirian Fernandez-Lorenzo, Ken Freeman, Raja Guhathakurta, Patrick Hall, Andrew Hopkins, Mike Hudson, Andrew Johnson, Nick Kaiser, Jun Koda, Iraklis Konstantopoulos, George Koshy, Khee-Gan Lee, Adi Nusser, Anna Pancoast, Eric Peng, Celine Peroux, Patrick Petitjean, Christophe Pichon, Bianca Poggianti, Carlo Schmid, Prajval Shastri, Yue Shen, Chris Willot, Scott Croom, Rosine Lallement, Carlo Schimd, Dan Smith, Matthew Walker, Jon Willis, Alessandro Bosselli Matthew Colless, Aruna Goswami, Matt Jarvis, Eric Jullo, Jean-Paul Kneib, Iraklis Konstantopoloulous, Jeff Newman, Johan Richard, Firoza Sutaria, Edwar Taylor, Ludovic van Waerbeke, Giuseppina Battaglia, Pat Hall, Misha Haywood, Charli Sakari, Carlo Schmid, Arnaud Seibert, Sivarani Thirupathi, Yuting Wang, Yiping Wang, Ferdinand Babas, Steve Bauman, Elisabetta Caffau, Mary Beth Laychak, David Crampton, Daniel Devost, Nicolas Flagey, Zhanwen Han, Clare Higgs, Vanessa Hill, Kevin Ho, Sidik Isani, Shan Mignot, Rick Murowinski, Gajendra Pandey, Derrick Salmon, Arnaud Siebert, Doug Simons, Else Starkenburg, Kei Szeto, Brent Tully, Tom Vermeulen, Kanoa Withington, Nobuo Arimoto, Martin Asplund, Herve Aussel, Michele Bannister, Harish Bhatt, SS Bhargavi, John Blakeslee, Joss Bland-Hawthorn, James Bullock, Denis Burgarella, Tzu-Ching Chang, Andrew Cole, Jeff Cooke, Andrew Cooper, Paola Di Matteo, Ginevra Favole, Hector Flores, Bryan Gaensler, Peter Garnavich, Karoline Gilbert, Rosa Gonzalez-Delgado, Puragra Guhathakurta, Guenther Hasinger, Falk Herwig, Narae Hwang, Pascale Jablonka, Matthew Jarvis, Umanath Kamath, Lisa Kewley, Damien Le Borgne, Geraint Lewis, Robert Lupton, Sarah Martell, Mario Mateo, Olga Mena, David Nataf, Jeffrey Newman, Enrique Pérez, Francisco Prada, Mathieu Puech, Alejandra Recio-Blanco, Annie Robin, Will Saunders, Daniel Smith, C. S. Stalin, Charling Tao, Karun Thanjuvur, Laurence Tresse, Ludo van Waerbeke, Jian-Min Wang, David Yong, Gongbo Zhao, Patrick Boisse, James Bolton, Piercarlo Bonifacio, Francois Bouchy, Len Cowie, Katia Cunha, Magali Deleuil, Ernst de Mooij, Patrick Dufour, Sebastien Foucaud, Karl Glazebrook, John Hutchings, Chiaki Kobayashi, Rolf-Peter Kudritzki, Yang-Shyang Li, Lihwai Lin, Yen-Ting Lin, Martin Makler, Norio Narita, Changbom Park, Ryan Ransom, Swara Ravindranath, Bacham Eswar Reddy, Marcin Sawicki, Luc Simard, Raghunathan Srianand, Thaisa Storchi-Bergmann, Keiichi Umetsu, Ting-Gui Wang, Jong-Hak Woo, Xue-Bing Wu

MSE is an 11.25m aperture observatory with a 1.5 square degree field of view that will be fully dedicated to multi-object spectroscopy. Read More

We study the dramatic decrease in iron absorption strength in the iron low-ionization broad absorption line quasar SDSS J084133.15+200525.8. Read More

The surface gravity on Mars is smaller than the surface gravity on Earth, resulting in longer falling times. This effect can be simulated on Earth by taking advantage of air resistance and buoyancy, which cause low density objects to fall slowly enough to approximate objects falling on the surface of Mars. We describe a computer simulation based on an experiment that approximates Martian gravity, and verify our numerical results by performing the experiment. Read More

Reverberation mapping (RM) measurements of broad-line region (BLR) lags in z>0.3 quasars are important for directly measuring black hole masses in these distant objects, but so far there have been limited attempts and success given the practical difficulties of RM in this regime. Here we report preliminary results of 15 BLR lag measurements from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project, a dedicated RM program with multi-object spectroscopy designed for RM over a wide redshift range. Read More

We explore the variability of quasars in the MgII and Hbeta broad emission lines and UV/optical continuum emission using the Sloan Digital Sky Survey Reverberation Mapping project (SDSS-RM). This is the largest spectroscopic study of quasar variability to date: our study includes 29 spectroscopic epochs from SDSS-RM over $6$ months, containing 357 quasars with MgII and 41 quasars with Hbeta . On longer timescales, the study is also supplemented with two-epoch data from SDSS-I/II. Read More

The leading theory for the origin of the Moon is the giant impact hypothesis, in which the Moon was formed out of the debris left over from the collision of a Mars-sized body with the Earth. Soon after its formation, the orbit of the Moon may have been very different than it is today. We have simulated the phases of the Moon in a model for its formation wherein the Moon develops a highly elliptical orbit with its major axis tangential to the Earth's orbit. Read More

2013Nov
Affiliations: 1Lanzhou University and York University, 2York University, 3York University, 4York University

A previously unknown optical transient (OT 120926) has been observed in the constellation Bootes. The transient flared to magnitude 4.7, which is comparable to the visual magnitudes of the nearby stars $\pi$ Boo and $\omicron$ Boo. Read More

2013Oct
Affiliations: 1Ball State University, 2University of Wyoming, 3University of Western Ontario, 4University of Michigan, Flint, 5Tianjin Normal University, 6University of Wyoming, 7Presidency University, Kolkata, India, 8National Radio Astronomy Observatory, 9University of California, Davis, 10York University, Toronto, Canada, 11Illinois Institute of Technology

We report the results of a new 60 ks Chandra X-ray Observatory Advanced CCD Imaging Spectrometer S-array (ACIS-S) observation of the reddened, radio-selected, highly polarized `FeLoBAL' quasar FIRST J1556+3517. We investigated a number of models of varied sophistication to fit the 531-photon spectrum. These models ranged from simple power laws to power laws absorbed by hydrogen gas in differing ionization states and degrees of partial covering. Read More

2013Aug
Affiliations: 1York University, Toronto, Canada, 2York University, Toronto, Canada, 3York University, Toronto, Canada, 4York University, Toronto, Canada, 5JILA

Microlensing observations indicate that quasar accretion discs have half-light radii larger than expected from standard theoretical predictions based on quasar fluxes or black hole masses. Blackburne and colleagues have also found a very weak wavelength dependence of these half-light radii. We consider disc temperature profile models that might match these observations. Read More

We report the discovery in the Sloan Digital Sky Survey and the SDSS-III Baryon Oscillation Spectroscopic Survey of seventeen broad absorption line (BAL) quasars with high-ionization troughs that include absorption redshifted relative to the quasar rest frame. The redshifted troughs extend to velocities up to v=12,000 km/s and the trough widths exceed 3000 km/s in all but one case. Approximately 1 in 1000 BAL quasars with blueshifted C IV absorption also has redshifted C IV absorption; objects with C IV absorption present only at redshifted velocities are roughly four times rarer. Read More

We study AGN emission line profiles combining an improved version of the accretion disc-wind model of Murray & Chiang with the magneto-hydrodynamic model of Emmering et al. We show how the shape, broadening and shift of the C IV line depend not only on the viewing angle to the object but also on the wind launching angle, especially for small launching angles. We have compared the dispersions in our model C IV linewidth distributions to observational upper limit on that dispersion, considering both smooth and clumpy torus models. Read More

We present the Data Release 9 Quasar (DR9Q) catalog from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey III. The catalog includes all BOSS objects that were targeted as quasar candidates during the survey, are spectrocopically confirmed as quasars via visual inspection, have luminosities Mi[z=2]<-20.5 (in a $\Lambda$CDM cosmology with H0 = 70 km/s/Mpc, $\Omega_{\rm M}$ = 0. Read More

2012Jul
Authors: Kyle S. Dawson, David J. Schlegel, Christopher P. Ahn, Scott F. Anderson, Éric Aubourg, Stephen Bailey, Robert H. Barkhouser, Julian E. Bautista, Alessandra Beifiori, Andreas A. Berlind, Vaishali Bhardwaj, Dmitry Bizyaev, Cullen H. Blake, Michael R. Blanton, Michael Blomqvist, Adam S. Bolton, Arnaud Borde, Jo Bovy, W. N. Brandt, Howard Brewington, Jon Brinkmann, Peter J. Brown, Joel R. Brownstein, Kevin Bundy, N. G. Busca, William Carithers, Aurelio R. Carnero, Michael A. Carr, Yanmei Chen, Johan Comparat, Natalia Connolly, Frances Cope, Rupert A. C. Croft, Antonio J. Cuesta, Luiz N. da Costa, James R. A. Davenport, Timothée Delubac, Roland de Putter, Saurav Dhital, Anne Ealet, Garrett L. Ebelke, Daniel J. Eisenstein, S. Escoffier, Xiaohui Fan, N. Filiz Ak, Hayley Finley, Andreu Font-Ribera, R. Génova-Santos, James E. Gunn, Hong Guo, Daryl Haggard, Patrick B. Hall, Jean-Christophe Hamilton, Ben Harris, David W. Harris, Shirley Ho, David W. Hogg, Diana Holder, Klaus Honscheid, Joe Huehnerhoff, Beatrice Jordan, Wendell P. Jordan, Guinevere Kauffmann, Eyal A. Kazin, David Kirkby, Mark A. Klaene, Jean-Paul Kneib, Jean-Marc Le Goff, Khee-Gan Lee, Daniel C. Long, Craig P. Loomis, Britt Lundgren, Robert H. Lupton, Marcio A. G. Maia, Martin Makler, Elena Malanushenko, Viktor Malanushenko, Rachel Mandelbaum, Marc Manera, Claudia Maraston, Daniel Margala, Karen L. Masters, Cameron K. McBride, Patrick McDonald, Ian D. McGreer, Richard McMahon, Olga Mena, Jordi Miralda-Escudé, Antonio D. Montero-Dorta, Francesco Montesano, Demitri Muna, Adam D. Myers, Tracy Naugle, Robert C. Nichol, Pasquier Noterdaeme, Sebastián E. Nuza, Matthew D. Olmstead, Audrey Oravetz, Daniel J. Oravetz, Russell Owen, Nikhil Padmanabhan, Nathalie Palanque-Delabrouille, Kaike Pan, John K. Parejko, Isabelle Pâris, Will J. Percival, Ismael Pérez-Fournon, Ignasi Pérez-Ràfols, Patrick Petitjean, Robert Pfaffenberger, Janine Pforr, Matthew M. Pieri, Francisco Prada, Adrian M. Price-Whelan, M. Jordan Raddick, Rafael Rebolo, James Rich, Gordon T. Richards, Constance M. Rockosi, Natalie A. Roe, Ashley J. Ross, Nicholas P. Ross, Graziano Rossi, J. A. Rubiño-Martin, Lado Samushia, Ariel G. Sánchez, Conor Sayres, Sarah J. Schmidt, Donald P. Schneider, C. G. Scóccola, Hee-Jong Seo, Alaina Shelden, Erin Sheldon, Yue Shen, Yiping Shu, Anže Slosar, Stephen A. Smee, Stephanie A. Snedden, Fritz Stauffer, Oliver Steele, Michael A. Strauss, Alina Streblyanska, Nao Suzuki, Molly E. C. Swanson, Tomer Tal, Masayuki Tanaka, Daniel Thomas, Jeremy L. Tinker, Rita Tojeiro, Christy A. Tremonti, M. Vargas Magana, Licia Verde, Matteo Viel, David A. Wake, Mike Watson, Benjamin A. Weaver, David H. Weinberg, Benjamin J. Weiner, Andrew A. West, Martin White, W. M. Wood-Vasey, Christophe Yeche, Idit Zehavi, Gong-Bo Zhao, Zheng Zheng

The Baryon Oscillation Spectroscopic Survey (BOSS) is designed to measure the scale of baryon acoustic oscillations (BAO) in the clustering of matter over a larger volume than the combined efforts of all previous spectroscopic surveys of large scale structure. BOSS uses 1.5 million luminous galaxies as faint as i=19. Read More

A search for emission lines in foreground galaxies in quasar spectra (z(gal) < z(QSO)) of the Sloan Digital Sky Survey (SDSS) data release 5 (DR5) reveals 23 examples of quasars shining through low redshift, foreground galaxies at small impact parameters (< 10 kpc). About 74,000 quasar spectra were examined by searching for narrow H{\alpha} emission lines at z < 0.38, at a flux level greater than 5 \times 10^-17 ergs cm^-2 s^-1, then confirming that other expected emission lines of the H II regions in the galaxy are detected. Read More

Broad Absorption Line (BAL) trough variability is predominantly due to cloud motion transverse to our line of sight. The rate at which the variability occurs indicates the velocity of the cloud, which can provide constraints on the cloud's distance from the central source. This requires detailed spectroscopy during a variability event. Read More

We present the final statistical sample of lensed quasars from the Sloan Digital Sky Survey (SDSS) Quasar Lens Search (SQLS). The well-defined statistical lens sample consists of 26 lensed quasars brighter than i=19.1 and in the redshift range of 0. Read More

We report on a population of X-ray weak quasars with similar UV emission-line properties to those of the remarkable quasar PHL 1811. All radio-quiet PHL 1811 analogs are notably X-ray weak by a mean factor of ~13, with hints of heavy X-ray absorption. Correlations between the X-ray weakness and UV emission-line properties suggest that PHL 1811 analogs may have extreme wind-dominated broad emission-line regions (BELRs). Read More

We test whether the Tinker & Chen model of MgII absorption due to the gaseous halo around a galaxy can reproduce absorption in quasar pairs (both lensed and physical) and lensed triples and quads from the literature. These quasars exhibit absorption from a total of 38 MgII systems spanning z=0.043 - 2. Read More

2011Dec
Affiliations: 1Sussex, 2IAP, Potsdam, 3NRAO, 4European University Cyprus, 5University of Lisbon, 6McGill, 7York, 8NRAO, 9Caltech, 10Caltech, 11Caltech, 12UCLA

We present optical to far-infrared photometry of 31 reddened QSOs that show evidence for radiatively driven outflows originating from AGN in their rest-frame UV spectra. We use these data to study the relationships between the AGN-driven outflows, and the AGN and starburst infrared luminosities. We find that FeLoBAL QSOs are invariably IR-luminous, with IR luminosities exceeding 10^{12} Solar luminosities in all cases. Read More

2011Dec
Affiliations: 1Sussex, 2IAP, Potsdam, 3NRAO, 4European University Cyprus, 5University of Lisbon, 6McGill, 7York, 8NRAO, 9Caltech, 10Caltech, 11Caltech, 12UCLA

We use SDSS spectra and optical to far-infrared photometry for a sample of 31 FeLoBAL QSOs to study the relationship between the AGN-driven outflows, and obscured star formation in their host galaxies. We find that FeLoBAL QSOs invariably have IR luminosities exceeding 10^12 Solar luminosities. The AGN supplies 75% of the total IR emission, on average, but with a range from 20% to 100%. Read More

We provide a quantitative description and statistical interpretation of the optical continuum variability of quasars. The Sloan Digital Sky Survey (SDSS) has obtained repeated imaging in five UV-to-IR photometric bands for 33,881 spectroscopically confirmed quasars. About 10,000 quasars have an average of 60 observations in each band obtained over a decade along Stripe 82 (S82), whereas the remaining ~25,000 have 2-3 observations due to scan overlaps. Read More

2011Sep
Affiliations: 1Drexel University, 2Drexel University, 3UWO, 4UWO, 5York University, 6IoA Cambridge, 7University of Oklahoma, 8Drexel University, 9UNLV

In the restframe UV, two of the parameters that best characterize the range of emission-line properties in quasar broad emission-line regions are the equivalent width and the blueshift of the CIV line relative to the quasar rest frame. We explore the connection between these emission-line properties and the UV through X-ray spectral energy distribution (SED) for radio-quiet (RQ) quasars. Our sample consists of a heterogeneous compilation of 406 quasars from the Sloan Digital Sky Survey and Palomar-Green survey that have well-measured CIV emission-line and X-ray properties (including 164 objects with measured Gamma). Read More

2011May

It has been argued that certain broad absorption line quasars are viewed within 35 degrees of the axis of a relativistic radio jet, based on two-epoch radio flux density variability. It is true if the surface brightness of a radio source is observed to change by a sufficiently large amount, the inferred brightness temperature will exceed 10^12 K and Doppler beaming in our direction must be invoked to avoid a Compton cooling catastrophe. However, flux density changes cannot be linked to surface brightness changes without knowledge of the size of the source. Read More

We report the results from Chandra and XMM-Newton observations of a sample of 10 type 1 quasars selected to have unusual UV emission-line properties (weak and blueshifted high-ionization lines; strong UV Fe emission) similar to those of PHL 1811, a confirmed intrinsically X-ray weak quasar. These quasars were identified by the Sloan Digital Sky Survey at high redshift (z~2.2); eight are radio quiet while two are radio intermediate. Read More

We present MgII-based black hole mass estimates for 27,602 quasars with rest-frame UV spectra available in the Sloan Digital Sky Survey Data Release Three. This estimation is possible due to the existence of an empirical correlation between the radius of the broad line region and the continuum luminosity at 3000 Angstroms. We regenerate this correlation by applying our measurement method to UV spectra of low-redshift quasars in the HST/IUE databases which have corresponding reverberation mapping estimates of the Hbeta broad line region's radius. Read More

2010Nov
Affiliations: 1Drexel University, 2Drexel University, 3University of Western Ontario, 4York University, 5IoA Cambridge, 6University of Oklahoma, 7Drexel University, 8Drexel University, 9Harvard CfA

Using a sample of 30,000 quasars from SDSS-DR7, we explore the range of properties exhibited by high-ionization, broad emission lines, such as CIV 1549. Specifically we investigate the anti-correlation between L_UV and emission line EQW (the Baldwin Effect) and the "blueshifting" of high-ionization emission lines. The blueshift of the CIV emission line is nearly ubiquitous, with a mean shift of 810 km/s for radio-quiet (RQ) quasars and 360 km/s for radio-loud (RL) quasars, and the Baldwin Effect is present in both RQ and RL samples. Read More

We find that the recently reported departure from the Eddington luminosity limit for the highest quasar black hole masses at a given redshift is an artifact due to biases in black hole mass measurements. This sub-Eddington boundary (with non-unity slope) in the quasar mass-luminosity plane was initially reported by Steinhardt & Elvis (2010a) using the FWHM-based black hole mass catalogue of Shen et al. (2008). Read More

2010Oct
Affiliations: 1York U., 2York U., 3STScI, 4Penn State, 5UC Davis and IGPP/LLNL, 6U. Washington, 7UC Davis and IGPP/LLNL, 8Penn State

We have observed a dramatic change in the spectrum of the formerly heavily absorbed `overlapping-trough' iron low-ionization broad absorption line (FeLoBAL) quasar FBQS J1408+3054. Over a time span of between 0.6 to 5 rest-frame years, the Mg II trough outflowing at 12,000 km/s decreased in equivalent width by a factor of two and the Fe II troughs at the same velocity disappeared. Read More

We report the detection of OVI 1031,1037 and NV 1238,1242 absorption in a system of "mini-broad" absorption lines (mini-BALs) previously reported to have variable CIV 1548,1550 in the quasar PG0935+417. The formation of these lines in an extreme high-velocity quasar outflow (with v ~ -50000 km/s) is confirmed by the line variability, broad smooth absorption profiles, and partial covering of the background light source. HI and lower ionization metals are not clearly present. Read More

We report sensitive Chandra X-ray non-detections of two unusual, luminous Iron Low-Ionization Broad Absorption Line Quasars (FeLoBALs). The observations do detect a non-BAL, wide-binary companion quasar to one of the FeLoBAL quasars. We combine X-ray-derived column density lower limits (assuming solar metallicity) with column densities measured from ultraviolet spectra and CLOUDY photoionization simulations to explore whether constant density slabs at broad line region densities can match the physical parameters of these two BAL outflows, and find that they cannot. Read More

We present a compilation of properties of the 105,783 quasars in the SDSS Data Release 7 (DR7) quasar catalog. In this value-added product, we compile continuum and emission line measurements around the Halpha, Hbeta, MgII and CIV regions, as well as other quantities such as radio properties, broad absorption line quasar (BALQSO) flags, and disk emitters. We also compile virial black hole mass estimates based on various calibrations. Read More

We present the second report of our systematic search for strongly lensed quasars from the data of the Sloan Digital Sky Survey (SDSS). From extensive follow-up observations of 136 candidate objects, we find 36 lenses in the full sample of 77,429 spectroscopically confirmed quasars in the SDSS Data Release 5. We then define a complete sample of 19 lenses, including 11 from our previous search in the SDSS Data Release 3, from the sample of 36,287 quasars with i<19. Read More

2010Feb
Affiliations: 1Steward Observatory, 2York University, 3Steward Observatory, 4Steward Observatory, 5Cosmic Radiation Laboratory, 6National Astronomical Observatory of Japan, 7Princeton University Observatory, 8Pennsylvania State University, 9Steward Observatory

We report the discovery of a gravitationally lensed quasar identified serendipitously in the Sloan Digital Sky Survey (SDSS). The object, SDSS J094604.90+183541. Read More

We report the discovery and confirmation of eight new two-image lensed quasars by the Sloan Digital Sky Survey (SDSS) Quasar Lens Search. The lenses are SDSSJ0904+1512 (image separation \theta=1"13, source redshift z_s=1.826), SDSSJ1054+2733 (\theta=1"27, z_s=1. Read More

2009Mar
Affiliations: 1The Pennsylvania State University, 2Princeton, 3Princeton, 4The Pennsylvania State University, 5University of Washington, 6Drexel University, 7The Pennsylvania State University, 8Ohio State University, 9York University, 10Princeton, 11University of Illinois at Urbana-Champaign

We present measurements of the quasar two-point correlation function, \xi_{Q}, over the redshift range z=0.3-2.2 based upon data from the SDSS. Read More

We present a new K-selected, optical-to-near-infrared photometric catalog of the Extended Chandra Deep Field South (ECDFS), making it publicly available to the astronomical community. The dataset is founded on publicly available imaging, supplemented by original zJK imaging data obtained as part of the MUltiwavelength Survey by Yale-Chile (MUSYC). The final photometric catalog consists of photometry derived from nine band U-K imaging covering the full 0. Read More

Using a homogenous sample of 38,208 quasars with a sky coverage of $4000 {\rm deg^2}$ drawn from the SDSS Data Release Five quasar catalog, we study the dependence of quasar clustering on luminosity, virial black hole mass, quasar color, and radio loudness. At $z<2.5$, quasar clustering depends weakly on luminosity and virial black hole mass, with typical uncertainty levels $\sim 10%$ for the measured correlation lengths. Read More

We present a catalog of 5039 broad absorption line (BAL) quasars (QSOs) in the Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5) QSO catalog that have absorption troughs covering a continuous velocity range >= 2000 km/s. We have fit ultraviolet (UV) continua and line emission in each case, enabling us to report common diagnostics of BAL strengths and velocities in the range -25,000 to 0 km/s for SiIV $\lambda$1400, CIV $\lambda$1549, AlIII $\lambda$1857, and MgII $\lambda$2799. We calculate these diagnostics using the spectrum listed in the DR5 QSO catalog, and also for spectra from additional SDSS observing epochs when available. Read More

2008Apr
Affiliations: 1York U., 2Ruhr-Universitat Bochum, 3USNO, 4Emery Collegiate Institute and York U., 5Gemini, 6Ohio State U., 7U. Washington, 8U. Chicago
Category: Astrophysics

We report the discovery of a nearby, old, halo white dwarf candidate from the Sloan Digital Sky Survey. SDSS J110217.48+411315. Read More

We present a large sample of 501 radio-selected BL Lac candidates from the combination of the Sloan Digital Sky Survey (SDSS) Data Release 5 optical spectroscopy and from the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) radio survey; this is one of the largest BL Lac samples yet assembled, and each object emerges with homogeneous data coverage. Each candidate is detected in the radio from FIRST and confirmed in SDSS optical spectroscopy to have: (1) no emission feature with measured rest equivalent width larger than 5 Angstroms; and (2) no measured Ca II H/K depression larger than 40%. We subdivide our sample into 426 higher confidence candidates and 75 lower confidence candidates. Read More

Wang et al. (2006) estimated an average radiative efficiency of 30% -- 35% for quasars at moderate redshift. We find that their method is not independent of quasar lifetimes and thus that quasars do not necessarily have such high efficiencies. Read More

2008Mar
Affiliations: 1Departamento de Astronomía, Universidad de Chile, Chile, 2Departamento de Astronomía, Universidad de Chile, Chile, 3Departamento de Astronomía, Pontificia Universidad Católica de Chile, Chile, 4Departamento de Astronomía, Pontificia Universidad Católica de Chile, Chile, 5Departamento de Astronomía, Universidad de Chile, Chile, 6Leiden Observatory, Leiden University, Netherlands, 7Astronomy Department, Yale University, USA, 8Astronomy Department, Yale University, USA, 9Departamento de Astronomía, Pontificia Universidad Católica de Chile, Chile, 10Department of Physics and Astronomy, Rutgers University, USA, 11Department of Physics and Astronomy, York University, Canada, 12Department of Physics and Astronomy, University of Victoria, Canada, 13National Optical Astronomy Observatory, USA, 14Departamento de Astronomía, Universidad de Chile, Chile
Category: Astrophysics

We present K-band imaging of two ~30'x30' fields covered by the MUSYC Wide NIR Survey. The 1030 and 1255 fields were imaged with ISPI on the 4m Blanco telescope at CTIO to a 5 sigma point-source limiting depth of K~20 (Vega). Combining this data with the MUSYC Optical UBVRIz imaging, we created multi-band K-selected source catalogs for both fields. Read More