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Sample records for bright quasar survey

  1. Seoul National University Bright Quasar Survey in Optical (SNUQSO) I: First Phase Observations and Results

    CERN Document Server

    Lee, Induk; Kim, Minjin; Kang, Eugene; Shim, Hyunjin; Richards, Gordon T; Edge, Alastair C; Lee, Myung Gyoon; Park, Changbom; Park, Myeong-Gu

    2008-01-01

    We present results from the first phase of the Seoul National University Bright Quasar Survey in Optical (SNUQSO) as well as its basic observational setup. Previous and current large-area surveys have been successful in identifying many quasars, but they could have missed bright quasars due to their survey design. In order to help complete the census of bright quasars, we have performed spectroscopic observations of new bright quasar candidates selected from various methods based on optical colors, near-infrared colors, radio, and X-ray data. In 2005/2006, we observed 55 bright quasar candidates using the Bohyunsan Optical Echelle Spectrograph (BOES) on the 1.8 m telescope at the Bohyunsan Optical Astronomy Observatory in Korea. We identify 14 quasars/Seyferts from our observation, including an optically bright quasar with i=14.98 mag at z=0.092 (SDSS J003236.59-091026.2). Non-quasar/Seyfert objects are found to be mostly stars, among which there are five M-type stars and one cataclysmic variable. Our result ...

  2. The SDSS view of the Palomar-Green bright quasar survey

    Energy Technology Data Exchange (ETDEWEB)

    Jester, Sebastian; Schneider, Donald P.; Richards, Gordon T.; Green, Richard F.; Schmidt, Maarten; Hall, Patrick B.; Strauss, Michael A.; Vanden Berk, Daniel E.; Stoughton, Chris; Gunn, James E.; Brinkmann, Jon; Kent, Stephen M.; Smith, J.Allyn; Tucker, Douglas, L.; Yanny, Brian; /Fermilab /Penn State U., Astron. Astrophys. /Princeton U.

    2005-02-01

    The author investigates the extent to which the Palomar-Green (PG) Bright Quasar Survey (BQS) is complete and representative of the general quasar population by comparing with imaging and spectroscopy from the Sloan Digital Sky Survey. A comparison of SDSS and PG photometry of both stars and quasars reveals the need to apply a color and magnitude recalibration to the PG data. Using the SDSS photometric catalog, they define the PG's parent sample of objects that are not main-sequence stars and simulate the selection of objects from this parent sample using the PG photometric criteria and errors. This simulation shows that the effective U-B cut in the PG survey is U-B < -0.71, implying a color-related incompleteness. As the color distribution of bright quasars peaks near U-B = -0.7 and the 2-{sigma} error in U-B is comparable to the full width of the color distribution of quasars, the color incompleteness of the BQS is approximately 50% and essentially random with respect to U-B color for z < 0.5. There is however, a bias against bright quasars at 0.5 < z < 1, which is induced by the color-redshift relation of quasars (although quasars at z > 0.5 are inherently rare in bright surveys in any case). They find no evidence for any other systematic incompleteness when comparing the distributions in color, redshift, and FIRST radio properties of the BQS and a BQS-like subsample of the SDSS quasar sample. However, the application of a bright magnitude limit biases the BQS toward the inclusion of objects which are blue in g-i, in particular compared to the full range of g-i colors found among the i-band limited SDSS quasars, and even at i-band magnitudes comparable to those of the BQS objects.

  3. Mass Functions of the Active Black Holes in Distant Quasars from the Large Bright Quasar Survey, the Bright Quasar Survey, and the Color-Selected Sample of the SDSS Fall Equatorial Stripe

    DEFF Research Database (Denmark)

    Vestergaard, Marianne; Osmer, Patrick S.

    2009-01-01

    We present mass functions of distant actively accreting supermassive black holes residing in luminous quasars discovered in the Large Bright Quasar Survey, the Bright Quasar Survey, and the Fall Equatorial Stripe of the Sloan Digital Sky Survey (SDSS). The quasars cover a wide range of redshifts (0...... functions at similar redshifts based on the SDSS Data Release 3 quasar catalog presented by Vestergaard et al. We see clear evidence of cosmic downsizing in the comoving space density distribution of active black holes in the LBQS sample alone. In forthcoming papers, further analysis, comparison......, and discussion of these mass functions will be made with other existing black hole mass functions, notably that based on the SDSS DR3 quasar catalog. We present the relationships used to estimate the black hole mass based on the MgII emission line; the relations are calibrated to the Hbeta and CIV relations...

  4. The SDSS View of the Palomar-Green Bright Quasar Survey

    CERN Document Server

    Jester, S; Richards, G T; Green, R F; Schmidt, M; Hall, P B; Strauss, M A; Vanden Berk, Daniel E; Stoughton, C; Gunn, J E; Brinkmann, J; Kent, S M; Smith, J A; Tucker, D L; Yanny, B; Jester, Sebastian; Schneider, Donald P.; Richards, Gordon T.; Green, Richard F.; Schmidt, Maarten; Hall, Patrick B.; Strauss, Michael A.; Berk, Daniel E. Vanden; Stoughton, Chris; Gunn, James E.; Brinkmann, Jon; Kent, Stephen M.; Tucker, Douglas L.; Yanny, Brian

    2005-01-01

    We investigate the extent to which the Palomar-Green (PG) Bright Quasar Survey (BQS) is complete and representative of the general quasar population by comparing with imaging and spectroscopy from the Sloan Digital Sky Survey. A comparison of SDSS and PG photometry of both stars and quasars reveals the need to apply a color and magnitude recalibration to the PG data. Using the SDSS photometric catalog, we define the PG's parent sample of objects that are not main-sequence stars and simulate the selection of objects from this parent sample using the PG photometric criteria and errors. This simulation shows that the effective U-B cut in the PG survey is U-B 0.5 are inherently rare in bright surveys in any case). We find no evidence for any other systematic incompleteness when comparing the distributions in color, redshift, and FIRST radio properties of the BQS and a BQS-like subsample of the SDSS quasar sample. However, the application of a bright magnitude limit biases the BQS toward the inclusion of objects w...

  5. A survey of luminous high-redshift quasars with SDSS and WISE II. the bright end of the quasar luminosity function at z ~ 5

    CERN Document Server

    Yang, Jinyi; Wu, Xue-Bing; Fan, Xiaohui; McGreer, Ian D; Bian, Fuyan; Yi, Weimin; Yang, Qian; Ai, Yanli; Dong, Xiaoyi; Zuo, Wenwen; Green, Richard; Jiang, Linhua; Wang, Shu; Wang, Ran; Yue, Minghao

    2016-01-01

    This is the second paper in a series on a new luminous z ~ 5 quasar survey using optical and near-infrared colors. Here we present a new determination of the bright end of the quasar luminosity function (QLF) at z ~ 5. Combined our 45 new quasars with previously known quasars that satisfy our selections, we construct the largest uniform luminous z ~ 5 quasar sample to date, with 99 quasars in the range 4.7 <= z < 5.4 and -29 < M1450 <= -26.8, within the Sloan Digital Sky Survey (SDSS) footprint. We use a modified 1/Va method including flux limit correction to derive a binned QLF, and we model the parametric QLF using maximum likelihood estimation. With the faint-end slope of the QLF fixed as alpha = -2.03 from previous deeper samples, the best fit of our QLF gives a flatter bright end slope beta = -3.58+/-0.24 and a fainter break magnitude M*1450 = -26.98+/-0.23 than previous studies at similar redshift. Combined with previous work at lower and higher redshifts, our result is consistent with a lum...

  6. The XMM-Newton Bright Survey sample of absorbed quasars: X-ray and accretion properties

    CERN Document Server

    Ballo, L; Della Ceca, R; Caccianiga, A; Vignali, C; Carrera, F J; Corral, A; Mateos, S

    2014-01-01

    Although absorbed quasars are extremely important for our understanding of the energetics of the Universe, the main physical parameters of their central engines are still poorly known. In this work we present and study a complete sample of 14 quasars (QSOs) that are absorbed in the X-rays (column density NH>4x10^21 cm-2 and X-ray luminosity L(2-10 keV)>10^44 ergs/s; XQSO2) belonging to the XMM-Newton Bright Serendipitous Survey (XBS). From the analysis of their ultraviolet-to-mid-infrared spectral energy distribution we can separate the nuclear emission from the host galaxy contribution, obtaining a measurement of the fundamental nuclear parameters, like the mass of the central supermassive black hole and the value of Eddington ratio, lambda_Edd. Comparing the properties of XQSO2s with those previously obtained for the X-ray unabsorbed QSOs in the XBS, we do not find any evidence that the two samples are drawn from different populations. In particular, the two samples span the same range in Eddington ratios, ...

  7. LAMOST Quasar Survey

    CERN Document Server

    Wu, Xue-Bing

    2011-01-01

    The main objective of the Chinese LAMOST spectroscopic quasar survey is to discover 0.4 million new quasars from 1 million quasar candidates brighter than the magnitude limit i=20.5 in the next 5 years. This will hopefully provide the largest quasar sample for the further studies of AGN physics and cosmology. The improved quasar selection criteria based on the UKIDSS near-IR and SDSS optical colors are presented, and their advantages in uncovering the missing quasars in the quasar 'redshift desert' are demonstrated. In addition, some recent discoveries of new quasars during the LAMOST commissioning phase are presented.

  8. VizieR Online Data Catalog: The UV-bright Quasar Survey (UVQS) DR1 (Monroe+, 2016)

    Science.gov (United States)

    Monroe, T. R.; Prochaska, J. X.; Tejos, N.; Worseck, G.; Hennawi, J. F.; Schmidt, T.; Tumlinson, J.; Shen, Y.

    2016-09-01

    We have performed an all-sky survey for z~1, FUV-bright quasars selected from GALEX and WISE photometry. We generated a list of 1450 primary candidates (Table1). In several of the observing runs, conditions were unexpectedly favorable and we exhausted the primary candidates at certain right ascension ranges. To fill the remaining observing time, we generated a secondary candidate list. This secondary set of candidates is provided in Table2. We proceeded to obtain discovery-quality longslit spectra (i.e., low-dispersion, large wavelength coverage, modest signal-to-noise ratio (S/N) of our UV-bright Quasar Survey (UVQS) candidates in one calendar year. Our principal facilities were: (i) the dual Kast spectrometer on the 3m Shane telescope at the Lick Observatory; (ii) the Boller & Chivens (BCS) spectrometer on the Irenee du Pont 100'' telescope at the Las Campanas Observatory; and (iii) the Calar Alto Faint Object Spectrograph on the CAHA 2.2m telescope at the Calar Alto Observatory (CAHA). We acquired an additional ~20 spectra on larger aperture telescopes (Keck/ESI, MMT/MBC, Magellan/MagE) during twilight or under poor observing conditions. Typical exposure times were limited to <~200s, with adjustments for fainter sources or sub-optimal observing conditions. Table3 provides a list of the observed candidates. There are 93 sources with a good quality spectrum for which we cannot recover a secure redshift. The majority of these have been previously cataloged as blazars (or BL Lac objects). Table6 lists the sample of these unknowns. (6 data files).

  9. Spectroscopy of bright quasars: emission lines and internal extinction

    CERN Document Server

    Bachev, R; Semkov, E; Mihov, B

    2008-01-01

    The main purpose of this work is to improve the existing knowledge about the most powerful engines in the Universe - quasars. Although a lot is already known, we still have only a vague idea how these engines work exactly, why they behave as they do, and what the relation is between their evolution and the evolution of their harboring galaxy. Methods we used are based on optical spectroscopy of visually bright quasars, many of which have recently been discovered as X-ray sources, but eventually missed in color-selected surveys. The spectra typically cover the 4200-7000 AA region, allowing measurements of the characteristics of the hydrogen lines, the FeII contribution, and other lines of interest. We present accurate redshift estimates and Seyfert type classification of the objects. We also show that the contribution of the host galaxy to the optical continuum is non-negligible in many cases, as is the intrinsic AGN absorption. Consequences of not correcting for those factors when estimating different quasar ...

  10. New lensed quasars from the MUSCLES survey

    CERN Document Server

    Jackson, Neal; Ofek, Eran O; Shin, Min-Su

    2011-01-01

    Gravitational lens systems containing lensed quasars are important as cosmological probes, as diagnostics of structural properties of the lensing galaxies and as tools to study the quasars themselves. The largest lensed quasar sample is the SDSS Quasar Lens Search, drawn from the Sloan Digital Sky Survey (SDSS). We are attempting to extend this survey using observations of lens candidates selected from a combination of the quasar sample from the SDSS and the UKIRT Infrared Deep Sky Survey (UKIDSS). This adds somewhat higher image quality together with a wider range of wavelength for the selection process. In previous pilot surveys we observed 5 objects, finding 2 lenses; here we present further observations of 20 objects in which we find 4 lenses, of which 2 are independently discovered in SQLS (in preparation). Following earlier work on the combination of these two surveys, we have refined our method and find that use of a colour-separation diagnostic, where we select for separations between components which...

  11. THE SUBARU HIGH-z QUASAR SURVEY: DISCOVERY OF FAINT z ∼ 6 QUASARS

    Energy Technology Data Exchange (ETDEWEB)

    Kashikawa, Nobunari; Furusawa, Hisanori; Niino, Yuu [Optical and Infrared Astronomy Division, National Astronomical Observatory, Mitaka, Tokyo 181-8588 (Japan); Ishizaki, Yoshifumi; Onoue, Masafusa; Toshikawa, Jun; Ishikawa, Shogo [Department of Astronomy, School of Science, Graduate University for Advanced Studies, Mitaka, Tokyo 181-8588 (Japan); Willott, Chris J. [Herzberg Institute of Astrophysics, National Research Council, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Im, Myungshin [Center for the Exploration of the Origin of the Universe (CEOU), Astronomy Program, Department of Physics and Astronomy, Seoul National University, 1 Gwanak-rho, Gwanak-gu, Seoul 151-742 (Korea, Republic of); Shimasaku, Kazuhiro [Department of Astronomy, University of Tokyo, Hongo, Tokyo 113-0033 (Japan); Ouchi, Masami [Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8582 (Japan); Hibon, Pascale, E-mail: n.kashikawa@nao.ac.jp [Gemini Observatory, La Serena (Chile)

    2015-01-01

    We present the discovery of one or two extremely faint z ∼ 6 quasars in 6.5 deg{sup 2} utilizing a unique capability of the wide-field imaging of the Subaru/Suprime-Cam. The quasar selection was made in (i'-z{sub B} ) and (z{sub B} -z{sub R} ) colors, where z{sub B} and z{sub R} are bandpasses with central wavelengths of 8842 Å and 9841 Å, respectively. The color selection can effectively isolate quasars at z ∼ 6 from M/L/T dwarfs without the J-band photometry down to z{sub R} < 24.0, which is 3.5 mag deeper than the Sloan Digital Sky Survey (SDSS). We have selected 17 promising quasar candidates. The follow-up spectroscopy for seven targets identified one apparent quasar at z = 6.156 with M {sub 1450} = –23.10. We also identified one possible quasar at z = 6.041 with a faint continuum of M {sub 1450} = –22.58 and a narrow Lyα emission with HWHM =427 km s{sup –1}, which cannot be distinguished from Lyman α emitters. We derive the quasar luminosity function at z ∼ 6 by combining our faint quasar sample with the bright quasar samples by SDSS and CFHQS. Including our data points invokes a higher number density in the faintest bin of the quasar luminosity function than the previous estimate employed. This suggests a steeper faint-end slope than lower z, though it is yet uncertain based on a small number of spectroscopically identified faint quasars, and several quasar candidates still remain to be diagnosed. The steepening of the quasar luminosity function at the faint end does increase the expected emission rate of the ionizing photon; however, it only changes by a factor of approximately two to six. This was found to still be insufficient for the required photon budget of reionization at z ∼ 6.

  12. The SDSS Quasar Survey: Quasar Luminosity Function from Data Release Three

    CERN Document Server

    Richards, G T; Barentine, J C; Brewington, H J; Brinkmann, J; Brunner, R J; Fukugita, M; Gray, J; Gunn, J E; Hall, P B; Harvanek, M; Ivezic, Z; Jester, S; Kent, S M; Kirkland, M E; Kleinman, S J; Knapp, G R; Krzesínski, J; Long, D C; Loveday, J; Lupton, R H; Meiksin, A; Nash, T; Neilsen, E H; Nitta, A; Pope, A; Schlegel, D J; Schneider, D P; Snedden, S A; Stoughton, C; Strauss, M A; Szalay, A S; Thakar, A R; Vanden Berk, Daniel E; Xiaohui F; Yanny, B; York, Do G; Anderson, Scott F.; Berk, Daniel E. Vanden; Brunner, Robert J.; Fan, Xiaohui; Gray, Jim; Gunn, James E.; Hall, Patrick B.; Ivezic, Zeljko; Jester, Sebastian; Kirkland, Margaret E.; Loveday, Jon; Meiksin, Avery; Pope, Adrian; Richards, Gordon T.; Schneider, Donald P.; Stoughton, Chris; Strauss, Michael A.; Szalay, Alexander S.; Thakar, Anirudda R.; Yanny, Brian; York, Donald G.

    2006-01-01

    We determine the number counts and z=0-5 luminosity function for a well-defined, homogeneous sample of quasars from the Sloan Digital Sky Survey (SDSS). We conservatively define the most uniform statistical sample possible, consisting of 15,343 quasars within an effective area of 1622 deg^2 that was derived from a parent sample of 46,420 spectroscopically confirmed broad-line quasars in the 5282 deg^2 of imaging data from SDSS Data Release Three. The sample extends from i=15 to i=19.1 at z3. The number counts and luminosity function agree well with the results of the 2dF QSO Survey, but the SDSS data probe to much higher redshifts than does the 2dF sample. The number density of luminous quasars peaks between redshifts 2 and 3, although uncertainties in the selection function in this range do not allow us to determine the peak redshift more precisely. Our best fit model has a flatter bright end slope at high redshift than at low redshift. For z5-sigma level, must be accounted for in models of the evolution of ...

  13. Discovery of the optically bright, wide separation double quasar SDSS J1442+4055

    CERN Document Server

    Sergeyev, Alexey V; Shalyapin, Vyacheslav N; Goicoechea, Luis J

    2015-01-01

    Optically bright, wide separation double (gravitationally lensed) quasars can be easily monitored, leading to light curves of great importance in determining the Hubble constant and other cosmological parameters, as well as the structure of active nuclei and halos of galaxies. Searching for new double quasars in the SDSS-III database, we discovered SDSS J1442+4055. This consists of two bright images (18-19 magnitudes in the r band) of the same distant quasar at redshift z = 2.575. The two quasar images are separated by about 2.1 arcsec, show significant parallel flux variations and can be monitored from late 2015. We also found other two double quasar candidates, SDSS J1617+3827 (z = 2.079) and SDSS J1642+3200 (z = 2.264), displaying evidence for the presence of a lensing object and parallel flux variations, but requiring further spectroscopic observations to be confirmed as lensed quasars.

  14. Subaru high-$z$ exploration of low-luminosity quasars (SHELLQs). I. Discovery of 15 quasars and bright galaxies at $5.7 < z < 6.9$

    CERN Document Server

    Matsuoka, Yoshiki; Kashikawa, Nobunari; Iwasawa, Kazushi; Strauss, Michael A; Nagao, Tohru; Imanishi, Masatoshi; Niida, Mana; Toba, Yoshiki; Akiyama, Masayuki; Asami, Naoko; Bosch, James; Foucaud, Sébastien; Furusawa, Hisanori; Goto, Tomotsugu; Gunn, James E; Harikane, Yuichi; Ikeda, Hiroyuki; Kawaguchi, Toshihiro; Kikuta, Satoshi; Komiyama, Yutaka; Lupton, Robert H; Minezaki, Takeo; Miyazaki, Satoshi; Morokuma, Tomoki; Murayama, Hitoshi; Nishizawa, Atsushi J; Ono, Yoshiaki; Ouchi, Masami; Price, Paul A; Sameshima, Hiroaki; Silverman, John D; Sugiyama, Naoshi; Tait, Philip J; Takada, Masahiro; Takata, Tadafumi; Tanaka, Masayuki; Tang, Ji-Jia; Utsumi, Yousuke

    2016-01-01

    We report the discovery of 15 quasars and bright galaxies at $5.7 < z < 6.9$. This is the initial result from the Subaru High-$z$ Exploration of Low-Luminosity Quasars (SHELLQs) project, which exploits the exquisite multi-band imaging data produced by the Subaru Hyper Suprime-Cam (HSC) Strategic Program survey. The candidate selection is performed by combining several photometric approaches including a Bayesian probabilistic algorithm to reject stars and dwarfs. The spectroscopic identification was carried out with the Gran Telescopio Canarias and the Subaru Telescope for the first 80 deg$^2$ of the survey footprint. The success rate of our photometric selection is quite high, approaching 100 % at the brighter magnitudes ($z_{\\rm AB} < 23.5$ mag). Our selection also recovered all the known high-$z$ quasars on the HSC images. Among the 15 discovered objects, six are likely quasars, while the other six with interstellar absorption lines and in some cases narrow emission lines are likely bright Lyman-br...

  15. THE SLOAN DIGITAL SKY SURVEY QUASAR LENS SEARCH. II. STATISTICAL LENS SAMPLE FROM THETHIRD DATA RELEASE

    Energy Technology Data Exchange (ETDEWEB)

    Inada, N; Oguri, M; Becker, R H; Shin, M; Richards, G T; Hennawi, J F; White, R L; Pindor, B; Strauss, M A; Kochanek, C S; Johnston, D E; Gregg, M D; Kayo, I; Eisenstein, D; Hall, P B; Castander, F J; Clocchiatti, A; Chiu, K; Kawano, Y; Scranton, R; Frieman, J; Keeton, C R; Morokuma, T; Rix, H; Turner, E L; Burless, S; Brunner, R J; Sheldon, E S; Bahcall, N A; Fukugita, M

    2007-09-13

    We report the first results of our systematic search for strongly lensed quasars using the spectroscopically confirmed quasars in the Sloan Digital Sky Survey (SDSS). Among 46,420 quasars from the SDSS Data Release 3 ({approx}4188 deg{sup 2}), we select a subsample of 22,683 quasars that are located at redshifts between 0.6 and 2.2 and are brighter than the Galactic extinction corrected i-band magnitude of 19.1. We identify 220 lens candidates from the quasar subsample, for which we conduct extensive and systematic follow-up observations in optical and near-infrared wavebands, in order to construct a complete lensed quasar sample at image separations between 1-inch and 20-inch and flux ratios of faint to bright lensed images larger than 10{sup -0.5}. We construct a statistical sample of 11 lensed quasars. Ten of these are galaxy-scale lenses with small image separations ({approx} 1-inch - 2-inch) and one is a large separation (15-inch) system which is produced by a massive cluster of galaxies, representing the first statistical sample of lensed quasars including both galaxy- and cluster-scale lenses. The Data Release 3 spectroscopic quasars contain an additional 11 lensed quasars outside the statistical sample.

  16. The SDSS-III BOSS quasar lens survey: discovery of 13 gravitationally lensed quasars

    Science.gov (United States)

    More, Anupreeta; Oguri, Masamune; Kayo, Issha; Zinn, Joel; Strauss, Michael A.; Santiago, Basilio X.; Mosquera, Ana M.; Inada, Naohisa; Kochanek, Christopher S.; Rusu, Cristian E.; Brownstein, Joel R.; da Costa, Luiz N.; Kneib, Jean-Paul; Maia, Marcio A. G.; Quimby, Robert M.; Schneider, Donald P.; Streblyanska, Alina; York, Donald G.

    2016-02-01

    We report the discovery of 13 confirmed two-image quasar lenses from a systematic search for gravitationally lensed quasars in the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). We adopted a methodology similar to that used in the SDSS Quasar Lens Search (SQLS). In addition to the confirmed lenses, we report 11 quasar pairs with small angular separations ( ≲ 2 arcsec) confirmed from our spectroscopy, which are either projected pairs, physical binaries, or possibly quasar lens systems whose lens galaxies have not yet been detected. The newly discovered quasar lens system, SDSS J1452+4224 at zs ≈ 4.8 is one of the highest redshift multiply imaged quasars found to date. Furthermore, we have over 50 good lens candidates yet to be followed up. Owing to the heterogeneous selection of BOSS quasars, the lens sample presented here does not have a well-defined selection function.

  17. The SDSS-III BOSS quasar lens survey: discovery of thirteen gravitationally lensed quasars

    CERN Document Server

    More, Anupreeta; Kayo, Issha; Zinn, Joel; Strauss, Michael A; Santiago, Basilio X; Mosquera, Ana M; Inada, Naohisa; Kochanek, Christopher S; Rusu, Cristian E; Brownstein, Joel R; da Costa, Luiz N; Kneib, Jean-Paul; Maia, Marcio A G; Quimby, Robert M; Schneider, Donald P; Streblyanska, Alina; York, Donald G

    2015-01-01

    We report the discovery of 13 confirmed two-image quasar lenses from a systematic search for gravitationally lensed quasars in the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). We adopted a methodology similar to that used in the SDSS Quasar Lens Search (SQLS). In addition to the confirmed lenses, we report 11 quasar pairs with small angular separations ($\\lesssim$2") confirmed from our spectroscopy, which are either projected pairs, physical binaries, or possibly quasar lens systems whose lens galaxies have not yet been detected. The newly discovered quasar lens system, SDSS J1452+4224 at zs$\\approx$4.8 is one of the highest redshift multiply imaged quasars found to date. Furthermore, we have over 50 good lens candidates yet to be followed up. Owing to the heterogeneous selection of BOSS quasars, the lens sample presented here does not have a well-defined selection function.

  18. Four Quasars above Redshift 6 Discovered by the Canada-France High-z Quasar Survey

    Science.gov (United States)

    Willott, Chris J.; Delorme, Philippe; Omont, Alain; Bergeron, Jacqueline; Delfosse, Xavier; Forveille, Thierry; Albert, Loic; Reylé, Céline; Hill, Gary J.; Gully-Santiago, Michael; Vinten, Phillip; Crampton, David; Hutchings, John B.; Schade, David; Simard, Luc; Sawicki, Marcin; Beelen, Alexandre; Cox, Pierre

    2007-12-01

    The Canada-France High-z Quasar Survey (CFHQS) is an optical survey designed to locate quasars during the epoch of reionization. In this paper we present the discovery of the first four CFHQS quasars at redshifts greater than 6, including the most distant known quasar, CFHQS J2329-0301 at z = 6.43. We describe the observational method used to identify the quasars and present optical, infrared, and millimeter photometry and optical and near-infrared spectroscopy. We investigate the dust properties of these quasars, finding an unusual dust extinction curve for one quasar and a high far-infrared luminosity due to dust emission for another. The mean millimeter continuum flux for CFHQS quasars is substantially lower than that for SDSS quasars at the same redshift, likely due to a correlation with quasar UV luminosity. For two quasars with sufficiently high signal-to-noise ratio optical spectra, we use the spectra to investigate the ionization state of hydrogen at z > 5. For CFHQS J1509-1749 at z = 6.12 we find significant evolution (beyond a simple extrapolation of lower redshift data) in the Gunn-Peterson optical depth at z > 5.4. The line of sight to this quasar has one of the highest known optical depths at z approx 5.8. An analysis of the sizes of the highly ionized near-zones in the spectra of two quasars at z = 6.12 and 6.43 suggest that the intergalactic medium surrounding these quasars was substantially ionized before these quasars turned on. Together, these observations point toward an extended reionization process, but we caution that cosmic variance is still a major limitation in z > 6 quasar observations.

  19. False periodicities in quasar time-domain surveys

    OpenAIRE

    Vaughan, S.; Uttley, P.; Markowitz, A. G.; Huppenkothen, D.; Middleton, M. J.; Alston, W.N.; Scargle, J. D.; Farr, W. M.

    2016-01-01

    There have recently been several reports of apparently periodic variations in the light curves of quasars, e.g. PG 1302-102 by Graham et al. (2015a). Any quasar showing periodic oscillations in brightness would be a strong candidate to be a close binary supermassive black hole and, in turn, a candidate for gravitational wave studies. However, normal quasars -- powered by accretion onto a single, supermassive black hole -- usually show stochastic variability over a wide range of timescales. It...

  20. Four quasars above redshift 6 discovered by the Canada-France High-z Quasar Survey

    CERN Document Server

    Willott, Chris J; Omont, Alain; Bergeron, Jacqueline; Delfosse, Xavier; Forveille, Thierry; Albert, Loic; Reyle, Celine; Hill, Gary J; Gully-Santiago, Michael; Vinten, Phillip; Crampton, David; Hutchings, John B; Schade, David; Simard, Luc; Sawicki, Marcin; Beelen, Alexandre; Cox, Pierre

    2007-01-01

    The Canada-France High-z Quasar Survey (CFHQS) is an optical survey designed to locate quasars during the epoch of reionization. In this paper we present the discovery of the first four CFHQS quasars at redshift greater than 6, including the most distant known quasar, CFHQS J2329-0301 at z=6.43. We describe the observational method used to identify the quasars and present optical, infrared, and millimeter photometry and optical and near-infrared spectroscopy. We investigate the dust properties of these quasars finding an unusual dust extinction curve for one quasar and a high far-infrared luminosity due to dust emission for another. The mean millimeter continuum flux for CFHQS quasars is substantially lower than that for SDSS quasars at the same redshift, likely due to a correlation with quasar UV luminosity. For two quasars with sufficiently high signal-to-noise optical spectra, we use the spectra to investigate the ionization state of hydrogen at z>5. For CFHQS J1509-1749 at z=6.12, we find significant evol...

  1. THE MAGELLANIC QUASARS SURVEY. III. SPECTROSCOPIC CONFIRMATION OF 758 ACTIVE GALACTIC NUCLEI BEHIND THE MAGELLANIC CLOUDS

    International Nuclear Information System (INIS)

    The Magellanic Quasars Survey (MQS) has now increased the number of quasars known behind the Magellanic Clouds by almost an order of magnitude. All survey fields in the Large Magellanic Cloud (LMC) and 70% of those in the Small Magellanic Cloud (SMC) have been observed. The targets were selected from the third phase of the Optical Gravitational Lensing Experiment (OGLE-III) based on their optical variability, mid-IR, and/or X-ray properties. We spectroscopically confirmed 758 quasars (565 in the LMC and 193 in the SMC) behind the clouds, of which 94% (527 in the LMC and 186 in the SMC) are newly identified. The MQS quasars have long-term (12 yr and growing for OGLE), high-cadence light curves, enabling unprecedented variability studies of quasars. The MQS quasars also provide a dense reference grid for measuring both the internal and bulk proper motions of the clouds, and 50 quasars are bright enough (I ∼< 18 mag) for absorption studies of the interstellar/intergalactic medium of the clouds

  2. Double Lobed Radio Quasars from the Sloan Digital Sky Survey

    Energy Technology Data Exchange (ETDEWEB)

    de Vries, W H; Becker, R H; White, R L

    2005-11-10

    We have combined a sample of 44 984 quasars, selected from the Sloan Digital Sky Survey (SDSS) Data Release 3, with the FIRST radio survey. Using a novel technique where the optical quasar position is matched to the complete radio environment within 450'', we are able to characterize the radio morphological make-up of what is essentially an optically selected quasar sample, regardless of whether the quasar (nucleus) itself has been detected in the radio. About 10% of the quasar population have radio cores brighter than 0.75 mJy at 1.4 GHz, and 1.7% have double lobed FR2-like radio morphologies. About 75% of the FR2 sources have a radio core (> 0.75mJy). A significant fraction ({approx}40%) of the FR2 quasars are bent by more than 10 degrees, indicating either interactions of the radio plasma with the ICM or IGM. We found no evidence for correlations with redshift among our FR2 quasars: radio lobe flux densities and radio source diameters of the quasars have similar distributions at low (mean 0.77) and high (mean 2.09) redshifts. Using a smaller high reliability FR2 sample of 422 quasars and two comparison samples of radio-quiet and non-FR2 radio-loud quasars, matched in their redshift distributions, we constructed composite optical spectra from the SDSS spectroscopic data. Based on these spectra we can conclude that the FR2 quasars have stronger high-ionization emission lines compared to both the radio quiet and non-FR2 radio loud sources. This is consistent with the notion that the emission lines are brightened by ongoing shock ionization of ambient gas in the quasar host as the radio source expands.

  3. The Sloan Digital Sky Survey quasar catalog: tenth data release

    CERN Document Server

    Pâris, Isabelle; Aubourg, Éric; Ross, Nicholas P; Myers, Adam D; Streblyanska, Alina; Bailey, Stephen; Hall, Patrick B; Strauss, Michael A; Anderson, Scott F; Bizyaev, Dmitry; Borde, Arnaud; Brinkmann, Jon; Bovy, Jo; Brandt, William N; Brewington, Howard; Brownstein, Joel R; Cook, Benjamin A; Ebelke, Garrett; Fan, Xiaohui; Ak, Nurten Filiz; Finley, Hayley; Font-Ribera, Andreu; Ge, Jian; Hamann, Fred; Ho, Shirley; Jiang, Linhua; Kinemuchi, Karen; Malanushenko, Elena; Malanushenko, Viktor; Marchante, Moses; McGreer, Ian D; McMahon, Richard G; Miralda-Escudé, Jordi; Muna, Demitri; Noterdaeme, Pasquier; Oravetz, Daniel; Palanque-Delabrouille, Nathalie; Pan, Kaike; Perez-Fournon, Ismaël; Pieri, Matthew; Riffel, Rogério; Schlegel, David J; Schneider, Donald P; Simmons, Audrey; Viel, Matteo; Weaver, Benjamin A; Wood-Vasey, W Michael; Yèche, Christophe; York, Donald G

    2013-01-01

    We present the Data Release 10 Quasar (DR10Q) 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 first 2.5 years of the survey and that are confirmed as quasars via visual inspection of the spectra. The catalog also includes known quasars (mostly from SDSS-I and II) that were reobserved by BOSS. The catalog contains 166,583 quasars (74,454 are new discoveries since SDSS-DR9) detected over 6,373 deg$^{2}$ with robust identification and redshift measured by a combination of principal component eigenspectra. The number of quasars with $z>2.15$ (117,668) is $\\sim$5 times greater than the number of $z>2.15$ quasars known prior to BOSS. Redshifts and FWHMs are provided for the strongest emission lines (CIV, CIII, MgII). The catalog identifies 16,461 broad absorption line quasars and gives their characteristics. For each object, the catalog presents five-band (u, g, r, i, z) CCD-...

  4. False periodicities in quasar time-domain surveys

    CERN Document Server

    Vaughan, S; Markowitz, A G; Huppenkothen, D; Middleton, M J; Alston, W N; Scargle, J D; Farr, W M

    2016-01-01

    There have recently been several reports of apparently periodic variations in the light curves of quasars, e.g. PG 1302-102 by Graham et al. (2015a). Any quasar showing periodic oscillations in brightness would be a strong candidate to be a close binary supermassive black hole and, in turn, a candidate for gravitational wave studies. However, normal quasars -- powered by accretion onto a single, supermassive black hole -- usually show stochastic variability over a wide range of timescales. It is therefore important to carefully assess the methods for identifying periodic candidates from among a population dominated by stochastic variability. Using a Bayesian analysis of the light curve of PG 1302-102, we find that a simple stochastic process is preferred over a sinusoidal variations. We then discuss some of the problems one encounters when searching for rare, strictly periodic signals among a large number of irregularly sampled, stochastic time series, and use simulations of quasar light curves to illustrate ...

  5. THE LARGE SKY AREA MULTI-OBJECT FIBER SPECTROSCOPIC TELESCOPE QUASAR SURVEY: QUASAR PROPERTIES FROM THE FIRST DATA RELEASE

    Energy Technology Data Exchange (ETDEWEB)

    Ai, Y. L.; Wu, Xue-Bing; Yang, Jinyi; Yang, Qian; Wang, Feige; Guo, Rui; Dong, Xiaoyi [Department of Astronomy, School of Physics, Peking University, Beijing 100871 (China); Zuo, Wenwen; Shen, S.-Y. [Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030 (China); Zhang, Y.-X.; Yuan, H.-L.; Song, Y.-H.; Yang, M.; Wu, H.; Shi, J.-R.; He, B.-L.; Lei, Y.-J.; Li, Y.-B. [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences 100012, Beijing (China); Wang, Jianguo; Dong, Xiaobo, E-mail: aiyl@pku.edu.cn [Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China); and others

    2016-02-15

    We present preliminary results of the quasar survey in the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) first data release (DR1), which includes the pilot survey and the first year of the regular survey. There are 3921 quasars reliably identified, among which 1180 are new quasars discovered in the survey. These quasars are at low to median redshifts, with a highest z of 4.83. We compile emission line measurements around the Hα, Hβ, Mg ii, and C iv regions for the new quasars. The continuum luminosities are inferred from SDSS photometric data with model fitting, as the spectra in DR1 are non-flux-calibrated. We also compile the virial black hole mass estimates, with flags indicating the selection methods, and broad absorption line quasars. The catalog and spectra for these quasars are also available. Of the 3921 quasars, 28% are independently selected with optical–infrared colors, indicating that the method is quite promising for the completeness of the quasar survey. LAMOST DR1 and the ongoing quasar survey will provide valuable data for studies of quasars.

  6. The Multi-Wavelength Quasar Survey Ⅲ.Quasars in Field 836

    Institute of Scientific and Technical Information of China (English)

    Yu Bai; Yang Chen; Xiang-Tao He; Jiang-Hua Wu; Qing-Kang Li; Richard F.Green; Wolfgang Voges

    2007-01-01

    This is the third Paper in a series connected with our Multiwavelength Quasar Survey.The survey is aimed to provide a quasar sample more complete than any previous survey by using a combined selection technique to reduce selection effects.we present the observational results for the X-ray candidates in field f836.We found 15 X-ray AGNs in this field of which eight are new discoveries.The X-ray data and optical spectra of these AGNs are given.We give the X-ray candidate selection criteria.which proved to be highly efficient in isolating X-ray AGNs.

  7. RADIOASTRON OBSERVATIONS OF THE QUASAR 3C273: A CHALLENGE TO THE BRIGHTNESS TEMPERATURE LIMIT

    Energy Technology Data Exchange (ETDEWEB)

    Kovalev, Y. Y.; Kardashev, N. S.; Voitsik, P. A.; Kovalev, Yu. A.; Lisakov, M. M.; Sokolovsky, K. V. [Astro Space Center of Lebedev Physical Institute, Profsoyuznaya 84/32, 117997 Moscow (Russian Federation); Kellermann, K. I. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475 (United States); Lobanov, A. P.; Zensus, J. A.; Anderson, J. M.; Bach, U.; Kraus, A. [Max-Planck-Institute for Radio Astronomy, Auf dem Hügel 69, D-53121 (Germany); Johnson, M. D. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Gurvits, L. I. [Joint Institute for VLBI ERIC, P.O. Box 2, 7990 AA Dwingeloo (Netherlands); Jauncey, D. L. [CSIRO Astronomy and Space Sciences, Epping, NSW 1710 (Australia); Ghigo, F. [National Radio Astronomy Observatory, Rt. 28/92, Green Bank, WV 24944-0002 (United States); Ghosh, T.; Salter, C. J. [Arecibo Observatory, NAIC, HC3 Box 53995, Arecibo, Puerto Rico, PR 00612 (United States); Petrov, L. Yu. [Astrogeo Center, 7312 Sportsman Drive, Falls Church, VA 22043 (United States); Romney, J. D. [National Radio Astronomy Observatory, P.O. Box O, 1003 Lopezville Road, Socorro, NM 87801-0387 (United States)

    2016-03-20

    Inverse Compton cooling limits the brightness temperature of the radiating plasma to a maximum of 10{sup 11.5} K. Relativistic boosting can increase its observed value, but apparent brightness temperatures much in excess of 10{sup 13} K are inaccessible using ground-based very long baseline interferometry (VLBI) at any wavelength. We present observations of the quasar 3C 273, made with the space VLBI mission RadioAstron on baselines up to 171,000 km, which directly reveal the presence of angular structure as small as 26 μas (2.7 light months) and brightness temperature in excess of 10{sup 13} K. These measurements challenge our understanding of the non-thermal continuum emission in the vicinity of supermassive black holes and require a much higher Doppler factor than what is determined from jet apparent kinematics.

  8. The Sloan Digital Sky Survey quasar catalog: ninth data release

    CERN Document Server

    Pâris, Isabelle; Aubourg, Eric; Bailey, Stephen; Ross, Nicholas P; Myers, Adam D; Strauss, Michael A; Anderson, Scott F; Arnau, Eduard; Bautista, Julian; Bizyaev, Dmitry; Bolton, Adam S; Bovy, Jo; Brandt, William N; Brewington, Howard; Brownstein, Joel R; Busca, Nicolas; Capellupo, Daniel; Carithers, William; Croft, Rupert A C; Dawson, Kyle; Delubac, Timothée; Ebelke, Garrett; Eisenstein, Daniel J; Engelke, Philip; Fan, Xiaohui; Ak, Nur Filiz; Finley, Hayley; Font-Ribera, Andreu; Ge, Jian; Gibson, Robert R; Hall, Patrick B; Hamann, Fred; Hennawi, Joseph F; Ho, Shirley; Hogg, David W; Ivezic, Zeljko; Jiang, Linhua; Kimball, Amy E; Kirkby, David; Kirkpatrick, Jessica A; Lee, Khee-Gan; Goff, Jean-Marc Le; Lundgren, Britt; MacLeod, Chelsea L; Malanushenko, Elena; Malanushenko, Viktor; Maraston, Claudia; McGreer, Ian D; McMahon, Richard G; Miralda-Escudé, Jordi; Muna, Demitri; Noterdaeme, Pasquier; Oravetz, Daniel; Palanque-Delabrouille, Nathalie; Pan, Kaike; Perez-Fournon, Ismaël; Pieri, Matthew M; Richards, Gordon T; Rollinde, Emmanuel; Sheldon, Erin S; Schlegel, David J; Schneider, Donald P; Slosar, Anze; Shelden, Alaina; Shen, Yue; Simmons, Audrey; Snedden, Stephanie; Suzuki, Nao; Tinker, Jeremy; Viel, Matteo; Weaver, Benjamin A; Weinberg, David H; White, Martin; Wood-Vasey, W Michael; Yèche, Christophe

    2012-01-01

    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]2.15$ (61,931) is ~2.8 times larger than the number of z>2.15 quasars previously known. Redshifts and FWHMs are provided for the strongest emission lines (CIV, CIII], MgII). The catalog identifies 7,533 broad absorption line quasars and gives their characteristics. For each object the catalog presents five-band (u,g,r,i,z) CCD-based photometry with typical accuracy of 0.03 mag, and information on the morphology and selection method. The catalog also contains X-ray, ultraviolet, near-infrared, and radio emission properties of the quasars, when available, from other large-area surveys.

  9. First results from the Isaac Newton Telescope Wide Angle Survey The z>5 quasar survey

    CERN Document Server

    Sharp, R G; Irwin, M J; Hodgkin, S T

    2001-01-01

    We report the discovery and spectra of 3 i4.4) quasars, including one with z>5. At z=5.17, this is the fourth highest redshift quasar currently known. The quasars were discovered as part of a deep multi-colour CCD survey designed to be sensitive enough to constrain the total luminosity density of z>5 quasars. When completed the survey will provide a firm constraint on the contribution to the ionizing UV background in the redshift range 4.5-5.5 from quasars by determining the faint end slope of the quasar luminosity function. The survey uses imaging data taken with the 2.5m Isaac Newton Telescope as part of the Public Isaac Newton Group Wide Field Survey (WFS). This initial sample of objects is taken from two fields of effective area $\\sim$12.5deg$^2$ from the final $\\sim$100deg$^2$.

  10. The Sloan Digital Sky Survey Quasar Catalog: twelfth data release

    CERN Document Server

    Pâris, Isabelle; Ross, Nicholas P; Myers, Adam D; Aubourg, Éric; Streblyanska, Alina; Bailey, Stephen; Armengaud, Éric; Palanque-Delabrouille, Nathalie; Yèche, Christophe; Hamann, Fred; Strauss, Michael A; Albareti, Franco D; Bovy, Jo; Bizyaev, Dmitry; Brandt, W Niel; Brusa, Marcella; Buchner, Johannes; Comparat, Johan; Croft, Rupert A C; Dwelly, Tom; Fan, Xiaohui; Font-Ribera, Andreu; Ge, Jian; Georgakakis, Antonis; Hall, Patrick B; Jian, Linhua; Kinemuchi, Karen; Malanushenko, Elena; Malanushenko, Viktor; McMahon, Richard G; Menzel, Marie-Luise; Merloni, Andrea; Nandra, Kirpal; Noterdaeme, Pasquier; Oravetz, Daniel; Pan, Kaike; Pieri, Matthew M; Prada, Francisco; Salvato, Mara; Schlegel, David J; Schneider, Donald P; Simmons, Audrey; Viel, Matteo; Weinberg, David H; Zhu, Liu

    2016-01-01

    We present the Data Release 12 Quasar catalog (DR12Q) from the Baryon Oscillation Spectroscopic Survey (BOSS) of the SDSS-III. This catalog includes all SDSS-III/BOSS objects that were spectroscopically targeted as quasar candidates during the full survey and that are confirmed as quasars via visual inspection of the spectra, have luminosities Mi[z=2]2.15 is about an order of magnitude greater than the number of z>2.15 quasars known prior to BOSS. Redshifts and FWHMs are provided for the strongest emission lines (CIV, CIII], MgII). The catalog identifies 29,580 broad absorption line quasars and lists their characteristics. For each object, the catalog presents five-band (u, g, r, i, z) CCD-based photometry together with some information on the optical morphology and the selection criteria. When available, the catalog also provides information on the optical variability of quasars using SDSS and PTF multi-epoch photometry. The catalog also contains X-ray, ultraviolet, near-infrared, and radio emission properti...

  11. A survey of z > 5.7 quasars in the sloan digital sky survey. 4. discovery of seven additional quasars

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Xiao-Hui; Strauss, Michael A.; Richards, Gordon T.; Hennawi, Joseph F.; Becker, Robert H.; White, Richard L.; Diamond-Stanic, Aleksandar M.; onley, Jennifer L.D; Jiang, Lin-Hua; Kim, J.Serena; Vestergaard, Marianne; Young, Jason E.; Gunn, James E.; Lupton, Robert H.; Knapp, Gillian R.; Schneider, Donald P.; Brandt, W.N.; Bahcall, Neta A.; Barentine, J.C.; Brinkmann, J.; Brewington, Howard J.; /Arizona U., Astron. Dept. - Steward Observ. /Princeton U. Observ. /Johns Hopkins U. /UC, Berkeley, Astron. Dept. /UC, Davis

    2005-12-01

    We present the discovery of seven quasars at z > 5.7, selected from {approx}2000 deg{sup 2} of multicolor imaging data of the Sloan Digital Sky Survey (SDSS). The new quasars have redshifts z from 5.79 to 6.13. Five are selected as part of a complete flux-limited sample in the SDSS Northern Galactic Cap; two have larger photometric errors and are not part of the complete sample. One of the new quasars, SDSS J1335+3533 (z = 5.93), exhibits no emission lines; the 3-{sigma} limit on the rest-frame equivalent width of Ly{alpha} + NV line is 5 {angstrom}. It is the highest redshift lineless quasar known, and could be a gravitational lensed galaxy, a BL Lac object or a new type of quasar. Two new z > 6 quasars, SDSS 1250+3130 (z = 6.13) and SDSS J1137+3549 (z = 6.01), show deep Gunn-Peterson absorption gaps in Ly{alpha}. These gaps are narrower the complete Gunn-Peterson absorption troughs observed among quasars at z > 6.2 and do not have complete Ly{beta} absorption.

  12. The Large Sky Area Multi-Object Fiber Spectroscopic Telescope Quasar Survey: Quasar Properties from First Data Release

    CERN Document Server

    Ai, Y L; Yang, Jinyi; Yang, Qian; Wang, Feige; Guo, Rui; Zuo, Wenwen; Dong, Xiaoyi; Zhang, Y -X; Yuan, H -L; Song, Y -H; Wang, Jianguo; Dong, Xiaobo; Yang, M; Wu, H; Shen, S -Y; Shi, J -R; He, B -L; Lei, Y -J; Li, Y -B; Luo, A -L; Zhao, Y -H; Zhang, Hao-Tong

    2015-01-01

    We present preliminary results of the quasar survey in Large Sky Area Multi- Object Fiber Spectroscopic Telescope (LAMOST) first data release (DR1), which includes pilot survey and the first year regular survey. There are 3921 quasars identified with reliability, among which 1180 are new quasars discovered in the survey. These quasars are at low to median redshifts, with highest z of 4.83. We compile emission line measurements around the H{\\alpha}, H{\\beta}, Mg II, and C IV regions for the new quasars. The continuum luminosities are inferred from SDSS photo- metric data with model fitting as the spectra in DR1 are non-flux-calibrated. We also compile the virial black hole mass estimates, and flags indicating the selec- tion methods, broad absorption line quasars. The catalog and spectra for these quasars are available online. 28% of the 3921 quasars are selected with optical- infrared colours independently, indicating that the method is quite promising in completeness of quasar survey. LAMOST DR1 and the on-g...

  13. The extended Baryon Oscillation Spectroscopic Survey: Variability selection and quasar luminosity function

    Science.gov (United States)

    Palanque-Delabrouille, N.; Magneville, Ch.; Yèche, Ch.; Pâris, I.; Petitjean, P.; Burtin, E.; Dawson, K.; McGreer, I.; Myers, A. D.; Rossi, G.; Schlegel, D.; Schneider, D.; Streblyanska, A.; Tinker, J.

    2016-03-01

    The extended Baryon Oscillation Spectroscopic Survey of the Sloan Digital Sky Survey (SDSS-IV/eBOSS) has an extensive quasar program that combines several selection methods. Among these, the photometric variability technique provides highly uniform samples, which are unaffected by the redshift bias of traditional optical-color selections, when z = 2.7-3.5 quasars cross the stellar locus or when host galaxy light affects quasar colors at z 2.2. Both models are constrained to be continuous at z = 2.2. They present a flattening of the bright-end slope at high redshift. The LEDE model indicates a reduction of the break density with increasing redshift, but the evolution of the break magnitude depends on the parameterization. The models are in excellent accord, predicting quasar counts that agree within 0.3% (resp., 1.1%) to g< 22.5 (resp., g< 23). The models are also in good agreement over the entire redshift range with models from previous studies.

  14. 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

    CERN Document Server

    Huo, Zhi-Ying; Xiang, Mao-Sheng; Yuan, Hai-Bo; Huang, Yang; Zhang, Hui-Hua; Yan, Lin; 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; 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, Zhi-Gang; Lu, Qi-Shuai; Luo, A-Li; Luo, Yu; Men, Li; Ni, Ji-Jun; Qi, Yong-Jun; Qi, Zhao-Xiang; Shi, Jian-Rong; Shi, Huo-Ming; 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; Xue, Xiang-Xiang; Yao, Zheng-Qiu; Yu, Yong; Yuan, Hui; Zhai, Chao; Zhang, En-Peng; Zhang, Hao-Tong; 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

    2013-01-01

    We present new quasars discovered in the vicinity of the Andromeda and Triangulum galaxies with the LAMOST during the 2010 and 2011 observational seasons. Quasar candidates are selected based on the available SDSS, KPNO 4 m telescope, XSTPS optical, and WISE near infrared photometric data. We present 509 new quasars discovered in a stripe of ~135 sq. deg from M31 to M33 along the Giant Stellar Stream in the 2011 pilot survey datasets, and also 17 new quasars discovered in an area of ~100 sq. deg that covers the central region and the southeastern halo of M31 in the 2010 commissioning datasets. These 526 new quasars have i magnitudes ranging from 15.5 to 20.0, redshifts from 0.1 to 3.2. They represent a significant increase of the number of identified quasars in the vicinity of M31 and M33. There are now 26, 62 and 139 known quasars in this region of the sky with i magnitudes brighter than 17.0, 17.5 and 18.0 respectively, of which 5, 20 and 75 are newly-discovered. These bright quasars provide an invaluable c...

  15. THE HALO OCCUPATION DISTRIBUTION OF X-RAY-BRIGHT ACTIVE GALACTIC NUCLEI: A COMPARISON WITH LUMINOUS QUASARS

    Energy Technology Data Exchange (ETDEWEB)

    Richardson, Jonathan [Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60605 (United States); Chatterjee, Suchetana; Myers, Adam D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82072 (United States); Zheng Zheng [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Hickox, Ryan, E-mail: jonathan.richardson@uchicago.edu, E-mail: schatte1@uwyo.edu [Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755 (United States)

    2013-09-10

    We perform halo occupation distribution (HOD) modeling of the projected two-point correlation function (2PCF) of high-redshift (z {approx} 1.2) X-ray-bright active galactic nuclei (AGNs) in the XMM-COSMOS field measured by Allevato et al. The HOD parameterization is based on low-luminosity AGNs in cosmological simulations. At the median redshift of z {approx} 1.2, we derive a median mass of 1.02{sub -0.23}{sup +0.21} Multiplication-Sign 10{sup 13} h{sup -1} M{sub sun} for halos hosting central AGNs and an upper limit of {approx}10% on the AGN satellite fraction. Our modeling results indicate (at the 2.5{sigma} level) that X-ray AGNs reside in more massive halos compared to more bolometrically luminous, optically selected quasars at similar redshift. The modeling also yields constraints on the duty cycle of the X-ray AGN, and we find that at z {approx} 1.2 the average duration of the X-ray AGN phase is two orders of magnitude longer than that of the quasar phase. Our inferred mean occupation function of X-ray AGNs is similar to recent empirical measurements with a group catalog and suggests that AGN halo occupancy increases with increasing halo mass. We project the XMM-COSMOS 2PCF measurements to forecast the required survey parameters needed in future AGN clustering studies to enable higher precision HOD constraints and determinations of key physical parameters like the satellite fraction and duty cycle. We find that N {sup 2}/A {approx} 5 Multiplication-Sign 10{sup 6} deg{sup -2} (with N the number of AGNs in a survey area of A deg{sup 2}) is sufficient to constrain the HOD parameters at the 10% level, which is easily achievable by upcoming and proposed X-ray surveys.

  16. False periodicities in quasar time-domain surveys

    Science.gov (United States)

    Vaughan, S.; Uttley, P.; Markowitz, A. G.; Huppenkothen, D.; Middleton, M. J.; Alston, W. N.; Scargle, J. D.; Farr, W. M.

    2016-09-01

    There have recently been several reports of apparently periodic variations in the light curves of quasars, e.g. PG 1302-102 by Graham et al. Any quasar showing periodic oscillations in brightness would be a strong candidate to be a close binary supermassive black hole and, in turn, a candidate for gravitational wave studies. However, normal quasars - powered by accretion on to a single, supermassive black hole - usually show stochastic variability over a wide range of time-scales. It is therefore important to carefully assess the methods for identifying periodic candidates from among a population dominated by stochastic variability. Using a Bayesian analysis of the light curve of PG 1302-102, we find that a simple stochastic process is preferred over a sinusoidal variation. We then discuss some of the problems one encounters when searching for rare, strictly periodic signals among a large number of irregularly sampled, stochastic time series, and use simulations of quasar light curves to illustrate these points. From a few thousand simulations of steep spectrum (`red noise') stochastic processes, we find many simulations that display few-cycle periodicity like that seen in PG 1302-102. We emphasize the importance of calibrating the false positive rate when the number of targets in a search is very large.

  17. Long-term Optical Variability of Radio-Selected Quasars from the FIRST Survey

    CERN Document Server

    Helfand, D J; Willman, B; White, R L; Becker, R H; Price, T; Gregg, M D; McMahon, R G; Helfand, David J.; Stone, Remington P.S.; Willman, Beth; White, Richard L.; Becker, Robert H.; Price, Trevor; Gregg, Michael D.; Mahon, Richard G. Mc

    2001-01-01

    We have obtained single-epoch optical photometry for 201 quasars, taken from the FIRST Bright Quasar Survey, which span a wide range in radio loudness. Comparison with the magnitudes of these objects on the POSS-I plates provides by far the largest sample of long-term variability amplitudes for radio-selected quasars yet produced. We find the quasars to be more variable in the blue than in the red band, consistent with work on optically selected samples. The previously noted trend of decreasing variability with increasing optical luminosity applies only to radio-quiet objects. Furthermore, we do not confirm a rise in variability amplitude with redshift, nor do we see any dependence on radio flux or luminosity. The variability over a radio-optical flux ratio range spanning a factor of 60,000 from radio-quiet to extreme radio-loud objects is largely constant, although there is a suggestion of greater variability in the extreme radio-loud objects. We demonstrate the importance of Malmquist bias in variability st...

  18. Spectral Variability of Quasars in the Sloan Digital Sky Survey. I: Wavelength Dependence

    CERN Document Server

    Wilhite, B C; Kron, R G; Schneider, D P; Pereyra, N; Brunner, R J; Richards, G T; Brinkmann, J; Wilhite, Brian C.; Berk, Daniel E. Vanden; Kron, Richard G.; Schneider, Donald P.; Pereyra, Nicholas; Brunner, Robert J.; Richards, Gordon T.; Brinkmann, Jonathan V.

    2005-01-01

    Sloan Digital Sky Survey (SDSS) repeat spectroscopic observations have resulted in multiple-epoch spectroscopy for roughly 2500 quasars observed more than 50 days apart. From this sample, we identify 315 quasars that have varied significantly between observations. We create an ensemble difference spectrum (bright phase minus faint phase) covering rest-frame wavelengths from 1000 to 6000 Angstroms. This average difference spectrum is bluer than the average single-epoch quasar spectrum; a power-law fit to the difference spectrum yields a spectral index alpha_lambda = -2.00, compared to an index of alpha_lambda = -1.35 for the single-epoch spectrum. The strongest emission lines vary only 30% as much as the continuum. Due to the lack of variability of the lines, measured photometric color is not always bluer in brighter phases, but depends on redshift and the filters used. Lastly, the difference spectrum is bluer than the ensemble quasar spectrum only for lambda_rest < 2500 Angstroms, indicating that the varia...

  19. A Survey of z>5.7 Quasars in the Sloan Digital Sky Survey IV

    DEFF Research Database (Denmark)

    Fan, Xiaohui; Strauss, Michael A.; Richards, Gordon T.;

    2005-01-01

    We present the discovery of seven quasars at z>5.7, selected from ~2000 deg^2 of multicolor imaging data of the Sloan Digital Sky Survey (SDSS). The new quasars have redshifts z from 5.79 to 6.13. Five are selected as part of a complete flux-limited sample in the SDSS Northern Galactic Cap; two...

  20. Rapid infrared and optical variability in the bright quasar 3C273

    Energy Technology Data Exchange (ETDEWEB)

    Courvoisier, T.J.-L.; Robson, E.I.; Hughes, D.H.; Blecha, A.; Bouchet, P.; Schwarz, H.E.; Krisciunas, K.

    1988-09-22

    We have observed variations by a factor of two in the infrared flux from the bright quasar 3C273 on a timescale as short as one day. In February 1988, the behaviour of the source changed from having a stable infrared flux and slow optical variations to a state characterized by recurrent infrared and optical flaring. The optical variations were of several per cent per day, changing from increase to decrease approximately every week. The amplitude of the repeated optical flares was 30-40%. The data are consistent with re-injection/acceleration of electrons followed by rapid cooling. The inferred magnetic field is 0.7 gauss and the data are marginally consistent with no relativistic beaming.

  1. The Bright SHARC Survey The Cluster Catalog

    CERN Document Server

    Romer, A K; Holden, B P; Ulmer, M P; Pildis, R A; Merrelli, A J; Adami, C; Burke, D J; Collins, C A; Metevier, A J; Kron, Richard G; Commons, K

    1999-01-01

    We present the Bright SHARC (Serendipitous High-Redshift Archival ROSAT Cluster) Survey, which is an objective search for serendipitously detected extended X-ray sources in 460 deep ROSAT PSPC pointings. The Bright SHARC Survey covers an area of 178.6 sq.deg and has yielded 374 extended sources. We discuss the X-ray data reduction, the candidate selection and present results from our on-going optical follow-up campaign. The optical follow-up concentrates on the brightest 94 of the 374 extended sources and is now 97% complete. We have identified thirty-seven clusters of galaxies, for which we present redshifts and luminosities. The clusters span a redshift range of 0.0696Bright SHARC clusters have not been listed in any previously ...

  2. The very first Pop III stars and their relation to bright z~6 quasars

    CERN Document Server

    Trenti, M

    2007-01-01

    We discuss the link between dark matter halos hosting the first PopIII stars formed at redshift z > 40 and the rare, massive, halos that are generally considered to host bright z~6 quasars. We show that within the typical volume occupied by one bright high-z QSO the remnants of the first several thousands PopIII stars formed do not end up in the most massive halos at z~6, but rather live in a large variety of environments. The black hole seeds planted by these very first PopIII stars can easily grow to M > 10^{9.5} Msun by z=6 assuming Eddington accretion with radiative efficiency epsilon~0.1. Therefore quenching of the accretion is crucial to avoid an overabundance of supermassive black holes. We implement a simple feedback model for the growth of the seeds planted by PopIII stars and obtain a z~6 BH mass function consistent with the observed QSO luminosity function.

  3. 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

    International Nuclear Information System (INIS)

    We present new quasars discovered in the vicinity of the Andromeda and Triangulum galaxies with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, also named the Guoshoujing Telescope, during the 2010 and 2011 observational seasons. Quasar candidates are selected based on the available Sloan Digital Sky Survey, Kitt Peak National Observatory 4 m telescope, Xuyi Schmidt Telescope Photometric Survey optical, and Wide-field Infrared Survey Explorer near-infrared photometric data. We present 509 new quasars discovered in a stripe of ∼135 deg2 from M31 to M33 along the Giant Stellar Stream in the 2011 pilot survey data sets, and also 17 new quasars discovered in an area of ∼100 deg2 that covers the central region and the southeastern halo of M31 in the 2010 commissioning data sets. These 526 new quasars have i magnitudes ranging from 15.5 to 20.0, redshifts from 0.1 to 3.2. They represent a significant increase of the number of identified quasars in the vicinity of M31 and M33. There are now 26, 62, and 139 known quasars in this region of the sky with i magnitudes brighter than 17.0, 17.5, and 18.0, respectively, of which 5, 20, and 75 are newly discovered. These bright quasars provide an invaluable collection with which to probe the kinematics and chemistry of the interstellar/intergalactic medium in the Local Group of galaxies. A total of 93 quasars are now known with locations within 2.°5 of M31, of which 73 are newly discovered. Tens of quasars are now known to be located behind the Giant Stellar Stream, and hundreds are behind the extended halo and its associated substructures of M31. The much enlarged sample of known quasars in the vicinity of M31 and M33 can potentially be utilized to construct a perfect astrometric reference frame to measure the minute proper motions (PMs) of M31 and M33, along with the PMs of substructures associated with the Local Group of galaxies. Those PMs are some of the most fundamental properties of the Local Group.

  4. 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

    Energy Technology Data Exchange (ETDEWEB)

    Huo, Zhi-Ying; Bai, Zhong-Rui; Chen, Jian-Jun; Chen, Xiao-Yan; Du, Bing; Jia, Lei; Lei, Ya-Juan [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Liu, Xiao-Wei; Yuan, Hai-Bo [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China); Xiang, Mao-Sheng; Huang, Yang; Zhang, Hui-Hua [Department of Astronomy, Peking University, Beijing 100871 (China); Yan, Lin [Infrared Processing and Analysis Center, California Institute of Technology, MS 100-22, Pasadena, CA 91125 (United States); Chu, Jia-Ru; Chu, Yao-Quan; Hu, Hong-Zhuan [University of Science and Technology of China, Hefei 230026 (China); Cui, Xiang-Qun; Hou, Yong-Hui; Hu, Zhong-Wen; Jiang, Fang-Hua, E-mail: zhiyinghuo@bao.ac.cn [Nanjing Institute of Astronomical Optics and Technology, National Astronomical Observatories, Chinese Academy of Sciences, Nanjing 210042 (China); and others

    2013-06-01

    We present new quasars discovered in the vicinity of the Andromeda and Triangulum galaxies with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, also named the Guoshoujing Telescope, during the 2010 and 2011 observational seasons. Quasar candidates are selected based on the available Sloan Digital Sky Survey, Kitt Peak National Observatory 4 m telescope, Xuyi Schmidt Telescope Photometric Survey optical, and Wide-field Infrared Survey Explorer near-infrared photometric data. We present 509 new quasars discovered in a stripe of ∼135 deg{sup 2} from M31 to M33 along the Giant Stellar Stream in the 2011 pilot survey data sets, and also 17 new quasars discovered in an area of ∼100 deg{sup 2} that covers the central region and the southeastern halo of M31 in the 2010 commissioning data sets. These 526 new quasars have i magnitudes ranging from 15.5 to 20.0, redshifts from 0.1 to 3.2. They represent a significant increase of the number of identified quasars in the vicinity of M31 and M33. There are now 26, 62, and 139 known quasars in this region of the sky with i magnitudes brighter than 17.0, 17.5, and 18.0, respectively, of which 5, 20, and 75 are newly discovered. These bright quasars provide an invaluable collection with which to probe the kinematics and chemistry of the interstellar/intergalactic medium in the Local Group of galaxies. A total of 93 quasars are now known with locations within 2.°5 of M31, of which 73 are newly discovered. Tens of quasars are now known to be located behind the Giant Stellar Stream, and hundreds are behind the extended halo and its associated substructures of M31. The much enlarged sample of known quasars in the vicinity of M31 and M33 can potentially be utilized to construct a perfect astrometric reference frame to measure the minute proper motions (PMs) of M31 and M33, along with the PMs of substructures associated with the Local Group of galaxies. Those PMs are some of the most fundamental properties of the Local

  5. ALMA Science Verification Data: Millimeter Continuum Polarimetry of the Bright Radio Quasar 3C 286

    CERN Document Server

    Nagai, H; Paladino, R; Hull, C L H; Cortes, P; Moellenbrock, G; Fomalont, E; Asada, K; Hada, K

    2016-01-01

    We present full-polarization observations of the compact, steep-spectrum radio quasar 3C~286 made with the ALMA at 1.3~mm. These are the first full-polarization ALMA observations, which were obtained in the framework of Science Verification. A bright core and a south-west component are detected in the total intensity image, similar to previous centimeter images. Polarized emission is also detected toward both components. The fractional polarization of the core is about 17\\%, this is higher than the fractional polarization at centimeter wavelengths, suggesting that the magnetic field is even more ordered in the millimeter radio core than it is further downstream in the jet. The observed polarization position angle (or EVPA) in the core is $\\sim$\\,$39^{\\circ}$, which confirms the trend that the EVPA slowly increases from centimeter to millimeter wavelengths. With the aid of multi-frequency VLBI observations, we argue that this EVPA change is associated with the frequency-dependent core position. We also report ...

  6. ALMA Science Verification Data: Millimeter Continuum Polarimetry of the Bright Radio Quasar 3C 286

    Science.gov (United States)

    Nagai, H.; Nakanishi, K.; Paladino, R.; Hull, C. L. H.; Cortes, P.; Moellenbrock, G.; Fomalont, E.; Asada, K.; Hada, K.

    2016-06-01

    We present full-polarization observations of the compact, steep-spectrum radio quasar 3C 286 made with the Atacama Large Millimeter and Submillimeter Array (ALMA) at 1.3 mm. These are the first full-polarization ALMA observations, which were obtained in the framework of Science Verification. A bright core and a south–west component are detected in the total intensity image, similar to previous centimeter images. Polarized emission is also detected toward both components. The fractional polarization of the core is about 17%; this is higher than the fractional polarization at centimeter wavelengths, suggesting that the magnetic field is even more ordered in the millimeter radio core than it is further downstream in the jet. The observed polarization position angle (or electric vector position angle (EVPA)) in the core is ˜39◦, which confirms the trend that the EVPA slowly increases from centimeter to millimeter wavelengths. With the aid of multi-frequency VLBI observations, we argue that this EVPA change is associated with the frequency-dependent core position. We also report a serendipitous detection of a sub-mJy source in the field of view, which is likely to be a submillimeter galaxy.

  7. Interferometer observations of quasars from the Jodrell Bank 966-MHz survey

    International Nuclear Information System (INIS)

    Radio observations are reported of the 68 quasars with blue magnitudes < or =19.0 identified in the Jodrell Bank 966-MHz survey. The observations were made with the Green Bank interferometer at 2695 MHz with baselines ranging from 300 m to 35 km. Model brightness distributions are presented consisting of one to four elliptical Gaussian components. A limiting resolution of 0.1 arcsec was obtained in the best cases. For radio sources with steep spectra, angular sizes ranged from <0.2 to 85 arcsec. Only two of the sources with steep radio spectra were unresolved. The median angular size for the entire sample is 8 arcsec. For quasars larger than 10 arcsec, the structures can almost always be described in triple. Twenty-nine of the 30 such sources have outer lobes on either side of the optical source and 24 of the 30 have detectable central components. The ratio of the flux densities of the outer lobes varies over a wide range but has a median value of 1.8. The ratio of the flux density of the central component to the total flux density at 2695 MHz ranges from 1% to 95%, with a median value near 10%. The existence of triple structure in the vast majority of quasars, along the with failure to detect central components in blank field sources, suggests a close connection between the nuclear activity in the radio and optical regions of the spectrum. It is also consistent with a picture in which the difference between blank fields and quasars is just transient activity in the nucleus of a distant parent galaxy

  8. The Multi-Wavelength Quasar Survey Ⅳ. Quasars in the Leo Cluster

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    We aim to provide a quasar sample that is more complete than any previous surveys by using a combined selection technique to reduce the selection effects. Here we present the observational results for the X-ray candidates in the field of the Leo Cluster. We found 33 X-ray AGNs in this field of which 10 are new discoveries. The X-ray data and optical spectra of these AGNs are given. We also study the near-IR properties of the X-ray-selected AGNs by using the data from 2MASS. Most of the AGNs in our sample span the color range 0.0 < B- J < 2.5, 1.0 < J-Ks < 2.0 and 0.5 < H-Ks < 1.2.

  9. The SDSS-IV extended Baryonic Oscillation Spectroscopic Survey: Quasar Target Selection

    CERN Document Server

    Myers, Adam D; Prakash, Abhishek; Pâris, Isabelle; Yeche, Christophe; Dawson, Kyle S; Bovy, Jo; Lang, Dustin; Schlegel, David J; Newman, Jeffrey A; Petitjean, Patrick; Kneib, Jean Paul; Laurent, Pierre; Percival, Will J; Ross, Ashley J; Seo, Hee-Jong; Tinker, Jeremy L; Armengaud, Eric; Brownstein, Joel; Burtin, Etienne; Cai, Zheng; Comparat, Johan; Kasliwal, Mansi; Kulkarni, Shrinivas R; Laher, Russ; Levitan, David; McBride, Cameron K; McGreer, Ian D; Miller, Adam A; Nugent, Peter; Ofek, Eran; Rossi, Graziano; Ruan, John; Schneider, Donald P; Sesar, Branimir; Streblyanska, Alina; Surace, Jason

    2015-01-01

    As part of the SDSS-IV the extended Baryon Oscillation Spectroscopic Survey (eBOSS) will perform measurements of the cosmological distance scale via application of the Baryon Acoustic Oscillation (BAO) method to samples of quasars and galaxies. Quasar surveys are particularly useful in the BAO context as they can trace extremely large volumes back to moderately high redshift. eBOSS will adopt two approaches to target quasars over a 7500 sq. deg. area. First, z > 2.1 quasars will be targeted to improve BAO measurements in the Lyman-Alpha Forest. Second, a homogeneously selected "CORE" sample of quasars at 0.9 2.1 quasars. A supplemental selection based on variability of quasars in multi-epoch imaging from the Palomar Transient Factory should recover an additional ~3-4 per sq. deg. z > 2.1 quasars to g 500,000 new spectroscopically confirmed quasars and > 500,000 uniformly selected spectroscopically confirmed 0.9 < z < 2.2 quasars. At the conclusion of SDSS-IV, the SDSS will have provided unique spectra...

  10. The Discovery of Three New z>5 Quasars in the AGN and Galaxy Evolution Survey

    CERN Document Server

    Cool, R J; Brown, M J I; Dey, A; Eisenhardt, P R M; Eisenstein, D J; Elston, R J; Fan, X; González, A H; Green, R F; Jannuzi, B T; Kochanek, C S; McKenzie, E H; Rieke, G H; Rieke, M; Soifer, B T; Spinrad, H; Stern, D; Brand, Kate; Brown, Michael J. I.; Cool, Richard J.; Dey, Arjun; Eisenhardt, Peter R.; Eisenstein, Daniel J.; Elston, Richard J.; Fan, Xiaohui; Gonzalez, Anthony H.; Green, Richard F.; Jannuzi, Buell T.; Kenzie, Eric H. Mc; Kochanek, Christopher S.; Rieke, George H.; Rieke, Marcia; Soifer, Baruch T.; Spinrad, Hyron; Stern, Daniel

    2006-01-01

    We present the discovery of three z>5 quasars in the AGN and Galaxy Evolution Survey (AGES) spectroscopic observations of the NOAO Deep Wide-Field Survey (NDWFS) Bootes Field. These quasars were selected as part of a larger Spitzer mid-infrared quasar sample with no selection based on optical colors. The highest redshift object, NDWFS J142516.3+325409, z=5.85, is the lowest-luminosity z>5.8 quasar currently known. We compare mid-infrared techniques for identifying z>5 quasars to more traditional optical techniques and show that mid-infrared colors allow for selection of high-redshift quasars even at redshifts where quasars lie near the optical stellar locus and at z>7 where optical selection is impossible. Using the superb multi-wavelength coverage available in the NDWFS Bootes field, we construct the spectral energy distributions (SEDs) of high-redshift quasars from observed Bw-band to 24 microns (rest-frame 600 Angstroms - 3.7 microns). We show that the three high-redshift quasars have quite similar SEDs, a...

  11. The extended High A(V) Quasar Survey: Searching for dusty absorbers toward mid-infrared selected quasars

    CERN Document Server

    Krogager, J -K; Heintz, K E; Geier, S; Ledoux, C; Møller, P; Noterdaeme, P; Venemans, B P; Vestergaard, M

    2016-01-01

    We present the results of a new spectroscopic survey for dusty intervening absorption systems, particularly damped Ly$\\alpha$ absorbers (DLAs), towards reddened quasars. The candidate quasars are selected from mid-infrared photometry from the Wide-field Infrared Survey Explorer combined with optical and near-infrared photometry. Out of 1073 candidates, we secure low-resolution spectra for 108 using the Nordic Optical Telescope on La Palma, Spain. Based on the spectra, we are able to classify 100 of the 108 targets as quasars. A large fraction (50 %) is observed to have broad absorption lines (BALs). Moreover, we find 6 quasars with strange breaks in their spectra, which are not consistent with regular dust reddening. Using template fitting we infer the amount of reddening along each line of sight ranging from A(V)$\\approx$0.1 mag to 1.2 mag (assuming an SMC extinction curve). In four cases, the reddening is consistent with dust exhibiting the 2175{\\AA} feature caused by an intervening absorber, and for two of...

  12. Probabilistic Selection of High-redshfit Quasars with Subaru / Hyper Suprime-Cam Survey

    Science.gov (United States)

    Onoue, Masafusa

    2015-08-01

    High-redshift quasrs are an important probe of the distant Universe. They enable observational studies of the early growth of supermassive blackholes, cosmic reionization, chemical enrichment of host galaxies, and so on. We are now starting a new ground-breaking survey of high-redsfhit quasars (z>6) using the exquisite imaging data provided by the Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP) Survey. With the extremely wide-area coverage and high sensitivity thorugh five optical bands (1,400 deg2 to the depth of r~26 in Wide layer), it is one of the most powerful contemporary surveys that makes it possible for the HSC-AGN collaboration to increase the number of z>6 quasars by almost an order of magnitude, i.e., 300 at z~6 and 50 at z~7 based on the current estimate of the QLF at z>6 (Willott et al. 2010).One of the biggest challenges in the candidate selection is the significant contamination of Galactic brown dwarfs, which have the same point-like appearance as and similarly red colors to z>6 quasars. To overcome this issue, we have developed template SED fitting method optimized to high-redshift quasars selection for constructing the largest z>6 quasar sample with the HSC survey. Since 500 deg2 of the footprints of the HSC survey overlaps with the VISTA/VIKING survey, it is expected that z>6 quasars, with characteristic large Lyman break and flat red-continuum in its SED, can be separated out from contaminating sources by applying SED fitting with multi-wavelength photometric data. In practice, its application with 27 photometric bands to the COSMOS quasars at 36 quasar search with the first-year data products of the HSC survey, which results in extracting several promising candidates including one possible highest-redshift quasar at zphoto=7.3.

  13. First discoveries of z~6 quasars with the Kilo Degree Survey and VISTA Kilo-Degree Infrared Galaxy survey

    CERN Document Server

    Venemans, B P; Mwebaze, J; Valentijn, E A; Bañados, E; Decarli, R; de Jong, J T A; Findlay, J R; Kuijken, K H; La Barbera, F; McFarland, J P; McMahon, R G; Napolitano, N; Sikkema, G; Sutherland, W J

    2015-01-01

    We present the results of our first year of quasar search in the on-going ESO public Kilo Degree Survey (KiDS) and VISTA Kilo-Degree Infrared Galaxy (VIKING) surveys. These surveys go up to 2 magnitudes fainter than other wide-field imaging surveys that uncovered predominantly very luminous quasars at z~6. This allows us to probe a more common, fainter population of z~6 quasars. From this first set of combined survey catalogues covering ~250 deg^2 we selected point sources down to Z_AB=22 that had a very red i-Z (i-Z>2.2) colour. After follow-up imaging and spectroscopy, we discovered four new quasars in the redshift range 5.8quasars fainter than M^*, which at z=6 has been estimated to be between M^*=-25.1 and M^*=-27.6. The discovery of 4 quasars in 250 deg^2 of survey data is consistent with predictions based on the z~6 quasar luminosity function. We discuss variou...

  14. The Extended Baryon Oscillation Spectroscopic Survey: Variability Selection and Quasar Luminosity Function

    CERN Document Server

    Palanque-Delabrouille, N; Yèche, Ch; Pâris, I; Petitjean, P; Burtin, E; Dawson, K; McGreer, I; Myers, A D; Rossi, G; Schlegel, D; Schneider, D; Streblyanska, A; Tinker, J

    2015-01-01

    The SDSS-IV/eBOSS has an extensive quasar program that combines several selection methods. Among these, the photometric variability technique provides highly uniform samples, unaffected by the redshift bias of traditional optical-color selections, when $z= 2.7 - 3.5$ quasars cross the stellar locus or when host galaxy light affects quasar colors at $z 2.2$. Both models are constrained to be continuous at $z=2.2$. They present a flattening of the bright-end slope at large redshift. The LEDE model indicates a reduction of the break density with increasing redshift, but the evolution of the break magnitude depends on the parameterization. The models are in excellent accord, predicting quasar counts that agree within 0.3\\% (resp., 1.1\\%) to $g<22.5$ (resp., $g<23$). The models are also in good agreement over the entire redshift range with models from previous studies.

  15. The SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Quasar Target Selection

    OpenAIRE

    Myers, Adam D.; Palanque-Delabrouille, Nathalie; Prakash, Abhishek; Pâris, Isabelle; Yeche, Christophe,; Dawson, Kyle S.; Bovy, Jo; Lang, Dustin; Schlegel, David J.; Newman, Jeffrey A.; Petitjean, Patrick; Kneib, Jean Paul; Laurent, Pierre; Percival, Will J.; Ross, Ashley J.

    2015-01-01

    As part of the Sloan Digital Sky Survey IV the extended Baryon Oscillation Spectroscopic Survey (eBOSS) will improve measurements of the cosmological distance scale by applying the Baryon Acoustic Oscillation (BAO) method to quasar samples. eBOSS will adopt two approaches to target quasars over 7500 sq. deg. First, a "CORE" quasar sample will combine optical selection in ugriz using a likelihood-based routine called XDQSOz, with a mid-IR-optical color-cut. eBOSS CORE selection (to g < 22 OR r...

  16. The Pittsburgh Sloan Digital Sky Survey Mg II Quasar Absorption-line Survey Catalog

    Science.gov (United States)

    Quider, Anna M.; Nestor, Daniel B.; Turnshek, David A.; Rao, Sandhya M.; Monier, Eric M.; Weyant, Anja N.; Busche, Joseph R.

    2011-04-01

    We present a catalog of intervening Mg II quasar absorption-line systems in the redshift interval 0.36 <= z <= 2.28. The catalog was built from Sloan Digital Sky Survey Data Release Four (SDSS DR4) quasar spectra. Currently, the catalog contains ~17, 000 measured Mg II doublets. We also present data on the ~44, 600 quasar spectra which were searched to construct the catalog, including redshift and magnitude information, continuum-normalized spectra, and corresponding arrays of redshift-dependent minimum rest equivalent widths detectable at our confidence threshold. The catalog is available online. A careful second search of 500 random spectra indicated that, for every 100 spectra searched, approximately one significant Mg II system was accidentally rejected. Current plans to expand the catalog beyond DR4 quasars are discussed. Many Mg II absorbers are known to be associated with galaxies. Therefore, the combination of large size and well understood statistics makes this catalog ideal for precision studies of the low-ionization and neutral gas regions associated with galaxies at low to moderate redshift. An analysis of the statistics of Mg II absorbers using this catalog will be presented in a subsequent paper.

  17. The radio structure of a sample of 101 quasars from the Parkes +- 40 survey

    International Nuclear Information System (INIS)

    Long-baseline interferometers at Jodrell Bank have been used to investigate the radio structure of 101 quasar candidates from the Parkes 2700-MHz survey of the +- 40 declination zone. These observations show that quasars with flat or inverted radio spectra have radio structures which are smaller than 0.1 arcsec. The steep-spectrum quasars from the Parkes sample are more extended, and have a distribution of angular sizes similar to that of quasars of the same spectral type identified from the lower-frequency 4C catalogue. All 10 of the quasars with concave spectra have radio emission from the vicinity of the optical nucleus, usually from regions smaller than 0.1 arcsec. (author)

  18. A Spectroscopic Survey of WISE-selected Obscured Quasars with the Southern African Large Telescope

    CERN Document Server

    Hainline, Kevin N; Carroll, Christopher M; Myers, Adam D; DiPompeo, Michael A; Trouille, Laura

    2014-01-01

    We present the results of an optical spectroscopic survey of a sample of 40 candidate obscured quasars identified on the basis of their mid-infrared emission detected by the Wide-Field Infrared Survey Explorer (WISE). Optical spectra for this survey were obtained using the Robert Stobie Spectrograph (RSS) on the Southern African Large Telescope (SALT). Our sample was selected with WISE colors characteristic of AGNs, as well as red optical to mid-IR colors indicating that the optical/UV AGN continuum is obscured by dust. We obtain secure redshifts for the majority of the objects that comprise our sample (35/40), and find that sources that are bright in the WISE W4 (22$\\mu$m) band are typically at moderate redshift ( = 0.35$) while sources fainter in W4 are at higher redshifts ( = 0.73$). The majority of the sources have narrow emission lines, with optical colors and emission line ratios of our WISE-selected sources that are consistent with the locus of AGN on the rest-frame $g-z$ color vs. [NeIII]$\\lambda$3869...

  19. PHOTOMETRIC REDSHIFTS FOR QUASARS IN MULTI-BAND SURVEYS

    International Nuclear Information System (INIS)

    The Multi Layer Perceptron with Quasi Newton Algorithm (MLPQNA) is a machine learning method that can be used to cope with regression and classification problems on complex and massive data sets. In this paper, we give a formal description of the method and present the results of its application to the evaluation of photometric redshifts for quasars. The data set used for the experiment was obtained by merging four different surveys (Sloan Digital Sky Survey, GALEX, UKIDSS, and WISE), thus covering a wide range of wavelengths from the UV to the mid-infrared. The method is able (1) to achieve a very high accuracy, (2) to drastically reduce the number of outliers and catastrophic objects, and (3) to discriminate among parameters (or features) on the basis of their significance, so that the number of features used for training and analysis can be optimized in order to reduce both the computational demands and the effects of degeneracy. The best experiment, which makes use of a selected combination of parameters drawn from the four surveys, leads, in terms of Δznorm (i.e., (zspec – zphot)/(1 + zspec)), to an average of Δznorm = 0.004, a standard deviation of σ = 0.069, and a median absolute deviation, MAD = 0.02, over the whole redshift range (i.e., zspec ≤ 3.6), defined by the four-survey cross-matched spectroscopic sample. The fraction of catastrophic outliers, i.e., of objects with photo-z deviating more than 2σ from the spectroscopic value, is <3%, leading to σ = 0.035 after their removal, over the same redshift range. The method is made available to the community through the DAMEWARE Web application

  20. Probabilistic Selection of High-redshift Quasars with Subaru/Hyper Suprime-Cam Survey

    Science.gov (United States)

    Onoue, Masafusa

    High-redshift quasars are an important probe of the distant Universe. They enable observational studies of the early growth of supermassive blackholes, cosmic reionization, chemical enrichment of host galaxies, and so on. Through pioneering optical and near-infrared wide-area surveys such as the SDSS and the VIKING Survey, about one hundred quasars have been found at z > 6 (e.g., Fan et al. (2006b), Venemans et al. (2013)). However, its current small sample size and the fact that most of them are the most luminous (M 1450 6 quasars, especially low-luminous or z > 7 quasars, is highly desired for further understanding of the early universe. We are now starting a new ground-breaking survey of high-redshift (z > 6) quasars using the exquisite imaging data provided by the Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP) Survey. Thanks to its extremely wide coverage and its high sensitivity thorough five optical bands (1,400 deg2 to the depth of r ~ 26 in HSC-Wide layer), it is one of the most powerful contemporary surveys that makes it possible for us to increase the number of z > 6 quasars by almost an order of magnitude, i.e., 300 at z ~ 6 and 50 at z ~ 7, based on the current estimate of the QLF at z > 6 by Willott et al. (2010b). One of the biggest challenges in z > 6 quasar candidate selection is contamination of Galactic brown dwarfs, which have the same point-like appearance as and similarly red colors to the quasars. To overcome this issue and maximize the selection efficiency, we apply a double-layered approach to the HSC survey products, namely combination of two probabilistic selections: SED-fitting and Bayesian selection. In particular, we have developed a template SED fitting method optimized to high-redshift quasars selection. Its application with 27 photometric bands to the COSMOS quasars at 3 6 quasar selection, and it is expected that the first HSC quasar discovery will be in the near future.

  1. BINARY QUASARS IN THE SLOAN DIGITAL SKY SURVEY: EVIDENCE FOR EXCESS CLUSTERING ON SMALL SCALES

    Energy Technology Data Exchange (ETDEWEB)

    Hennawi, J F; Strauss, M A; Oguri, M; Inada, N; Richards, G T; Pindor, B; Schneider, D P; Becker, R H; Gregg, M D; Hall, P B; Johnston, D E; Fan, X; Burles, S; Schlegel, D J; Gunn, J E; Lupton, R; Bahcall, N A; Brunner, R J; Brinkman, J

    2005-11-10

    We present a sample of 218 new quasar pairs with proper transverse separations R{sub prop} < 1 h{sup -1} Mpc over the redshift range 0.5 < z < 3.0, discovered from an extensive follow up campaign to find companions around the Sloan Digital Sky Survey and 2dF Quasar Redshift Survey quasars. This sample includes 26 new binary quasars with separations R{sub prop} < 50 h{sup -1} kpc ({theta} < 10''), more than doubling the number of such systems known. We define a statistical sample of binaries selected with homogeneous criteria and compute its selection function, taking into account sources of incompleteness. The first measurement of the quasar correlation function on scales 10 h{sup -1} kpc < R{sub prop} < 400 h{sup -1} kpc is presented. For R{sub prop} {approx}< 40 h{sup -1} kpc, we detect an order of magnitude excess clustering over the expectation from the large scale (R{sub prop} {approx}> 3 h{sup -1} Mpc) quasar correlation function, extrapolated down as a power law to the separations probed by our binaries. The excess grows to {approx}30 at R{sub prop} {approx} 10 h{sup -1} kpc, and provides compelling evidence that the quasar autocorrelation function gets progressively steeper on sub-Mpc scales. This small scale excess can likely be attributed to dissipative interaction events which trigger quasar activity in rich environments. Recent small scale measurements of galaxy clustering and quasar-galaxy clustering are reviewed and discussed in relation to our measurement of small scale quasar clustering.

  2. Photometric Redshifts for Quasars in Multi-band Surveys

    Science.gov (United States)

    Brescia, M.; Cavuoti, S.; D'Abrusco, R.; Longo, G.; Mercurio, A.

    2013-08-01

    The Multi Layer Perceptron with Quasi Newton Algorithm (MLPQNA) is a machine learning method that can be used to cope with regression and classification problems on complex and massive data sets. In this paper, we give a formal description of the method and present the results of its application to the evaluation of photometric redshifts for quasars. The data set used for the experiment was obtained by merging four different surveys (Sloan Digital Sky Survey, GALEX, UKIDSS, and WISE), thus covering a wide range of wavelengths from the UV to the mid-infrared. The method is able (1) to achieve a very high accuracy, (2) to drastically reduce the number of outliers and catastrophic objects, and (3) to discriminate among parameters (or features) on the basis of their significance, so that the number of features used for training and analysis can be optimized in order to reduce both the computational demands and the effects of degeneracy. The best experiment, which makes use of a selected combination of parameters drawn from the four surveys, leads, in terms of Δz norm (i.e., (z spec - z phot)/(1 + z spec)), to an average of Δz norm = 0.004, a standard deviation of σ = 0.069, and a median absolute deviation, MAD = 0.02, over the whole redshift range (i.e., z spec objects with photo-z deviating more than 2σ from the spectroscopic value, is <3%, leading to σ = 0.035 after their removal, over the same redshift range. The method is made available to the community through the DAMEWARE Web application.

  3. Dust and gas obscuration in ELAIS Deep X-ray Survey reddened quasars

    CERN Document Server

    Willott, C J; Almaini, O; Johnson, O; Lawrence, A; Dunlop, J S; Roche, N D; Mann, R G; Manners, J C; González-Solares, E A; Pérez-Fournon, I; Ivison, R J; Serjeant, S; Oliver, S J; McMahon, R G; Rowan-Robinson, M; Willott, Chris J.; Simpson, Chris; Almaini, Omar; Johnson, Olivia; Lawrence, Andrew; Dunlop, James S.; Roche, Nathan D.; Mann, Robert G.; Manners, James C.; Gonzalez-Solares, Eduardo; Perez-Fournon, Ismael; Ivison, Rob J.; Serjeant, Stephen; Oliver, Seb J.; Mahon, Richard G. Mc; Rowan-Robinson, Michael

    2004-01-01

    Hard X-ray surveys have uncovered a large population of heavily obscured AGN. They also reveal a population of quasars with moderate obscuration at both visible and X-ray wavelengths. We use Chandra selected samples of quasars from the ELAIS Deep X-ray Survey (EDXS) and CDF-N to investigate the obscuration towards the nuclei of moderately obscured AGN. We find an inverse correlation between the optical to X-ray flux ratio and the X-ray hardness ratio which can be interpreted as due to obscuration at visible and X-ray wavelengths. We present detailed optical and near-infrared data for a sample of optically-faint (R>23) quasars from the EDXS. These are used to constrain the amount of rest-frame UV/optical reddening towards these quasars. It is found that optically-faint quasars are mostly faint due to obscuration, not because they are intrinsically weak. After correcting for reddening, the optical magnitudes of most of these quasars are similar to the brighter quasars at these X-ray fluxes. Combining with gas c...

  4. An Empirical Calibration of the Completeness of the SDSS Quasar Survey

    CERN Document Server

    Vanden Berk, Daniel E; Richards, G T; Hall, P B; Strauss, M A; Brunner, R J; Fan, X; Baldry, I K; York, D G; Gunn, J E; Nichol, R C; Meiksin, A; Brinkmann, J; Berk, Daniel E. Vanden; Schneider, Donald P.; Richards, Gordon T.; Hall, Patrick B.; Strauss, Michael A.; Brunner, Robert; Fan, Xiaohui; Baldry, Ivan K.; York, Donald G.; Gunn, James E.; Nichol, Robert C.; Meiksin, Avery; Brinkmann, Jon

    2005-01-01

    Spectra of nearly 20000 point-like objects to a Galactic reddening corrected magnitude of i=19.1 have been obtained to test the completeness of the SDSS quasar survey. The spatially-unresolved objects were selected from all regions of color space, sparsely sampled from within a 278 sq. deg. area of sky covered by this study. Only ten quasars were identified that were not targeted as candidates by the SDSS quasar survey (including both color and radio source selection). The inferred density of unresolved quasars on the sky that are missed by the SDSS algorithm is 0.44 per sq. deg, compared to 8.28 per sq. deg. for the selected quasar density, giving a completeness of 94.9(+2.6,-3.8) to the limiting magnitude. Omitting radio selection reduces the color-only selection completeness by about 1%. Of the ten newly identified quasars, three have detected broad absorption line systems, six are significantly redder than other quasars at the same redshift, and four have redshifts between 2.7 and 3.0 (the redshift range ...

  5. Photometric redshifts for Quasars in multi band Surveys

    CERN Document Server

    Brescia, M; D'Abrusco, R; Longo, G; Mercurio, A

    2013-01-01

    MLPQNA stands for Multi Layer Perceptron with Quasi Newton Algorithm and it is a machine learning method which can be used to cope with regression and classification problems on complex and massive data sets. In this paper we give the formal description of the method and present the results of its application to the evaluation of photometric redshifts for quasars. The data set used for the experiment was obtained by merging four different surveys (SDSS, GALEX, UKIDSS and WISE), thus covering a wide range of wavelengths from the UV to the mid-infrared. The method is able i) to achieve a very high accuracy; ii) to drastically reduce the number of outliers and catastrophic objects; iii) to discriminate among parameters (or features) on the basis of their significance, so that the number of features used for training and analysis can be optimized in order to reduce both the computational demands and the effects of degeneracy. The best experiment, which makes use of a selected combination of parameters drawn from ...

  6. Nitrogen Enriched Quasars in the Sloan Digital Sky Survey First Data Release

    CERN Document Server

    Bentz, M C; Osmer, P S; Bentz, Misty C.; Hall, Patrick B.; Osmer, Patrick S.

    2004-01-01

    The quasar Q0353-383 has long been known to have extremely strong nitrogen intercombination lines at 1486 and 1750 Angstroms, implying an anomalously high nitrogen abundance of ~15 times solar. A search for similar nitrogen-rich quasars in the Sloan Digital Sky Survey First Data Release catalog has yielded 20 candidates, including four with nitrogen emission as strong or stronger than that seen in Q0353-383. Our results indicate that only about 1 in 1700 of quasars have nitrogen abundances similar to Q0353-383, while up to 1 in 140 may be in the process of extreme nitrogen enrichment.

  7. Nitrogen Enriched Quasars in the Sloan Digital Sky Survey First Data Release

    OpenAIRE

    Bentz, Misty C.; Hall, Patrick B.; Osmer, Patrick S.

    2004-01-01

    The quasar Q0353-383 has long been known to have extremely strong nitrogen intercombination lines at 1486 and 1750 Angstroms, implying an anomalously high nitrogen abundance of ~15 times solar. A search for similar nitrogen-rich quasars in the Sloan Digital Sky Survey First Data Release catalog has yielded 20 candidates, including four with nitrogen emission as strong or stronger than that seen in Q0353-383. Our results indicate that only about 1 in 1700 of quasars have nitrogen abundances si...

  8. The Pan-STARRS1 distant z>5.6 quasar survey: more than 100 quasars within the first Gyr of the universe

    CERN Document Server

    Bañados, E; Decarli, R; Farina, E P; Mazzucchelli, C; Walter, F; Fan, X; Stern, D; Schlafly, E; Chambers, K C; Rix, H-W; Jiang, L; McGreer, I; Simcoe, R; Wang, F; Yang, J; Morganson, E; De Rosa, G; Greiner, J; Baloković, M; Burgett, W S; Cooper, T; Draper, P W; Flewelling, H; Hodapp, K W; Jun, H D; Kaiser, N; Kudritzki, R -P; Magnier, E A; Metcalfe, N; Miller, D; Schindler, J -T; Tonry, J L; Wainscoat, R J; Waters, C; Yang, Q

    2016-01-01

    Luminous quasars at z>5.6 can be studied in detail with the current generation of telescopes and provide us with unique information on the first gigayear of the universe. Thus far these studies have been statistically limited by the number of quasars known at these redshifts. Such quasars are rare and therefore wide-field surveys are required to identify them and multiwavelength data are needed to separate them efficiently from their main contaminants, the far more numerous cool dwarfs. In this paper, we update and extend the selection for z~6 quasars presented in Banados et al. (2014) using the Pan-STARRS1 (PS1) survey. We present the PS1 distant quasar sample, which currently consists of 124 quasars in the redshift range 5.65.6 presented in this work almost double the quasars previously known at these redshifts, marking a transition phase from studies of individual sources to statistical studies of the high-redshift quasar population, which was impossible with earlier, smaller samples.

  9. An X-Shooter composite of bright 1 < z < 2 quasars from UV to infrared

    Science.gov (United States)

    Selsing, J.; Fynbo, J. P. U.; Christensen, L.; Krogager, J.-K.

    2016-01-01

    Quasi-stellar object (QSO) spectral templates are important both to QSO physics and for investigations that use QSOs as probes of intervening gas and dust. However, combinations of various QSO samples obtained at different times and with different instruments so as to expand a composite and to cover a wider rest frame wavelength region may create systematic effects, and the contribution from QSO hosts may contaminate the composite. We have constructed a composite spectrum from luminous blue QSOs at 1 github.com/jselsing/QuasarComposite

  10. The 2dF-SDSS LRG and QSO Survey: The z<2.1 Quasar Luminosity Function from 5645 Quasars to g=21.85

    CERN Document Server

    Richards, G T; Anderson, S F; Bland-Hawthorn, J; Boyle, B J; De Propris, R; Drinkwater, M J; Fan, X; Gunn, J E; Ivezic, Z; Jester, S; Loveday, J; Meiksin, A; Miller, L; Myers, A; Nichol, R C; Outram, P J; Pimbblet, K A; Roseboom, I G; Ross, N; Schneider, D P; Shanks, T; Sharp, R G; Stoughton, C; Strauss, M A; Szalay, A S; Vanden Berk, Daniel E; York, D G

    2005-01-01

    We have used the 2dF instrument on the AAT to obtain redshifts of a sample of z21 deep surveys. The 2SLAQ data exhibit no well defined ``break'' but do clearly flatten with increasing magnitude. The shape of the quasar luminosity function derived from 2SLAQ is in good agreement with that derived from type I quasars found in hard X-ray surveys. [Abridged

  11. Multiwavelength polarization observations of the γ-ray bright quasar PKS 0420-014

    Directory of Open Access Journals (Sweden)

    Troitskiy I.S.

    2013-12-01

    Full Text Available We analyze total and polarized intensity images of the quasar PKS 0420-014 obtained monthly with the VLBA at 43 GHz during 2008–2012 along with γ-ray data provided by the Fermi Large Area Telescope and multi-color photometric and polarimetric measurements collected by different optical telescopes. During this period the quasar underwent a number of optical flares, which were accompanied by rapid rotation of polarization angle, an increase of activity in γ-rays, and the appearance of new superluminal knots in the parsec-scale jet. We investigate the fine structure of the flares at different wavelengths and in polarized light, and determine kinematic parameters of the knots. We compare the rapid evolution of the optical polarization with the polarization of the VLBI core and knots. We interpret the multi-wavelength behavior within a model that places the blazar “dissipation zone” at the millimeter-wave core of the parsec-scale jet.

  12. High-Redshift Quasars Found in Sloan Digital Sky Survey Commissioning Data VI. Sloan Digital Sky Survey Spectrograph Observations

    CERN Document Server

    Anderson, S F; Richards, G T; Schneider, D P; Strauss, M A; Vanden Berk, Daniel E; Gunn, J E; Anderson, Scott F.; Fan, Xiaohui; Richards, Gordon T.; Schneider, Donald P.; Strauss, Michael A.; Berk, Daniel E. Vanden; Gunn, James E.

    2001-01-01

    We present results on over 100 high-redshift quasars found in the Sloan Digital Sky Survey (SDSS), using automated selection algorithms applied to SDSS imaging data and with spectroscopic confirmation obtained during routine spectroscopic operations of the Sloan 2.5-m telescope. The SDSS spectra cover the wavelength range 3900--9200 Angstroms at a spectral resolution of 1800, and have been obtained for 116 quasars with redshifts greater than 3.94; 92 of these objects were previously uncataloged, significantly increasing the current tally of published z>4 quasars. The paper also reports observations of five additional new z>4.6 quasars; all were found from the SDSS imaging survey and spectroscopically confirmed with data from the Apache Point Observatory's 3.5-m telescope. The i' magnitudes of the quasars range from 18.03 to 20.56. Of the 97 new objects in this paper, 13 are Broad Absorption Line quasars. Five quasars, including one object at a redshift of 5.11, have 20 cm peak flux densities greater than 1 mJ...

  13. The Sloan Digital Sky Survey Reverberation Mapping Project: Velocity Shifts of Quasar Emission Lines

    CERN Document Server

    Shen, Yue; Denney, Kelly D; Greene, Jenny E; Grier, C J; Ho, Luis C; Peterson, Bradley M; Petitjean, Patrick; Richards, Gordon T; Schneider, Donald P; Tao, Charling; Trump, Jonathan R

    2016-01-01

    Quasar emission lines are often shifted from the systemic velocity due to various dynamical and radiative processes in the line-emitting region. The level of these velocity shifts depends both on the line species and on quasar properties. We study velocity shifts for the line peaks of various narrow and broad quasar emission lines relative to systemic using a sample of 849 quasars from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project. The coadded (from 32 epochs) spectra of individual quasars have sufficient signal-to-noise ratio (SNR) to measure stellar absorption lines to provide reliable systemic velocity estimates, as well as weak narrow emission lines. The sample also covers a large dynamic range in quasar luminosity (~2 dex), allowing us to explore potential luminosity dependence of the velocity shifts. We derive average line peak velocity shifts as a function of quasar luminosity for different lines, and quantify their intrinsic scatter. We further quantify how well the peak velocit...

  14. SDSS J0246-0825: A New Gravitationally Lensed Quasar from the Sloan Digital Sky Survey

    Energy Technology Data Exchange (ETDEWEB)

    Inada, N; Burles, S; Gregg, M D; Becker, R H; Schechter, P L; Eisenstein, D J; Oguri, M; Castander, F J; Hall, P B; Johnston, D E; Pindor, B; Richards, G T; Schneider, D P; White, R L; Brinkmann, J; Szalay, A; York, D G

    2005-11-10

    We report the discovery of a new two-image gravitationally lensed quasar, SDSS J024634.11-082536.2 (SDSS J0246-0825). This object was selected as a lensed quasar candidate from the Sloan Digital Sky Survey (SDSS) by the same algorithm that was used to discover other SDSS lensed quasars (e.g., SDSS J0924+0219). Multicolor imaging with the Magellan Consortium's Walter Baade 6.5-m telescope and the spectroscopic observations using the W. M. Keck Observatory's Keck II telescope confirm that SDSS J0246-0825 consists of two lensed images ({Delta}{theta} = 1''.04) of a source quasar at z = 1.68. Imaging observations with the Keck telescope and the Hubble Space Telescope reveal an extended object between the two quasar components, which is likely to be a lensing galaxy of this system. From the absorption lines in the spectra of quasar components and the apparent magnitude of the galaxy, combined with the expected absolute magnitude from the Faber-Jackson relation, we estimate the redshift of the lensing galaxy to be z = 0.724. A highly distorted ring is visible in the Hubble Space Telescope images, which is likely to be the lensed host galaxy of the source quasar. Simple mass modeling predicts the possibility that there is a small (faint) lensing object near the primary lensing galaxy.

  15. THE SDSS-III BARYON OSCILLATION SPECTROSCOPIC SURVEY: THE QUASAR LUMINOSITY FUNCTION FROM DATA RELEASE NINE

    Energy Technology Data Exchange (ETDEWEB)

    Ross, Nicholas P.; White, Martin; Bailey, Stephen [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 92420 (United States); McGreer, Ian D. [Steward Observatory, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Richards, Gordon T. [Department of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Myers, Adam D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Palanque-Delabrouille, Nathalie; Yeche, Christophe [CEA, Centre de Saclay, IRFU, F-91191 Gif-sur-Yvette (France); Strauss, Michael A. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Anderson, Scott F. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Shen, Yue; Swanson, Molly E. C. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Brandt, W. N. [Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States); Aubourg, Eric [APC, University of Paris Diderot, CNRS/IN2P3, CEA/IRFU, Observatoire de Paris, Sorbonne Paris Cite (France); Bizyaev, Dmitry; Brewington, Howard; Brinkmann, J. [Apache Point Observatory, P.O. Box 59, Sunspot, NM 88349-0059 (United States); Bovy, Jo [Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States); DeGraf, Colin; Di Matteo, Tiziana, E-mail: npross@lbl.gov [McWilliams Center for Cosmology, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); and others

    2013-08-10

    We present a new measurement of the optical quasar luminosity function (QLF), using data from the Sloan Digital Sky Survey-III: Baryon Oscillation Spectroscopic Survey (SDSS-III: BOSS). From the SDSS-III Data Release Nine, a uniform sample of 22,301 i {approx}< 21.8 quasars are selected over an area of 2236 deg{sup 2}, with confirmed spectroscopic redshifts between 2.2 < z < 3.5, filling in a key part of the luminosity-redshift plane for optical quasar studies. The completeness of the survey is derived through simulated quasar photometry, and this completeness estimate is checked using a sample of quasars selected by their photometric variability within the BOSS footprint. We investigate the level of systematics associated with our quasar sample using the simulations, in the process generating color-redshift relations and a new quasar K-correction. We probe the faint end of the QLF to M{sub i} (z = 2.2) Almost-Equal-To -24.5 and see a clear break in the QLF at all redshifts up to z = 3.5. A log-linear relation (in log {Phi}* - M*) for a luminosity evolution and density evolution model is found to adequately describe our data within the range 2.2 < z < 3.5; across this interval the break luminosity increases by a factor of {approx}2.6 while {Phi}* declines by a factor of {approx}8. At z {approx}< 2.2 our data are reasonably well fit by a pure luminosity evolution model, and only a weak signature of ''AGN downsizing'' is seen, in line with recent studies of the hard X-ray luminosity function. We compare our measured QLF to a number of theoretical models and find that models making a variety of assumptions about quasar triggering and halo occupation can fit our data over a wide range of redshifts and luminosities.

  16. A ROSAT Bright Source Catalog Survey with the Swift Satellite

    CERN Document Server

    Fox, D B

    2004-01-01

    We consider the prospects for a complete survey of the 18,811 sources of the ROSAT All-Sky Survey Bright Source Catalog (BSC) with NASA's Swift gamma-ray burst (GRB) mission. By observing each BSC source for 500 s with the satellite's imaging X-ray and UV/optical telescopes, this "Swift Bright (Source) Catalog Survey" (Swift-BCS) would derive ~20 mCrab, 10-100 keV) with the wide-field Burst Alert Telescope (BAT); and a two-year all-sky BAT survey down to >~1 mCrab. The resulting expansion of the catalog of identified X-ray sources from 2000 to 18,000 will provide a greatly-enriched set of targets for observation by XMM-Newton, Chandra, and future high-energy observatories.

  17. Revisiting the Completeness and the Luminosity Function in High-Redshift Low-Luminosity Quasar Surveys

    CERN Document Server

    Niida, Mana; Ikeda, Hiroyuki; Matsuoka, Kenta; Kobayashi, Masakazu A R; Toba, Yoshiki; Taniguchi, Yoshiaki

    2016-01-01

    Recent studies have derived quasar luminosity functions (QLFs) at various redshifts. However, the faint side of the QLF at high redshifts is still too uncertain. An accurate estimate of the survey completeness is essential to derive an accurate QLF for use in studying the luminosity-dependent density evolution of the quasar population. Here we investigate how the luminosity dependence of quasar spectra (the Baldwin effect) and the attenuation model for the inter-galactic medium (IGM) affect the completeness estimates. For this purpose, we revisit the completeness of quasar surveys specifically at $z\\sim4-5$, using the COSMOS images observed with Subaru/Suprime-Cam. As the result, we find that the completeness estimates are sensitive to the luminosity dependence of the quasar spectrum and difference in the IGM attenuation models. At $z\\sim4$, the number density of quasars when we adopt the latest IGM model and take the luminosity dependence of spectra into account are $(3.49\\pm1.62)\\times10^{-7}$ Mpc$^{-3}$ ma...

  18. The Sloan Digital Sky Survey Quasar Catalog V. Seventh Data Release

    CERN Document Server

    Schneider, Donald P; Hall, Patrick B; Strauss, Michael A; Anderson, Scott F; Boroson, Todd A; Ross, Nicholas P; Shen, Yue; Brandt, W N; Fan, Xiaohui; Inada, Naohisa; Jester, Sebastian; Knapp, G R; Krawczyk, Coleman M; Thakar, Anirudda R; Berk, Daniel E Vanden; Voges, Wolfgang; Yanny, Brian; York, Donald G; Bahcall, Neta A; Bizyaev, Dmitry; Blanton, Michael R; Brewington, Howard; Brinkmann, J; Eisenstein, Daniel; Frieman, Joshua A; Fukugita, Masataka; Gray, Jim; Gunn, James E; Hibon, Pascale; Ivezic, Zeljko; Kent, Stephen M; Kron, Richard G; Lee, Myung Gyoon; Lupton, Robert H; Malanushenko, Elena; Malanushenko, Viktor; Oravetz, Dan; Pan, K; Pier, Jeffrey R; Price, Ted N; Saxe, David H; Schlegel, David J; Simmons, Audry; Snedden, Stephanie A; SubbaRao, Mark U; Szalay, Alexander S; Weinberg, David H

    2010-01-01

    We present the fifth edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog, which is based upon the SDSS Seventh Data Release. The catalog, which contains 105,783 spectroscopically confirmed quasars, represents the conclusion of the SDSS-I and SDSS-II quasar survey. The catalog consists of the SDSS objects that have luminosities larger than M_i = -22.0 (in a cosmology with H_0 = 70 km/s/Mpc Omega_M = 0.3, and Omega_Lambda = 0.7) have at least one emission line with FWHM larger than 1000 km/s or have interesting/complex absorption features, are fainter than i > 15.0 and have highly reliable redshifts. The catalog covers an area of 9380 deg^2. The quasar redshifts range from 0.065 to 5.46, with a median value of 1.49; the catalog includes 1248 quasars at redshifts greater than four, of which 56 are at redshifts greater than five. The catalog contains 9210 quasars with i < 18; slightly over half of the entries have i< 19. For each object the catalog presents positions accurate to better than 0.1" r...

  19. Close companions to two high-redshift quasars

    Energy Technology Data Exchange (ETDEWEB)

    McGreer, Ian D.; Fan, Xiaohui; Bian, Fuyan [Steward Observatory, The University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721-0065 (United States); Strauss, Michael A. [Princeton University Observatory, Peyton Hall, Princeton, NJ 08544 (United States); Haiman, Zoltàn [Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Richards, Gordon T. [Department of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Jiang, Linhua [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States); Schneider, Donald P., E-mail: imcgreer@as.arizona.edu [Department of Astronomy and Astrophysics and the Institute for Gravitation and the Cosmos, The Pennsylvania State University, University Park, PA 16802 (United States)

    2014-10-01

    We report the serendipitous discoveries of companion galaxies to two high-redshift quasars. SDSS J025617.7+001904 is a z = 4.79 quasar included in our recent survey of faint quasars in the SDSS Stripe 82 region. The initial MMT slit spectroscopy shows excess Lyα emission extending well beyond the quasar's light profile. Further imaging and spectroscopy with LBT/MODS1 confirms the presence of a bright galaxy (i {sub AB} = 23.6) located 2'' (12 kpc projected) from the quasar with strong Lyα emission (EW{sub 0} ≈ 100 Å) at the redshift of the quasar, as well as faint continuum. The second quasar, CFHQS J005006.6+344522 (z = 6.25), is included in our recent HST SNAP survey of z ∼ 6 quasars searching for evidence of gravitational lensing. Deep imaging with ACS and WFC3 confirms an optical dropout ∼4.5 mag fainter than the quasar (Y {sub AB} = 25) at a separation of 0.''9. The red i {sub 775} – Y {sub 105} color of the galaxy and its proximity to the quasar (5 kpc projected if at the quasar redshift) strongly favor an association with the quasar. Although it is much fainter than the quasar, it is remarkably bright when compared to field galaxies at this redshift, while showing no evidence for lensing. Both systems may represent late-stage mergers of two massive galaxies, with the observed light for one dominated by powerful ongoing star formation and for the other by rapid black hole growth. Observations of close companions are rare; if major mergers are primarily responsible for high-redshift quasar fueling then the phase when progenitor galaxies can be observed as bright companions is relatively short.

  20. Efficient Photometric Selection of Quasars from the Sloan Digital Sky Survey: 100,000 z<3 Quasars from Data Release One

    CERN Document Server

    Richards, G T; Gray, A G; Brunner, R J; Lupton, R H; Vanden Berk, Daniel E; Chong, S S; Weinstein, M A; Schneider, D P; Anderson, S F; Munn, J A; Harris, H C; Strauss, M A; Fan, X; Gunn, J E; Ivezic, Z; York, D G; Brinkmann, J; Richards, Gordon T.; Nichol, Robert C.; Gray, Alexander G.; Brunner, Robert J.; Lupton, Robert H.; Berk, Daniel E. Vanden; Chong, Shang Shan; Weinstein, Michael A.; Schneider, Donald P.; Anderson, Scott F.; Munn, Jeffrey A.; Harris, Hugh C.; Strauss, Michael A.; Fan, Xiaohui; Gunn, James E.; Ivezic, Zeljko; York, Donald G.

    2004-01-01

    We present a catalog of 100,563 unresolved, UV-excess (UVX) quasar candidates to g=21 from 2099 deg^2 of the Sloan Digital Sky Survey (SDSS) Data Release One (DR1) imaging data. Existing spectra of 22,737 sources reveals that 22,191 (97.6%) are quasars; accounting for the magnitude dependence of this efficiency, we estimate that 95,502 (95.0%) of the objects in the catalog are quasars. Such a high efficiency is unprecedented in broad-band surveys of quasars. This ``proof-of-concept'' sample is designed to be maximally efficient, but still has 94.7% completeness to unresolved, g<~19.5, UVX quasars from the DR1 quasar catalog. This efficient and complete selection is the result of our application of a probability density type analysis to training sets that describe the 4-D color distribution of stars and spectroscopically confirmed quasars in the SDSS. Specifically, we use a non-parametric Bayesian classification, based on kernel density estimation, to parameterize the color distribution of astronomical sour...

  1. Growing the first bright quasars in cosmological simulations of structure formation

    Science.gov (United States)

    Sijacki, Debora; Springel, Volker; Haehnelt, Martin G.

    2009-11-01

    We employ cosmological hydrodynamical simulations to study the growth of massive black holes (BHs) at high redshifts subject to BH merger recoils from gravitational wave emission. As a promising host system of a powerful high-redshift quasar, we select the most massive dark matter halo at z = 6 from the Millennium simulation, and resimulate its formation at much higher resolution including gas physics and a model for BH seeding, growth and feedback. Assuming that the initial BH seeds are relatively massive, of the order of 105Msolar, and that seeding occurs around z ~ 15 in dark matter haloes of mass ~109-1010Msolar, we find that it is possible to build up supermassive BHs (SMBHs) by z = 6 that assemble most of their mass during extended Eddington-limited accretion periods. The properties of the simulated SMBHs are consistent with observations of z = 6 quasars in terms of the estimated BH masses and bolometric luminosities, the amount of star formation occurring within the host halo, and the presence of highly enriched gas in the innermost regions of the host galaxy. After a peak in the BH accretion rate at z = 6, the most massive BH has become sufficiently massive for the growth to enter into a much slower phase of feedback-regulated accretion. We extend our basic BH model by incorporating prescriptions for the BH recoils caused by gravitational wave emission during BH merger events, taking into account the newest numerical relativity simulations of merging BH binaries. In order to explore the full range of expected recoils and radiative efficiencies, we also consider models with spinning BHs. In the most `pessimistic' case where BH spins are initially high, we find that the growth of the SMBHs can be potentially hampered if they grow mostly in isolation and experience only a small number of mergers. On the other hand, whereas BH kicks can expel a substantial fraction of low-mass BHs, they do not significantly affect the build-up of the SMBHs. On the contrary, a

  2. Growing the first bright quasars in cosmological simulations of structure formation

    CERN Document Server

    Sijacki, Debora; Haehnelt, Martin G

    2009-01-01

    We employ cosmological hydrodynamical simulations to study the growth of massive black holes (BHs) at high redshifts subject to BH merger recoils from gravitational wave emission. We select the most massive dark matter halo at z=6 from the Millennium simulation, and resimulate its formation at much higher resolution including gas physics and a model for BH seeding, growth and feedback. Assuming that the initial BH seeds are relatively massive, of the order of 10^5 Msun, and that seeding occurs around z~15 in dark matter haloes of mass 10^9-10^10 Msun, we find that it is possible to build up supermassive BHs (SMBHs) by z=6 that assemble most of their mass during extended Eddington-limited accretion periods. The properties of the simulated SMBHs are consistent with observations of z=6 quasars in terms of the estimated BH masses and bolometric luminosities, the amount of star formation occurring within the host halo, and the presence of highly enriched gas in the innermost regions of the host galaxy. After a pea...

  3. Black-hole mass estimates for a homogeneous sample of bright flat-spectrum radio quasars

    CERN Document Server

    Castignani, Gianluca; Lapi, Andrea; De Zotti, Gianfranco; Celotti, Annalisa; Danese, Luigi

    2013-01-01

    We have selected a complete sample of flat-spectrum radio quasars (FSRQs) from the WMAP 7-yr catalog within the SDSS area, all with measured redshift, and have compared the black hole mass estimates based on fitting a standard accretion disk model to the `blue bump' with those obtained from the commonly used single epoch virial method. The sample comprises 79 objects with a flux density limit of 1 Jy at 23 GHz, 54 of which (68%) have a clearly detected `blue bump'. Thirty-four of the latter have, in the literature, black hole mass estimates obtained with the virial method. The mass estimates obtained from the two methods are well correlated. If the calibration factor of the virial relation is set to $f=4.5$, well within the range of recent estimates, the mean logarithmic ratio of the two mass estimates is equal to zero with a dispersion close to the estimated uncertainty of the virial method. The fact that the two independent methods agree so closely in spite of the potentially large uncertainties associated ...

  4. The discovery of the first luminous z~6 quasar in the UKIDSS Large Area Survey

    CERN Document Server

    Venemans, B P; Warren, S J; González-Solares, E A; Hewett, P C; Mortlock, D J; Dye, S; Sharp, R G

    2006-01-01

    We present the initial results from our search for high redshift, z > 6, quasars using near infrared data from the UKIRT Infrared Deep Sky Survey (UKIDSS) Large Area Survey (LAS). Our analysis of the first 106 deg^2 of sky has resulted in the discovery of ULAS J020332.38+001229.2, a luminous (J_AB=20.0, J_Vega=19.1, M_1450=-26.2) quasar at z=5.86. Following candidate selection from the combined IR and optical catalogue data and stacking of multiple epoch Sloan Digital Sky Survey (SDSS) data, we have obtained optical spectroscopy for two candidates. The VLT FORS2 spectrum of ULAS J020332.38+001229.2 shows broad Ly alpha + NV1240 emission at ~8350 A and an abrupt continuum break due to absorption by the Ly alpha forest. The quasar is not present in the SDSS DR5 catalogue and the continuum spectral index of alpha=-1.4 (F_nu~nu^alpha) is redder than a composite of SDSS quasars at similar redshifts (alpha=-0.5). The discovery of one z~6 quasar in ~100 deg^2 down to Y_AB=20.4 (7 sigma) is consistent with existing S...

  5. Discovery of two gravitationally lensed quasars in the Dark Energy Survey

    Science.gov (United States)

    Agnello, A.; Treu, T.; Ostrovski, F.; Schechter, P. L.; Buckley-Geer, E. J.; Lin, H.; Auger, M. W.; Courbin, F.; Fassnacht, C. D.; Frieman, J.; Kuropatkin, N.; Marshall, P. J.; McMahon, R. G.; Meylan, G.; More, A.; Suyu, S. H.; Rusu, C. E.; Finley, D.; Abbott, T.; Abdalla, F. B.; Allam, S.; Annis, J.; Banerji, M.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Burke, D. L.; Rosell, A. Carnero; Kind, M. Carrasco; Carretero, J.; Cunha, C. E.; D'Andrea, C. B.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Dietrich, J. P.; Doel, P.; Eifler, T. F.; Estrada, J.; Neto, A. Fausti; Flaugher, B.; Fosalba, P.; Gerdes, D. W.; Gruen, D.; Gutierrez, G.; Honscheid, K.; James, D. J.; Kuehn, K.; Lahav, O.; Lima, M.; Maia, M. A. G.; March, M.; Marshall, J. L.; Martini, P.; Melchior, P.; Miller, C. J.; Miquel, R.; Nichol, R. C.; Ogando, R.; Plazas, A. A.; Reil, K.; Romer, A. K.; Roodman, A.; Sako, M.; Sanchez, E.; Santiago, B.; Scarpine, V.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thaler, J.; Tucker, D.; Walker, A. R.; Wechsler, R. H.; Zhang, Y.

    2015-12-01

    We present spectroscopic confirmation of two new gravitationally lensed quasars, discovered in the Dark Energy Survey (DES) and Wide-field Infrared Survey Explorer (WISE) based on their multiband photometry and extended morphology in DES images. Images of DES J0115-5244 show a red galaxy with two blue point sources at either side, which are images of the same quasar at zs = 1.64 as obtained by our long-slit spectroscopic data. The Einstein radius estimated from the DES images is 0.51 arcsec. DES J2146-0047 is in the area of overlap between DES and the Sloan Digital Sky Survey (SDSS). Two blue components are visible in the DES and SDSS images. The SDSS fibre spectrum shows a quasar component at zs = 2.38 and absorption by Mg II and Fe II at zl = 0.799, which we tentatively associate with the foreground lens galaxy. Our long-slit spectra show that the blue components are resolved images of the same quasar. The Einstein radius is 0.68 arcsec, corresponding to an enclosed mass of 1.6 × 1011 M⊙. Three other candidates were observed and rejected, two being low-redshift pairs of starburst galaxies, and one being a quasar behind a blue star. These first confirmation results provide an important empirical validation of the data mining and model-based selection that is being applied to the entire DES data set.

  6. A Catalog of Broad Absorption Line Quasars from the Sloan Digital Sky Survey Third Data Release

    CERN Document Server

    Trump, J R; Brinkman, J; Fan, X; Hall, P B; Kleinman, S J; Knapp, G R; Nitta, A; Reichard, T A; Richards, G T; Schneider, D P; Vanden Berk, Daniel E; Anderson, Scott F.; Berk, Daniel E. Vanden; Fan, Xiaohui; Hall, Patrick B.; Knapp, Gillian R.; Nitta, Atsuko; Reichard, Timothy A.; Richards, Gordon T.; Schneider, Donald P.; Trump, Jonathan R.

    2006-01-01

    We present a total of 4784 unique broad absorption line quasars from the Sloan Digital Sky Survey Third Data Release. An automated algorithm was used to match a continuum to each quasar and to identify regions of flux at least 10% below the continuum over a velocity range of at least 1000 km/s in the CIV and MgII absorption regions. The model continuum was selected as the best-fit match from a set of template quasar spectra binned in luminosity, emission line width, and redshift, with the power-law spectral index and amount of dust reddening as additional free parameters. We characterize our sample through the traditional ``balnicity'' index and a revised absorption index, as well as through parameters such as the width, outflow velocity, fractional depth and number of troughs. From a sample of 16883 quasars at 1.7 \\le z \\le 4.38, we identify 4386 (26.0%) quasars with broad CIV absorption, of which 1756 (10.4%) satisfy traditional selection criteria. From a sample of 34973 quasars at 0.5 \\le z \\le 2.15, we id...

  7. The Sloan Digital Sky Survey Reverberation Mapping Project: Ensemble Spectroscopic Variability of Quasar Broad Emission Lines

    CERN Document Server

    Sun, Mouyuan; Shen, Yue; Brandt, W N; Dawson, Kyle; Denney, Kelly D; Hall, Patrick B; Ho, Luis C; Horne, Keith; Jiang, Linhua; Richards, Gordon T; Schneider, Donald P; Bizyaev, Dmitry; Kinemuchi, Karen; Oravetz, Daniel; Pan, Kaike; Simmons, Audrey

    2015-01-01

    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. The SDSS-I/II data include an additional $2854$ quasars with MgII and 572 quasars with Hbeta. The MgII emission line is significantly variable ($\\Delta f/f$ 10% on 100-day timescales), indicating that it is feasible to use the broad MgII line for reverberation mapping studies. The data also confirm that continuum variability increases with timescale and decreases with luminosity, and the continuum light curves are consistent with a damped random-walk model on rest-frame timescales of $\\gtrsim 5$ days. We compare the emission-line and...

  8. The Magellanic Quasars Survey. III. Spectroscopic Confirmation of 758 Active Galactic Nuclei behind the Magellanic Clouds

    OpenAIRE

    Kozłowski, Szymon; Onken, Christopher A.; Kochanek, Christopher S.; Udalski, Andrzej; Szymański, M. K.; Kubiak, M.; Pietrzyński, G.; Soszyński, I.; Wyrzykowski, Ł.; Ulaczyk, K.; Poleski, R.; Pietrukowicz, P.; Skowron, J.; Meixner, M.; Bonanos, A. Z.

    2013-01-01

    The Magellanic Quasars Survey (MQS) has now increased the number of quasars known behind the Magellanic Clouds by almost an order of magnitude. All survey fields in the Large Magellanic Cloud (LMC) and 70% of those in the Small Magellanic Cloud (SMC) have been observed. The targets were selected from the third phase of the Optical Gravitational Lensing Experiment (OGLE-III) based on their optical variability, mid-IR and/or X-ray properties. We spectroscopically confirmed 758 (565 LMC and 193 ...

  9. THE MAGELLANIC QUASARS SURVEY. II. CONFIRMATION OF 144 NEW ACTIVE GALACTIC NUCLEI BEHIND THE SOUTHERN EDGE OF THE LARGE MAGELLANIC CLOUD

    International Nuclear Information System (INIS)

    We quadruple the number of quasars known behind the Large Magellanic Cloud (LMC) from 56 (42 in the Optical Gravitational Lensing Experiment (OGLE)-III LMC fields) to 200 by spectroscopically confirming 169 (144 new) quasars from a sample of 845 observed candidates in four ∼3 deg2 Anglo-Australian Telescope/AAOmega fields south of the LMC center. The candidates were selected based on their Spitzer mid-infrared colors, X-ray emission, and/or optical variability properties in the database of the OGLE microlensing survey. The contaminating sources can be divided into 115 young stellar objects (YSOs), 17 planetary nebulae (PNe), 39 Be and 24 blue stars, 68 red stars, and 12 objects classed as either YSO/PN or blue star/YSO. There are also 402 targets with either featureless spectra or too low signal-to-noise ratios for source classification. Our quasar sample is 50% (30%) complete at I = 18.6 mag (19.3 mag). The newly discovered active galactic nuclei (AGNs) provide many additional reference points for proper motion studies of the LMC, and the sample includes 10 bright AGNs (I < 18 mag) that are potentially suitable for absorption line studies. Their primary use, however, is for detailed studies of quasar variability, as they all have long-term, high cadence, continuously growing light curves from the microlensing surveys of the LMC. Completing the existing Magellanic Quasars Survey fields in the LMC and Small Magellanic Cloud should yield a sample of ∼700 well-monitored AGNs, and expanding it to the larger regions covered by the OGLE-IV survey should yield a sample of ∼3600 AGNs.

  10. Distribution of the very first PopIII stars and their relation to bright z~6 quasars

    CERN Document Server

    Trenti, M

    2007-01-01

    We discuss the link between dark matter halos hosting the first PopIII stars and the rare, massive, halos that are generally considered to host bright quasars at high redshift z~6. The main question that we intend to answer is whether the super-massive black holes powering these QSOs grew out from the seeds planted by the first intermediate massive black holes created in the universe. This question involves a dynamical range of 10^13 in mass and we address it by combining N-body simulations of structure formation to identify the most massive halos at z~6 with a Monte Carlo method based on linear theory to obtain the location and formation times of the first light halos within the whole simulation box. We show that the descendants of the first ~10^6 Msun virialized halos do not, on average, end up in the most massive halos at z~6, but rather live in a large variety of environments. The oldest PopIII progenitors of the most massive halos at z~6, form instead from density peaks that are on average one and a half...

  11. Broad-band spectral energy distribution of 3000 Å break quasars from the Sloan Digital Sky Survey

    Science.gov (United States)

    Meusinger, H.; Schalldach, P.; Mirhosseini, A.; Pertermann, F.

    2016-03-01

    Context. In past decades, huge surveys have confirmed the existence of populations of exotic and hitherto unknown quasar types. The discovery and investigation of these rare peculiar objects is important because they may represent links to special evolutionary stages and hold clues to the evolution of quasars and galaxies. Aims: The Sloan Digital Sky Survey (SDSS) discovered the unusual quasars J010540.75-003313.9 and J220445.27+003141.8 and a small number of similar objects. Their spectra are characterised by a break in the continuum around 3000 Å that neither shows the typical structure of broad absorption line (BAL) troughs nor is explained by typical intrinsic dust reddening. The main aim of the present paper was twofold. First, a new target-oriented search was performed in the spectra database of the SDSS to construct a sizable sample of such 3000 Å break quasars. Second, their broad-band spectral energy distribution (SED) was compared with SEDs of BAL quasars. Methods: We used the method of Kohonen self-organising maps for data mining in the SDSS spectra archive to search for more quasars with properties comparable to the prototypes J010540.75-003313.9 and J220445.27+003141.8. We constructed a sample of 3000 Å break quasars and comparison samples of quasars with similar properties, to some extent, but also showing indications for typical BAL features. Particular attention was payed to a possible contamination by rare stellar spectral types, in particular DQ white dwarfs. We construct ensemble-averaged broad-band SEDs based on archival data from SDSS, GALEX, 2MASS, UKIDSS, WISE, and other surveys. The SEDs were corrected for dust absorption at the systemic redshifts of the quasars by the comparison with the average SED of normal quasars. Results: We compiled a list of 23 quasars classified as 3000 Å break quasars with properties similar to 010540.75-003313.9 and J220445.27+003141.8. Their de-reddened arithmetic median composite SED is indistinguishable

  12. A Comparison of BBN, ADTree and MLP in separating Quasars from Large Survey Catalogues

    Institute of Scientific and Technical Information of China (English)

    Yan-Xia Zhang; Yong-Heng Zhao

    2007-01-01

    We compare the performance of Bayesian Belief Networks (BBN), Multilayer Perception (MLP) networks and Alternating Decision Trees (ADtree) on separating quasars from stars with the database from the 2MASS and FIRST survey catalogs. Having a training sample of sources of known object types, the classifiers are trained to separate quasars from stars. By the statistical properties of the sample, the features important for classification are selected. We compare the classification results with and without feature selection.Experiments show that the results with feature selection are better than those without feature selection. From the high accuracy found, it is concluded that these automated methods are robust and effective for classifying point sources. They may all be applied to large survey projects (e.g. selecting input catalogs) and for other astronomical issues, such as the parameter measurement of stars and the redshift estimation of galaxies and quasars.

  13. A Survey of z>5.8 Quasars in the Sloan Digital Sky Survey. I. Discovery of Three New Quasars and the Spatial Density of Luminous Quasars at z~6

    Science.gov (United States)

    Fan, Xiaohui; Narayanan, Vijay K.; Lupton, Robert H.; Strauss, Michael A.; Knapp, Gillian R.; Becker, Robert H.; White, Richard L.; Pentericci, Laura; Leggett, S. K.; Haiman, Zoltán; Gunn, James E.; Ivezić, Željko; Schneider, Donald P.; Anderson, Scott F.; Brinkmann, J.; Bahcall, Neta A.; Connolly, Andrew J.; Csabai, István; Doi, Mamoru; Fukugita, Masataka; Geballe, Tom; Grebel, Eva K.; Harbeck, Daniel; Hennessy, Gregory; Lamb, Don Q.; Miknaitis, Gajus; Munn, Jeffrey A.; Nichol, Robert; Okamura, Sadanori; Pier, Jeffrey R.; Prada, Francisco; Richards, Gordon T.; Szalay, Alex; York, Donald G.

    2001-12-01

    We present the results from a survey of i-dropout objects selected from ~1550 deg2 of multicolor imaging data from the Sloan Digital Sky Survey to search for luminous quasars at z>~5.8. Objects with i*-z*>2.2 and z*0.90. The ARC 3.5 m spectrum of SDSSp J103027.10+052455.0 shows that over a range of ~300 Å immediately blueward of the Lyα emission, the average transmitted flux is only 0.003+/-0.020 times that of the continuum level, consistent with zero flux over a ~300 Å range of the Lyα forest region and suggesting a tentative detection of the complete Gunn-Peterson trough. The existence of strong metal lines in the quasar spectra suggests early metal enrichment in the quasar environment. The three new objects, together with the previously published z=5.8 quasar SDSSp J104433.04-012502.2, form a complete color-selected flux-limited sample at z>~5.8. We estimate the selection function of this sample, taking into account the estimated variations in the quasar spectral energy distribution, as well as observational photometric errors. We find that at z=6, the comoving density of luminous quasars at M1450Australian Research Council (Australia), CNPq (Brazil), and CONICET (Argentina) on observations obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration, made possible by the generous financial support of the W. M. Keck Foundation; on observations obtained at the German-Spanish Astronomical Centre, Calar Alto Observatory, operated by the Max Planck Institute for Astronomy, Heidelberg, jointly with the Spanish National Commission for Astronomy; and on observations obtained at UKIRT, which is operated by the Joint Astronomy Centre on behalf of the UK Particle Physics and Astronomy Research Council.

  14. The quest for Type 2 quasars: Chandra observations of luminous obscured quasars in the Sloan Digital Sky Survey

    CERN Document Server

    Vignali, C; Comastri, A

    2006-01-01

    We report on new Chandra exploratory observations of six candidate Type 2 quasars at z=0.49-0.73 selected among the most [OIII] luminous emitters from the Sloan Digital Sky Survey (SDSS). Under the assumption that [OIII] is a proxy for the intrinsic luminosity of the central source, their predicted rest-frame X-ray luminosities are L(2-10keV)~10^45 erg/s. For two of the targets, the photon statistics are good enough to allow for basic X-ray spectral analyses, which indicate the presence of intrinsic absorption (~10^{22-23} cm^-2) and luminous X-ray emission (L_X>10^44 erg/s). Of the remaining four targets, two are detected with only a few (3-6) X-ray counts, and two are undetected by Chandra. If these four sources have the large intrinsic X-ray luminosities predicted by the [OIII] emission, then their nuclei must be heavily obscured (N_H>few 10^23 cm^-2) and some might be Compton thick (N_H>1.5 10^24 cm^-2). We also present the results for two Type 2 quasar candidates serendipitously lying in the fields of th...

  15. A Search for Nitrogen Enriched Quasars in the Sloan Digital Sky Survey Early Data Release

    OpenAIRE

    Bentz, Misty C.; Osmer, Patrick S.

    2003-01-01

    A search for nitrogen-rich quasars in the Sloan Digital Sky Survey Early Data Release (SDSS EDR) catalog has yielded 16 candidates, including five with very prominent emission, but no cases with nitrogen emission as strong as in Q0353-383. The quasar Q0353-383 has long been known to have extremely strong nitrogen intercombination lines at lambda 1486 and lambda 1750 Angstroms, implying an anomalously high nitrogen abundance of about 15 times solar. It is still the only one of its kind known. ...

  16. First lensed quasar system(s) from the VST-ATLAS survey: one quad and three nearly identical pairs

    CERN Document Server

    Schechter, Paul L; Chehade, B; Metcalfe, N; Shanks, T; McDonald, Michael

    2016-01-01

    We have analyzed images from the VST ATLAS survey to identify candidate gravitationally lensed quasar systems in a sample of WISE sources with W1 - W2 > 0.7. Results from followup spectroscopy with the Baade 6.5 m telescope are presented for seven systems. One of these is a quadruply lensed quasar. Two are projected superpositions of two quasars at different redshifts. In one system two quasars, though at the same redshift, have very different emission line profiles, and constitute a physical binary. In three systems the component spectra are consistent with the lensing hypothesis, after allowing for micro-lensing. But as no lensing galaxy is detected in these three, we classify them as nearly identical quasar pairs. More extensive observations are needed to establish whether they are lensed quasars or physical binaries.

  17. Close companions to two high-redshift quasars

    CERN Document Server

    McGreer, Ian D; Strauss, Michael A; Haiman, Zoltan; Richards, Gordon T; Jiang, Linhua; Bian, Fuyan; Schneider, Donald P

    2014-01-01

    We report the serendipitous discoveries of companion galaxies to two high-redshift quasars. SDSS J025617.7+001904 is a z=4.79 quasar included in our recent survey of faint quasars in the SDSS Stripe 82 region. The initial MMT slit spectroscopy shows excess Lyman alpha emission extending well beyond the quasar's light profile. Further imaging and spectroscopy with LBT/MODS1 confirms the presence of a bright galaxy (i_AB = 23.6) located 2arcsec (11 kpc projected) from the quasar with strong Lyman alpha emission (EW_0 ~ 100Ang) at the redshift of the quasar, as well as faint continuum. The second quasar, CFHQS J005006.6+344522 (z=6.25), is included in our recent HST SNAP survey of z~6 quasars searching for evidence of gravitational lensing. Deep imaging with ACS and WFC3 confirms an optical dropout ~4.5 mag fainter than the quasar (Y_AB=25) at a separation of 0.9 arcsec. The red i_775-Y_105 color of the galaxy and its proximity to the quasar (7 kpc projected if at the quasar redshift) strongly favor an associati...

  18. THE SDSS-III BARYON OSCILLATION SPECTROSCOPIC SURVEY: QUASAR TARGET SELECTION FOR DATA RELEASE NINE

    Energy Technology Data Exchange (ETDEWEB)

    Ross, Nicholas P.; Kirkpatrick, Jessica A.; Carithers, William C.; Ho, Shirley [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Myers, Adam D. [Department of Astronomy, MC-221, University of Illinois, 1002 West Green Street, Urbana, IL 61801 (United States); Sheldon, Erin S. [Brookhaven National Laboratory, Blgd 510, Upton, NY 11375 (United States); Yeche, Christophe; Aubourg, Eric [CEA, Centre de Saclay, IRFU, 91191 Gif-sur-Yvette (France); Strauss, Michael A.; Lee, Khee-Gan [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Bovy, Jo; Blanton, Michael R.; Hogg, David W. [Center for Cosmology and Particle Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Richards, Gordon T. [Department of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Brandt, W. N. [Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States); Croft, Rupert A. C. [Bruce and Astrid McWilliams Center for Cosmology, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Da Silva, Robert [Department of Astronomy and Astrophysics, University of California, Santa Cruz, Santa Cruz, CA 95064 (United States); Dawson, Kyle [Department of Physics and Astronomy, University of Utah, UT (United States); Eisenstein, Daniel J. [Steward Observatory, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Hennawi, Joseph F., E-mail: npross@lbl.gov [Max-Planck-Institut fuer Astronomie, Konigstuhl 17, 69117 Heidelberg (Germany); and others

    2012-03-01

    The SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS), a five-year spectroscopic survey of 10,000 deg{sup 2}, achieved first light in late 2009. One of the key goals of BOSS is to measure the signature of baryon acoustic oscillations (BAOs) in the distribution of Ly{alpha} absorption from the spectra of a sample of {approx}150,000 z > 2.2 quasars. Along with measuring the angular diameter distance at z Almost-Equal-To 2.5, BOSS will provide the first direct measurement of the expansion rate of the universe at z > 2. One of the biggest challenges in achieving this goal is an efficient target selection algorithm for quasars in the redshift range 2.2 < z < 3.5, where their colors tend to overlap those of the far more numerous stars. During the first year of the BOSS survey, quasar target selection (QTS) methods were developed and tested to meet the requirement of delivering at least 15 quasars deg{sup -2} in this redshift range, with a goal of 20 out of 40 targets deg{sup -2} allocated to the quasar survey. To achieve these surface densities, the magnitude limit of the quasar targets was set at g {<=} 22.0 or r {<=} 21.85. While detection of the BAO signature in the distribution of Ly{alpha} absorption in quasar spectra does not require a uniform target selection algorithm, many other astrophysical studies do. We have therefore defined a uniformly selected subsample of 20 targets deg{sup -2}, for which the selection efficiency is just over 50% ({approx}10 z > 2.20 quasars deg{sup -2}). This 'CORE' subsample will be fixed for Years Two through Five of the survey. For the remaining 20 targets deg{sup -2}, we will continue to develop improved selection techniques, including the use of additional data sets beyond the Sloan Digital Sky Survey (SDSS) imaging data. In this paper, we describe the evolution and implementation of the BOSS QTS algorithms during the first two years of BOSS operations (through 2011 July), in support of the science investigations

  19. The Sloan Digital Sky Survey Quasar Catalog. 4. Fifth Data Release

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, Donald P.; Hall, Patrick B.; Richards, Gordon T.; Strauss, Michael A.; Vanden Berk, Daniel E.; Anderson, Scott F.; Brandt, W.N.; Fan, Xiao-Hui; Jester,; Gray, Jim; Gunn, James E.; /Penn State U., Astron. Astrophys. /York U., Canada /Johns Hopkins U. /Princeton U. Observ. /Washington U., Seattle, Astron. Dept. /Arizona

    2007-04-01

    We present the fourth edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog. The catalog contains 77,429 objects; this is an increase of over 30,000 entries since the previous edition. The catalog consists of the objects in the SDSS Fifth Data Release that have luminosities larger than M{sub i} = -22.0 (in a cosmology with H{sub 0} = 70 km s{sup -1} Mpc{sup -1}, {Omega}{sub M} = 0.3, and {Omega}{sub {Lambda}} = 0.7), have at least one emission line with FWHM larger than 1000 km s{sup -1} or have interesting/complex absorption features, are fainter than i {approx} 15.0, and have highly reliable redshifts. The area covered by the catalog is {approx} 5740 deg{sup 2}. The quasar redshifts range from 0.08 to 5.41, with a median value of 1.48; the catalog includes 891 quasars at redshifts greater than four, of which 36 are at redshifts greater than five. Approximately half of the catalog quasars have i < 19; nearly all have i < 21. For each object the catalog presents positions accurate to better than 0.2-minutes rms per coordinate, five-band (ugriz) CCD-based photometry with typical accuracy of 0.03 mag, and information on the morphology and selection method. The catalog also contains basic radio, near-infrared, and X-ray emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra cover the wavelength region 3800-9200 {angstrom} at a spectral resolution of {approx_equal} 2000; the spectra can be retrieved from the public database using the information provided in the catalog. The average SDSS colors of quasars as a function of redshift, derived from the catalog entries, are presented in tabular form. Approximately 96% of the objects in the catalog were discovered by the SDSS.

  20. The Sloan Digital Sky Survey Quasar Catalog V. Seventh Data Release

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, Donald P.; /Penn State U.; Richards, Gordon T.; /Drexel U.; Hall, Patrick B.; /York U., Canada; Strauss, Michael A.; /Princeton U. Observ.; Anderson, Scott F.; /Washington U., Seattle, Astron. Dept.; Boroson, Todd A.; /Kitt Peak Observ.; Ross, Nicholas P.; /Penn State U.; Shen, Yue; /Princeton U. Observ.; Brandt, W.N.; /Penn State U.; Fan, Xiaohui; /Arizona U., Astron. Dept. - Steward Observ.; Inada, Naohisa; /Wako, RIKEN /Southampton U. /Heidelberg, Max Planck Inst. Astron.

    2010-04-01

    We present the fifth edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog, which is based upon the SDSS Seventh Data Release. The catalog, which contains 105,783 spectroscopically confirmed quasars, represents the conclusion of the SDSS-I and SDSS-II quasar survey. The catalog consists of the SDSS objects that have luminosities larger than M{sub i} = -22.0 (in a cosmology with H{sub 0} = 70 km s{sup -1} Mpc{sup -1}, {Omega}{sub M} = 0.3, and {Omega}{sub {Lambda}} = 0.7), have at least one emission line with FWHM larger than 1000 km s{sup -1} or have interesting/complex absorption features, are fainter than i {approx} 15.0, and have highly reliable redshifts. The catalog covers an area of {approx} 9380 deg{sup 2}. The quasar redshifts range from 0.065 to 5.46, with a median value of 1.49; the catalog includes 1248 quasars at redshifts greater than 4, of which 56 are at redshifts greater than 5. The catalog contains 9210 quasars with i < 18; slightly over half of the entries have i < 19. For each object the catalog presents positions accurate to better than 0.1-inch rms per coordinate, five-band (ugriz) CCD-based photometry with typical accuracy of 0.03 mag, and information on the morphology and selection method. The catalog also contains radio, near-infrared, and X-ray emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra cover the wavelength region 3800-9200 {angstrom} at a spectral resolution of {approx_equal} 2000; the spectra can be retrieved from the SDSS public database using the information provided in the catalog. Over 96% of the objects in the catalog were discovered by the SDSS. We also include a supplemental list of an additional 207 quasars with SDSS spectra whose archive photometric information is incomplete.

  1. Bright [CII] and dust emission in three z>6.6 quasar host galaxies observed by ALMA

    CERN Document Server

    Venemans, B P; Zschaechner, L; Decarli, R; De Rosa, G; Findlay, J R; McMahon, R G; Sutherland, W J

    2015-01-01

    We present ALMA detections of the [CII] 158 micron emission line and the underlying far-infrared continuum of three quasars at 6.6~6 quasar hosts correlate with the quasar's bolometric luminosity. In one quasar, the [CII] line is significantly redshifted by ~1700 km/s with respect to the MgII broad emission line. Comparing to values in the literature, we find that, on average, the MgII is blueshifted by 480 km/s (with a standard deviation of 630 km/s) with respect to the host galaxy redshift, i.e. one of our quasars is an extreme outlier. Through modeling we can rule out a flat rotation curve for our brightest [CII] emitter. Finally, we find that the ratio of black hole mass to host galaxy (dynamical) mass is higher by a factor 3-4 (with significant scatter) than local relations.

  2. The Final SDSS High-Redshift Quasar Sample of 52 Quasars at z>5.7

    CERN Document Server

    Jiang, Linhua; Fan, Xiaohui; Strauss, Michael A; Banados, Eduardo; Becker, Robert H; Bian, Fuyan; Farnsworth, Kara; Shen, Yue; Wang, Feige; Wang, Ran; Wang, Shu; White, Richard L; Wu, Jin; Wu, Xue-Bing; Yang, Jinyi; Yang, Qian

    2016-01-01

    We present the discovery of nine quasars at $z\\sim6$ identified in the Sloan Digital Sky Survey (SDSS) imaging data. This completes our survey of $z\\sim6$ quasars in the SDSS footprint. Our final sample consists of 52 quasars at $5.7quasars with $z_{\\rm AB}\\le20$ mag selected from 11,240 deg$^2$ of the SDSS single-epoch imaging survey (the main survey), 10 quasars with $20\\le z_{\\rm AB}\\le20.5$ selected from 4223 deg$^2$ of the SDSS overlap regions (regions with two or more imaging scans), and 13 quasars down to $z_{\\rm AB}\\approx22$ mag from the 277 deg$^2$ in Stripe 82. They span a wide luminosity range of $-29.0\\le M_{1450}\\le-24.5$. This well-defined sample is used to derive the quasar luminosity function (QLF) at $z\\sim6$. After combining our SDSS sample with two faint ($M_{1450}\\ge-23$ mag) quasars from the literature, we obtain the parameters for a double power-law fit to the QLF. The bright-end slope $\\beta$ of the QLF is well constrained to be $\\beta=-2.8\\pm0.2$. Due to the...

  3. DES J0454$-$4448: Discovery of the First Luminous z $\\ge$ 6 Quasar from the Dark Energy Survey

    CERN Document Server

    Reed, S L; Banerji, M; Becker, G D; Gonzalez-Solares, E; Martini, P; Ostrovski, F; Rauch, M; Abbott, T; Abdalla, F B; Allam, S; Benoit-Levy, A; Bertin, E; Buckley-Geer, E; Burke, D; Rosell, A Carnero; da Costa, L N; ĎAndrea, C; DePoy, D L; Desai, S; Diehl, H T; Doel, P; Cunha, C E; Estrada, J; Evrard, A E; Neto, A Fausti; Finley, D A; Fosalba, P; Frieman, J; Gruen, D; Honscheid, K; James, D; Kent, S; Kuehn, K; Kuropatkin, N; Lahav, O; Maia, M A G; Makler, M; Marshall, J; Merritt, K; Miquel, R; Mohr, J; Nord, B; Ogando, R; Plazas, A; Romer, K; Roodman, A; Rykoff, E; Sako, M; Sanchez, E; Santiago, B; Schubnell, M; Sevilla, I; Smith, C; Soares-Santos, M; Suchyta, E; Swanson, M E C; Tarle, G; Thomas, D; Tucker, D; Walker, A; Wechsler, R H

    2015-01-01

    We present the first results of a survey for high redshift, z $\\ge$ 6, quasars using izY multi-colour photometric observations from the Dark Energy Survey (DES). Here we report the discovery and spectroscopic confirmation of the $\\rm z_{AB}, Y_{AB}$ = 20.2, 20.2 (M$_{1450}$ = $-$26.5) quasar DES J0454$-$4448 with an emission line redshift of z = 6.10$\\pm$0.03 and a HI near zone size of 4.6 $\\pm$ 1.7 Mpc.The quasar was selected as an i-band drop out with i$-$z = 2.46 and z$_{AB} $ 50-100 new quasars with z $>$ 6 including 3-10 with z $>$ 7 dramatically increasing the numbers of quasars currently known that are suitable for detailed studies including determination of the neutral HI fraction of the intergalactic medium (IGM) during the epoch of Hydrogen reionization.

  4. THE z = 5 QUASAR LUMINOSITY FUNCTION FROM SDSS STRIPE 82

    Energy Technology Data Exchange (ETDEWEB)

    McGreer, Ian D.; Fan Xiaohui [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721-0065 (United States); Jiang Linhua [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States); Richards, Gordon T. [Department of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Strauss, Michael A. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Ross, Nicholas P.; White, Martin [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 92420 (United States); Shen Yue [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Schneider, Donald P.; Brandt, W. Niel [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States); Myers, Adam D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); DeGraf, Colin [McWilliams Center for Cosmology, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); Glikman, Eilat [Department of Physics and Yale Center for Astronomy and Astrophysics, Yale University, P.O. Box 208121, New Haven, CT 06520-8121 (United States); Ge Jian [Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611 (United States); Streblyanska, Alina, E-mail: imcgreer@as.arizona.edu [Instituto de Astrofisica de Canarias (IAC), E-38200 La Laguna, Tenerife (Spain)

    2013-05-10

    We present a measurement of the Type I quasar luminosity function at z = 5 using a large sample of spectroscopically confirmed quasars selected from optical imaging data. We measure the bright end (M{sub 1450} < -26) with Sloan Digital Sky Survey (SDSS) data covering {approx}6000 deg{sup 2}, then extend to lower luminosities (M{sub 1450} < -24) with newly discovered, faint z {approx} 5 quasars selected from 235 deg{sup 2} of deep, coadded imaging in the SDSS Stripe 82 region (the celestial equator in the Southern Galactic Cap). The faint sample includes 14 quasars with spectra obtained as ancillary science targets in the SDSS-III Baryon Oscillation Spectroscopic Survey, and 59 quasars observed at the MMT and Magellan telescopes. We construct a well-defined sample of 4.7 < z < 5.1 quasars that is highly complete, with 73 spectroscopic identifications out of 92 candidates. Our color selection method is also highly efficient: of the 73 spectra obtained, 71 are high-redshift quasars. These observations reach below the break in the luminosity function (M{sub 1450}{sup *}{approx}-27). The bright-end slope is steep ({beta} {approx}< -4), with a constraint of {beta} < -3.1 at 95% confidence. The break luminosity appears to evolve strongly at high redshift, providing an explanation for the flattening of the bright-end slope reported previously. We find a factor of {approx}2 greater decrease in the number density of luminous quasars (M{sub 1450} < -26) from z = 5 to z = 6 than from z = 4 to z = 5, suggesting a more rapid decline in quasar activity at high redshift than found in previous surveys. Our model for the quasar luminosity function predicts that quasars generate {approx}30% of the ionizing photons required to keep hydrogen in the universe ionized at z = 5.

  5. Broad-band spectral energy distribution of 3000 Angstroem break quasars from the Sloan Digital Sky Survey

    CERN Document Server

    Meusinger, H; Mirhosseini, A; Pertermann, F

    2016-01-01

    The Sloan Digital Sky Survey (SDSS) discovered a few unusual quasars with a characteristic break in the continuum around 3000 A that neither shows the typical structure of broad absorption line (BAL) troughs nor is explained by typical intrinsic dust reddening. We used the method of Kohonen self-organising maps for a systematical search for quasars with such properties in the SDSS spectra archive. We constructed a sample of 23 quasars classified as 3000 A break quasars and two comparison samples of quasars with similar properties, to some extent, but also showing typical BAL features. We computed ensemble-averaged broad-band SEDs based on archival data from SDSS, GALEX, 2MASS, UKIDSS, and WISE. The SEDs were corrected for intrinsic dust absorption by the comparison with the average SED of normal quasars. The de-reddened arithmetic median composite SED of the 3000 A break quasars is found to be indistinguishable from that of the unusual BAL quasars. We conclude that 3000 A break quasars are most likely extreme...

  6. Discovery of two gravitationally lensed quasars in the Dark Energy Survey

    CERN Document Server

    Agnello, Adriano; Ostrovski, Fernanda; Schechter, Paul L; Buckley-Geer, Elizabeth J; Lin, Huan; Auger, Matthew W; Courbin, Frederic; Fassnacht, Christopher D; Frieman, Josh; Kuropatkin, Nikolay; Marshall, Philip J; McMahon, Richard G; Meylan, Georges; More, Anupreeta; Suyu, Sherry H; Rusu, Cristian E; Finley, David; Abbott, Tim; Abdalla, Filipe B; Allam, Sahar; Annis, James; Banerji, Manda; Benoit-Lévy, Aurélien; Bertin, Emmanuel; Brooks, David; Burke, David L; Rosell, Aurelio Carnero; Kind, Matias Carrasco; Carretero, Jorge; Cunha, Carlos E; D'Andrea, Chris B; da Costa, Luiz N; Desai, Shantanu; Diehl, H Thomas; Dietrich, Jörg P; Doel, Peter; Eifler, Tim F; Estrada, Juan; Neto, Angelo Fausti; Flaugher, Brenna; Fosalba, Pablo; Gerdes, David W; Gruen, Daniel; Gutierrez, Gaston; Honscheid, Klaus; James, David J; Kuehn, Kyler; Lahav, Ofer; Lima, Marco; Maia, Marcio A G; March, Marina; Marshall, Jennifer L; Martini, Paul; Melchior, Peter; Miller, Christopher J; Miquel, Ramon; Nichol, Robert C; Ogando, Ricardo; Plazas, Andres A; Reil, Kevin; Romer, A Kathy; Roodman, Aaron; Sako, Masao; Sanchez, Eusebio; Santiago, Basilio; Scarpine, Vic; Schubnell, Michael; Sevilla-Noarbe, Ignacio; Smith, R Chris; Soares-Santos, Marcelle; Sobreira, Flavia; Suchyta, Eric; Swanson, Molly E C; Tarle, Gregory; Thaler, Jon; Tucker, Douglas; Walker, Alistair R; Wechsler, Risa H; Zhang, Yuanyuan

    2015-01-01

    We present spectroscopic confirmation of two new lensed quasars via data obtained at the 6.5m Magellan/Baade Telescope. The lens candidates have been selected from the Dark Energy Survey (DES) and WISE based on their multi-band photometry and extended morphology in DES images. Images of DES J0115-5244 show two blue point sources at either side of a red galaxy. Our long-slit data confirm that both point sources are images of the same quasar at $z_{s}=1.64.$ The Einstein Radius estimated from the DES images is $0.51$". DES J2200+0110 is in the area of overlap between DES and the Sloan Digital Sky Survey (SDSS). Two blue components are visible in the DES and SDSS images. The SDSS fiber spectrum shows a quasar component at $z_{s}=2.38$ and absorption compatible with Mg II and Fe II at $z_{l}=0.799$, which we tentatively associate with the foreground lens galaxy. The long-slit Magellan spectra show that the blue components are resolved images of the same quasar. The Einstein Radius is $0.68$" corresponding to an e...

  7. The BTC40 Survey for Quasars at 4.8 < z < 6

    CERN Document Server

    Monier, E M; Hall, P B; Osmer, P S; Smith, M G; Dalton, G B; Green, R F

    2002-01-01

    The BTC40 Survey for high-redshift quasars is a multicolor search using images obtained with the Big Throughput Camera (BTC) on the CTIO 4-m telescope in V, I, and z filters to search for quasars at redshifts of 4.8 < z < 6. The survey covers 40 sq. deg. in B, V, & I and 36 sq. deg. in z. Limiting magnitudes (3 sigma) reach to V = 24.6, I = 22.9 and z = 22.9. We used the (V-I) vs. (I-z) two-color diagram to select high-redshift quasar candidates from the objects classified as point sources in the imaging data. Follow-up spectroscopy with the AAT and CTIO 4-m telescopes of candidates having I < 21.5 has yielded two quasars with redshifts of z = 4.6 and z = 4.8 as well as four emission line galaxies with z = 0.6. Fainter candidates have been identified down to I = 22 for future spectroscopy on 8-m class telescopes.

  8. An X-shooter composite of bright 1 < z < 2 quasars from UV to infrared

    CERN Document Server

    Selsing, Jonatan; Christensen, Lise; Krogager, Jens-Kristian

    2016-01-01

    Quasi-stellar object (QSO) spectral templates are important both to QSO physics and for investigations that use QSOs as probes of intervening gas and dust. However, combinations of various QSO samples obtained at different times and with different instruments so as to expand a composite and to cover a wider rest frame wavelength region may create systematic effects, and the contribution from QSO hosts may contaminate the composite. We have constructed a composite spectrum from luminous blue QSOs at 1 < z < 2.1 selected from the Sloan Digital Sky Survey (SDSS). The observations with X-shooter simultaneously cover ultraviolet (UV) to near- infrared (NIR) light, which ensures that the composite spectrum covers the full rest-frame range from Ly$\\beta$ to 11350 $\\AA$ without any significant host contamination. Assuming a power-law continuum for the composite we find a spectral slope of $\\alpha_\\lambda$ = 1.70+/-0.01, which is steeper than previously found in the literature. We attribute the differences to ou...

  9. Reddening Independent Quasar Selection from a Wide Field Optical and Near-IR Imaging Survey

    CERN Document Server

    Sabbey, C N; Vivas, A K; Hodgkin, S T; Coppi, P S; McMahon, R G

    2000-01-01

    We present preliminary results from a wide field near-IR imaging survey that uses the Cambridge InfraRed Survey Instrument (CIRSI) on the 2.5m Isaac Newton Telescope (INT). CIRSI is a JH-band mosaic imager that contains 4 Rockwell 1024$^{2}$ HgCdTe detectors (the largest IR camera in existence), allowing us to survey approximately 4 deg^2 per night to H ~ 19. Combining CIRSI observations with the deep optical imaging from the INT Wide Field Survey, we demonstrate a reddening independent quasar selection technique based on the (g - z) / (z - H) color diagram.

  10. A Spectroscopic Survey of Faint Quasars in the SDSS Deep Stripe: I. Preliminary Results from the Co-added Catalog

    CERN Document Server

    Jiang, L; Cool, R J; Eisenstein, D J; Fan, X; Johnston, D; Richards, G T; Schneider, D P; Scranton, R; Strauss, M A; Zehavi, I

    2006-01-01

    In this paper we present the first results of a deep spectroscopic survey of faint quasars in the Sloan Digital Sky Survey (SDSS) Southern Survey, a deep survey carried out by repeatedly imaging a 270 deg^2 area. Quasar candidates were selected from the deep data with good completeness over 02.0) at the faint end, indicating a break in the QLF slope. Using a luminosity-dependent density evolution model, we find that the quasar density at M_{g}<-22.5 peaks at z~2, which is later in cosmic time than the peak of z~2.5 found from surveys of more luminous objects. The SFQS QLF is consistent with the results of the 2dF QSO Redshift Survey, the SDSS, and the 2dF-SDSS LRG and QSO Survey, but probes fainter quasars. We plan to obtain more quasars from future observations and establish a complete faint quasar sample with more than 1000 objects over 10 deg^2.

  11. A Systematic Meta-Survey of High Redshift Quasars Probing their Environments and Evolution

    Science.gov (United States)

    Gobeille, Doug B. P.

    We have constructed a meta-survey of 298 quasars in the window from 7 to 17.5 hours in right ascension and 0 to 65 degrees in declination. These quasars span three decades of total power and redshifts from 0.158 to 5.284. All sources had a flux density of greater than 70 mJy at 1.4 GHz. At redshifts z > 2.5 our sample is complete. It is also complete for z 1027.55 W/Hz. Our quasar sample is built from archival Very Large Array (VLA) observations, as well as three observations in 2007 and 2008. This sample represents one of the most complete meta-surveys to date of the high redshift universe. In the 1980's, two competing groups (Ne, Gower and Hutchings, and Barthel, Miley, and Lonsdale) investigated the high redshift universe, seeking to investigate the dependence of largest linear size (LLS) and bending angles on redshift, core power, and extended power. Using our sample we test the differing results of these groups and build our own model of source evolution with redshift and power. We also seek a relationship between bending angles and core dominance, modeling this dependence on the thoughts of Orr & Browne showing that projected bending angles grow as the angle to the line of sight approaches the intrinsic bending angle of the quasar. We will also present an additional component of our high redshift quasar observations seeking arcsecond scale jets to be observed with the space based Chandra x-ray telescope. These observations will be used to investigate the nature of x-ray emission from the knots of kiloparsec jets in the high redshift universe.

  12. The Sloan Digital Sky Survey Quasar Catalog. 3. Third data release

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, Donald P.; Hall, Patrick B.; Richards, Gordon T.; Vanden Berk, Daniel E.; Anderson, Scott F.; Fan, Xiao-Hui; Jester, Sebastian; Stoughton, Chris; Strauss,; SubbaRao, Mark; Brandt, W.N.; Gunn, James E.; Yanny, Brian; Bahcall, Neta A.; Barentine, J.C.; Blanton, Michael R.; Boroski, William N.; Brewington, Howard J.; Brinkmann, J.; Brunner, Robert; Csabai, Istvan; /Penn State U., Astron. Astrophys. /York U., Canada /Princeton U. Observ. /Washington U., Seattle, Astron. Dept. /Arizona U.,

    2005-03-01

    We present the third edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog. The catalog consists of the 46,420 objects in the SDSS Third Data Release that have luminosities larger than M{sub i} = -22 (in a cosmology with H{sub 0} = 70 km s{sup -1} Mpc{sup -1}, {Omega}{sub M} = 0.3, and {Omega}{sub {Lambda}} = 0.7), have at least one emission line with FWHM larger than 1000 km s{sup -1} or are unambiguously broad absorption line quasars, are fainter than i = 15.0, and have highly reliable redshifts. The area covered by the catalog is {approx} 4188 deg{sup 2}. The quasar redshifts range from 0.08 to 5.41, with a median value of 1.47; the high-redshift sample includes 520 quasars at redshifts greater than four, of which 17 are at redshifts greater than five. For each object the catalog presents positions accurate to better than 0.2'' rms per coordinate, five-band (ugriz) CCD-based photometry with typical accuracy of 0.03 mag, and information on the morphology and selection method. The catalog also contains radio, near-infrared, and X-ray emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra cover the wavelength region 3800-9200 at a spectral resolution of {approx} 2000; the spectra can be retrieved from the public database using the information provided in the catalog. A total of 44,221 objects in the catalog were discovered by the SDSS; 28,400 of the SDSS discoveries are reported here for the first time.

  13. Measuring large-scale structure with quasars in narrow-band filter surveys

    Science.gov (United States)

    Abramo, L. Raul; Strauss, Michael A.; Lima, Marcos; Hernández-Monteagudo, Carlos; Lazkoz, Ruth; Moles, Mariano; de Oliveira, Claudia Mendes; Sendra, Irene; Sodré, Laerte; Storchi-Bergmann, Thaisa

    2012-07-01

    We show that a large-area imaging survey using narrow-band filters could detect quasars in sufficiently high number densities, and with more than sufficient accuracy in their photometric redshifts, to turn them into suitable tracers of large-scale structure. If a narrow-band optical survey can detect objects as faint as i= 23, it could reach volumetric number densities as high as 10-4 h3 Mpc-3 (comoving) at z˜ 1.5. Such a catalogue would lead to precision measurements of the power spectrum up to z˜ 3-4. We also show that it is possible to employ quasars to measure baryon acoustic oscillations at high redshifts, where the uncertainties from redshift distortions and non-linearities are much smaller than at z≲ 1. As a concrete example we study the future impact of the Javalambre Physics of the Accelerating Universe Astrophysical Survey (J-PAS), which is a narrow-band imaging survey in the optical over 1/5 of the unobscured sky with 42 filters of ˜100-Å full width at half-maximum. We show that J-PAS will be able to take advantage of the broad emission lines of quasars to deliver excellent photometric redshifts, σz≃ 0.002 (1 +z), for millions of objects.

  14. Sloan Digital Sky Survey III photometric quasar clustering: probing the initial conditions of the Universe

    Science.gov (United States)

    Ho, Shirley; Agarwal, Nishant; Myers, Adam D.; Lyons, Richard; Disbrow, Ashley; Seo, Hee-Jong; Ross, Ashley; Hirata, Christopher; Padmanabhan, Nikhil; O'Connell, Ross; Huff, Eric; Schlegel, David; Slosar, Anže; Weinberg, David; Strauss, Michael; Ross, Nicholas P.; Schneider, Donald P.; Bahcall, Neta; Brinkmann, J.; Palanque-Delabrouille, Nathalie; Yèche, Christophe

    2015-05-01

    The Sloan Digital Sky Survey has surveyed 14,555 square degrees of the sky, and delivered over a trillion pixels of imaging data. We present the large-scale clustering of 1.6 million quasars between z=0.5 and z=2.5 that have been classified from this imaging, representing the highest density of quasars ever studied for clustering measurements. This data set spans 0~ 11,00 square degrees and probes a volume of 80 h-3 Gpc3. In principle, such a large volume and medium density of tracers should facilitate high-precision cosmological constraints. We measure the angular clustering of photometrically classified quasars using an optimal quadratic estimator in four redshift slices with an accuracy of ~ 25% over a bin width of δl ~ 10-15 on scales corresponding to matter-radiation equality and larger (0l ~ 2-3). Observational systematics can strongly bias clustering measurements on large scales, which can mimic cosmologically relevant signals such as deviations from Gaussianity in the spectrum of primordial perturbations. We account for systematics by employing a new method recently proposed by Agarwal et al. (2014) to the clustering of photometrically classified quasars. We carefully apply our methodology to mitigate known observational systematics and further remove angular bins that are contaminated by unknown systematics. Combining quasar data with the photometric luminous red galaxy (LRG) sample of Ross et al. (2011) and Ho et al. (2012), and marginalizing over all bias and shot noise-like parameters, we obtain a constraint on local primordial non-Gaussianity of fNL = -113+154-154 (1σ error). We next assume that the bias of quasar and galaxy distributions can be obtained independently from quasar/galaxy-CMB lensing cross-correlation measurements (such as those in Sherwin et al. (2013)). This can be facilitated by spectroscopic observations of the sources, enabling the redshift distribution to be completely determined, and allowing precise estimates of the bias

  15. A photometric catalogue of quasars and other point sources in the Sloan Digital Sky Survey

    Science.gov (United States)

    Abraham, Sheelu; Philip, Ninan Sajeeth; Kembhavi, Ajit; Wadadekar, Yogesh G.; Sinha, Rita

    2012-01-01

    We present a catalogue of about six million unresolved photometric detections in the Sloan Digital Sky Survey (SDSS) Seventh Data Release, classifying them into stars, galaxies and quasars. We use a machine learning classifier trained on a subset of spectroscopically confirmed objects from 14th to 22nd magnitude in the SDSS i band. Our catalogue consists of 2 430 625 quasars, 3 544 036 stars and 63 586 unresolved galaxies from 14th to 24th magnitude in the SDSS i band. Our algorithm recovers 99.96 per cent of spectroscopically confirmed quasars and 99.51 per cent of stars to i ˜ 21.3 in the colour window that we study. The level of contamination due to data artefacts for objects beyond i = 21.3 is highly uncertain and all mention of completeness and contamination in the paper are valid only for objects brighter than this magnitude. However, a comparison of the predicted number of quasars with the theoretical number counts shows reasonable agreement.

  16. The Sloan Digital Sky Survey Quasar Catalog IV. Fifth Data Release

    CERN Document Server

    Schneider, Donald P; Richards, Gordon T; Strauss, Michael A; Berk, Daniel E Vanden; Anderson, Scott F; Brandt, W N; Fan, Xiaohui; Jester, Sebastian; Gray, Jim; Gunn, James E; SubbaRao, Mark U; Thakar, Anirudda R; Stoughton, Chris; Szalay, Alexander S; Yanny, Brian; York, Donald G; Bahcall, Neta A; Barentine, J; Blanton, Michael R; Brewington, Howard; Brinkmann, J; Brunner, Robert J; Castander, Francisco J; Csabai, Istvan; Frieman, Joshua A; Fukugita, Masataka; Harvanek, Michael; Hogg, David W; Ivezic, Zeljko; Kent, Stephen M; Kleinman, S J; Knapp, G R; Kron, Richard G; Krzesinski, Jurek; Long, Daniel C; Lupton, Robert H; Nitta, Atsuko; Pier, Jeffrey R; Saxe, David H; Shen, Yue; Snedden, Stephanie A; Weinberg, David H; Wu, Jian

    2007-01-01

    We present the fourth edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog. The catalog contains 77,429 objects; this is an increase of over 30,000 entries since the previous edition. The catalog consists of the objects in the SDSS Fifth Data Release that have luminosities larger than M_i = -22.0 (in a cosmology with H_0 = 70 km/s/Mpc, Omega_M = 0.3, and Omega_Lambda = 0.7) have at least one emission line with FWHM larger than 1000 km/s, or have interesting/complex absorption features, are fainter than i=15.0, and have highly reliable redshifts. The area covered by the catalog is 5740 sq. deg. The quasar redshifts range from 0.08 to 5.41, with a median value of 1.48; the catalog includes 891 quasars at redshifts greater than four, of which 36 are at redshifts greater than five. Approximately half of the catalog quasars have i < 19; nearly all have i < 21. For each object the catalog presents positions accurate to better than 0.2 arcsec. rms per coordinate, five-band (ugriz) CCD-based photometry...

  17. The Sloan Digital Sky Survey Quasar Catalog III. Third Data Release

    CERN Document Server

    Schneider, D P; Richards, G T; Vanden Berk, Daniel E; Anderson, S F; Fan, X; Jester, S; Stoughton, C; Strauss, M A; Subba-Rao, M; Brandt, W; Gunn, J E; Yanny, B; Bahcall, Neta A; Barentine, J C; Blanton, M R; Boroski, W N; Brewington, H J; Brinkmann, J; Brunner, R; Csabai, I; Doi, M; Eisenstein, D J; Frieman, J A; Fukugita, M; Gray, J; Harvanek, M; Heckman, T M; Ivezic, Z; Kent, S; Kleinman, S; Knapp, G R; Kron, R G; Krzesínski, J; Long, D C; Loveday, J; Lupton, R H; Margon, B; Munn, J A; Neilsen, E H; Newberg, H J; Newman, P R; Nichol, R; Nitta, A; Pier, J R; Rockosi, C M; Saxe, D H; Schlegel, D J; Snedden, S A; Szalay, A S; Thakar, A R; Uomoto, A; York, D G

    2005-01-01

    We present the third edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog. The catalog consists of the 46,420 objects in the SDSS Third Data Release that have luminosities larger than M_i = -22 (in a cosmology with H_0 = 70 km/s/Mpc, Omega_M = 0.3, and Omega_Lambda = 0.7), have at least one emission line with FWHM larger than 1000 km/s or are unambiguously broad absorption line quasars, are fainter than i = 15.0, and have highly reliable redshifts. The area covered by the catalog is 4188 sq. deg. The quasar redshifts range from 0.08 to 5.41, with a median value of 1.47; the high-redshift sample includes 520 quasars at redshifts greater than four, of which 17 are at redshifts greater than five. For each object the catalog presents positions accurate to better than 0.2 arcsec. rms per coordinate, five-band (ugriz) CCD-based photometry with typical accuracy of 0.03 mag, and information on the morphology and selection method. The catalog also contains radio, near-infrared, and X-ray emission properties o...

  18. CIV Broad Absorption Line Acceleration in Sloan Digital Sky Survey Quasars

    CERN Document Server

    Grier, C J; Hall, P B; Trump, J R; Ak, N Filiz; Anderson, S F; Green, Paul J; Schneider, D P; Sun, M; Vivek, M; Beatty, T G; Brownstein, Joel R; Roman-Lopes, Alexandre

    2016-01-01

    We present results from the largest systematic investigation of broad absorption line (BAL) acceleration to date. We use spectra of 140 quasars from three Sloan Digital Sky Survey programs to search for global velocity offsets in BALs over timescales of ~2.5-5.5 years in the quasar rest frame. We carefully select acceleration candidates by requiring monolithic velocity shifts over the entire BAL trough, avoiding BALs with velocity shifts that might be caused by profile variability. The CIV BALs of two quasars show velocity shifts consistent with the expected signatures of BAL acceleration, and the BAL of one quasar shows a velocity-shift signature of deceleration. In our two acceleration candidates, we see evidence that the magnitude of the acceleration is not constant over time; the magnitudes of the change in acceleration for both acceleration candidates are difficult to produce with a standard disk-wind model or via geometric projection effects. We measure upper limits to acceleration and deceleration for ...

  19. The Sloan Digital Sky Survey Reverberation Mapping Project: Post-Starburst Signatures in Quasar Host Galaxies at z < 1

    CERN Document Server

    Matsuoka, Yoshiki; Shen, Yue; Brandt, William N; Greene, Jenny E; Ho, Luis C; Schneider, Donald P; Sun, Mouyuan; Trump, Jonathan R

    2015-01-01

    Quasar host galaxies are key for understanding the relation between galaxies and the supermassive black holes (SMBHs) at their cores. We present a study of 191 unobscured quasars and their host galaxies at z < 1, using high signal-to-noise ratio (SNR) spectra produced by the Sloan Digital Sky Survey Reverberation Mapping project. Clear detection of stellar absorption lines allows a reliable decomposition of the observed spectra into nuclear and host components, using spectral models of quasar and stellar radiations as well as emission lines from the interstellar medium. We estimate age, mass (M*), and velocity dispersion (sigma*) of the host stars, the star formation rate (SFR), quasar luminosity, and SMBH mass (Mbh), for each object. The quasars are preferentially hosted by massive galaxies with M* ~ 10^{11} Msun characterized by stellar ages around a billion years, which coincides with the transition phase of normal galaxies from the blue cloud to the red sequence. The host galaxies have relatively low S...

  20. Radio Luminosity,Black Hole Mass and Eddington Ratio for Quasars from the Sloan Digital Sky Survey

    Institute of Scientific and Technical Information of China (English)

    Wei-Hao Bian; Yan-Mei Chen; Chen Hu; Kai Huang; Yan Xu

    2008-01-01

    We investigate the MBH-O'.relation for radio-loud quasars with redshift z<0.83 in Data Release 3 of the Sloan Digital Sky Survey (SDSS).The sample consists of 3772 quasars with better models of the H/~ and [O III] lines and available radio luminosity,including 306 radio-loud quasars,3466 radio-quiet quasars with measured radio luminosity or upper-limit of radio luminosity (181 radio-quiet quasars with measured radio luminosity).The virial supermassive black hole mass (MBH) is calculated from the broad H/line,and the host stellar velocity dispersion (σ*) is traced by the core [O III] gaseous velocity dispersion.The radio luminosity and radio loudness are derived from the FIRST catalog.Our results are as follows:(1) For radio-quiet quasars,we confirm that there is no obvious deviation from the MBH-O".relation defined for inactive galaxies when the uncertainties in MBH and the luminosity bias are concerned.(2) We find that the radio-loud quasars deviate more from the MBH-σ.relation than do the radio-quiet quasars.This deviation is only partly due to a possible cosmological evolution of the MBH-σ* relation and the luminosity bias.(3) The radioluminosity is proportional to M128+0.23-0.16 BH(LBol/LEdd)1.29+0.31-0.24 for radio-quiet quasars and to M3.10+0.6.-0.70(LBol.LEdd)4.18+1.40-1.10 for radio-loud quasars.The weaker dependence of the radio luminosity on the mass and the Eddington ratio for radio-loud quasars shows that other physical effects would account for their radio luminosities,such as the spin of the black hole.

  1. Discovery of three z>6.5 quasars in the VISTA Kilo-degree Infrared Galaxy (VIKING) survey

    CERN Document Server

    Venemans, B P; Sutherland, W J; De Rosa, G; McMahon, R G; Simcoe, R; Gonzalez-Solares, E A; Kuijken, K; Lewis, J R

    2013-01-01

    Studying quasars at the highest redshifts can constrain models of galaxy and black hole formation, and it also probes the intergalactic medium in the early universe. Optical surveys have to date discovered more than 60 quasars up to z~6.4, a limit set by the use of the z-band and CCD detectors. Only one z>6.4 quasar has been discovered, namely the z=7.08 quasar ULAS J1120+0641, using near-infrared imaging. Here we report the discovery of three new z>6.4 quasars in 332 square degrees of the Visible and Infrared Survey Telescope for Astronomy Kilo-degree Infrared Galaxy (VIKING) survey, thus extending the number from 1 to 4. The newly discovered quasars have redshifts of z=6.61, 6.75, and 6.89. The absolute magnitudes are between -26.0 and -25.5, 0.6-1.1 mag fainter than ULAS J1120+0641. Near-infrared spectroscopy revealed the MgII emission line in all three objects. The quasars are powered by black holes with masses of ~(1-2)x10^9 M_sun. In our probed redshift range of 6.4410^9 M_sun) > 1.1x10^(-9) Mpc^(-3). T...

  2. Clustering of High Redshift (z>2.9) Quasars from the Sloan Digital Sky Survey

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Yue; Strauss, Michael A.; Oguri, Masamune; Hennawi, Joseph F.; Fan, Xiaohui; Richards, Gordon T.; Hall, Patrick B.; Schneider, Donald P.; Szalay, Alexander S.; Thakar, Anirudda R.; Berk, Daniel E.Vanden; Anderson, Scott F.; Bahcall, Neta A.; /KIPAC, Menlo Park

    2006-11-30

    We study the two-point correlation function of a uniformly selected sample of 4,428 optically selected luminous quasars with redshift 2.9 {le} z {le} 5.4 selected over 4041 deg{sup 2} from the Fifth Data Release of the Sloan Digital Sky Survey. We fit a power-law to the projected correlation function w{sub p}(r{sub p}) to marginalize over redshift space distortions and redshift errors. For a real-space correlation function of the form {zeta}(r) = (r/r{sub 0}){sup -{gamma}}, the fitted parameters in comoving coordinates are r{sub 0} = 15.2 {+-} 2.7 h{sup -1} Mpc and {gamma} = 2.0 {+-} 0.3, over a scale range 4 {le} r{sub p} {le} 150 h{sup -1} Mpc. Thus high-redshift quasars are appreciably more strongly clustered than their z {approx} 1.5 counterparts, which have a comoving clustering length r{sub 0} {approx} 6.5 h{sup -1} Mpc. Dividing our sample into two redshift bins: 2.9 {le} z {le} 3.5 and z {ge} 3.5, and assuming a power-law index {gamma} = 2.0, we find a correlation length of r{sub 0} = 16.9 {+-} 1.7 h{sup -1} Mpc for the former, and r{sub 0} = 24.3 {+-} 2.4 h{sup -1} Mpc for the latter. Strong clustering at high redshift indicates that quasars are found in very massive, and therefore highly biased, halos. Following Martini & Weinberg, we relate the clustering strength and quasar number density to the quasar lifetimes and duty cycle. Using the Sheth & Tormen halo mass function, the quasar lifetime is estimated to lie in the range 4 {approx} 50 Myr for quasars with 2.9 {le} z {le} 3.5; and 30 {approx} 600 Myr for quasars with z {ge} 3.5. The corresponding duty cycles are 0.004 {approx} 0.05 for the lower redshift bin and 0.03 {approx} 0.6 for the higher redshift bin. The minimum mass of halos in which these quasars reside is 2-3 x 10{sup 12} h{sup -1} M{sub {circle_dot}} for quasars with 2.9 {le} z {le} 3.5 and 4-6 x 10{sup 12} h{sup -1} M{sub {circle_dot}} for quasars with z {ge} 3.5; the effective bias factor b{sub eff} increases with redshift, e.g., b

  3. High-Redshift Quasars Found in Sloan Digital Sky Survey Commissioning Data. II. The Spring Equatorial Stripe

    International Nuclear Information System (INIS)

    This is the second paper in a series aimed at finding high-redshift quasars from five-color (u' g' r' i' z') imaging data taken along the Celestial Equator by the Sloan Digital Sky Survey (SDSS) during its commissioning phase. In this paper, we present 22 high-redshift quasars (z>3.6) discovered from ∼250 deg2 of data in the spring Equatorial Stripe, plus photometry for two previously known high-redshift quasars in the same region of the sky. Our success rate in identifying high-redshift quasars is 68%. Five of the newly discovered quasars have redshifts higher than 4.6 (z=4.62, 4.69, 4.70, 4.92, and 5.03). All the quasars have i* B 0 =0.5). Several of the quasars show unusual emission and absorption features in their spectra, including an object at z=4.62 without detectable emission lines, and a broad absorption line (BAL) quasar at z=4.92. (c) (c) 2000. The American Astronomical Society

  4. Measuring large-scale structure with quasars in narrow-band filter surveys

    CERN Document Server

    Abramo, L Raul; Lima, Marcos; Hernández-Monteagudo, Carlos; Lazkoz, Ruth; Moles, Mariano; de Oliveira, Cláudia M; Sendra, Irene; Sodré, Laerte

    2011-01-01

    We show that a large-area imaging survey using narrow-band filters could detect quasars in sufficiently high number densities, and with more than sufficient accuracy in their photometric redshifts, to turn them into suitable tracers of large-scale structure. If a narrow-band optical survey can detect objects as faint as i=23, it could reach volumetric number densities as high as 10^{-4} h^3 Mpc^{-3} (comoving) at z~1.5 . Such a catalog would lead to precision measurements of the power spectrum up to z~3-4. We also show that it is possible to employ quasars to measure baryon acoustic oscillations at high redshifts, where the uncertainties from redshift distortions and nonlinearities are much smaller than at z<1. As a concrete example we study the future impact of J-PAS, which is a narrow-band imaging survey in the optical over 1/5 of the unobscured sky with 42 filters of ~100 A full-width at half-maximum. We show that J-PAS will be able to take advantage of the broad emission lines of quasars to deliver exc...

  5. The Sloan Digital Sky Survey Quasar Catalog II. First Data Release

    CERN Document Server

    Schneider, D P; Hall, P B; Jester, S; Richards, G T; Stoughton, C; Strauss, M A; Subba-Rao, M; Vanden Berk, Daniel E; Anderson, S F; Brandt, W N; Gunn, J E; Gray, J; Trump, J R; Voges, W; Yanny, B; Schneider, Donald P.; Fan, Xiaohui; Hall, Patrick B.; Jester, Sebastian; Richards, Gordon T.; Stoughton, Chris; Strauss, Michael A.; Rao, Mark Subba; Berk, Daniel E. Vanden; Anderson, Scott F.; Gunn, James E.; Gray, Jim; Trump, Jonathan R.; Voges, Wolfgang; Yanny, Brian

    2003-01-01

    We present the second edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog. The catalog consists of 16713 objects in the SDSS First Data Release (DR1) that have luminosities larger than M_i=-22 (H_0=70 km/s, Omega_M=0.3, Omega_Lambda=0.7), have at least one emission line with FWHM larger than 1000 km/s, and have highly reliable redshifts. The area covered is ~1360 deg^2 and the redshifts range from 0.08 to 5.41, with a median value of 1.43. Each object has positions accurate to better than 0.2" rms per coordinate, five-band (ugriz) CCD-based photometry with typical accuracy of 0.03 mag, and information on the morphology and selection method, in addition to radio, near-infrared, and X-ray emission properties of the quasars, when available, from other large area surveys. Calibrated digital spectra covering 3800-9200 Angstroms at a spectral resolution 1800-2100, are available. This publication supersedes the first SDSS Quasar Catalog, which was based on material from the SDSS Early Data Release. A summa...

  6. New Challenges in Cosmology Posed by the Sloan Digital Sky Survey Quasar Data

    Science.gov (United States)

    Banerjee, Adrija; Kumar Pal, Arnab

    2014-05-01

    For SDSS quasar data (2005) we have truncated data structure whereas for the survey of 2007 the data is no longer truncated. This calls for development or use of completely different statistical methodology to study the data for the evolution of the same objects like quasars. These different methodologies suggest different interpretation for a particular phenomenon in nature. This leads to the issue of validation of the data. More intriguing and challenging issue crops up as, given all of the data, what can be said about the laws of physics that have been operating over the universe? Over here we have used the concept of Neural Network to model the relationship between redshift and apparent magnitude.

  7. Broad Absorption Line Variability in Repeat Quasar Observations from the Sloan Digital Sky Survey

    CERN Document Server

    Lundgren, B F; Brunner, R J; Hall, P B; Schneider, D P; York, D G; Vanden Berk, D E; Brinkmann, J; Lundgren, Britt F.; Wilhite, Brian C.; Brunner, Robert J.; Hall, Patrick B.; Schneider, Donald P.; York, Donald G.; Berk, Daniel E. Vanden; Brinkmann, Jonathan

    2006-01-01

    We present a time-variability analysis of 29 broad absorption line quasars (BALQSOs) observed in two epochs by the Sloan Digital Sky Survey (SDSS). These spectra are selected from a larger sample of BALQSOs with multiple observations by virtue of exhibiting a broad CIV $\\lambda$1549 absorption trough separated from the rest frame of the associated emission peak by more than 3600 km s$^{-1}$. Detached troughs facilitate higher precision variability measurements, since the measurement of the absorption in these objects is not complicated by variation in the emission line flux. We have undertaken a statistical analysis of these detached-trough BALQSO spectra to explore the relationships between BAL features that are seen to vary and the dynamics of emission from the quasar central engine. We have measured variability within our sample, which includes three strongly variable BALs. We have also verified that the statistical behavior of the overall sample agrees with current model predictions and previous studies o...

  8. Exploiting the full potential of photometric quasar surveys: Optimal power spectra through blind mitigation of systematics

    CERN Document Server

    Leistedt, Boris

    2014-01-01

    We present optimal measurements of the angular power spectrum of the XDQSOz catalogue of photometric quasars from the Sloan Digital Sky Survey. These measurements rely on a quadratic maximum likelihood estimator that simultaneously measures the auto- and cross-power spectra of four redshift samples, and provides minimum-variance, unbiased estimates even at the largest angular scales. Since photometric quasars are known to be strongly affected by systematics such as spatially-varying depth and stellar contamination, we introduce a new framework of extended mode projection to robustly mitigate the impact of systematics on the power spectrum measurements. This technique involves constructing template maps of potential systematics, decorrelating them on the sky, and projecting out modes which are significantly correlated with the data. Our method is able to simultaneously process several thousands of nonlinearly-correlated systematics, and mode projection is performed in a blind fashion. Using our final power spe...

  9. The ROSAT All-Sky Survey Bright Source Catalogue

    CERN Document Server

    Voges, W; Boller, T; Bräuninger, H; Briel, U G; Burkert, W K A; Dennerl, K; Englhauser, J; Gruber, R; Haberl, F; Hartner, G; Hasinger, G; Pfeffermann, E; Pietsch, W; Predehl, P; Rosso, C; Schmitt, J H M M; Trümper, J E; Zimmermann, H U; Voges, Wolfgang; Aschenbach, Bernd; Boller, Thomas; Braeuninger, Heinrich; Briel, Ulrich; Burkert, Wolfgang; Dennerl, Konrad; Englhauser, Jakob; Gruber, Rainer; Haberl, Frank; Hartner, Gisela; Hasinger, Guenther; Pfeffermann, Elmar; Pietsch, Wolfgang; Predehl, Peter; Rosso, Cristina; Schmitt, Juergen H.M.M.; Truemper, Joachim; Zimmermann, Hans-Ulrich

    1999-01-01

    We present the ROSAT All-Sky Survey Bright Source Catalogue (RASS-BSC, revision 1RXS) derived from the all-sky survey performed during the first half year (1990/91) of the ROSAT mission. 18,811 sources are catalogued (i) down to a limiting ROSAT PSPC count-rate of 0.05 cts/s in the 0.1-2.4 keV energy band, (ii) with a detection likelihood of at least 15 and (iii) at least 15 source counts. The 18,811 sources underwent both an automatic validation and an interactive visual verification process in which for 94% of the sources the results of the standard processing were confirmed. The remaining 6% have been analyzed using interactive methods and these sources have been flagged. Flags are given for (i) nearby sources; (ii) sources with positional errors; (iii) extended sources; (iv) sources showing complex emission structures; and (v) sources which are missed by the standard analysis software. Broad band (0.1-2.4 keV) images are available for sources flagged by (ii), (iii) and (iv). For each source the ROSAT name...

  10. Nature and statistical properties of quasar associated absorption systems in the XQ-100 Legacy Survey

    CERN Document Server

    Perrotta, Serena; Prochaska, J Xavier; Cristiani, Stefano; Cupani, Guido; Ellison, Sara; Lòpez, Sebastian; Becker, George D; Berg, Trystyn A M; Christensen, Lise; Denney, Kelly D; Hamann, Frederick; Pâris, Isabelle; Vestergaard, Marianne; Worseck, Gábor

    2016-01-01

    We statistically study the physical properties of a sample of narrow absorption line (NAL) systems looking for empirical evidences to distinguish between intrinsic and intervening NALs without taking into account any a priori definition or velocity cut-off. We analyze the spectra of 100 quasars with 3.5 < z$\\rm_{em}$ < 4.5, observed with X-shooter/VLT in the context of the XQ-100 Legacy Survey. We detect a $\\sim$ 8 $\\sigma$ excess in the number density of absorbers within 10,000 km/s of the quasar emission redshift with respect to the random occurrence of NALs. This excess does not show a dependence on the quasar bolometric luminosity and it is not due to the redshift evolution of NALs. It extends far beyond the standard 5000 km/s cut-off traditionally defined for associated absorption lines. We propose to modify this definition, extending the threshold to 10,000 km/s when also weak absorbers (equivalent width < 0.2 \\AA) are considered. We infer NV is the ion that better traces the effects of the qua...

  11. Simulations of BAO reconstruction with a quasar Lyman-alpha survey

    CERN Document Server

    Goff, J -M Le; Rollinde, E; Peirani, S; Petitjean, P; Pichon, C; Rich, J; Yeche, C; Aubourg, E; Busca, N; Charlassier, R; Delubac, T; Hamilton, J C; Delabrouille, N Palanque; Paris, I; Vargas, M

    2011-01-01

    The imprint of Baryonic Acoustic Oscillations (BAO) on the matter power spectrum can be constrained using the neutral hydrogen density in the intergalactic medium as a tracer of the matter density. One of the goals of the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey (SDSS-III) is to derive the Hubble expansion rate and the angular scale from the BAO signal in the IGM. To this aim, the Lyman-alpha forest of 10^5 quasars will be observed in the redshift range 2.2survey to estimate the statistical accuracy on the BAO scale determination provided by such a large scale survey. In particular, we discuss the effect of the poorly constrained estimate of the unabsorbed intrinsic quasar spectrum. The volume of current N-body simulations being too small for such studies, we resorted to Gaussian random field (GRF) simulations. We validated the use of GRFs by comparing the output of GRF simulations with that of the Horizon N-bo...

  12. The Environments of Obscured Quasars

    Science.gov (United States)

    Jones, Kristen M.; Lacy, Mark; Nielsen, Danielle

    2016-01-01

    Supermassive Black Hole (SMBH) feedback is prescribed for driving the high-end shape of the galaxy luminosity function, clearing the circumnuclear environment during the end stages of mergers, and eventually turning off its own accretion. Yet the dominant processes and characteristics of active galactic nuclei are indistinct. Chief among this confusion is how significant the role of dust is in each galaxy. Orientation of the dusty torus is attributed to causing the differences between Sy1 and Sy2, but whether obscured quasars are found in particularly dusty host galaxies, if they exist at a different stage in the merger process (early on, before the dust is blown out), or if they are merely oriented differently than optical quasars is not yet so well distinguished. With obscured quasars now observed to make up 50% or greater of the population of quasars, the question of what causes obscuration becomes vital to address. With this in mind, I study matched samples of obscured and unobscured quasars to characterize their environments, with the intent of addressing what contribution environment has to obscuration levels. I investigate the megaparsec-scale environments of SIRTF Wide-field Infra-Red Extragalactic Survey (SWIRE) quasars at z ˜ 1-3 by cross-correlating the sample with 3.8 million galaxies from the Spitzer Extragalactic Representative Volume Survey (SERVS). Optically obscured quasars are compared to a control sample of optically-bright quasars via selection in the mid-infrared. Environments were observed at 3.6 and 4.5 μm to a depth of ≈ 2 μJy (AB = 23.1). Recent work has found diverse results in such studies, with dependence of environmental richness on both redshift and level of obscuration. I find that, within reasonable error, on average there is no distinct difference between the level of clustering for obscured and normal quasars, and that there is no dependence on redshift of this result within the range of 1.3 < z < 2.5. I compare our results

  13. A survey of luminous high-redshift quasars with SDSS and WISE. I. target selection and optical spectroscopy

    CERN Document Server

    Wang, Feige; Fan, Xiaohui; Yang, Jinyi; Yi, Weimin; Bian, Fuyan; McGreer, Ian D; Yang, Qian; Ai, Yanli; Dong, Xiaoyi; Zuo, Wenwen; Jiang, Linhua; Green, Richard; Wang, Shu; Cai, Zheng; Wang, Ran; Yue, Minghao

    2016-01-01

    High-redshift quasars are important tracers of structure and evolution in the early universe. However, they are very rare and difficult to find when using color selection because of contamination from late-type dwarfs. High-redshift quasar surveys based on only optical colors suffer from incompleteness and low identification efficiency, especially at $z\\gtrsim4.5$. We have developed a new method to select $4.7\\lesssim z \\lesssim 5.4$ quasars with both high efficiency and completeness by combining optical and mid-IR Wide-field Infrared Survey Explorer (WISE) photometric data, and are conducting a luminous $z\\sim5$ quasar survey in the whole Sloan Digital Sky Survey (SDSS) footprint. We have spectroscopically observed 99 out of 110 candidates with $z$-band magnitudes brighter than 19.5 and 64 (64.6\\%) of them are quasars with redshifts of $4.4\\lesssim z \\lesssim 5.5$ and absolute magnitudes of $-29\\lesssim M_{1450} \\lesssim -26.4$. In addition, we also observed 14 fainter candidates selected with the same crite...

  14. Narrow C IV absorption doublets on quasar spectra of the Baryon Oscillation Spectroscopic Survey

    CERN Document Server

    Zhi-fu, Chen; Luwenjia, Zhou; Yanmei, Chen

    2016-01-01

    In this paper, we extend our works of Papers I and II, which are assigned to systematically survey \\CIVab\\ narrow absorption lines (NALs) with \\zabs$\\ll$\\zem\\ on quasar spectra of the Baryon Oscillation Spectroscopic Survey (BOSS), to collect \\CIV\\ NALs with \\zabs$\\approx$\\zem\\ from blue to red wings of \\CIVwave\\ emission lines. Together with Papers I and II, we have collected a total number of 41,479 \\CIV\\ NALs with $1.4544\\le$\\zabs$\\le4.9224$ in surveyed spectral region redward of \\lya\\ until red wing of \\CIVwave\\ emission line. We find that the stronger \\CIV\\ NALs tend to be the more saturated absorptions, and associated systems (\\zabs$\\approx$\\zem) seem to have larger absorption strengths when compared to intervening ones (\\zabs$\\ll$\\zem). The redshift density evolution behavior of absorbers (the number of absorbers per redshift path) is similar to the history of the cosmic star formation. When compared to the quasar-frame velocity ($\\beta$) distribution of \\MgII\\ absorbers, the $\\beta$ distribution of \\C...

  15. On the peculiar X-ray properties of the bright nearby radio-quiet quasar PDS456

    OpenAIRE

    Vignali, C; Comastri, A.; F. Nicastro; Matt, G.; Fiore, F.; Palumbo, G. G. C.

    2000-01-01

    BeppoSAX and ASCA observations of the nearby (z=0.184), high-luminosity, radio-quiet quasar PDS456 are presented. The X-ray spectrum is characterized by a prominent ionized edge at 8-9 keV (originally discovered by RXTE, Reeves et al. 2000) and by a soft excess below 1.5 keV. The lack of any significant iron K alpha emission line suggests for the edge an origin from line-of-sight material rather than from reflection from a highly ionized accretion disc. The hard X-ray continuum is indeed well...

  16. Binary Quasars in the Sloan Digital Sky Survey: Evidence for Excess Clustering on Small Scales

    CERN Document Server

    Hennawi, J F; Oguri, M; Inada, N; Richards, G T; Pindor, B; Schneider, D P; Becker, R H; Gregg, M D; Hall, P B; Johnston, D E; Fan, X; Burles, S; Schlegel, D J; Gunn, J E; Lupton, R; Bahcall, Neta A; Brunner, R J; Brinkmann, J; Hennawi, Joseph F.; Strauss, Michael A.; Oguri, Masamune; Inada, Naohisa; Richards, Gordon T.; Pindor, Bartosz; Schneider, Donald P.; Becker, Robert H.; Gregg, Michael D.; Hall, Patrick B.; Johnston, David E.; Fan, Xiaohui; Burles, Scott; Schlegel, David J.; Gunn, James E.; Lupton, Robert; Bahcall, Neta A.; Brunner, Robert J.; Brinkman, Jon

    2006-01-01

    We present a sample of 218 new quasar pairs with proper transverse separations R_prop 3 Mpc/h quasar correlation function, extrapolated down as a power law to the separations probed by our binaries. The excess grows to ~ 30 at R_prop ~ 10 kpc/h, and provides compelling evidence that the quasar autocorrelation function gets progressively steeper on sub-Mpc scales. This small scale excess can likely be attributed to dissipative interaction events which trigger quasar activity in rich environments. Recent small scale measurements of galaxy clustering and quasar-galaxy clustering are reviewed and discussed in relation to our measurement of small scale quasar clustering.

  17. THE SDSS-III BARYON OSCILLATION SPECTROSCOPIC SURVEY: THE QUASAR LUMINOSITY FUNCTION FROM DATA RELEASE NINE

    International Nuclear Information System (INIS)

    We present a new measurement of the optical quasar luminosity function (QLF), using data from the Sloan Digital Sky Survey-III: Baryon Oscillation Spectroscopic Survey (SDSS-III: BOSS). From the SDSS-III Data Release Nine, a uniform sample of 22,301 i ∼2, with confirmed spectroscopic redshifts between 2.2 i (z = 2.2) ≈ –24.5 and see a clear break in the QLF at all redshifts up to z = 3.5. A log-linear relation (in log Φ* – M*) for a luminosity evolution and density evolution model is found to adequately describe our data within the range 2.2 < z < 3.5; across this interval the break luminosity increases by a factor of ∼2.6 while Φ* declines by a factor of ∼8. At z ∼< 2.2 our data are reasonably well fit by a pure luminosity evolution model, and only a weak signature of ''AGN downsizing'' is seen, in line with recent studies of the hard X-ray luminosity function. We compare our measured QLF to a number of theoretical models and find that models making a variety of assumptions about quasar triggering and halo occupation can fit our data over a wide range of redshifts and luminosities

  18. Bright [CII] 158$\\mu$m emission in a quasar host galaxy at $z=6.54$

    CERN Document Server

    Bañados, E; Walter, F; Venemans, B P; Farina, E P; Fan, X

    2015-01-01

    The [CII] 158$\\mu$m fine-structure line is known to trace regions of active star formation and is the main coolant of the cold, neutral atomic medium. In this \\textit{Letter}, we report a strong detection of the [CII] line in the host galaxy of the brightest quasar known at $z>6.5$, the Pan-STARRS1 selected quasar PSO J036.5078+03.0498 (hereafter P036+03), using the IRAM NOEMA millimeter interferometer. Its [CII] and total far-infrared luminosities are $(5.8 \\pm 0.7) \\times 10^9 \\,L_\\odot$ and $(7.6\\pm1.5) \\times 10^{12}\\,L_\\odot$, respectively. This results in a $L_{[CII]} /L_{TIR}$ ratio of $\\sim 0.8\\times 10^{-3}$, which is at the high end for those found for active galaxies, though it is lower than the average found in typical main sequence galaxies at $z\\sim 0$. We also report a tentative additional line which we identify as a blended emission from the $3_{22} - 3_{13}$ and $5_{23} - 4_{32}$ H$_2$O transitions. If confirmed, this would be the most distant detection of water emission to date. P036+03 riva...

  19. The Sloan Digital Sky Survey Quasar Lens Search. III Constraints on Dark Energy From The Third Data Release Quasar Lens Catalog

    Energy Technology Data Exchange (ETDEWEB)

    Oguri, M; Inada, N; Strauss, M A; Kochanek, C S; Richards, G T; Schneider, D P; Becker, R H; Fukugita, M; Gregg, M D; Hall, P B; Hennawi, J F; Johnston, D E; Kayo, I; Keeton, C R; Pindor, B; Shin, M; Turner, E; White, R L; York, D G; Anderson, S F; Bahcall, N A; Brunner, R J; Burles, S; Castander, F J; Chiu, K; Clocchiatti, A; Einsenstein, D; Frieman, J; Kawano, Y; Lupton, R; Morokuma, T; Rix, H; Scranton, R; Sheldon, E S

    2007-09-12

    We present cosmological results from the statistics of lensed quasars in the Sloan Digital Sky Survey (SDSS) Quasar Lens Search. By taking proper account of the selection function, we compute the expected number of quasars lensed by early-type galaxies and their image separation distribution assuming a flat universe, which is then compared with 7 lenses found in the SDSS Data Release 3 to derive constraints on dark energy under strictly controlled criteria. For a cosmological constant model (w = -1) we obtain {Omega}{sub {Lambda}} = 0.74{sub -0.15}{sup +0.11}(stat.){sub -0.06}{sup +0.13}(syst.). Allowing w to be a free parameter we find {Omega}{sub M} = 0.26{sub -0.06}{sup +0.07}(stat.){sub -0.05}{sup +0.03}(syst.) and w = -1.1 {+-} 0.6(stat.){sub -0.5}{sup +0.3}(syst.) when combined with the constraint from the measurement of baryon acoustic oscillations in the SDSS luminous red galaxy sample. Our results are in good agreement with earlier lensing constraints obtained using radio lenses, and provide additional confirmation of the presence of dark energy consistent with a cosmological constant, derived independently of type Ia supernovae.

  20. Implications for the Number Density of Quasars at z > 4.8 Using VIZJ Imaging from the BTC40 Multicolor Survey

    Science.gov (United States)

    Bursick, Shelly; Kennefick, J. D.; Smith, M.; Monier, E.; Hall, P.; Osmer, P.; Dalton, G.; Green, R.

    2009-01-01

    We present the results of optical spectroscopy of four faint high redshift quasar candidates taken with the GMOS -S instrument on Gemini South during the spring 08’ and fall 06’ semesters. These candidates were selected as part of the VIZ and J multicolor BTC40 survey for z > 4.8 quasars. We will discuss implications for the number density of quasars at these redshifts.

  1. Multi-Epoch VLBA Observations of EGRET-Detected Quasars and BL Lac Objects Superluminal Motion of Gamma-Ray Bright Blazars

    CERN Document Server

    Jorstad, S G; Mattox, J R; Wehrle, A E; Bloom, S D; Yurchenko, A V; Jorstad, Svetlana G; Marscher, Alan P; Mattox, John R; Wehrle, Ann E; Bloom, Steven D; Yurchenko, Alexei V

    2001-01-01

    We present the results of a program to monitor the structure of the radio emission in 42 $\\gamma$-ray bright blazars (31 quasars and 11 BL Lac objects) with the VLBA at 43, 22, and occasionally 15 and 8.4 GHz, over the period from November 1993 to July 1997. We determine proper motions in 33 sources and find that the apparent superluminal motions in $\\gamma$-ray sources are much faster than for the general population of bright compact radio sources. This follows the strong dependence of the $\\gamma$-ray flux on the level of relativistic beaming for both external-radiation Compton and synchrotron self-Compton emission. There is a positive correlation (correlation coefficient $r$=0.45) between the flux density of the VLBI core and the $\\gamma$-ray flux and a moderate correlation (partial correlation coefficient $r$=0.31) between $\\gamma$-ray apparent luminosity and superluminal velocities of jet components, as expected if the $\\gamma$-ray emission originates in a very compact region of the relativistic jet and ...

  2. Machine learning techniques for astrophysical modelling and photometric redshift estimation of quasars in optical sky surveys

    CERN Document Server

    Kumar, N Daniel

    2008-01-01

    Machine learning techniques are utilised in several areas of astrophysical research today. This dissertation addresses the application of ML techniques to two classes of problems in astrophysics, namely, the analysis of individual astronomical phenomena over time and the automated, simultaneous analysis of thousands of objects in large optical sky surveys. Specifically investigated are (1) techniques to approximate the precise orbits of the satellites of Jupiter and Saturn given Earth-based observations as well as (2) techniques to quickly estimate the distances of quasars observed in the Sloan Digital Sky Survey. Learning methods considered include genetic algorithms, particle swarm optimisation, artificial neural networks, and radial basis function networks. The first part of this dissertation demonstrates that GAs and PSOs can both be efficiently used to model functions that are highly non-linear in several dimensions. It is subsequently demonstrated in the second part that ANNs and RBFNs can be used as ef...

  3. The Pittsburgh Sloan Digital Sky Survey MgII Quasar Absorption-Line Survey Catalog

    CERN Document Server

    Quider, Anna M; Turnshek, David A; Rao, Sandhya M; Monier, Eric M; Weyant, Anja N; Busche, Joseph R

    2011-01-01

    We present a catalog of intervening MgII quasar absorption-line systems in the redshift interval 0.36 17,000 measured MgII doublets. We also present data on the ~44,600 quasar spectra which were searched to construct the catalog, including redshift and magnitude information, continuum-normalized spectra, and corresponding arrays of redshift-dependent minimum rest equivalent widths detectable at our confidence threshold. The catalog is available on the web. A careful second search of 500 random spectra indicated that, for every 100 spectra searched, approximately one significant MgII system was accidentally rejected. Current plans to expand the catalog beyond DR4 quasars are discussed. Many MgII absorbers are known to be associated with galaxies. Therefore, the combination of large size and well understood statistics makes this catalog ideal for precision studies of the low-ionization and neutral gas regions associated with galaxies at low to moderate redshift. An analysis of the statistics of MgII absorbers ...

  4. Finding the Most Distant Quasars Using Bayesian Selection Methods

    CERN Document Server

    Mortlock, Daniel

    2014-01-01

    Quasars, the brightly glowing disks of material that can form around the super-massive black holes at the centres of large galaxies, are amongst the most luminous astronomical objects known and so can be seen at great distances. The most distant known quasars are seen as they were when the Universe was less than a billion years old (i.e., $\\sim\\!7%$ of its current age). Such distant quasars are, however, very rare, and so are difficult to distinguish from the billions of other comparably-bright sources in the night sky. In searching for the most distant quasars in a recent astronomical sky survey (the UKIRT Infrared Deep Sky Survey, UKIDSS), there were $\\sim\\!10^3$ apparently plausible candidates for each expected quasar, far too many to reobserve with other telescopes. The solution to this problem was to apply Bayesian model comparison, making models of the quasar population and the dominant contaminating population (Galactic stars) to utilise the information content in the survey measurements. The result wa...

  5. On the peculiar X-ray properties of the bright nearby radio-quiet quasar PDS456

    CERN Document Server

    Vignali, C; Nicastro, F; Matt, G; Fiore, F; Palumbo, G G C

    2000-01-01

    BeppoSAX and ASCA observations of the nearby (z=0.184), high-luminosity, radio-quiet quasar PDS456 are presented. The X-ray spectrum is characterized by a prominent ionized edge at 8-9 keV (originally discovered by RXTE, Reeves et al. 2000) and by a soft excess below 1.5 keV. The lack of any significant iron K alpha emission line suggests for the edge an origin from line-of-sight material rather than from reflection from a highly ionized accretion disc. The hard X-ray continuum is indeed well modelled by transmission through a highly-ionized medium with a large column density (N_H warm = 4.5 x 10^24 cm^-2) plus an additional cold absorber with a lower column density (N_H cold = 2.7 x 10^22 cm^-2).

  6. THE BLACK HOLE MASS-GALAXY LUMINOSITY RELATIONSHIP FOR SLOAN DIGITAL SKY SURVEY QUASARS

    International Nuclear Information System (INIS)

    We investigate the relationship between the mass of the central supermassive black hole, M BH, and the host galaxy luminosity, L gal, in a sample of quasars from the Sloan Digital Sky Survey Data Release 7. We use composite quasar spectra binned by black hole mass and redshift to assess galaxy features that would otherwise be overwhelmed by noise in individual spectra. The black hole mass is calculated using the photoionization method, and the host galaxy luminosity is inferred from the depth of the Ca II H+K features in the composite spectra. We evaluate the evolution in the M BH-L gal relationship by examining the redshift dependence of Δ log M BH, the offset in M BH from the local M BH-L gal relationship. There is little systematic trend in Δ log M BH out to z = 0.8. Using the width of the [O III] emission line as a proxy for the stellar velocity dispersion, σ*, we find agreement of our derived host luminosities with the locally observed Faber-Jackson relation. This supports the utility of the width of the [O III] line as a proxy for σ* in statistical studies

  7. THE BLACK HOLE MASS-GALAXY LUMINOSITY RELATIONSHIP FOR SLOAN DIGITAL SKY SURVEY QUASARS

    Energy Technology Data Exchange (ETDEWEB)

    Salviander, S.; Shields, G. A. [Department of Astronomy, University of Texas, Austin, TX 78712 (United States); Bonning, E. W., E-mail: triples@astro.as.utexas.edu, E-mail: shields@astro.as.utexas.edu, E-mail: erin.bonning@emory.edu [Department of Physics, Emory University, Atlanta, GA 30322 (United States)

    2015-02-01

    We investigate the relationship between the mass of the central supermassive black hole, M {sub BH}, and the host galaxy luminosity, L {sub gal}, in a sample of quasars from the Sloan Digital Sky Survey Data Release 7. We use composite quasar spectra binned by black hole mass and redshift to assess galaxy features that would otherwise be overwhelmed by noise in individual spectra. The black hole mass is calculated using the photoionization method, and the host galaxy luminosity is inferred from the depth of the Ca II H+K features in the composite spectra. We evaluate the evolution in the M {sub BH}-L {sub gal} relationship by examining the redshift dependence of Δ log M {sub BH}, the offset in M {sub BH} from the local M {sub BH}-L {sub gal} relationship. There is little systematic trend in Δ log M {sub BH} out to z = 0.8. Using the width of the [O III] emission line as a proxy for the stellar velocity dispersion, σ{sub *}, we find agreement of our derived host luminosities with the locally observed Faber-Jackson relation. This supports the utility of the width of the [O III] line as a proxy for σ{sub *} in statistical studies.

  8. Discovery of four doubly imaged quasar lenses from the Sloan digital sky survey

    Energy Technology Data Exchange (ETDEWEB)

    Inada, Naohisa [Department of Physics, Nara National College of Technology, Yamatokohriyama, Nara 639-1080 (Japan); Oguri, Masamune [Department of Physics, Graduate School of Science, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033 (Japan); Rusu, Cristian E. [Optical and Infrared Astronomy Division, National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo 181-8588 (Japan); Kayo, Issha [Department of Physics, Toho University, Funabashi, Chiba 274-8510 (Japan); Morokuma, Tomoki [Institute of Astronomy, Faculty of Science, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan)

    2014-06-01

    We report the discovery of four doubly imaged quasar lenses. All the four systems are selected as lensed quasar candidates from the Sloan Digital Sky Survey data. We confirm their lensing hypothesis with additional imaging and spectroscopic follow-up observations. The discovered lenses are SDSS J0743+2457 with the source redshift z{sub s} = 2.165, the lens redshift z{sub l} = 0.381, and the image separation θ = 1.''034, SDSS J1128+2402 with z{sub s} = 1.608 and θ = 0.''844, SDSS J1405+0959 with z{sub s} = 1.810, z{sub l} ≈ 0.66, and θ = 1.''978, and SDSS J1515+1511 with z{sub s} = 2.054, z{sub l} = 0.742, and θ = 1.''989. It is difficult to estimate the lens redshift of SDSS J1128+2402 from the current data. Two of the four systems (SDSS J1405+0959 and SDSS J1515+1511) are included in our final statistical lens sample to derive constraints on dark energy and the evolution of massive galaxies.

  9. VPMS J1342+2840 - an unusual quasar from the variability and proper motion survey

    CERN Document Server

    Meusinger, H; Haas, M; Irwin, M; Laget, M; Scholz, R D

    2005-01-01

    We report the discovery of the highly peculiar, radio-loud quasar VPMS J1342+2840 (z ~ 1.3) from the variability and proper motion survey. We present spectroscopic, imaging and photometric observations. The unusual spectrum shows a strong depression of the continuum over a wide wavelength range in the blue part without the typical structures of broad absorption line (BAL) troughs. The image of the quasar is unresolved and there is no evidence for a foreground object on the line of sight. The broad-band spectral energy distribution is not consistent with obvious dust reddening with the standard SMC extinction curve. The downturn of the continuum flux of VPMS J1342+2840 at short wavelengths can be caused by dust reddening only if the reddening curve is steeper then the SMC curve in the ultraviolet and is very flat at longer wavelengths. Alternatively, the dominant spectral features can be explained by low-ionization BALs forming unusually wide, overlapping absorption troughs.

  10. Color Effects Associated with the 1999 Microlensing Brightness Peaks in Gravitationally Lensed Quasar Q2237+0305

    CERN Document Server

    Vakulik, V G; Dudinov, V N; Minakov, A A; Nuritdinov, S N; Tsvetkova, V S; Zheleznyak, A P; Konichek, V V; Sinelnikov, I Y; Burkhonov, O M; Artamonov, B P; Bruevich, V V

    2003-01-01

    Photometry of the Q2237+0305gravitational lens in VRI spectral bands with the 1.5-m telescope of the high-altitude Maidanak observatory in 1995-2000 is presented. Monitoring of Q2237+0305 in July-October 2000, made at nearly daily basis, did not reveal rapid (night-to-night and intranight) variations of brightness of the components during this time period. Rather slow changes of magnitudes of the components were observed, such as 0.08 mag fading of B and C components and 0.05 mag brightening of D in R band during July 23 - October 7, 2000. By good luck three nights in 1999 were almost at the time of the strong brightness peak of image C, and approximately in the middle of the ascending slope of the image A brightness peak. The C component was the most blue one in the system in 1998 and 1999, having changed its (V-I) color from 0.56 mag to 0.12 mag since August 1997, while its brightness increased almost 1.2 mag during this time period. The A component behaved similarly between August 1998 and August 2000, hav...

  11. Selection constraints on high redshift quasar searches in the VISTA kilo-degree infrared galaxy survey

    CERN Document Server

    Findlay, J R; Venemans, B P; Reyle, C; Robin, A C; Bonfield, D G; Bruce, V A; Jarvis, M J

    2011-01-01

    The European Southern Observatory's (ESO) Visible and Infrared Survey Telescope for Astronomy (VISTA) is a 4-m class survey telescope for wide-field near-infrared imaging. VISTA is currently running a suite of six public surveys, which will shortly deliver their first Europe wide public data releases to ESO. The VISTA Kilo-degree Infrared Galaxy Survey (VIKING) forms a natural intermediate between current wide shallow, and deeper more concentrated surveys, by targeting two patches totalling 1500 sq.deg in the northern and southern hemispheres with measured 5-sigma limiting depths of Z ~ 22.4, Y ~ 21.4, J ~ 20.9, H ~ 19.9 and Ks ~19.3 (Vega). This architecture forms an ideal working parameter space for the discovery of a significant sample of 6.5 <= z <= 7.5 quasars. In the first data release priority has been placed on small areas encompassing a number of fields well sampled at many wavelengths, thereby optimising science gains and synergy whilst ensuring a timely release of the first products. For rare...

  12. Data Mining for Gravitationally Lensed Quasars

    CERN Document Server

    Agnello, Adriano; Treu, Tommaso; Marshall, Philip J

    2014-01-01

    Gravitationally lensed (GL) quasars are brighter than their unlensed counterparts and produce images with distinctive morphological signatures. Past searches and target selection algorithms, in particular the Sloan Quasar Lens Search (SQLS), have relied on basic morphological criteria, which were applied to samples of bright, spectroscopically confirmed quasars. The SQLS techniques are not sufficient for searching into new surveys (e.g. DES, PS1, LSST), because spectroscopic information is not readily available and the large data volume requires higher purity in target/candidate selection. We carry out a systematic exploration of machine learning techniques and demonstrate that a two step strategy can be highly effective. In the first step we use catalog-level information ($griz$+WISE magnitudes, second moments) to preselect targets, using artificial neural networks. The accepted targets are then inspected with pixel-by-pixel pattern recognition algorithms (Gradient-Boosted Trees), to form a final set of cand...

  13. The Sloan Digital Sky Survey Reverberation Mapping Project: Post-Starburst Signatures in Quasar Host Galaxies at z > 1

    Science.gov (United States)

    Matsuoka, Yoshiki; Strauss, Michael A.; Shen, Yue; Brandt, William N.; Greene, Jenny E.; Ho, Luis C.; Schneider, Donald P.; Sun, Mouyuan; Trump, Jonathan R.

    2015-10-01

    Quasar host galaxies are key for understanding the relation between galaxies and the supermassive black holes (SMBHs) at their centers. We present a study of 191 broad-line quasars and their host galaxies at z\\lt 1, using high signal-to-noise ratio (S/N) spectra produced by the Sloan Digital Sky Survey Reverberation Mapping project. Clear detection of stellar absorption lines allows a reliable decomposition of the observed spectra into nuclear and host components, using spectral models of quasar and stellar radiations as well as emission lines from the interstellar medium. We estimate age, mass {M}*, and velocity dispersion {σ }* of the host stars, the star formation rate (SFR), quasar luminosity, and SMBH mass {M}\\bullet , for each object. The quasars are preferentially hosted by massive galaxies with {M}*˜ {10}11 {M}⊙ characterized by stellar ages around 1 billion yr, which coincides with the transition phase of normal galaxies from the blue cloud to the red sequence. The host galaxies have relatively low SFRs and fall below the main sequence of star-forming galaxies at similar redshifts. These facts suggest that the hosts have experienced an episode of major star formation sometime in the past 1 billion yr, which was subsequently quenched or suppressed. The derived {M}\\bullet -{σ }* and {M}\\bullet -{M}* relations agree with our past measurements and are consistent with no evolution from the local universe. The present analysis demonstrates that reliable measurements of stellar properties of quasar host galaxies are possible with high-S/N fiber spectra, which will be acquired in large numbers with future powerful instruments such as the Subaru Prime Focus Spectrograph.

  14. Estimating Photometric Redshifts of Quasars via K-nearest Neighbor Approach Based on Large Survey Databases

    CERN Document Server

    Yanxia, Zhang; Nanbo, Peng; Yongheng, Zhao; Xue-bing, Wu

    2013-01-01

    We apply one of lazy learning methods named k-nearest neighbor algorithm (kNN) to estimate the photometric redshifts of quasars, based on various datasets from the Sloan Digital Sky Survey (SDSS), UKIRT Infrared Deep Sky Survey (UKIDSS) and Wide-field Infrared Survey Explorer (WISE) (the SDSS sample, the SDSS-UKIDSS sample, the SDSS-WISE sample and the SDSS-UKIDSS-WISE sample). The influence of the k value and different input patterns on the performance of kNN is discussed. kNN arrives at the best performance when k is different with a special input pattern for a special dataset. The best result belongs to the SDSS-UKIDSS-WISE sample. The experimental results show that generally the more information from more bands, the better performance of photometric redshift estimation with kNN. The results also demonstrate that kNN using multiband data can effectively solve the catastrophic failure of photometric redshift estimation, which is met by many machine learning methods. By comparing the performance of various m...

  15. Observed Quasar Structure

    Science.gov (United States)

    Schild, Rudolph E.

    2011-05-01

    With the introduction of microlensing (nano-lensing) and reverberation analysis, understanding of the luminous structure surrounding quasars has gone from theoretical speculation to an observer's sport. Micro-lensing with day timescale has demonstrated that quasars have structure on scales of 1 R_G which we attribute to the inner edge of the accretion disc, at central distance 70 R_G in lo-hard state (radio loud) Q0957 quasar, indicated by reverberation. Reverberation of the dominant optical continuum has been detected in all 55 hi-soft quasars with brightness data, originating in the dusty torus observed in UV-optical and IR reverberation. Microlensing simulation compared to brightness monitoring shows that 2/3 of the UV-optical continuum originates in the outer torus. The observed color effects observed in the microlensing support the existence of inner and outer luminous structure.

  16. Gravitational lensing of quasars

    CERN Document Server

    Eigenbrod, Alexander

    2013-01-01

    The universe, in all its richness, diversity and complexity, is populated by a myriad of intriguing celestial objects. Among the most exotic of them are gravitationally lensed quasars. A quasar is an extremely bright nucleus of a galaxy, and when such an object is gravitationally lensed, multiple images of the quasar are produced – this phenomenon of cosmic mirage can provide invaluable insights on burning questions, such as the nature of dark matter and dark energy. After presenting the basics of modern cosmology, the book describes active galactic nuclei, the theory of gravitational lensing, and presents a particular numerical technique to improve the resolution of astronomical data. The book then enters the heart of the subject with the description of important applications of gravitational lensing of quasars, such as the measurement of the famous Hubble constant, the determination of the dark matter distribution in galaxies, and the observation of the mysterious inner parts of quasars with much higher r...

  17. Large Scale Clustering of Sloan Digital Sky Survey Quasars: Impact of the Baryon Density and the Cosmological Constant

    CERN Document Server

    Yahata, K; Kayo, I; Matsubara, T; Connolly, A; Vanden Berk, Daniel E; Sheth, R; Szapudi, I; Anderson, S F; Bahcall, Neta A; Brinkmann, J; Csabai, I; Fan, X; Loveday, J; York, A S; Yahata, Kazuhiro; Suto, Yasushi; Kayo, Issha; Matsubara, Takahiko; Connolly, Andrew; Berk, Daniel Vanden; Sheth, Ravi; Szapudi, Istvan; Anderson, Scott F.; Bahcall, Neta; Brinkmann, Jon; Csabai, Istvan; Fan, Xiaohui; Loveday, Jon; York, Alexander S. Szalay and Donald

    2004-01-01

    We report the first result of the clustering analysis of Sloan Digital Sky Survey (SDSS) quasars. We compute the two-point correlation function (2PCF) of SDSS quasars in redshift space at $10h^{-1}{\\rm Mpc} < s < 1h^{-1}{\\rm Gpc}$, with particular attention to its baryonic signature. Our sample consists of 20303 quasars extracted from the SDSS Data Release 3 (DR3). The redshift range of the sample is $0.16 \\le z \\le 2.24$ and the reddening-corrected $i$-band apparent magnitude range is $15.0 \\le m_{i,{\\rm rc}} \\le 19.1$. Due to the relatively low number density of the quasar sample, the bump in the power spectrum due to the baryon density, $\\Omega_{\\rm b}$, is not clearly visible. The effect of the baryon density is, however, to shift the zero-crossing scale $s_{\\rm zero}$ of the 2PCF. The sensitivity of the zero crossing to the baryon density makes it an interesting alternate measure of the baryonic signature. Assuming a scale-independent linear bias and the spatially flat universe, i.e., $\\Omega_{\\rm ...

  18. Clustering of High Redshift ($z\\ge 2.9$) Quasars from the Sloan Digital Sky Survey

    CERN Document Server

    Shen, Y; Oguri, M; Hennawi, J F; Fan, X; Richards, G T; Hall, P B; Gunn, J E; Schneider, D P; Szalay, A S; Thakar, A R; Vanden Berk, D E; Anderson, S F; Bahcall, N A; Connolly, A J; Knapp, G R; Shen, Yue; Strauss, Michael A.; Oguri, Masamune; Hennawi, Joseph F.; Fan, Xiaohui; Richards, Gordon T.; Hall, Patrick B.; Gunn, James E.; Schneider, Donald P.; Szalay, Alexander S.; Thakar, Anirudda R.; Berk, Daniel E. Vanden; Anderson, Scott F.; Bahcall, Neta A.; Connolly, Andrew J.; Knapp, Gillian R.

    2007-01-01

    (Abridged) We study the two-point correlation function of a uniformly selected sample of 4,426 luminous optical quasars with redshift $2.9 \\le z\\le 5.4$ selected over 4041 deg$^2$ from the Fifth Data Release of the Sloan Digital Sky Survey. For a real-space correlation function of the form $\\xi(r)=(r/r_0)^{-\\gamma}$, the fitted parameters in comoving coordinates are $r_0 = 15.2 \\pm 2.7 h^{-1}$ Mpc and $\\gamma = 2.0 \\pm 0.3$, over a scale range $4\\le r_p\\le 150 h^{-1}$ Mpc. Thus high-redshift quasars are appreciably more strongly clustered than their $z \\approx 1.5$ counterparts, which have a comoving clustering length $r_0 \\approx 6.5 h^{-1}$ Mpc. Dividing our sample into two redshift bins: $2.9\\le z\\le 3.5$ and $z\\ge 3.5$, and assuming a power-law index $\\gamma=2.0$, we find a correlation length of $r_0 = 16.9 \\pm 1.7 h^{-1}$ Mpc for the former, and $r_0 = 24.3 \\pm 2.4 h^{-1}$ Mpc for the latter. Following Martini & Weinberg, we relate the clustering strength and quasar number density to the quasar lifet...

  19. Luminosity and surface brightness distribution of K-band galaxies from the UKIDSS Large Area Survey

    CERN Document Server

    Smith, Anthony J; Cross, Nicholas J G

    2008-01-01

    We present luminosity and surface brightness distributions of 36,663 galaxies with K-band photometry from the UKIRT Infrared Deep Sky Survey (UKIDSS) Large Area Survey (LAS), Data Release 3 and optical photometry from Data Release 5 of the Sloan Digital Sky Survey (SDSS). Various features and limitations of the new UKIDSS data are examined, such as a problem affecting Petrosian magnitudes of extended sources. Selection limits in K- and r-band magnitude, K-band surface brightness and K-band radius are included explicitly in the 1/Vmax estimation of the space density and luminosity function. The bivariate brightness distribution in K-band absolute magnitude and surface brightness is presented and found to display a clear luminosity-surface brightness correlation that flattens at high luminosity and broadens at low luminosity, consistent with similar analyses at optical wavelengths. Best fitting Schechter function parameters for the K-band luminosity function are found to be M*-5log h=-23.17 +/- 0.04, alpha=-0.8...

  20. A Catalog of Broad Absorption Line Quasars in Sloan Digital Sky Survey Data Release 5

    CERN Document Server

    Gibson, Robert R; Brandt, W N; Hall, Patrick B; Shen, Yue; Wu, Jianfeng; Anderson, Scott F; Schneider, Donald P; Berk, Daniel Vanden; Gallagher, S C; Fan, Xiaohui; York, Donald G

    2008-01-01

    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. In cases where BAL QSOs have been observed with Chandra or XMM-Newton, we report the X-ray monochromatic luminosities of these sources. We confirm and extend previous findings that BAL QSOs are more strongly reddened in the rest-frame UV than non-BAL QSOs and that BAL QSOs are relatively X-ray weak compared to non-BAL QSOs. The observed BAL fraction is dependent on the spectral s...

  1. Spectral Variability of Quasars in the Sloan Digital Sky Survey. II: The C IV Line

    CERN Document Server

    Wilhite, B C; Brunner, R J; Brinkmann, J

    2006-01-01

    We examine the variability of the high-ionizaton C IV line in a sample of 105 quasars observed at multiple epochs by the Sloan Digital Sky Survey. We find a strong correlation between the change in the C IV line flux and the change in the line width, but no correlations between the change in flux and changes in line center and skewness. The relation between line flux change and line width change is consistent with a model in which a broad line base varies with greater amplitude than the line core. The objects studied here are more luminous and at higher redshift than those normally studied for variability, ranging in redshift from 1.65 to 4.00 and in absolute r-band magnitude from roughly -24 to -28. Using moment analysis line-fitting techniques, we measure line fluxes, centers, widths and skewnesses for the C IV line at two epochs for each object. The well-known Baldwin Effect is seen for these objects, with a slope beta = -0.22. The sample has a median intrinsic Baldwin Effect slope of beta = -0.85; the C I...

  2. Photometric classification of quasars from RCS-2 using Random Forest

    Science.gov (United States)

    Carrasco, D.; Barrientos, L. F.; Pichara, K.; Anguita, T.; Murphy, D. N. A.; Gilbank, D. G.; Gladders, M. D.; Yee, H. K. C.; Hsieh, B. C.; López, S.

    2015-12-01

    The classification and identification of quasars is fundamental to many astronomical research areas. Given the large volume of photometric survey data available in the near future, automated methods for doing so are required. In this article, we present a new quasar candidate catalog from the Red-Sequence Cluster Survey 2 (RCS-2), identified solely from photometric information using an automated algorithm suitable for large surveys. The algorithm performance is tested using a well-defined SDSS spectroscopic sample of quasars and stars. The Random Forest algorithm constructs the catalog from RCS-2 point sources using SDSS spectroscopically-confirmed stars and quasars. The algorithm identifies putative quasars from broadband magnitudes (g, r, i, z) and colors. Exploiting NUV GALEX measurements for a subset of the objects, we refine the classifier by adding new information. An additional subset of the data with WISE W1 and W2 bands is also studied. Upon analyzing 542 897 RCS-2 point sources, the algorithm identified 21 501 quasar candidates with a training-set-derived precision (the fraction of true positives within the group assigned quasar status) of 89.5% and recall (the fraction of true positives relative to all sources that actually are quasars) of 88.4%. These performance metrics improve for the GALEX subset: 6529 quasar candidates are identified from 16 898 sources, with a precision and recall of 97.0% and 97.5%, respectively. Algorithm performance is further improved when WISE data are included, with precision and recall increasing to 99.3% and 99.1%, respectively, for 21 834 quasar candidates from 242 902 sources. We compiled our final catalog (38 257) by merging these samples and removing duplicates. An observational follow up of 17 bright (r < 19) candidates with long-slit spectroscopy at DuPont telescope (LCO) yields 14 confirmed quasars. The results signal encouraging progress in the classification of point sources with Random Forest algorithms to search

  3. The LEGUE high latitude bright survey design for the LAMOST pilot survey

    Institute of Scientific and Technical Information of China (English)

    Yue-Yang Zhang; Shuang Gao; Norbert Christlieb; Zhan-Wen Han; Jin-Liang Hou; Hsu-Tai Lee; Xiao-Wei Liu; Kai-Ke Pan; Hong-Chi Wang; Jeffrey L.Carlin; Fan Yang; Chao Liu; Li-Cai Deng; Heidi Jo Newberg; Hao-Tong Zhang; Sébastien Lépine; Yan Xu

    2012-01-01

    We describe the footprint and input catalog for bright nights in the LAMOST Pilot Survey,which began in October 2011.Targets are selected from two stripes in the north and south Galactic Cap regions,centered at δ =29°,with 10° width in declination,covering right ascensions of 135°to 290°and-30°to 30°respectively.We selected spectroscopic targets from a combination of the SDSS and 2MASS point source catalogs.The catalog of stars defining the field centers(as required by the Shack-Hartmann wavefront sensor at the center of the LAMOST field)consists of all V < 8m stars from the Hipparcos catalog.We employ a statistical selection algorithm that assigns priorities to targets based on their positions in multidimensional color/magnitude space.This scheme overemphasizes rare objects and de-emphasizes more populated regions of magnitude and color phase space,while ensuring a smooth,well-understood selection function.A demonstration of plate design is presented based on the Shack-Hartmann star catalog and an input catalog that was generated by our target selection routines.

  4. The LBT Bootes Field Survey: I. The Rest-frame UV and Luminosity Functions and Clustering of Bright Lyman Break Galaxies at z~3

    CERN Document Server

    Bian, Fuyan; Jiang, Linhua; McGreer, Ian; Dey, Arjun; Green, Richard; Maiolino, Roberto; Walter, Fabian; Lee, Kyoung-Soo; Dave, Romeel

    2013-01-01

    We present a deep LBT/LBC U-band imaging survey (9 deg2) covering the NOAO Bootes field. A total of 14,485 Lyman Break Galaxies (LBGs) at z~3 are selected, which are used to measure the rest-frame UV luminosity function (LF). The large sample size and survey area reduce the LF uncertainties due to Poisson statistics and cosmic variance by >3 compared to previous studies. At the bright end, the LF shows excess power compared to the best-fit Schechter function, which can be attributed to the contribution of $z\\sim3$ quasars. We compute the rest-frame near-infrared LF and stellar mass function (SMF) of z~3 LBGs based on the R-band and IRAC [4.5 micro m]-band flux relation. We investigate the evolution of the UV LFs and SMFs between z~7 and z~3, which supports a rising star formation history in the LBGs. We study the spatial correlation function of two bright LBG samples and estimate their average host halo mass. We find a tight relation between the host halo mass and the galaxy star formation rate (SFR),which fo...

  5. The Sloan Digital Sky Survey Reverberation Mapping Project: Biases in z>1.46 Redshifts due to Quasar Diversity

    CERN Document Server

    Denney, K D; Brandt, W N; Grier, C J; Ho, Luis C; Peterson, B M; Trump, J R; Ge, J

    2016-01-01

    We use the coadded spectra of 32 epochs of Sloan Digital Sky Survey (SDSS) Reverberation Mapping Project observations of 482 quasars with z>1.46 to highlight systematic biases in the SDSS- and BOSS-pipeline redshifts due to the natural diversity of quasar properties. We investigate the characteristics of this bias by comparing the BOSS-pipeline redshifts to an estimate from the centroid of HeII 1640. HeII has a low equivalent width but is often well-defined in high-S/N spectra, does not suffer from self-absorption, and has a narrow component that, when present (the case for about half of our sources), produces a redshift estimate that, on average, is consistent with that determined from [OII] to within 1-sigma of the quadrature sum of the HeII and [OII] centroid measurement uncertainties. The large redshift differences of ~1000 km/s, on average, between the BOSS-pipeline and HeII-centroid redshifts suggest there are significant biases in a portion of BOSS quasar redshift measurements. Adopting the HeII-based ...

  6. The Sloan Digital Sky Survey Quasar Lens Search. VI. Constraints on Dark Energy and the Evolution of Massive Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Oguri, Masamune [Univ. of Tokyo (Japan); et al.

    2012-05-01

    We present a statistical analysis of the final lens sample from the Sloan Digital Sky Survey Quasar Lens Search (SQLS). The number distribution of a complete subsample of 19 lensed quasars selected from 50,836 source quasars is compared with theoretical expectations, with particular attention to the selection function. Assuming that the velocity function of galaxies does not evolve with redshift, the SQLS sample constrains the cosmological constant to \\Omega_\\Lambda=0.79^{+0.06}_{-0.07}(stat.)^{+0.06}_{-0.06}(syst.) for a flat universe. The dark energy equation of state is found to be consistent with w=-1 when the SQLS is combined with constraints from baryon acoustic oscillation (BAO) measurements or results from the Wilkinson Microwave Anisotropy Probe (WMAP). We also obtain simultaneous constraints on cosmological parameters and redshift evolution of the galaxy velocity function, finding no evidence for redshift evolution at z<1 in any combinations of constraints. For instance, number density evolution quantified as \

  7. Discovery of two gravitationally lensed quasars with image separations of 3 arcseconds from the Sloan Digital Sky Survey

    Energy Technology Data Exchange (ETDEWEB)

    Oguri, Masamune; Inada, Naohisa; Hennawi, Joseph F.; Richards, Gordon T.; Johnston, David E.; Frieman, Joshua A.; Pindor, Bartosz; Strauss, Michael A.; Brunner, Robert; Becker, Robert H.; Castander, Francisco J.; Gregg, Michael D.; Hall, Patrick B.; Rix, Hans-Walter; Schneider, Donald P.; Bahcall, Neta A.; Brinkmann, Jonathan; York, Donald G.

    2004-11-01

    We report the discovery of two doubly-imaged quasars, SDSS J100128.61+502756.9 and SDSS J120629.65+433217.6, at redshifts of 1.838 and 1.789 and with image separations of 2.86'' and 2.90'', respectively. The objects were selected as lens candidates from the Sloan Digital Sky Survey (SDSS). Based on the identical nature of the spectra of the two quasars in each pair and the identification of the lens galaxies, we conclude that the objects are gravitational lenses. The lenses are complicated; in both systems there are several galaxies in the fields very close to the quasars, in addition to the lens galaxies themselves. The lens modeling implies that these nearby galaxies contribute significantly to the lens potentials. On larger scales, we have detected an enhancement in the galaxy density near SDSS J100128.61+502756.9. The number of lenses with image separation of {approx} 3'' in the SDSS already exceeds the prediction of simple theoretical models based on the standard Lambda-dominated cosmology and observed velocity function of galaxies.

  8. Hubble Space Telescope Ultraviolet Spectroscopy of Fourteen Low-Redshift Quasars

    DEFF Research Database (Denmark)

    Ganguly, Rajib; Brotherton, Michael S.; Arav, Nahum;

    2007-01-01

    We present low-resolution ultraviolet spectra of 14 low redshift (z zz 1.4 Large Bright Quasar samples. By design, our objects sample luminosities in between these two surveys, and our four absorbed objects are consistent with the v ~ L^0.62 relation derived by Laor & Brandt (2002). Another quasa...

  9. Cross-Correlation of SDSS DR7 Quasars and DR10 BOSS Galaxies: The Weak Luminosity Dependence of Quasar Clustering at z~0.5

    CERN Document Server

    Shen, Yue; White, Martin; Zheng, Zheng; Myers, Adam D; Guo, Hong; Kirkpatrick, Jessica A; Padmanabhan, Nikhil; Parejko, John K; Ross, Nicholas P; Schlegel, David J; Schneider, Donald P; Streblyanska, Alina; Swanson, Molly E C; Zehavi, Idit; Pan, Kaike; Bizyaev, Dmitry; Brewington, Howard; Ebelke, Garrett; Malanushenko, Viktor; Malanushenko, Elena; Oravetz, Daniel; Simmons, Audrey; Snedden, Stephanie

    2012-01-01

    We present the measurement of the two-point cross-correlation function (CCF) of 8,198 Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) quasars and 349,608 DR10 CMASS galaxies from the Baryonic Oscillation Spectroscopic Survey (BOSS) at redshift ~0.5 (0.3=0.53 from the CCF measurements. This linear bias corresponds to a characteristic host halo mass of ~4x10^12 M_sun/h, compared to ~10^13 M_sun/h characteristic host halo mass for CMASS galaxies. We divide the quasar sample in luminosity and constrain the luminosity dependence of quasar bias to be db_Q/dlogL=0.20+-0.34 or 0.11+-0.32 (depending on different luminosity divisions) for quasar luminosities -23.5>M_i(z=2)>-25.5, implying a weak luminosity dependence of quasar clustering for the bright end of the quasar population at ~0.5. We compare our measurements with theoretical predictions, Halo Occupation Distribution (HOD) models and mock catalogs. These comparisons suggest quasars reside in a broad range of host halos, and the host halo mass distributions...

  10. ESTIMATING PHOTOMETRIC REDSHIFTS OF QUASARS VIA THE k-NEAREST NEIGHBOR APPROACH BASED ON LARGE SURVEY DATABASES

    International Nuclear Information System (INIS)

    We apply one of the lazy learning methods, the k-nearest neighbor (kNN) algorithm, to estimate the photometric redshifts of quasars based on various data sets from the Sloan Digital Sky Survey (SDSS), the UKIRT Infrared Deep Sky Survey (UKIDSS), and the Wide-field Infrared Survey Explorer (WISE; the SDSS sample, the SDSS-UKIDSS sample, the SDSS-WISE sample, and the SDSS-UKIDSS-WISE sample). The influence of the k value and different input patterns on the performance of kNN is discussed. kNN performs best when k is different with a special input pattern for a special data set. The best result belongs to the SDSS-UKIDSS-WISE sample. The experimental results generally show that the more information from more bands, the better performance of photometric redshift estimation with kNN. The results also demonstrate that kNN using multiband data can effectively solve the catastrophic failure of photometric redshift estimation, which is met by many machine learning methods. Compared with the performance of various other methods of estimating the photometric redshifts of quasars, kNN based on KD-Tree shows superiority, exhibiting the best accuracy.

  11. Towards a comprehensive picture of powerful quasars, their host galaxies and quasar winds at z ~ 0.5

    CERN Document Server

    Wylezalek, Dominika; Liu, Guilin; Obied, Georges

    2016-01-01

    Luminous type-2 quasars in which the glow from the central black hole is obscured by dust are ideal targets for studying their host galaxies and the quasars' effect on galaxy evolution. Such feedback appears ubiquitous in luminous obscured quasars where high velocity ionized nebulae have been found. We present rest-frame yellow-band (~5000 Angstroms) observations using the Hubble Space Telescope for a sample of 20 luminous quasar host galaxies at 0.2 < z < 0.6 selected from the Sloan Digital Sky Survey. For the first time, we combine host galaxy observations with geometric measurements of quasar illumination using blue-band HST observations and [OIII] integral field unit observations probing the quasar winds. The HST images reveal bright merger signatures in about half the galaxies; a significantly higher fraction than in comparison inactive ellipticals. We show that the host galaxies are primarily bulge-dominated, with masses close to M*, but belong to < 30% of elliptical galaxies that are highly st...

  12. Nature and statistical properties of quasar associated absorption systems in the XQ-100 Legacy Survey

    DEFF Research Database (Denmark)

    Perrotta, Serena; D'Odorico, Valentina; Prochaska, J. Xavier;

    2016-01-01

    We statistically study the physical properties of a sample of narrow absorption line (NAL) systems looking for empirical evidences to distinguish between intrinsic and intervening NALs without taking into account any a priori definition or velocity cut-off. We analyze the spectra of 100 quasars w...

  13. Spectral Classification of Quasars in the Sloan Digital Sky Survey: Eigenspectra; Redshift and Luminosity Effects

    CERN Document Server

    Yip, C W; Vanden Berk, Daniel E; Ma, Z; Frieman, J A; Subba-Rao, M; Szalay, A S; Richards, G T; Hall, P B; Schneider, D P; Hopkins, A M; Trump, J; Brinkmann, J

    2004-01-01

    We study 16,707 quasar spectra from the SDSS using the Karhunen-Lo\\`eve (KL) transform (or Principal Component Analysis, PCA). The quasar eigenspectra of the full catalog reveal the following: 1st order - the mean spectrum; 2nd order - a host-galaxy component; 3rd order - the UV-optical continuum slope; 4th order - the correlations of Balmer emission lines. We find that the spectral classification of quasars is redshift and luminosity dependent, as such there does not exist a compact set ( 95%) of the entire catalog. We therefore construct several sets of eigenspectra in different redshift and luminosity bins. From these eigenspectra we find that quasar spectra can be classified (by the first two eigenspectra) into a sequence that is defined by a simple progression in the steepness of the slope of the continuum. We also find a dependence on redshift and luminosity in the eigencoefficients. The dominant redshift effect is a result of the evolution of the blended FeII emission (optical) and the Balmer continuum...

  14. Clustering of Low-Redshift (z <= 2.2) Quasars from the Sloan Digital Sky Survey

    CERN Document Server

    Ross, Nicholas P; Strauss, Michael A; Berk, Daniel E Vanden; Connolly, Andrew J; Richards, Gordon T; Schneider, Donald P; Weinberg, David H; Hall, Patrick B; Bahcall, Neta A; Brunner, Robert J

    2009-01-01

    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. Using a homogeneous sample of 30,239 quasars with spectroscopic redshifts from the DR5 Quasar Catalogue, our study represents the largest sample used for this type of investigation to date. With this redshift range and an areal coverage of approx 4,000 deg^2, we sample over 25 h^-3 Gpc^3 (comoving) assuming the current LCDM cosmology. Over this redshift range, we find that the redshift-space correlation function, xi(s), is adequately fit by a single power-law, with s_{0}=5.95+/-0.45 h^-1 Mpc and \\gamma_{s}=1.16+0.11-0.16 when fit over s=1-25 h^-1 Mpc. Using the projected correlation function we calculate the real-space correlation length, r_{0}=5.45+0.35-0.45 h^-1 Mpc and \\gamma=1.90+0.04-0.03, over scales of rp=1-130 h^-1 Mpc. Dividing the sample into redshift slices, we find very little, if any, evidence for the evolution of quasar clustering, with the redshift-spac...

  15. Ubiquitous Giant Lyα Nebulae around the Brightest Quasars at z ∼ 3.5 Revealed with MUSE

    Science.gov (United States)

    Borisova, Elena; Cantalupo, Sebastiano; Lilly, Simon J.; Marino, Raffaella A.; Gallego, Sofia G.; Bacon, Roland; Blaizot, Jeremy; Bouché, Nicolas; Brinchmann, Jarle; Carollo, C. Marcella; Caruana, Joseph; Finley, Hayley; Herenz, Edmund C.; Richard, Johan; Schaye, Joop; Straka, Lorrie A.; Turner, Monica L.; Urrutia, Tanya; Verhamme, Anne; Wisotzki, Lutz

    2016-11-01

    Direct Lyα imaging of intergalactic gas at z∼ 2 has recently revealed giant cosmological structures around quasars, e.g., the Slug Nebula. Despite their high luminosity, the detection rate of such systems in narrow-band and spectroscopic surveys is less than 10%, possibly encoding crucial information on the distribution of gas around quasars and the quasar emission properties. In this study, we use the MUSE integral-field instrument to perform a blind survey for giant {Ly}α nebulae around 17 bright radio-quiet quasars at 3\\lt z\\lt 4 that does not suffer from most of the limitations of previous surveys. After data reduction and analysis performed with specifically developed tools, we found that each quasar is surrounded by giant {Ly}α nebulae with projected sizes larger than 100 physical kiloparsecs and, in some cases, extending up to 320 kpc. The circularly averaged surface brightness profiles of the nebulae appear to be very similar to each other despite their different morphologies and are consistent with power laws with slopes ≈ -1.8. The similarity between the properties of all these nebulae and the Slug Nebula suggests a similar origin for all systems and that a large fraction of gas around bright quasars could be in a relatively “cold” (T ∼ 104 K) and dense phase. In addition, our results imply that such gas is ubiquitous within at least 50 kpc from bright quasars at 3\\lt z\\lt 4 independently of the quasar emission opening angle, or extending up to 200 kpc for quasar isotropic emission. Based on observations made with ESO Telescopes at the Paranal Observatory under programs 094.A-0396, 095.A-0708, 096.A-0345, 094.A-0131, 095.A-0200, and 096.A-0222.

  16. The Infrared Medium-Deep Survey. V. A New Selection Strategy for Quasars at z > 5 based on Medium-Band Observation with SQUEAN

    CERN Document Server

    Jeon, Yiseul; Pak, Soojong; Hyun, Minhee; Kim, Sanghyuk; Kim, Yongjung; Lee, Hye-In; Park, Woojin

    2016-01-01

    Multiple color selection techniques have been successful in identifying quasars from wide-field broad-band imaging survey data. Among the quasars that have been discovered so far, however, there is a redshift gap at $5 \\lesssim {\\rm z} \\lesssim 5.7$ due to the limitations of filter sets in previous studies. In this work, we present a new selection technique of high redshift quasars using a sequence of medium-band filters: nine filters with central wavelengths from 625 to 1025 nm and bandwidths of 50 nm. Photometry with these medium-bands traces the spectral energy distribution (SED) of a source, similar to spectroscopy with resolution R $\\sim$ 15. By conducting medium-band observations of high redshift quasars at 4.7 $\\leq$ z $\\leq$ 6.0 and brown dwarfs (the main contaminants in high redshift quasar selection) using the SED camera for QUasars in EArly uNiverse (SQUEAN) on the 2.1-m telescope at the McDonald Observatory, we show that these medium-band filters are superior to multi-color broad-band color sectio...

  17. A serendipitous all sky survey for bright objects in the outer solar system

    CERN Document Server

    Brown, M E; Schmidt, B P; Drake, A J; Djorgovski, S G; Graham, M J; Mahabal, A; Donalek, C; Larson, S; Christensen, E; Beshore, E; McNaught, R

    2015-01-01

    We use seven year's worth of observations from the Catalina Sky Survey and the Siding Spring Survey covering most of the northern and southern hemisphere at galactic latitudes higher than 20 degrees to search for serendipitously imaged moving objects in the outer solar system. These slowly moving objects would appear as stationary transients in these fast cadence asteroids surveys, so we develop methods to discover objects in the outer solar system using individual observations spaced by months, rather than spaced by hours, as is typically done. While we independently discover 8 known bright objects in the outer solar system, the faintest having $V=19.8\\pm0.1$, no new objects are discovered. We find that the survey is nearly 100% efficient at detecting objects beyond 25 AU for $V\\lesssim 19.1$ ($V\\lesssim18.6$ in the southern hemisphere) and that the probability that there is one or more remaining outer solar system object of this brightness left to be discovered in the unsurveyed regions of the galactic plan...

  18. A serendipitous all sky survey for bright objects in the outer solar system

    Energy Technology Data Exchange (ETDEWEB)

    Brown, M. E.; Drake, A. J.; Djorgovski, S. G.; Graham, M. J.; Mahabal, A.; Donalek, C. [California Institute of Technology, Pasadena, CA (United States); Bannister, M. T. [University of Victoria, Victoria, BC (Canada); Schmidt, B. P.; McNaught, R. [The Australian National University, Canberra (Australia); Larson, S.; Christensen, E.; Beshore, E. [The University of Arizona, Lunar and Planetary Laboratory, Tucson, AZ (United States)

    2015-02-01

    We use seven year's worth of observations from the Catalina Sky Survey and the Siding Spring Survey covering most of the northern and southern hemisphere at galactic latitudes higher than 20° to search for serendipitously imaged moving objects in the outer solar system. These slowly moving objects would appear as stationary transients in these fast cadence asteroids surveys, so we develop methods to discover objects in the outer solar system using individual observations spaced by months, rather than spaced by hours, as is typically done. While we independently discover eight known bright objects in the outer solar system, the faintest having V=19.8±0.1, no new objects are discovered. We find that the survey is nearly 100% efficient at detecting objects beyond 25 AU for V≲19.1 (V≲18.6 in the southern hemisphere) and that the probability that there is one or more remaining outer solar system object of this brightness left to be discovered in the unsurveyed regions of the galactic plane is approximately 32%.

  19. DES J0454-4448: discovery of the first luminous z ≥ 6 quasar from the Dark Energy Survey

    Energy Technology Data Exchange (ETDEWEB)

    Reed, S. L.; McMahon, R. G.; Banerji, M.; Becker, G. D.; Gonzalez-Solares, E.; Martini, P.; Ostrovski, F.; Rauch, M.; Abbott, T.; Abdalla, F. B.; Allam, S.; Benoit-Levy, A.; Bertin, E.; Buckley-Geer, E.; Burke, D.; Carnero Rosell, A.; da Costa, L. N.; D' Andrea, C.; DePoy, D. L.; Desai, S.; Diehl, H. T.; Doel, P.; Cunha, C. E.; Estrada, J.; Evrard, A. E.; Fausti Neto, A.; Finley, D. A.; Fosalba, P.; Frieman, J.; Gruen, D.; Honscheid, K.; James, D.; Kent, S.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Maia, M. A. G.; Makler, M.; Marshall, J.; Merritt, K.; Miquel, R.; Mohr, J.; Nord, B.; Ogando, R.; Plazas, A.; Romer, K.; Roodman, A.; Rykoff, E.; Sako, M.; Sanchez, E.; Santiago, B.; Schubnell, M.; Sevilla, I.; Smith, C.; Soares-Santos, M.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Tucker, D.; Walker, A.; Wechsler, R. H.

    2015-10-28

    We present the first results of a survey for high-redshift, z ≥ 6, quasars using izY multicolour photometric observations from the Dark Energy Survey (DES). Here we report the discovery and spectroscopic confirmation of the zAB, YAB = 20.2, 20.2 (M1450 = -26.5) quasar DES J0454-4448 with a redshift of z = 6.09±0.02 based on the onset of the Ly α forest and an H I near zone size of 4.1+1.1-1.2 proper Mpc. The quasar was selected as an i-band drop out with i-z = 2.46 and zAB < 21.5 from an area of ~300 deg2. It is the brightest of our 43 candidates and was identified for spectroscopic follow-up solely based on the DES i-z and z-Y colours. The quasar is detected by WISE and has W1AB = 19.68. The discovery of one spectroscopically confirmed quasar with 5.7 < z < 6.5 and zAB ≤ 20.2 is consistent with recent determinations of the luminosity function at z ~ 6. DES when completed will have imaged ~5000 deg2 to YAB = 23.0 (5σ point source) and we expect to discover 50–100 new quasars with z > 6 including 3–10 with z > 7 dramatically increasing the numbers of quasars currently known that are suitable for detailed studies.

  20. Surveying the Bright Stars by Optical Interferometry I: A Search for Multiplicity Among Stars of Spectral Types F - K

    CERN Document Server

    Hutter, Donald; Tycner, Christopher; Benson, James; Hummel, Christian; Sanborn, Jason; Franz, Otto G; Johnston, Kenneth

    2016-01-01

    We present the first results from an ongoing survey for multiplicity among the bright stars using the Navy Precision Optical Interferometer (NPOI). We first present a summary of NPOI observations of known multiple systems, including the first detection of the companion of $\\beta$ Scuti with precise relative astrometry, to illustrate the instrument's detection sensitivity for binaries at magnitude differences $\\Delta$$m$ $\\lessapprox$ 3 over the range of angular separation 3 - 860 milliarcseconds (mas). A limiting $\\Delta$$m_{700}$ $\\sim$ 3.5 is likely for binaries where the component spectral types differ by less than two. Model fits to these data show good agreement with published orbits, and we additionally present a new orbit solution for one of these stars, $\\sigma$ Her. We then discuss early results of the survey of bright stars at $\\delta$ $\\geq$ -20$\\deg$. This survey, which complements previous surveys of the bright stars by speckle interferometry, initially emphasizes bright stars of spectral types F...

  1. SDSSJ2222+2745 A Gravitationally Lensed Sextuple Quasar with Maximum Image Separation of 15.1" Discovered in the Sloan Giant Arcs Survey

    CERN Document Server

    Dahle, H; Sharon, K; Bayliss, M B; Wuyts, E; Abramson, L E; Koester, B P; Groeneboom, N; Brinckmann, T E; Kristensen, M T; Lindholmer, M O; Nielsen, A; Krogager, J -K; Fynbo, J P U

    2012-01-01

    We report the discovery of a unique gravitational lens system, SDSSJ2222+2745, producing five spectroscopically confirmed images of a z_s=2.82 quasar lensed by a foreground galaxy cluster at z_l=0.49. We also present photometric and spectroscopic evidence for a sixth lensed image of the same quasar. The maximum separation between the quasar images is 15.1". Both the large image separations and the high image multiplicity of the lensed quasar are in themselves exceptionally rare, and observing the combination of these two factors is an exceptionally unlikely occurrence in present datasets. This is only the third known case of a quasar lensed by a cluster, and the only one with six images. The lens system was discovered in the course of the Sloan Giant Arcs Survey, in which we identify candidate lenses in the Sloan Digital Sky Survey and target these for follow up and verification with the 2.56m Nordic Optical Telescope. Multi-band photometry obtained over multiple epochs from September 2011 to September 2012 r...

  2. A VLBI survey of compact broad absorption line quasars with balnicity index BI>0

    CERN Document Server

    Kunert-Bajraszewska, M; Katarzynski, K; Roskowinski, C

    2015-01-01

    We performed high resolution radio observations of a new sample of ten BAL quasars using both the VLBA and EVN at 5 GHz. All the selected sources have balnicity indices (BI) more than 0 and radio flux densities less than 80 mJy at 1.4 GHz. They are very compact with linear sizes of the order of a few tens of parsecs and radio luminosities at 1.4 GHz above the FRI-FRII luminosity threshold. Most of the observed objects have been resolved at 5 GHz showing one-sided, probably core-jet structures, typical for quasars. We discuss in detail their age and orientation based on the radio observations. We then used the largest available sample of BAL quasars to study the relationships between the radio and optical properties in these objects. We found that (1) the strongest absorption (high values of the balnicity index BI) is connected with the lower values of the radio-loudness parameter, logR_I<1.5, and thus probably with large viewing angles; (2) the large span of the BI values in each bin of the radio-loudness ...

  3. Dusty Quasars at High Redshifts

    Science.gov (United States)

    Weedman, Daniel; Sargsyan, Lusine

    2016-09-01

    A population of quasars at z ˜ 2 is determined based on dust luminosities νL ν (7.8 μm) that includes unobscured, partially obscured, and obscured quasars. Quasars are classified by the ratio νL ν (0.25 μm)/νL ν (7.8 μm) = UV/IR, assumed to measure obscuration of UV luminosity by the dust that produces IR luminosity. Quasar counts at rest-frame 7.8 μm are determined for quasars in the Boötes field of the NOAO Deep Wide Field Survey using 24 μm sources with optical redshifts from the AGN and Galaxy Evolution Survey (AGES) or infrared redshifts from the Spitzer Infrared Spectrograph. Spectral energy distributions are extended to far-infrared wavelengths using observations from the Herschel Space Observatory Spectral and Photometric Imaging Receiver (SPIRE), and new SPIRE photometry is presented for 77 high-redshift quasars from the Sloan Digital Sky Survey. It is found that unobscured and obscured quasars have similar space densities at rest-frame 7.8 μm, but the ratio L ν (100 μm)/L ν (7.8 μm) is about three times higher for obscured quasars than for unobscured, so that far-infrared or submillimeter quasar detections are dominated by obscured quasars. We find that only ˜5% of high-redshift submillimeter sources are quasars and that existing 850 μm surveys or 2 mm surveys should already have detected sources at z ˜ 10 if quasar and starburst luminosity functions remain the same from z = 2 until z = 10.

  4. Mock Quasar-Lyman-{\\alpha} Forest Data-sets for the SDSS-III Baryon Oscillation Spectroscopic Survey

    CERN Document Server

    Bautista, Julian E; Font-Ribera, Andreu; Pieri, Matthew M; Busca, Nicolás G; Miralda-Escudé, Jordi; Palanque-Delabrouille, Nathalie; Rich, James; Dawson, Kyle; Feng, Yu; Ge, Jian; Gontcho, Satya Gontcho A; Ho, Shirley; Goff, Jean Marc Le; Noterdaeme, Pasquier; Pâris, Isabelle; Rossi, Graziano; Schlegel, David

    2014-01-01

    We describe mock data-sets generated to simulate the high-redshift quasar sample in Data Release 11 (DR11) of the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). The mock spectra contain Ly{\\alpha} forest correlations useful for studying the 3D correlation function including Baryon Acoustic Oscillations (BAO). They also include astrophysical effects such as quasar continuum diversity and high-density absorbers, instrumental effects such as noise and spectral resolution, as well as imperfections introduced by the SDSS pipeline treatment of the raw data. The Ly{\\alpha} forest BAO analysis of the BOSS collaboration, described in Delubac et al. 2014, has used these mock data-sets to develop and cross-check analysis procedures prior to performing the BAO analysis on real data, and for continued systematic cross checks. Tests presented here show that the simulations reproduce sufficiently well important characteristics of real spectra. These mock data-sets will be made available together with the data at t...

  5. Far-infrared and Molecular CO Emission From the Host Galaxies of Faint Quasars at z~6

    CERN Document Server

    Wang, Ran; Carilli, Chris L; Neri, Roberto; Walter, Fabian; Omont, Alain; Riechers, Dominik A; Bertoldi, Frank; Menten, Karl M; Cox, Pierre; Strauss, Michael A; Fan, Xiaohui; Jiang, Linhua

    2011-01-01

    We present new millimeter and radio observations of nine z~6 quasars discovered in deep optical and near-infrared surveys. We observed the 250 GHz continuum in eight of the nine objects and detected three of them. New 1.4 GHz radio continuum data have been obtained for four sources, and one has been detected. We searched for molecular CO (6-5) line emission in the three 250 GHz detections and detected two of them. We study the FIR and radio emission and quasar-host galaxy evolution with a sample of 18 z~6 quasars that are faint at UV/optical wavelengths (rest-frame 1450A magnitudes of m_1450\\ge20.2). The average FIR-to-AGN UV luminosity ratio of this faint quasar sample is about two times higher than that of the bright quasars at z~6 (m_1450<20.2). A fit to the average FIR and AGN bolometric luminosities of both the UV/optically faint and bright z~6 quasars, and the average luminosities of samples of submillimeter /millimeter-observed quasars at z~2 to 5, yields a relationship of L_{FIR} {L_{bol}}^{0.62}. ...

  6. Bright microwave pulses from PSR B0531+21 observed with a prototype transient survey receiver

    Energy Technology Data Exchange (ETDEWEB)

    O' Dea, J. Andrew; Cheng, Tsan-Huei; Buu, Chau M.; Asmar, Sami W.; Armstrong, J. W. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91125 (United States); Jenet, F. A.; Beroiz, Martin [Department of Physics and Astronomy, University of Texas at Brownsville, Brownsville, TX 78520 (United States)

    2014-05-01

    Recent discoveries of transient radio events have renewed interest in time-variable astrophysical phenomena. Many radio transient events are rare, requiring long observing times for reliable statistical study. The National Aeronautics and Space Administration/Jet Propulsion Laboratory's Deep Space Network (DSN) tracks spacecraft nearly continuously with 13 large-aperture, low system temperature radio antennas. During normal spacecraft operations, the DSN processes only a small fraction of the pre-detection bandwidth available from these antennas; any information in the remaining bandwidth, e.g., from an astronomical source in the same antenna beam as the spacecraft, is currently ignored. As a firmware modification to the standard DSN tracking receiver, we built a prototype receiver that could be used for astronomical transient surveys. Here, we demonstrate the receiver's utility through observations of bright pulses from the Crab pulsar and describe attributes of potential transient survey observations piggybacking on operational DSN tracks.

  7. Cosmic evolution of Quasar radio structure

    Science.gov (United States)

    Hutchings, J. B.; Neff, S. G.

    1991-01-01

    We discuss the results of a survey of Quasar radio structures over redshifts from 0.6 to 3.7. There are clear evolutionary trends in size and luminosity, which suggest that the duty cycle of individual Quasars has increased over cosmic time. This affects source count statistics and gives clues on the evolution of Quasar environments.

  8. Spitzer 24 um Excesses for Bright Galactic Stars in Bootes and First Look Survey Fields

    CERN Document Server

    Hovhannisyan, L R; Weedman, D W; Le Floc'h, E; Houck, J R; Soifer, B T; Brand, K; Dey, A; Jannuzi, B T

    2009-01-01

    Optically bright Galactic stars (V 1 mJy are identified in Spitzer mid-infrared surveys within 8.2 square degrees for the Bootes field of the NOAO Deep Wide-Field Survey and within 5.5 square degrees for the First Look Survey (FLS). 128 stars are identified in Bootes and 140 in the FLS, and their photometry is given. (K-[24]) colors are determined using K magnitudes from the 2MASS survey for all stars in order to search for excess 24 um luminosity compared to that arising from the stellar photosphere. Of the combined sample of 268 stars, 141 are of spectral types F, G, or K, and 17 of these 141 stars have 24 um excesses with (K-[24]) > 0.2 mag. Using limits on absolute magnitude derived from proper motions, at least 8 of the FGK stars with excesses are main sequence stars, and estimates derived from the distribution of apparent magnitudes indicate that all 17 are main sequence stars. These estimates lead to the conclusion that between 9% and 17% of the main sequence FGK field stars in these samples have 24 u...

  9. BRIGHT ACTIVE GALACTIC NUCLEI SOURCE LIST FROM THE FIRST THREE MONTHS OF THE FERMI LARGE AREA TELESCOPE ALL-SKY SURVEY

    International Nuclear Information System (INIS)

    The first three months of sky-survey operation with the Large Area Telescope (LAT) onboard the Fermi Gamma-Ray Space Telescope reveal 132 bright sources at |b|>10 deg. with test statistic greater than 100 (corresponding to about 10σ). Two methods, based on the CGRaBS, CRATES, and BZCat catalogs, indicate high-confidence associations of 106 of these sources with known active galactic nuclei (AGNs). This sample is referred to as the LAT Bright AGN Sample (LBAS). It contains two radio galaxies, namely, Centaurus A and NGC 1275, and 104 blazars consisting of 58 flat spectrum radio quasars (FSRQs), 42 BL Lac objects, and 4 blazars with unknown classification. Four new blazars were discovered on the basis of the LAT detections. Remarkably, the LBAS includes 10 high-energy-peaked BL Lacs (HBLs), sources which were previously difficult to detect in the GeV range. Another 10 lower-confidence associations are found. Only 33 of the sources, plus two at |b| < 10 deg., were previously detected with Energetic Gamma-Ray Experiment Telescope(EGRET), probably due to variability. The analysis of the γ-ray properties of the LBAS sources reveals that the average GeV spectra of BL Lac objects are significantly harder than the spectra of FSRQs. No significant correlation between radio and peak γ-ray fluxes is observed. Blazar log N-log S distributions and luminosity functions are constructed to investigate the evolution of the different blazar classes, with positive evolution indicated for FSRQs but none for BL Lacs. The contribution of LAT blazars to the total extragalactic γ-ray intensity is estimated.

  10. The XXL Survey. II. The bright cluster sample: catalogue and luminosity function

    Science.gov (United States)

    Pacaud, F.; Clerc, N.; Giles, P. A.; Adami, C.; Sadibekova, T.; Pierre, M.; Maughan, B. J.; Lieu, M.; Le Fèvre, J. P.; Alis, S.; Altieri, B.; Ardila, F.; Baldry, I.; Benoist, C.; Birkinshaw, M.; Chiappetti, L.; Démoclès, J.; Eckert, D.; Evrard, A. E.; Faccioli, L.; Gastaldello, F.; Guennou, L.; Horellou, C.; Iovino, A.; Koulouridis, E.; Le Brun, V.; Lidman, C.; Liske, J.; Maurogordato, S.; Menanteau, F.; Owers, M.; Poggianti, B.; Pomarède, D.; Pompei, E.; Ponman, T. J.; Rapetti, D.; Reiprich, T. H.; Smith, G. P.; Tuffs, R.; Valageas, P.; Valtchanov, I.; Willis, J. P.; Ziparo, F.

    2016-06-01

    Context. The XXL Survey is the largest survey carried out by the XMM-Newton satellite and covers a total area of 50 square degrees distributed over two fields. It primarily aims at investigating the large-scale structures of the Universe using the distribution of galaxy clusters and active galactic nuclei as tracers of the matter distribution. The survey will ultimately uncover several hundreds of galaxy clusters out to a redshift of ~2 at a sensitivity of ~10-14 erg s-1 cm-2 in the [0.5-2] keV band. Aims: This article presents the XXL bright cluster sample, a subsample of 100 galaxy clusters selected from the full XXL catalogue by setting a lower limit of 3 × 10-14 erg s-1 cm-2 on the source flux within a 1' aperture. Methods: The selection function was estimated using a mixture of Monte Carlo simulations and analytical recipes that closely reproduce the source selection process. An extensive spectroscopic follow-up provided redshifts for 97 of the 100 clusters. We derived accurate X-ray parameters for all the sources. Scaling relations were self-consistently derived from the same sample in other publications of the series. On this basis, we study the number density, luminosity function, and spatial distribution of the sample. Results: The bright cluster sample consists of systems with masses between M500 = 7 × 1013 and 3 × 1014 M⊙, mostly located between z = 0.1 and 0.5. The observed sky density of clusters is slightly below the predictions from the WMAP9 model, and significantly below the prediction from the Planck 2015 cosmology. In general, within the current uncertainties of the cluster mass calibration, models with higher values of σ8 and/or ΩM appear more difficult to accommodate. We provide tight constraints on the cluster differential luminosity function and find no hint of evolution out to z ~ 1. We also find strong evidence for the presence of large-scale structures in the XXL bright cluster sample and identify five new superclusters. Based on

  11. The ACS Virgo Cluster Survey IV: Data Reduction Procedures for Surface Brightness Fluctuation Measurements with the Advanced Camera for Surveys

    CERN Document Server

    Mei, S; Tonry, J L; Jordan, A; Peng, E W; Côté, P; Ferrarese, L; Merritt, D; Milosavljevic, M; West, M J; Mei, Simona; Blakeslee, John P.; Tonry, John L.; Jordan, Andres; Peng, Eric W.; Cote, Patrick; Ferrarese, Laura; Merritt, David; Milosavljevic, Milos; West, Michael J.

    2005-01-01

    The Advanced Camera for Surveys (ACS) Virgo Cluster Survey is a large program to image 100 early-type Virgo galaxies using the F475W and F850LP bandpasses of the Wide Field Channel of the ACS instrument on the Hubble Space Telescope (HST). The scientific goals of this survey include an exploration of the three-dimensional structure of the Virgo Cluster and a critical examination of the usefulness of the globular cluster luminosity function as a distance indicator. Both of these issues require accurate distances for the full sample of 100 program galaxies. In this paper, we describe our data reduction procedures and examine the feasibility of accurate distance measurements using the method of surface brightness fluctuations (SBF) applied to the ACS Virgo Cluster Survey F850LP imaging. The ACS exhibits significant geometrical distortions due to its off-axis location in the HST focal plane; correcting for these distortions by resampling the pixel values onto an undistorted frame results in pixel correlations tha...

  12. The IAC Stripe 82 Legacy Project: a wide-area survey for faint surface brightness astronomy

    CERN Document Server

    Fliri, Juergen

    2016-01-01

    We present new deep co-adds of data taken within Stripe 82 of the Sloan Digital Sky Survey (SDSS), especially stacked to reach the faintest surface brightness limits of this data set. Stripe 82 covers 275 square degrees within -50 ~ 25.5 mag/arcsec^2. For point sources, we reach 50% completeness limits (3 sigma level) of (24.2,25.2,24.7,24.3,23.0) mag in (u,g,r,i,z). This is between 1.7 and 2.0 mag deeper than the single epoch SDSS releases. The co-adds show point spread functions with median FWHM values ranging between 1 arcsec in i and z to 1.3 arcsec in the u band. The imaging data are made publicly available at http://www.iac.es/proyecto/stripe82. The release includes deep co-adds and representations of the PSF for each field. Additionally, we provide object catalogues with stars and galaxies confidently separated until g~23 mag. The IAC Stripe 82 coadds offer a rather unique possibility to study the low surface brightness universe, exemplified by the discovery of stellar streams around NGC0426 and NGC09...

  13. The IAC Stripe 82 Legacy Project: a wide-area survey for faint surface brightness astronomy

    Science.gov (United States)

    Fliri, Jürgen; Trujillo, Ignacio

    2016-02-01

    We present new deep co-adds of data taken within Stripe 82 of the Sloan Digital Sky Survey (SDSS), especially stacked to reach the faintest surface brightness limits of this data set. Stripe 82 covers 275 ° ^2 within -50° ≤ RA ≤ +60° and -1.25° ≤ Dec. ≤ +1.25°. We discuss the steps of our reduction which puts special emphasis on preserving the characteristics of the background (sky + diffuse light) in the input images using a non-aggressive sky subtraction strategy. Our reduction reaches a limit of ˜28.5 mag arcsec-2 (3σ, 10 × 10 arcsec2) in the r band. The effective surface brightness limit (50 per cent completeness for exponential light distribution) lies at ˜ 25.5 mag arcsec-2. For point sources, we reach 50 per cent completeness limits (3σ level) of (24.2, 25.2, 24.7, 24.3, 23.0) mag in (u, g, r, i, z). This is between 1.7 and 2.0 mag deeper than the single-epoch SDSS releases. The co-adds show point spread functions (PSFs) with median full width at half-maximum values ranging from 1 arcsec in i and z to 1.3 arcsec in the u band. The imaging data are made publicly available at http://www.iac.es/proyecto/stripe82. The release includes deep co-adds and representations of the PSF for each field. Additionally, we provide object catalogues with stars and galaxies confidently separated until g ˜ 23 mag. The IAC Stripe 82 co-adds offer a rather unique possibility to study the low surface brightness Universe, exemplified by the discovery of stellar streams around NGC 0426 and NGC 0936. We also discuss further science cases like stellar haloes and disc truncations, low surface brightness galaxies, the intracluster light in galaxy clusters and the diffuse emission of Galactic dust known as Galactic Cirrus.

  14. The Redshift Distribution of Intervening Weak MgII Quasar Absorbers and a Curious Dependence on Quasar Luminosity

    CERN Document Server

    Evans, Jessica L; Murphy, Michael T; Nielsen, Nikole M; Klimek, Elizabeth S

    2013-01-01

    We have identified 469 MgII doublet systems having W_r >= 0.02 {\\AA} in 252 Keck/HIRES and UVES/VLT quasar spectra over the redshift range 0.1 = 1.0 {\\AA}) absorbers. For weak absorption, dN/dz toward bright quasars is ~ 25% higher than toward faint quasars (10 sigma at low redshift, 0.4 <= z <= 1.4, and 4 sigma at high redshift, 1.4 < z <= 2.34). For strong absorption the trend reverses, with dN/dz toward faint quasars being ~ 20% higher than toward bright quasars (also 10 sigma at low redshift and 4 sigma at high redshift). We explore scenarios in which beam size is proportional to quasar luminosity and varies with absorber and quasar redshifts. These do not explain dN/dz's dependence on quasar luminosity.

  15. The XXL Survey . IV. Mass-temperature relation of the bright cluster sample

    Science.gov (United States)

    Lieu, M.; Smith, G. P.; Giles, P. A.; Ziparo, F.; Maughan, B. J.; Démoclès, J.; Pacaud, F.; Pierre, M.; Adami, C.; Bahé, Y. M.; Clerc, N.; Chiappetti, L.; Eckert, D.; Ettori, S.; Lavoie, S.; Le Fevre, J. P.; McCarthy, I. G.; Kilbinger, M.; Ponman, T. J.; Sadibekova, T.; Willis, J. P.

    2016-06-01

    Context. The XXL Survey is the largest survey carried out by XMM-Newton. Covering an area of 50 deg2, the survey contains ~450 galaxy clusters out to a redshift ~2 and to an X-ray flux limit of ~ 5 × 10-15 erg s-1 cm-2. This paper is part of the first release of XXL results focussed on the bright cluster sample. Aims: We investigate the scaling relation between weak-lensing mass and X-ray temperature for the brightest clusters in XXL. The scaling relation discussed in this article is used to estimate the mass of all 100 clusters in XXL-100-GC. Methods: Based on a subsample of 38 objects that lie within the intersection of the northern XXL field and the publicly available CFHTLenS shear catalog, we derive the weak-lensing mass of each system with careful considerations of the systematics. The clusters lie at 0.1 http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/592/A2

  16. Testing sky brightness models against radial dependency: a dense two dimensional survey around the city of Madrid, Spain

    CERN Document Server

    Zamorano, Jaime; Ocaña, Francisco; Pila-Diez, Berenice; Castaño, José Gómez; Pascual, Sergio; Tapia, Carlos; Gallego, Jesús; Fernandez, Alberto; Nievas, Miguel

    2015-01-01

    We present a study of the night sky brightness around the extended metropolitan area of Madrid using Sky Quality Meter (SQM) photometers. The map is the first to cover the spatial distribution of the sky brightness in the center of the Iberian peninsula. These surveys are neccessary to test the light pollution models that predict night sky brightness as a function of the location and brightness of the sources of light pollution and the scattering of light in the atmosphere. We describe the data-retrieval methodology, which includes an automated procedure to measure from a moving vehicle in order to speed up the data collection, providing a denser and wider survey than previous works with similar time frames. We compare the night sky brightness map to the nocturnal radiance measured from space by the DMSP satellite. We find that i) a single source model is not enough to explain the radial evolution of the night sky brightness, despite the predominance of Madrid in size and population, and ii) that the orograph...

  17. Testing sky brightness models against radial dependency: A dense two dimensional survey around the city of Madrid, Spain

    Science.gov (United States)

    Zamorano, J.; Sánchez de Miguel, A.; Ocaña, F.; Pila-Díez, B.; Gómez Castaño, J.; Pascual, S.; Tapia, C.; Gallego, J.; Fernández, A.; Nievas, M.

    2016-09-01

    We present a study of the night sky brightness around the extended metropolitan area of Madrid using Sky Quality Meter (SQM) photometers. The map is the first to cover the spatial distribution of the sky brightness in the centre of the Iberian peninsula. These surveys are necessary to test the light pollution models that predict night sky brightness as a function of the location and brightness of the sources of light pollution and the scattering of light in the atmosphere. We describe the data-retrieval methodology, which includes an automated procedure to measure from a moving vehicle in order to speed up the data collection, providing a denser and wider survey than previous works with similar time frames. We compare the night sky brightness map to the nocturnal radiance measured from space by the DMSP satellite. We find that (i) a single source model is not enough to explain the radial evolution of the night sky brightness, despite the predominance of Madrid in size and population and (ii) that the orography of the region should be taken into account when deriving geo-specific models from general first-principles models. We show the tight relationship between these two luminance measures. This finding sets up an alternative roadmap to extended studies over the globe that will not require the local deployment of photometers or trained personnel.

  18. The KELT-North Transit Survey: Hot Planets around Hot, Bright Stars

    Science.gov (United States)

    Gaudi, B. Scott; Beatty, Thomas G.; Eastman, Jason D.; Lund, Michael; Penny, Matthew; Pepper, Joshua; Rodriguez, Joseph E.; Siverd, Robert; Stassun, Keivan; Stevens, Daniel J.; KELT-North Collaboration

    2015-01-01

    The KELT-North is a small-aperture, wide-angle automated telescope located in southern Arizona that has been surveying roughly 40% of the northern sky for transiting planets since 2006. By virtue of its small aperture and large field-of-view, KELT is most sensitive to hot Jupiters transiting relatively bright (V~8-10), and thus relatively hot stars. Roughly half of the over 200,000 dwarf stars targeted by KELT are hotter than 6250K; such stars pose novel challenges, but also provide unique opportunities. I will present the first transiting substellar companions discovered by KELT, focusing in detail on a few particularly interesting systems. I will discuss our plans for determining the frequency and demographics of short-period companions to hot stars from KELT; comparison with similar results for cooler stars may provide important constraints on theories of the emplacement and tidal evolution of low-mass stellar companions. Finally, I will speculate on how the lessons learned from KELT may inform the target selection and survey strategies for the TESS mission.This work was supported by NSF CAREER grant AST-1056524.

  19. Sharp Chandra View of ROSAT All-Sky Survey Bright Sources: I. Improvement of Positional Accuracy

    CERN Document Server

    Gao, Shuang; Liu, Jifeng

    2016-01-01

    The ROSAT All-Sky Survey (RASS) represents one of the most complete and sensitive soft X-ray all-sky surveys to date. However, the deficient positional accuracy of the RASS Bright Source Catalog (BSC) and subsequent lack of firm optical identifications affect the multi-wavelength studies of X-ray sources. The widely used positional errors $\\sigma_{pos}$ based on the Tycho Stars Catalog (Tycho-1) have previously been applied for identifying objects in the optical band. The considerably sharper Chandra view covers a fraction of RASS sources, whose $\\sigma_{pos}$ could be improved by utilizing the sub-arcsec positional accuracy of Chandra observations. We cross-match X-ray objects between the BSC and \\emph{Chandra} sources extracted from the Advanced CCD Imaging Spectrometer (ACIS) archival observations. A combined counterparts list (BSCxACIS) with \\emph{Chandra} spatial positions weighted by the X-ray flux of multi-counterparts is employed to evaluate and improve the former identifications of BSC with the other...

  20. The XXL Survey. II. The bright cluster sample: catalogue and luminosity function

    CERN Document Server

    Pacaud, F; Giles, P A; Adami, C; Sadibekova, T; Pierre, M; Maughan, B J; Lieu, M; Fèvre, J -P Le; Alis, S; Altieri, B; Ardila, F; Baldry, I; Benoist, C; Birkinshaw, M; Chiappetti, L; Démoclès, J; Eckert, D; Evrard, A E; Faccioli, L; Gastaldello, F; Guennou, L; Horellou, C; Iovino, A; Koulouridis, E; Brun, V Le; Lidman, C; Liske, J; Maurogordato, S; Menanteau, F; Owers, M; Poggianti, B; Pomarède, D; Pompei, E; Ponman, T J; Rapetti, D; Reiprich, T H; Smith, G P; Tuffs, R; Valageas, P; Valtchanov, I; Willis, J P; Ziparo, F

    2015-01-01

    Context. The XXL Survey is the largest survey carried out by the XMM-Newton satellite and covers a total area of 50 square degrees distributed over two fields. It primarily aims at investigating the large-scale structures of the Universe using the distribution of galaxy clusters and active galactic nuclei as tracers of the matter distribution. Aims. This article presents the XXL bright cluster sample, a subsample of 100 galaxy clusters selected from the full XXL catalogue by setting a lower limit of $3\\times 10^{-14}\\,\\mathrm{erg \\,s^{-1}cm^{-2}}$ on the source flux within a 1$^{\\prime}$ aperture. Methods. The selection function was estimated using a mixture of Monte Carlo simulations and analytical recipes that closely reproduce the source selection process. An extensive spectroscopic follow-up provided redshifts for 97 of the 100 clusters. We derived accurate X-ray parameters for all the sources. Scaling relations were self-consistently derived from the same sample in other publications of the series. On th...

  1. A Systematic Search for Periodically Varying Quasars in Pan-STARRS1: An Extended Baseline Test in Medium Deep Survey Field MD09

    CERN Document Server

    Liu, T; Burgett, W; Chambers, K; Draper, P; Hodapp, K; Huber, M; Kudritzki, R -P; Magnier, E; Metcalfe, N; Tonry, J; Wainscoat, R; Waters, C

    2016-01-01

    We present a systematic search for periodically varying quasars and supermassive black hole binary (SMBHB) candidates in the Pan-STARRS1 (PS1) Medium Deep Survey's MD09 field. From a color-selected sample of 670 quasars extracted from a multi-band deep-stack catalog of point sources, we locally select variable quasars and look for coherent periods with the Lomb-Scargle periodogram. 3 candidates from our sample demonstrate strong variability for more than ~3 cycles, and their PS1 light curves are well fitted to sinusoidal functions. We test the persistence of the candidates' apparent periodic variations detected during the 4.2 years of the PS1 survey with archival photometric data from the SDSS Stripe 82 survey or new monitoring with the Large Monolithic Imager at the Discovery Channel Telescope. None of the 3 periodic candidates (including PSO J334.2028+1.4075, Liu et al. (2015)) remain persistent over the extended baseline of 7 - 14 years, corresponding to a detection rate of 5 cycles) is crucial to our sear...

  2. The XXL Survey. III. Luminosity-temperature relation of the bright cluster sample

    Science.gov (United States)

    Giles, P. A.; Maughan, B. J.; Pacaud, F.; Lieu, M.; Clerc, N.; Pierre, M.; Adami, C.; Chiappetti, L.; Démoclés, J.; Ettori, S.; Le Févre, J. P.; Ponman, T.; Sadibekova, T.; Smith, G. P.; Willis, J. P.; Ziparo, F.

    2016-06-01

    Context. The XXL Survey is the largest homogeneous survey carried out with XMM-Newton. Covering an area of 50 deg2, the survey contains several hundred galaxy clusters out to a redshift of ~2 above an X-ray flux limit of ~5 × 10-15 erg cm-2 s-1. This paper belongs to the first series of XXL papers focusing on the bright cluster sample. Aims: We investigate the luminosity-temperature (LT) relation for the brightest clusters detected in the XXL Survey, taking fully into account the selection biases. We investigate the form of the LT relation, placing constraints on its evolution. Methods: We have classified the 100 brightest clusters in the XXL Survey based on their measured X-ray flux. These 100 clusters have been analysed to determine their luminosity and temperature to evaluate the LT relation. We used three methods to fit the form of the LT relation, with two of these methods providing a prescription to fully take into account the selection effects of the survey. We measure the evolution of the LT relation internally using the broad redshift range of the sample. Results: Taking fully into account selection effects, we find a slope of the bolometric LT relation of BLT = 3.08 ± 0.15, steeper than the self-similar expectation (BLT = 2). Our best-fit result for the evolution factor is E(z)1.64 ± 0.77, fully consistent with "strong self-similar" evolution where clusters scale self-similarly with both mass and redshift. However, this result is marginally stronger than "weak self-similar" evolution, where clusters scale with redshift alone. We investigate the sensitivity of our results to the assumptions made in our fitting model, finding that using an external LT relation as a low-z baseline can have a profound effect on the measured evolution. However, more clusters are needed in order to break the degeneracy between the choice of likelihood model and mass-temperature relation on the derived evolution. Based on observations obtained with XMM-Newton, an ESA science

  3. Discovery of eight z ~ 6 quasars from Pan-STARRS1

    CERN Document Server

    Bañados, E; Morganson, E; Decarli, R; Walter, F; Chambers, K C; Rix, H-W; Farina, E P; Fan, X; Jiang, L; McGreer, I; De Rosa, G; Simcoe, R; Weiß, A; Price, P A; Morgan, J S; Burgett, W S; Greiner, J; Kaiser, N; Kudritzki, R -P; Magnier, E A; Metcalfe, N; Stubbs, C W; Sweeney, W; Tonry, J L; Wainscoat, R J; Waters, C

    2014-01-01

    High-redshift quasars are currently the only probes of the growth of supermassive black holes and potential tracers of structure evolution at early cosmic time. Here we present our candidate selection criteria from the Panoramic Survey Telescope & Rapid Response System 1 and follow-up strategy to discover quasars in the redshift range 5.75.7 by more than 10%. We additionally recovered 18 previously known quasars. The eight quasars presented here span a large range of luminosities (-27.3 < M_{1450} < -25.4; 19.6 < z_ps1 < 21.2) and are remarkably heterogeneous in their spectral features: half of them show bright emission lines whereas the other half show a weak or no Ly$\\alpha$ emission line (25% with rest-frame equivalent width of the Ly$\\alpha$ + Nv line lower than 15{\\AA}). We find a larger fraction of weak-line emission quasars than in lower redshift studies. This may imply that the weak-line quasar population at the highest redshifts could be more abundant than previously thought. However,...

  4. HI 21-cm absorption survey of quasar-galaxy pairs: Distribution of cold gas around z<0.4 galaxies

    CERN Document Server

    Dutta, R; Gupta, N; Momjian, E; Noterdaeme, P; Petitjean, P; Rahmani, H

    2016-01-01

    We present the results from our survey of HI 21-cm absorption, using GMRT, VLA and WSRT, in a sample of 55 z<0.4 galaxies towards radio sources with impact parameters (b) in the range ~0-35 kpc. In our primary sample (defined for statistical analyses) of 40 quasar-galaxy-pairs (QGPs), probed by 45 sightlines, we have found seven HI 21-cm absorption detections, two of which are reported here for the first time. Combining our primary sample with measurements having similar optical depth sensitivity ($\\int\\tau dv$ <= 0.3 km/s) from the literature, we find a weak anti-correlation (rank correlation coefficient = -0.20 at 2.42sigma level) between $\\int\\tau dv$ and b, consistent with previous literature results. The covering factor of HI 21-cm absorbers (C_21) is estimated to be 0.24 (+0.12/-0.08) at b <= 15 kpc and 0.06 (+0.09/-0.04) at b = 15-35 kpc. $\\int\\tau dv$ and C_21 show similar declining trend with radial distance along the galaxy's major axis and distances scaled with the effective HI radius. The...

  5. Dusty Quasars at High Redshifts

    CERN Document Server

    Weedman, Daniel

    2016-01-01

    A population of quasars at z ~ 2 is determined based on dust luminosities vLv(7.8 um) that includes unobscured, partially obscured, and obscured quasars. Quasars are classified by the ratio vLv(0.25 um)/vLv(7.8 um) = UV/IR, assumed to measure obscuration of UV luminosity by the dust which produces IR luminosity. Quasar counts at rest frame 7.8 um are determined for quasars in the Bootes field of the NOAO Deep Wide Field Survey using 24 um sources with optical redshifts from the AGN and Galaxy Evolution Survey (AGES) or infrared redshifts from the Spitzer Infrared Spectrograph. Spectral energy distributions are extended to far infrared wavelengths using observations from the Herschel Space Observatory Spectral and Photometric Imaging Receiver (SPIRE), and new SPIRE photometry is presented for 77 high redshift quasars from the Sloan Digital Sky Survey. It is found that unobscured and obscured quasars have similar space densities at rest frame 7.8 um, but the ratio Lv(100 um)/Lv(7.8 um) is about three times high...

  6. Astrometric Redshifts for Quasars

    CERN Document Server

    Kaczmarczik, Michael C; Mehta, Sajjan S; Schlegel, David J

    2009-01-01

    The wavelength dependence of atmospheric refraction causes differential chromatic refraction (DCR), whereby objects imaged at different optical/UV wavelengths are observed at slightly different positions in the plane of the detector. Strong spectral features induce changes in the effective wavelengths of broad-band filters that are capable of producing significant positional offsets with respect to standard DCR corrections. We examine such offsets for broad-emission-line (type 1) quasars from the Sloan Digital Sky Survey (SDSS) spanning 0quasar spectrum with the SDSS bandpasses as a function of redshift and airmass. This astrometric information can be used to break degeneracies in photometric redshifts of quasars (or other emission-line sources) and, for extreme cases, may be suitable for determining "astrometric redshifts". On the SDSS's southern equatorial stripe, where it is pos...

  7. Dusty Quasars

    CERN Document Server

    Krawczyk, Coleman M; Gallagher, S C; Leighly, Karen M; Hewett, Paul C; Ross, Nicholas P; Hall, P B

    2014-01-01

    We explore the extinction/reddening of ~35,000 uniformly-selected quasars with 00.1 and 0.1% (1.3%) with E(B-V)>0.2. Simulations show both populations of quasars are intrinsically bluer than the mean composite, with a mean spectral index (${\\alpha}_{\\lambda}$) of -1.79 (-1.83). The emission and absorption-line properties of both samples reveal that quasars with intrinsically red continua have narrower Balmer lines and stronger ionizing spectral lines, the latter indicating a harder continuum in the extreme-UV and the former indicating either smaller BH mass or more face-on orientation.

  8. The Galactic O-Star Spectroscopic Survey (GOSSS). II. Bright Southern Stars

    CERN Document Server

    Sota, A; Morrell, N I; Barbá, R H; Walborn, N R; Gamen, R C; Arias, J I; Alfaro, E J

    2013-01-01

    We present the second installment of GOSSS, a massive spectroscopic survey of Galactic O stars, based on new homogeneous, high signal-to-noise ratio, R ~ 2500 digital observations from both hemispheres selected from the Galactic O-Star Catalog (GOSC). In this paper we include bright stars and other objects drawn mostly from the first version of GOSC, all of them south of delta = -20 degrees, for a total number of 258 O stars. We also revise the northern sample of paper I to provide the full list of spectroscopically classified Galactic O stars complete to B = 8, bringing the total number of published GOSSS stars to 448. Extensive sequences of exceptional objects are given, including the early Of/WN, O Iafpe, Ofc, ON/OC, Onfp, Of?p, and Oe types, as well as double/triple-lined spectroscopic binaries. The new spectral subtype O9.2 is also discussed. The magnitude and spatial distributions of the observed sample are analyzed. We also present new results from OWN, a multi-epoch high-resolution spectroscopic surve...

  9. A new bright eclipsing hot subdwarf binary from the ASAS and SuperWASP surveys

    CERN Document Server

    Schaffenroth, V; Drechsel, H; Heber, U; Wils, P; Oestensen, R H; Maxted, P F L; di Scala, G

    2013-01-01

    We report the discovery of a bright (V=11.6 mag) eclipsing hot subdwarf binary of spectral type B with a late main sequence companion from the All Sky Automated Survey (ASAS 102322-3737.0). Such systems are called HW Vir stars after the prototype. The lightcurve shows a grazing eclipse and a strong reflection effect. An orbital period of P=0.13927 d, an inclination of i=65.86{\\deg}, a mass ratio q=0.34, a radial velocity semiamplitude K_1=81.0 kms^-1, and other parameters are derived from a combined spectroscopic and photometric analysis. The short period can only be explained by a common envelope origin of the system. The atmospheric parameters (T_eff=28400 K, log g=5.60) are consistent with a core helium-burning star located on the extreme horizontal branch. In agreement with that we derived the most likely sdB mass to be M_sdB=0.46M_sun, close to the canonical mass of such objects. The companion is a late M-dwarf with a mass of M_comp=0.16 M_sun. ASAS 102322-3737.0 is the third brightest of only 12 known H...

  10. Spectral Variability in Hard X-rays and the Evidence for a 13.5 Years Period in the Bright Quasar 3C273

    Indian Academy of Sciences (India)

    R. K. Manchanda

    2002-09-01

    We report the observation of nearest quasar 3C273 made with LASE instrument on November 20th, 1998 as a part of our continuing programme of balloon borne hard X-ray observations in the 20–200 keV band using high sensitivity Large Area Scintillation counter Experiment. Our data clearly show a steep spectrum in the 20–200 keV with power law spectral index = 226 ± 0.07. This is in complete contrast to the reported data from OSSE and BeppoSAX which suggest the value of 1.3 to 1.6 for the power law index in the X-ray energy band, but is quite consistent with the value derived for the high energy gamma ray data. A single power law fit in the X-ray and gamma ray energy bands points to a common origin of these photons and the absence of spectral break around 1 MeV as suggested in literature. We have reanalyzed the available data to study the temporal variability of the spectrum in the hard X-ray band. Our analysis reveals that 50 keV flux from the source, shows a strong modulation with a period of about 13.5 years. The analysis of the optical light curve of the source also supports the 5000 day period.We discuss the emission mechanism and the possible sites for X-ray photons along with the implications of the long term periodicity with respect to source geometry.

  11. THE CLOWES-CAMPUSANO LARGE QUASAR GROUP SURVEY. I. GALEX SELECTED SAMPLE OF LYMAN BREAK GALAXIES AT z ∼ 1

    International Nuclear Information System (INIS)

    The nature of galaxy structures on large scales is a key observational prediction for current models of galaxy formation. The Sloan Digital Sky Survey (SDSS) and the 2dF galaxy survey have revealed a number of structures on 40-150 h-1 Mpc scales at low redshifts, and some even larger ones. To constrain galaxy number densities, luminosities, and stellar populations in large structures at higher redshift, we have investigated two sheet-like structures of galaxies at z = 0.8 and 1.3 spanning 150 h-1 comoving Mpc embedded in large quasar groups (LQGs) extending over at least 200 h-1 Mpc. We present first results of an analysis of these sheet-like structures using two contiguous 1 deg Galaxy Evolution Explorer (GALEX) fields (FUV and NUV) cross-correlated with optical data from the SDSS. We derive a sample of 462 Lyman break galaxy (LBG) candidates coincident with the sheets. Using the GALEX and SDSS data, we show that the overall average spectral energy distribution of a LBG galaxy at z ∼ 1 is flat (in fλ) in the rest-frame wavelength range from 1500 A to 4000 A, implying evolved populations of stars in the LBGs. From the luminosity functions we get indications for overdensities in the two LQGs compared to their foreground regions. Similar conclusions come from the calculation of the 2-point correlation function, showing a 2σ overdensity for the LBGs in the z ∼ 0.8 LQG on scales of 1.6 to 4.8 Mpc, indicating similar correlation scales for our LBG sample as their z ∼ 3 counterparts.

  12. Chitah: Strong-gravitational-lens hunter in imaging surveys

    CERN Document Server

    Chan, James H H; Chiueh, Tzihong; More, Anupreeta; Marshall, Philip J; Coupon, Jean; Oguri, Masamune; Price, Paul

    2014-01-01

    Strong gravitationally lensed quasars provide powerful means to study galaxy evolution and cosmology. Current and upcoming imaging surveys will contain thousands of new lensed quasars, augmenting the existing sample by at least two orders of magnitudes. To find such lens systems, we built a robot, Chitah, that hunts for lensed quasars by modeling the configuration of the multiple quasar images. Specifically, given an image of an object that might be a lensed quasar, Chitah first disentangles the light from the supposed lens galaxy and the light from the multiple quasar images based on color information. A simple rule is designed to categorize the given object into a potential four-image (quad) or two-image (double) lensed quasar system. The configuration of the identified quasar images is subsequently modeled to classify whether the object is a lensed quasar system. We test the performance of Chitah using simulated lens systems based on the Canada-France-Hawaii-Telescope Legacy Survey. For bright quads with l...

  13. The XXL Survey . IV. Mass-temperature relation of the bright cluster sample

    Science.gov (United States)

    Lieu, M.; Smith, G. P.; Giles, P. A.; Ziparo, F.; Maughan, B. J.; Démoclès, J.; Pacaud, F.; Pierre, M.; Adami, C.; Bahé, Y. M.; Clerc, N.; Chiappetti, L.; Eckert, D.; Ettori, S.; Lavoie, S.; Le Fevre, J. P.; McCarthy, I. G.; Kilbinger, M.; Ponman, T. J.; Sadibekova, T.; Willis, J. P.

    2016-06-01

    Context. The XXL Survey is the largest survey carried out by XMM-Newton. Covering an area of 50 deg2, the survey contains ~450 galaxy clusters out to a redshift ~2 and to an X-ray flux limit of ~ 5 × 10-15 erg s-1 cm-2. This paper is part of the first release of XXL results focussed on the bright cluster sample. Aims: We investigate the scaling relation between weak-lensing mass and X-ray temperature for the brightest clusters in XXL. The scaling relation discussed in this article is used to estimate the mass of all 100 clusters in XXL-100-GC. Methods: Based on a subsample of 38 objects that lie within the intersection of the northern XXL field and the publicly available CFHTLenS shear catalog, we derive the weak-lensing mass of each system with careful considerations of the systematics. The clusters lie at 0.1 relation. Results: The mass-temperature relation fit (M ∝ Tb) to the XXL clusters returns a slope and intrinsic scatter σlnM|T≃ 0.53; the scatter is dominated by disturbed clusters. The fit to the combined sample of 96 clusters is in tension with self-similarity, b = 1.67 ± 0.12 and σlnM|T ≃ 0.41. Conclusions: Overall our results demonstrate the feasibility of ground-based weak-lensing scaling relation studies down to cool systems of ~1 keV temperature and highlight that the current data and samples are a limit to our statistical precision. As such we are unable to determine whether the validity of hydrostatic equilibrium is a function of halo mass. An enlarged sample of cool systems, deeper weak-lensing data, and robust modelling of the selection function will help to explore these issues further. Based on observations obtained with XMM-Newton, an ESA sci- ence mission with instruments and contributions directly funded by ESA Member States and NASA. Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programme 089.A-0666 and LP191.A-0268.The Master catalogue is available at the CDS via anonymous ftp to http

  14. The Sloan Digital Sky Survey Reverberation Mapping Project: Stellar Velocity Dispersions of Quasar Hosts and the M-sigma Relation to z~1

    CERN Document Server

    Shen, Yue; Ho, Luis C; Brandt, W N; Denney, Kelly D; Horne, Keith; Jiang, Linhua; Kochanek, Christopher S; McGreer, Ian D; Merloni, Andrea; Peterson, Bradley M; Petitjean, Patrick; Schneider, Donald P; Schulze, Andreas; Strauss, Michael A; Tao, Charling; Trump, Jonathan R; Pan, Kaike; Bizyaev, Dmitry

    2015-01-01

    We present host stellar velocity dispersion measurements for a sample of 88 broad-line quasars at 0.10.6) from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project. High signal-to-noise ratio coadded spectra (average S/N~30 per 69 km/s pixel) from SDSS-RM allowed decomposition of the host and quasar spectra, and measurement of the host stellar velocity dispersions and black hole (BH) masses using the single-epoch (SE) virial method. The large sample size and dynamic range in luminosity (L5100=10^(43.2-44.7) erg/s) lead to the first clear detection of a correlation between SE virial BH mass and host stellar velocity dispersion far beyond the local universe. However, the observed correlation is significantly flatter than the local relation, suggesting that there are selection biases in high-z luminosity-threshold quasar samples for such studies. Our uniform sample and analysis enable an investigation of the redshift evolution of the M-sigma relation free of caveats by comparing different samples...

  15. Discovery of a Gravitationally Lensed Quasar from theSloan Digital Sky Survey: SDSS J133222.62+034739.9

    Energy Technology Data Exchange (ETDEWEB)

    Morokuma, Tomoki; Inada, Naohisa; Oguri, Masamune; Ichikawa, Shin-Ichi; Kawano, Yozo; Tokita, Kouichi; Kayo, Issha; Hall, Patrick B.; Kochanek, Christopher S.; Richards,; York, Donald G.; Schneider, Donald P.; /Tokyo U., Inst. Astron. /KIPAC, Menlo Park /Princeton U. /Tokyo, Astron. Observ. /Nagoya U. /York U., Canada /Ohio State U.,

    2006-09-28

    We report the discovery of the two-image gravitationally lensed quasar SDSS J133222.62+034739.9 (SDSS J1332+0347) with an image separation of {Delta}{theta} = 1.14''. This system consists of a source quasar at z{sub s} = 1.445 and a lens galaxy at z{sub l} = 0.191. The agreement of the luminosity, ellipticity and position angle of the lens galaxy with those expected from lens model confirms the lensing hypothesis.

  16. Metallicity and Quasar Outflows

    CERN Document Server

    Wang, Huiyuan; Yuan, Weimin; Wang, Tinggui

    2012-01-01

    Correlations are investigated of the outflow strength of quasars, as measured by the blueshift and asymmetry index (BAI) of the CIV line (Wang et al. 2011), with intensities and ratios of broad emission lines, based on composite quasar spectra built from the Sloan Digital Sky Survey. We find that most of the line ratios of other ions to CIV prominently increases with BAI. These behaviors can be well understood in the context of increasing metallicity with BAI. The strength of dominant coolant, CIV line, decreases and weak collisionally excited lines increase with gas metallicity as a result of the competition between different line coolants. Using SiIV+OIV]/CIV as an indicator of gas metallicity, we present, for the first time, a strong correlation between the metallicitiy and the outflow strength of quasars over a wide range of 1.7 to 6.9 times solar abundance. Our result implies that the metallicity plays an important role in the formation of quasar outflows, likely via affecting outflow acceleration. This ...

  17. The Stacked Lyman-Alpha Emission Profile from the Circum-Galactic Medium of z~2 Quasars

    CERN Document Server

    Battaia, Fabrizio Arrigoni; Cantalupo, Sebastiano; Prochaska, J Xavier

    2016-01-01

    In the context of the FLASHLIGHT survey, we obtained deep narrow band images of 15 $z\\sim2$ quasars with GMOS on Gemini-South in an effort to measure Ly$\\alpha$ emission from circum- and inter-galactic gas on scales of hundreds of kpc from the central quasar. We do not detect bright giant Ly$\\alpha$ nebulae (SB~10$^{-17}$ erg s$^{-1}$ cm$^{-2}$ arcsec$^{-2}$ at distances >50 kpc) around any of our sources, although we routinely ($\\simeq47$%) detect smaller scale <50 kpc Ly$\\alpha$ emission at this SB level emerging from either the extended narrow emission line regions powered by the quasars or by star-formation in their host galaxies. We stack our 15 deep images to study the average extended Ly$\\alpha$ surface brightness profile around $z\\sim2$ quasars, carefully PSF-subtracting the unresolved emission component and paying close attention to sources of systematic error. Our analysis, which achieves an unprecedented depth, reveals a surface brightness of SB$_{\\rm Ly\\alpha}\\sim10^{-19}$ erg s$^{-1}$ cm$^{-2}...

  18. Witnessing the Birth of a Quasar

    CERN Document Server

    Tanaka, Takamitsu; Menou, Kristen

    2010-01-01

    The coalescence of a supermassive black hole binary (SMBHB) is thought to be accompanied by an electromagnetic (EM) afterglow, produced by the viscous infall of the surrounding circumbinary gas disk after the merger. It has been proposed that once the merger has been detected in gravitational waves (GWs) by LISA, follow-up EM searches for this afterglow can help identify the EM counterpart of the LISA source. Here we study whether the afterglows may be sufficiently bright and numerous to be detectable in EM surveys alone. The viscous afterglow, which lasts for years to decades for SMBHBs in LISA's sensitivity window, is characterized by rapid increases in both the bolometric luminosity and in the spectral hardness of the source. If quasar activity is triggered by the same major galaxy mergers that produce SMBHBs, then the afterglow could be interpreted as a signature of the birth of a quasar. Using an idealized model for the post-merger viscous spreading of the circumbinary disk and the resulting light curve,...

  19. Data mining for gravitationally lensed quasars

    Science.gov (United States)

    Agnello, Adriano; Kelly, Brandon C.; Treu, Tommaso; Marshall, Philip J.

    2015-04-01

    Gravitationally lensed quasars are brighter than their unlensed counterparts and produce images with distinctive morphological signatures. Past searches and target-selection algorithms, in particular the Sloan Quasar Lens Search (SQLS), have relied on basic morphological criteria, which were applied to samples of bright, spectroscopically confirmed quasars. The SQLS techniques are not sufficient for searching into new surveys (e.g. DES, PS1, LSST), because spectroscopic information is not readily available and the large data volume requires higher purity in target/candidate selection. We carry out a systematic exploration of machine-learning techniques and demonstrate that a two-step strategy can be highly effective. In the first step, we use catalogue-level information (griz+WISE magnitudes, second moments) to pre-select targets, using artificial neural networks. The accepted targets are then inspected with pixel-by-pixel pattern recognition algorithms (gradient-boosted trees), to form a final set of candidates. The results from this procedure can be used to further refine the simpler SQLS algorithms, with a twofold (or threefold) gain in purity and the same (or 80 per cent) completeness at target-selection stage, or a purity of 70 per cent and a completeness of 60 per cent after the candidate-selection step. Simpler photometric searches in griz+WISE based on colour cuts would provide samples with 7 per cent purity or less. Our technique is extremely fast, as a list of candidates can be obtained from a Stage III experiment (e.g. DES catalogue/data base) in a few CPU hours. The techniques are easily extendable to Stage IV experiments like LSST with the addition of time domain information.

  20. The Spectral Slope and Escape Fraction of Bright Quasars at $z \\sim 3.8$: the Contribution to the Cosmic UV Background

    CERN Document Server

    Cristiani, Stefano; Fontanot, Fabio; Koothrappali, Rajesh R; Vanzella, Eros; Monaco, Pierluigi

    2016-01-01

    We use a sample of 1669 QSOs ($r<20.15$, $3.6survey to study the intrinsic shape of the continuum and the Lyman continuum photon escape fraction (f$_{\\rm esc,q}$), estimated as the ratio between the observed flux and the expected intrinsic flux (corrected for the intergalactic medium absorption). Modelling the intrinsic QSO continuum shape with a power-law, $F_{\\lambda}\\propto\\lambda^{-\\gamma}$, we find a median $\\gamma=1.36$ (with a dispersion of $0.36$, no dependence on the redshift and a mild intrinsic luminosity dependence) and a mean f$_{\\rm esc,q}=0.71$ (independent of the QSO luminosity and/or redshift). The f$_{\\rm esc,q}$ distribution shows a peak around zero and a long tail of higher values, with a resulting dispersion of $0.67$. If we assume for the QSO continuum a double power-law shape (also compatible with the data) with a break located at $\\lambda_{\\rm br}=1000$ \\AA \\ and a softening $\\Delta\\gamma=0.72 $ at wavelengths shorter than $\\lambda_{\\rm br}$, the mean f$...

  1. Galaxy Clusters in the Line of Sight to Background Quasars: I. Survey Design and Incidence of MgII Absorbers at Cluster Redshifts

    CERN Document Server

    López, S; Lira, P; Padilla, N; Gilbank, D G; Gladders, M D; Maza, J; Tejos, N; Vidal, M; Yee, H K C

    2008-01-01

    We describe the first optical survey of absorption systems associated with galaxy clusters at z= 0.3-0.9. We have cross-correlated SDSS DR3 quasars with high-redshift cluster/group candidates from the Red-Sequence Cluster Survey. We have found 442 quasar-cluster pairs for which the MgII doublet might be detected at a transverse (physical) distance d2.0 Ang.) near cluster redshifts shows a significant (>3 sigma) overabundance (up to a factor of 15) when compared with the 'field' population; (2) the overabundance is more evident at smaller distances (d<1 Mpc) than larger distances (d<2 Mpc) from the cluster center; and, (3) the population of weak MgII systems (W_0<0.3 Ang.) near cluster redshifts conform to the field statistics. Unlike in the field, this dichotomy makes n(W) in clusters appear flat and well fitted by a power-law in the entire W-range. A sub-sample of the most massive clusters yields a stronger and still significant signal. Since either the absorber number density or filling-factor/cros...

  2. Quasar redshifts: the intrinsic component

    Science.gov (United States)

    Hansen, Peter M.

    2016-09-01

    The large observed redshift of quasars has suggested large cosmological distances and a corresponding enormous energy output to explain the brightness or luminosity as seen at earth. Alternative or complementary sources of redshift have not been identified by the astronomical community. This study examines one possible source of additional redshift: an intrinsic component based on the plasma characteristics of high temperature and high electron density which are believed to be present.

  3. Spitzer/IRAC Imaging of Exceptionally Bright Cluster-Lensed Submillimeter Galaxies Discovered by the Herschel Lensing Survey

    Science.gov (United States)

    Egami, Eiichi; Ebeling, Harald; Rawle, Timothy; Clement, Benjamin; Walth, Gregory; Pereira, Maria; Richard, Johan; Kneib, Jean-Paul

    2012-12-01

    Over the last few years, discoveries of exceptionally bright (e.g., observed S_peak > 100 mJy in the Herschel/SPIRE bands) gravitationally lensed submillimeter galaxies (SMGs) have generated great excitement. This is because these gravitationally lensed SMGs are so bright that they enable us to perform a variety of follow-up observations using a suite of observing facilities in the submillimeter, millimeter, and radio now available on the ground. Using Herschel, our team has been conducting a survey of such bright lensed galaxies in the fields of massive galaxy clusters: ``The Herschel Lensing Survey (HLS)'' (PI: Egami; 419 hours). This large Herschel program targets a total of 581 X-ray/SZ-selected massive clusters, and is currently 80% complete. Cluster lenses are often more powerful than galaxy lenses, producing larger magnifications. For example, typical magnification factors for galaxy-lensed Herschel sources are x10 or less while cluster-lensed systems can often produce magnification factors of x20-30 and even above x100. Cluster lenses will therefore allow us to detect and study intrinsically less-luminous and/or more distant sources with the ability to provide a view of finer-scale (i.e., sub-kpc) structures. Here, we propose to conduct Spitzer/IRAC imaging of 56 bright lensed SMG candidates we have identified in the ~470 HLS cluster fields observed so far. The main scientific goal is twofold: (1) to locate the underlying stellar component, and (2) to study its properties (e.g., stellar mass, specific star-formation rate) by constraining the rest-frame near-infrared SED and comparing with the Herschel and other submillimeter/millimeter data (e.g., SMA, PdB, ALMA, etc.). These rare bright lensed SMGs will allow us to probe the population of heavily dust-obscured vigorously star-forming galaxies at high redshift (z>1), which is thought to play an important role in the cosmic star-formation history of the Universe and yet has been difficult to study due to the

  4. THE MAGELLANIC QUASARS SURVEY. I. DOUBLING THE NUMBER OF KNOWN ACTIVE GALACTIC NUCLEI BEHIND THE SMALL MAGELLANIC CLOUD

    International Nuclear Information System (INIS)

    We report the spectroscopic confirmation of 29 new, 12 plausible, and three previously known quasars behind the central ∼1.5 deg2 region of the Small Magellanic Cloud (SMC). These were identified in a single 2DF/AAOMEGA observation on the Anglo-Australian Telescope of 268 candidates selected primarily based on their mid-IR colors, along with a smaller number of optically variable sources in OGLE-II close to known X-ray sources. The low detection efficiency was partly expected from the high surface density of SMC as compared with the Large Magellanic Cloud targets and the faintness of many of them (149 with I>20 mag). The expected number of I < 20 mag quasars in the field is ≅38, and we found 15 (40%). We did not attempt to determine the nature of the remaining sources, although several appear to be new planetary nebulae. The newly discovered active galactic nuclei can be used as reference points for future proper-motion studies, to study absorption in the SMC interstellar medium, and to study the physics of quasar variability with the existing long-term, highly cadenced OGLE light curves.

  5. QUASARS PROBING QUASARS. IV. JOINT CONSTRAINTS ON THE CIRCUMGALACTIC MEDIUM FROM ABSORPTION AND EMISSION

    Energy Technology Data Exchange (ETDEWEB)

    Hennawi, Joseph F.; Prochaska, J. Xavier, E-mail: xavier@ucolick.org [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany)

    2013-03-20

    We have constructed a sample of 29 close projected quasar pairs where the background quasar spectrum reveals absorption from optically thick H I gas associated with the foreground quasar. These unique sightlines allow us to study the quasar circumgalactic medium (CGM) in absorption and emission simultaneously, because the background quasar pinpoints large concentrations of gas where Ly{alpha} emission, resulting from quasar-powered fluorescence, resonant Ly{alpha} scattering, and/or cooling radiation, is expected. A sensitive search (1{sigma} surface-brightness limits of SB{sub Ly{alpha}}{approx_equal}3 Multiplication-Sign 10{sup -18} erg s{sup -1} cm{sup -2} arcsec{sup -2}) for diffuse Ly{alpha} emission in the environments of the foreground (predominantly radio-quiet) quasars is conducted using Gemini/GMOS and Keck/LRIS slit spectroscopy. We fail to detect large-scale {approx}100 kpc Ly{alpha} emission, either at the location of the optically thick absorbers or in the foreground quasar halos, in all cases except a single system. We interpret these non-detections as evidence that the gas detected in absorption is shadowed from the quasar UV radiation due to obscuration effects, which are frequently invoked in unified models of active galactic nuclei. Small-scale R {approx}< 50 kpc extended Ly{alpha} nebulosities are detected in 34% of our sample, which are likely the high-redshift analogs of the extended emission-line regions (EELRs) commonly observed around low-redshift (z < 0.5) quasars. This may be fluorescent recombination radiation from a population of very dense clouds with a low covering fraction illuminated by the quasar. We also detect a compact high rest-frame equivalent width (W{sub Ly{alpha}} > 50 A) Ly{alpha}-emitter with luminosity L{sub Ly{alpha}} = 2.1 {+-} 0.32 Multiplication-Sign 10{sup 41} erg s{sup -1} at small impact parameter R = 134 kpc from one foreground quasar, and argue that it is more likely to result from quasar-powered fluorescence

  6. OBSERVATIONAL UPPER BOUND ON THE COSMIC ABUNDANCES OF NEGATIVE-MASS COMPACT OBJECTS AND ELLIS WORMHOLES FROM THE SLOAN DIGITAL SKY SURVEY QUASAR LENS SEARCH

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Ryuichi; Asada, Hideki [Faculty of Science and Technology, Hirosaki University, Hirosaki 036-8561 (Japan)

    2013-05-01

    The latest result in the Sloan Digital Sky Survey Quasar Lens Search (SQLS) has set the first cosmological constraints on negative-mass compact objects and Ellis wormholes. There are no multiple images lensed by the above two exotic objects for {approx}50, 000 distant quasars in the SQLS data. Therefore, an upper bound is put on the cosmic abundances of these lenses. The number density of negative-mass compact objects is n < 10{sup -8}(10{sup -4}) h {sup 3} Mpc{sup -3} at the mass scale |M| > 10{sup 15}(10{sup 12}) M{sub Sun }, which corresponds to the cosmological density parameter |{Omega}| < 10{sup -4} at the galaxy and cluster mass range |M| = 10{sup 12-15} M{sub Sun }. The number density of the Ellis wormhole is n < 10{sup -4} h {sup 3} Mpc{sup -3} for a range of the throat radius a = 10-10{sup 4} pc, which is much smaller than the Einstein ring radius.

  7. XQ-100: A legacy survey of one hundred 3.5 ≲ z ≲ 4.5 quasars observed with VLT/X-shooter

    Science.gov (United States)

    López, S.; D'Odorico, V.; Ellison, S. L.; Becker, G. D.; Christensen, L.; Cupani, G.; Denney, K. D.; Pâris, I.; Worseck, G.; Berg, T. A. M.; Cristiani, S.; Dessauges-Zavadsky, M.; Haehnelt, M.; Hamann, F.; Hennawi, J.; Iršič, V.; Kim, T.-S.; López, P.; Lund Saust, R.; Ménard, B.; Perrotta, S.; Prochaska, J. X.; Sánchez-Ramírez, R.; Vestergaard, M.; Viel, M.; Wisotzki, L.

    2016-10-01

    We describe the execution and data reduction of the European Southern Observatory Large Programme "Quasars and their absorption lines: a legacy survey of the high-redshift Universe with VLT/X-shooter" (hereafter "XQ-100"). XQ-100 has produced and made publicly available a homogeneous and high-quality sample of echelle spectra of 100 quasars (QSOs) at redshifts z ≃ 3.5-4.5 observed with full spectral coverage from 315 to 2500 nm at a resolving power ranging from R ~ 4000 to 7000, depending on wavelength. The median signal-to-noise ratios are 33, 25 and 43, as measured at rest-frame wavelengths 1700, 3000 and 3600 Å, respectively. This paper provides future users of XQ-100 data with the basic statistics of the survey, along with details of target selection, data acquisition and data reduction. The paper accompanies the public release of all data products, including 100 reduced spectra. XQ-100 is the largest spectroscopic survey to date of high-redshift QSOs with simultaneous rest-frame UV/optical coverage, and as such enables a wide range of extragalactic research, from cosmology and galaxy evolution to AGN astrophysics. Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programme ID 189.A-0424.The XQ-100 raw data and the XQ-100 Science Data Products can be found at http://archive.eso.org/eso/eso_archive_main.html and http://archive.eso.org/wdb/wdb/adp/phase3_main/form, respectively.

  8. Evidence for the alignment of quasar radio polarizations with large quasar group axes

    Science.gov (United States)

    Pelgrims, V.; Hutsemékers, D.

    2016-05-01

    Recently, evidence has been presented for the polarization vectors from quasars to preferentially align with the axes of the large quasar groups (LQG) to which they belong. This report was based on observations made at optical wavelengths for two LQGs at redshift ~1.3. The correlation suggests that the spin axes of quasars preferentially align with their surrounding large-scale structure that is assumed to be traced by the LQGs. Here, we consider a large sample of LQGs built from the Sloan Digital Sky Survey DR7 quasar catalogue in the redshift range 1.0-1.8. For quasars embedded in this sample, we collected radio polarization measurements with the goal to study possible correlations between quasar polarization vectors and the major axis of their host LQGs. Assuming the radio polarization vector is perpendicular to the quasar spin axis, we found that the quasar spin axis is preferentially parallel to the LQG major axis inside LQGs that have at least 20 members. This result independently supports the observations at optical wavelengths. We additionally found that when the richness of an LQG decreases, the quasar spin axis becomes preferentially perpendicular to the LQG major axis and that no correlation is detected for quasar groups with fewer than 10 members.

  9. THE MAGELLANIC QUASARS SURVEY. I. DOUBLING THE NUMBER OF KNOWN ACTIVE GALACTIC NUCLEI BEHIND THE SMALL MAGELLANIC CLOUD

    OpenAIRE

    Kozłowski, Szymon; Kochanek, Christopher S.; Udalski, Andrzej

    2011-01-01

    We report the spectroscopic confirmation of 29 new, 12 plausible, and 3 previously known quasars behind the central ~1.5 deg^2 region of the Small Magellanic Cloud. These were identified in a single 2df/AAOmega observation on the Anglo-Australian Telescope of 268 candidates selected primarily based on their mid-IR colors, along with a smaller number of optically variable sources in OGLE-II close to known X-ray sources. The low detection efficiency was partly expected from the high surface den...

  10. Testing Models of Quasar Hosts With Strong Gravitational Lensing by Quasar Hosts

    CERN Document Server

    Cen, Renyue

    2016-01-01

    We perform a statistical analysis of strong gravitational lensing by quasar hosts of background galaxies, in the two competing models of dark matter halos of quasars, HOD and CS models. Utilizing the BolshoiP Simulation we demonstrate that strong gravitational lensing provides a potentially very powerful test of models of quasar hosting halos. For quasars at $z=0.5$, the lensing probability by quasars of background galaxies in the HOD model is higher than that of the CS model by two orders of magnitude or more for lensing image separations in the range of $\\theta\\sim 1.2-12~$arcsec. To observationally test this, we show that, as an example, at the depth of the CANDELS wide field survey and with a quasar sample of $1000$ at $z=0.5$, the two models can be differentiated at $3-4\\sigma$ confidence level.

  11. The Giant Gemini GMOS survey of z>4.4 quasars - I. Measuring the mean free path across cosmic time

    CERN Document Server

    Worseck, Gábor; O'Meara, John M; Becker, George D; Ellison, Sara; Lopez, Sebastian; Meiksin, Avery; Ménard, Brice; Murphy, Michael T; Fumagalli, Michele

    2014-01-01

    We have obtained spectra of 163 quasars at $z_\\mathrm{em}>4.4$ with the Gemini Multi Object Spectrometers on the Gemini North and South telescopes, the largest publicly available sample of high-quality, low-resolution spectra at these redshifts. From this homogeneous data set, we generated stacked quasar spectra in three redshift intervals at $z\\sim 5$. We have modelled the flux below the rest-frame Lyman limit ($\\lambda_\\mathrm{r}<912$\\AA) to assess the mean free path $\\lambda_\\mathrm{mfp}^{912}$ of the intergalactic medium to HI-ionizing radiation. At mean redshifts $z_\\mathrm{q}=4.56$, 4.86 and 5.16, we measure $\\lambda_\\mathrm{mfp}^{912}=(22.2\\pm 2.3, 15.1\\pm 1.8, 10.3\\pm 1.6)h_{70}^{-1}$ proper Mpc with uncertainties dominated by sample variance. Combining our results with $\\lambda_\\mathrm{mfp}^{912}$ measurements from lower redshifts, the data are well modelled by a simple power-law $\\lambda_\\mathrm{mfp}^{912}=A[(1+z)/5]^\\eta$ with $A=(37\\pm 2)h_{70}^{-1}$ Mpc and $\\eta = -5.4\\pm 0.4$ between $z=2.3$...

  12. DGSAT: Dwarf Galaxy Survey with Amateur Telescopes I. Discovery of low surface brightness systems around nearby spiral galaxies

    CERN Document Server

    Javanmardi, B; Kroupa, P; Henkel, C; Crawford, K; Teuwen, K; Gabany, R J; Hanson, M; Neyer, F

    2015-01-01

    Context: We introduce the Dwarf Galaxy Survey with Amateur Telescopes (DGSAT) project and report the discovery of eleven Low Surface Brightness (LSB) galaxies in the fields of the nearby galaxies NGC 2683, NGC 3628, NGC 4594 (M104), NGC 4631, NGC 5457 (M101), and NGC7814. Aims: The DGSAT project aims at using the potential of small-sized telescopes to probe LSB features around large galaxies and to increase the sample size of the dwarf satellite galaxies in the Local Volume. Methods: Using long exposure images centred on the target, its field is explored for extended low surface brightness objects. After identifying dwarf galaxy candidates, their observed properties are extracted by fitting models to their light profiles. Results: We find three, one, three, one, one, and two new LSB galaxies in the fields of NGC 2683, 3628, 4594, 4631, 5457, and 7814, respectively. In addition to the newly found galaxies, we analyse the structural properties of 9 already known galaxies. All of these 20 dwarf galaxy candidates...

  13. A study of active galactic nuclei in low surface brightness galaxies with Sloan Digital Sky Survey spectroscopy

    Institute of Scientific and Technical Information of China (English)

    Lin Mei; Wei-Min Yuan; Xiao-Bo Dong

    2009-01-01

    Active galactic nuclei (AGNs) in low surface brightness galaxies (LSBGs) have received little attention in previous studies. We present a detailed spectral analysis of 194 LSBGs from the Impey et al. (1996) APM LSBG sample which has been observed spec-troscopically by the Sloan Digital Sky Survey Data Release 5 (SDSS DR5). Our elaborate spectral analysis enables us to carry out, for the first time, reliable spectral classification of nuclear processes in LSBGs based on the standard emission line diagnostic diagrams in a rigorous way. Star-forming galaxies are common, as found in about 52% of LSBGs. We find that, contrary to some previous claims, the fraction of galaxies that contain AGNs is significantly lower than that found in nearby normal galaxies of high surface brightness. This is qualitatively in line with the finding of Impey et al. This result holds true even within each morphological type from Sa to Sc. LSBGs that have larger central stellar ve-locity dispersions or larger physical sizes tend to have a higher chance of harboring an AGN. For three AGNs with broad emission lines, the black hole masses estimated from the emission lines are broadly consistent with the well known M-σ* relation established for normal galaxies and AGNs.

  14. Accretion Disc Structure and Orientation in the Lensed and Microlensed Q0957+561 Quasar

    CERN Document Server

    Schild, R E

    2005-01-01

    Because quasars are unresolved in optical imaging, their structures must presently be inferred. Gravitational microlensing offers the possibility to produce information about the luminous structure provided the Einstein ring diameter of the microlensing particle is comparable to or smaller than the radiating quasar components. The long brightness history measured for the Q0957 quasar has been analyzed previously for information about the microlensing particles, and evidence for the existence of a cosmologically significant population of planetary mass particles has been reported. The microlensing results have also directly determined the sizes of the ultraviolet light emitting surfaces in the quasar Autocorrelation analysis of the same brightness record has produced evidence for complex structure in the quasar; if the quasar suddenly brightens today, it is probable that it will brighten again after 129, 190, 540, and 620 days. We interpret these lags as the result of luminous structure around the quasar, and ...

  15. The Host Galaxies of High-Luminosity Obscured Quasars at 2.5

    Science.gov (United States)

    Ross, Nicholas; Strauss, M. A.; Greene, J. E.; Zakamska, N. L.; Brandt, W. N.; Alexandroff, R.; Liu, G.; Smith, P. S.; The SDSS-III BOSS Quasar Working Group

    2014-01-01

    Active Galactic Nuclei play a key role in the evolution of galaxies. However, very little is known about the host galaxies of the most luminous quasars at redshift 2.5, the epoch when massive black hole growth peaked. The brightness of the quasar itself, which can easily outshine a galaxy by a large factor, makes it very difficult to study emission from extended gas or stars in the host galaxy. However, we have imaged the extended emission from the host galaxies of a unique sample of six optically extinguished (Type II) luminous quasars with 2.5, with the Hubble Space Telescope (Cycle 20, GO 13014) using ACS/F814W to access the rest-frame near-ultraviolet, and WFC3/F160W for the rest-frame optical longward of 4000A. These objects are selected from the spectroscopic database of the SDSS/Baryon Oscillation Spectroscopic Survey to have strong, narrow emission lines and weak continua. With these images, we have quantified the luminosity, morphology, and dynamical state of the host galaxies, and searched for extended scattered light from the obscured central engine. These observations are the first comprehensive study of both host galaxy light and scattered light in high-luminosity quasars at the epoch of maximum black hole growth, and give insights into the relationship between host galaxies and black holes during this important, and yet largely unexplored period.

  16. The Stacked LYα Emission Profile from the Circum-Galactic Medium of z ˜ 2 Quasars

    Science.gov (United States)

    Arrigoni Battaia, Fabrizio; Hennawi, Joseph F.; Cantalupo, Sebastiano; Prochaska, J. Xavier

    2016-09-01

    In the context of the FLASHLIGHT survey, we obtained deep narrowband images of 15 z ˜ 2 quasars with the Gemini Multi-object Spectrograph on Gemini South in an effort to measure Lyα emission from circum- and intergalactic gas on scales of hundreds of kpc from the central quasar. We do not detect bright giant Lyα nebulae (SB ˜ 10-17 erg s-1 cm-2 arcsec-2 at distances >50 kpc) around any of our sources, although we routinely (≃47%) detect smaller-scale Tecnologia e Inovação (Brazil), and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina).

  17. XQ-100: A legacy survey of one hundred 3.5 z < 4.5 quasars observed with VLT/XSHOOTER

    CERN Document Server

    Lopez, S; Ellison, S L; Becker, G D; Christensen, L; Cupani, G; Denney, K D; Paris, I; Worseck, G; Berg, T A M; Cristiani, S; Dessauges-Zavadsky, M; Haehnelt, M; Hamann, F; Hennawi, J; Irsic, V; Kim, T -S; Lopez, P; Saust, R Lund; Menard, B; Perrotta, S; Prochaska, J X; Sanchez-Ramirez, R; Vestergaard, M; Viel, M; Wisotzki, L

    2016-01-01

    We describe the execution and data reduction of the European Southern Observatory Large Programme "Quasars and their absorption lines: a legacy survey of the high-redshift universe with VLT/XSHOOTER" (hereafter `XQ-100'). XQ-100 has produced and made publicly available an homogeneous and high-quality sample of echelle spectra of 100 QSOs at redshifts z~3.5-4.5 observed with full spectral coverage from 315 to 2500 nm at a resolving power ranging from R~4000 to 7000, depending on wavelength. The median signal-to-noise ratios are 33, 25 and 43, as measured at rest-frame wavelengths 1700, 3000 and 3600 Angstrom, respectively. This paper provides future users of XQ-100 data with the basic statistics of the survey, along with details of target selection, data acquisition and data reduction. The paper accompanies the public release of all data products, including 100 reduced spectra. XQ-100 is the largest spectroscopic survey to date of high-redshift QSOs with simultaneous rest-frame UV/optical coverage, and as such...

  18. Bright but slow - Type II supernovae from OGLE-IV - implications for magnitude-limited surveys

    Science.gov (United States)

    Poznanski, D.; Kostrzewa-Rutkowska, Z.; Wyrzykowski, L.; Blagorodnova, N.

    2015-05-01

    We study a sample of 11 Type II supernovae (SNe) discovered by the OGLE-IV survey. All objects have well-sampled I-band light curves, and at least one spectrum. We find that two or three of the 11 SNe have a declining light curve, and spectra consistent with other SNe II-L, while the rest have plateaus that can be as short as 70 d, unlike the 100 d typically found in nearby galaxies. The OGLE SNe are also brighter, and show that magnitude-limited surveys find SNe that are different than usually found in nearby galaxies. We discuss this sample in the context of understanding Type II SNe as a class and their suggested use as standard candles.

  19. Bright but slow - Type II supernovae from OGLE-IV & magnitude limited surveys

    CERN Document Server

    Poznanski, Dovi; Wyrzykowski, Lukasz; Blagorodnova, Nadejda

    2015-01-01

    We study a sample of 11 Type II supernovae (SNe) discovered by the OGLE-IV survey. All objects have well sampled I-band light curves, and at least one spectrum. We find that 3 or 4 of the 11 SNe have a declining light curve, making them SNe II-L, while the rest have plateaus that can be as short as 70d, unlike the 100d typically found in nearby galaxies. These SNe are also brighter than found in the local Universe, and show that magnitude limited surveys find SNe that are different than found in nearby galaxies. We discuss this sample in the context of understanding Type II SNe as a class and their suggested use as standard candles.

  20. Quasar Classification Using Color and Variability

    Science.gov (United States)

    Peters, Christina M.; Richards, Gordon

    2015-08-01

    We use the Non-parametric Bayesian Classification Kernel Density Estimation (NBC KDE) quasar selection algorithm (Richards et al. 2004) to identify 36,569 type 1 quasar candidates in the Sloan Digital Sky Survey (SDSS) Stripe 82 field using the combination of optical photometry and variability. 5-band coadded optical photometry is taken from the SDSS-I/II to a depth of r ~ 22.4; from these data variability parameters are calculated by fitting the structure function of each object in each band with a power law using 10 to >100 observations for timescales from ~1 day to ~8 years. Selection was based on a training sample of 13,221 spectroscopically-confirmed type 1 quasars from SDSS-I/II and the Baryon Oscillation Spectroscopic Survey (BOSS). Using variability alone, colors alone, and combining variability and colors we achieve 91%, 93%, and 97% quasar completeness and 98%, 98%, and 97% efficiency respectively, with particular improvement in the selection of quasars at 2.7 < z < 3.5 where quasars and stars have similar optical colors. The 23,043 quasar candidates that are not spectroscopically confirmed reach a depth of coadd i ~ 22: 0 and 21,380 (92.8%) are dimmer than coadded i -band magnitude of 20.2, the cut off for spectroscopic follow-up for SDSSDR7.

  1. Halo Occupation Distribution of Infrared Selected Quasars

    CERN Document Server

    Mitra, Kaustav

    2016-01-01

    We perform a Halo Occupation Distribution (HOD) modeling of the projected two-point correlation function (2PCF) of quasars that are observed in the Wide-field Infrared Survey Explorer (WISE) telescope with counter-parts in the Sloan Digital Sky Survey (SDSS) Data Release (DR)-8 quasar catalog at a median redshift of $z\\sim 1.04 (\\pm 0.58)$. Using a four parameter HOD model we derive the host mass scales of WISE selected quasars. Our results show that the median halo masses of central and satellite quasars lie in the range $M_{\\mathrm{cen}} = (5 \\pm 1.0) \\times 10^{12} M_{\\odot}$ and $M_{\\mathrm{sat}} = 8 (^{+7.8} _{-4.8}) \\times 10^{13} M_{\\odot}$, respectively. The derived satellite fraction is $f_{\\mathrm{sat}}= 5.5 (^{+35} _{-5.0})\\times 10^{-3}$. Previously Richardson et al.\\ used the SDSS DR7 quasar clustering data to obtain the halo mass distributions of $z\\sim 1.4$ quasars. Our results on the HOD of central quasars are in excellent agreement with Richardson et al.\\ but the host mass scale of satellite ...

  2. A Limit on the Number of Isolated Neutron Stars Detected in the ROSAT All-Sky Survey Bright Source Catalog

    CERN Document Server

    Turner, Monica L; Letcavage, Ryan; Shevchuk, Andrew S H; Fox, Derek B

    2010-01-01

    Using new and archival observations made with the Swift satellite and other facilities, we examine 147 X-ray sources selected from the ROSAT All-Sky-Survey Bright Source Catalog (RASS/BSC) to produce a new limit on the number of isolated neutron stars (INSs) in the RASS/BSC, the most constraining such limit to-date. Independent of X-ray spectrum and variability, the number of INSs is <=48 (90% confidence). Restricting attention to soft (having an effective temperature of < 200 eV), non-variable X-ray sources -- as in a previous study -- yields an all-sky limit of <=31 INSs. In the course of our analysis, we identify five new high-quality INS candidates for targeted follow-up observations. A future all-sky X-ray survey with eROSITA, or another mission with similar capabilities, can be expected to increase the detected population of X-ray-discovered INSs from the 8 to 50 in the BSC, to (for a disk population) 240 to 1500, which will enable a more detailed study of neutron star population models.

  3. DGSAT: Dwarf Galaxy Survey with Amateur Telescopes. I. Discovery of low surface brightness systems around nearby spiral galaxies

    Science.gov (United States)

    Javanmardi, B.; Martinez-Delgado, D.; Kroupa, P.; Henkel, C.; Crawford, K.; Teuwen, K.; Gabany, R. J.; Hanson, M.; Chonis, T. S.; Neyer, F.

    2016-04-01

    Context. We introduce the Dwarf Galaxy Survey with Amateur Telescopes (DGSAT) project and report the discovery of eleven low surface brightness (LSB) galaxies in the fields of the nearby galaxies NGC 2683, NGC 3628, NGC 4594 (M 104), NGC 4631, NGC 5457 (M 101), and NGC 7814. Aims: The DGSAT project aims to use the potential of small-sized telescopes to probe LSB features around large galaxies and to increase the sample size of the dwarf satellite galaxies in the Local Volume. Methods: Using long exposure images, fields of the target spiral galaxies are explored for extended LSB objects. After identifying dwarf galaxy candidates, their observed properties are extracted by fitting models to their light profiles. Results: We find three, one, three, one, one, and two new LSB galaxies in the fields of NGC 2683, 3628, 4594, 4631, 5457, and 7814, respectively. In addition to the newly found galaxies, we analyse the structural properties of nine already known galaxies. All of these 20 dwarf galaxy candidates have effective surface brightnesses in the range 25.3 ≲ μe ≲ 28.8 mag arcsec-2 and are fit with Sersic profiles with indices n ≲ 1. Assuming that they are in the vicinity of the above mentioned massive galaxies, their r-band absolute magnitudes, their effective radii, and their luminosities are in the ranges -15.6 ≲ Mr ≲ -7.8, 160 pc ≲ Re ≲ 4.1 kpc, and 0.1 × 106 ≲ (L/L⊙)r ≲ 127 × 106, respectively. To determine whether these LSB galaxies are indeed satellites of the above mentioned massive galaxies, their distances need to be determined via further observations. Conclusions: Using small telescopes, we are readily able to detect LSB galaxies with similar properties to the known dwarf galaxies of the Local Group.

  4. STRUCTURE FUNCTION ANALYSIS OF LONG-TERM QUASAR VARIABILITY

    Energy Technology Data Exchange (ETDEWEB)

    de Vries, W; Becker, R; White, R; Loomis, C

    2004-11-15

    In our second paper on long-term quasar variability, we employ a much larger database of quasars than in de Vries, Becker & White. This expanded sample, containing 35,165 quasars from the Sloan Digital Sky Survey Data Release 2, and 6,413 additional quasars in the same area of the sky taken from the 2dF QSO Redshift Survey, allows us to significantly improve on our earlier conclusions. As before, all the historic quasar photometry has been calibrated onto the SDSS scale by using large numbers of calibration stars around each quasar position. We find the following: (1) the outbursts have an asymmetric light-curve profile, with a fast-rise, slow-decline shape; this argues against a scenario in which micro-lensing events along the line-of-sight to the quasars are dominating the long-term variations in quasars; (2) there is no turnover in the Structure Function of the quasars up to time-scales of {approx}40 years, and the increase in variability with increasing time-lags is monotonic and constant; and consequently, (3) there is not a single preferred characteristic outburst time-scale for the quasars, but most likely a continuum of outburst time-scales, (4) the magnitude of the quasar variability is a function of wavelength: variability increases toward the blue part of the spectrum, (5) high-luminosity quasars vary less than low-luminosity quasars, consistent with a scenario in which variations have limited absolute magnitude. Based on this, we conclude that quasar variability is intrinsic to the Active Galactic Nucleus, is caused by chromatic outbursts/flares with a limited luminosity range and varying time-scales, and which have an overall asymmetric light-curve shape. Currently the model that has the most promise of fitting the observations is based on accretion disk instabilities.

  5. Catalog of candidates for quasars at 3 < z < 5.5 selected among X-Ray sources from the 3XMM-DR4 survey of the XMM-Newton observatory

    Science.gov (United States)

    Khorunzhev, G. A.; Burenin, R. A.; Meshcheryakov, A. V.; Sazonov, S. Yu.

    2016-05-01

    We have compiled a catalog of 903 candidates for type 1 quasars at redshifts 3 20° in Sloan Digital Sky Survey (SDSS) fields with a total area of about 300 deg2. Photometric SDSS data as well infrared 2MASS and WISE data were used to select the objects. We selected the point sources from the photometric SDSS catalog with a magnitude error δ mz' library that we compiled for these purposes using the EAZY software. Based on these data, we have rejected the objects whose spectral energy distributions are better described by the templates of stars at z = 0 and obtained a sample of quasars with photometric redshift estimates 2.75 3 in the investigated fields is shown to be about 80%. The normalized median absolute deviation (Δ z = | z spec - z phot|) is σ Δ z /(1+ z spec) = 0.07, while the outlier fraction is η = 9% when Δ z/(1 + z cпek.) > 0.2. The number of objects per unit area in our sample exceeds the number of quasars in the spectroscopic SDSS sample at the same redshifts approximately by a factor of 1.5. The subsequent spectroscopic testing of the redshifts of our selected candidates for quasars at 3 < z < 5.5 will allow the purity of this sample to be estimated more accurately.

  6. The XXL Survey. XIII. Baryon content of the bright cluster sample

    CERN Document Server

    Eckert, D; Coupon, J; Gastaldello, F; Pierre, M; Melin, J -B; Brun, A M C Le; McCarthy, I G; Adami, C; Chiappetti, L; Faccioli, L; Giles, P; Lavoie, S; Lefevre, J P; Lieu, M; Mantz, A; Maughan, B; McGee, S; Pacaud, F; Paltani, S; Sadibekova, T; Smith, G P; Ziparo, F

    2015-01-01

    Traditionally, galaxy clusters have been expected to retain all the material accreted since their formation epoch. For this reason, their matter content should be representative of the Universe as a whole, and thus their baryon fraction should be close to the Universal baryon fraction. We make use of the sample of the 100 brightest galaxy clusters discovered in the XXL Survey to investigate the fraction of baryons in the form of hot gas and stars in the cluster population. We measure the gas masses of the detected halos and use a mass--temperature relation directly calibrated using weak-lensing measurements for a subset of XXL clusters to estimate the halo mass. We find that the weak-lensing calibrated gas fraction of XXL-100-GC clusters is substantially lower than was found in previous studies using hydrostatic masses. Our best-fit relation between gas fraction and mass reads $f_{\\rm gas,500}=0.055_{-0.006}^{+0.007}\\left(M_{\\rm 500}/10^{14}M_\\odot\\right)^{0.21_{-0.10}^{+0.11}}$. The baryon budget of galaxy c...

  7. The XXL Survey. XIII. Baryon content of the bright cluster sample

    Science.gov (United States)

    Eckert, D.; Ettori, S.; Coupon, J.; Gastaldello, F.; Pierre, M.; Melin, J.-B.; Le Brun, A. M. C.; McCarthy, I. G.; Adami, C.; Chiappetti, L.; Faccioli, L.; Giles, P.; Lavoie, S.; Lefèvre, J. P.; Lieu, M.; Mantz, A.; Maughan, B.; McGee, S.; Pacaud, F.; Paltani, S.; Sadibekova, T.; Smith, G. P.; Ziparo, F.

    2016-06-01

    Traditionally, galaxy clusters have been expected to retain all the material accreted since their formation epoch. For this reason, their matter content should be representative of the Universe as a whole, and thus their baryon fraction should be close to the Universal baryon fraction Ωb/ Ωm. We make use of the sample of the 100 brightest galaxy clusters discovered in the XXL Survey to investigate the fraction of baryons in the form of hot gas and stars in the cluster population. Since it spans a wide range of mass (1013-1015 M⊙) and redshift (0.05-1.1) and benefits from a large set of multiwavelength data, the XXL-100-GC sample is ideal for measuring the global baryon budget of massive halos. We measure the gas masses of the detected halos and use a mass-temperature relation directly calibrated using weak-lensing measurements for a subset of XXL clusters to estimate the halo mass. We find that the weak-lensing calibrated gas fraction of XXL-100-GC clusters is substantially lower than was found in previous studies using hydrostatic masses. Our best-fit relation between gas fraction and mass reads fgas,500 = 0.055-0.006+0.007(M500/1014 M⊙)0.21-0.10+0.11. The baryon budget of galaxy clusters therefore falls short of the Universal baryon fraction by about a factor of two at r500,MT. Our measurements require a hydrostatic bias 1-b = MX/MWL = 0.72-0.07+0.08 to match the gas fraction obtained using lensing and hydrostatic equilibrium, which holds independently of the instrument considered. Comparing our gas fraction measurements with the expectations from numerical simulations, we find that our results favour an extreme feedback scheme in which a significant fraction of the baryons are expelled from the cores of halos. This model is, however, in contrast with the thermodynamical properties of observed halos, which might suggest that weak-lensing masses are overestimated. In light of these results, we note that a mass bias 1-b = 0.58 as required to reconcile Planck

  8. The LBT Boötes Field Survey. I. The Rest-frame Ultraviolet and Near-infrared Luminosity Functions and Clustering of Bright Lyman Break Galaxies at Z ~ 3

    Science.gov (United States)

    Bian, Fuyan; Fan, Xiaohui; Jiang, Linhua; McGreer, Ian; Dey, Arjun; Green, Richard F.; Maiolino, Roberto; Walter, Fabian; Lee, Kyoung-Soo; Davé, Romeel

    2013-09-01

    We present a deep LBT/LBC U spec-band imaging survey (9 deg2) covering the NOAO Boötes field. A total of 14,485 Lyman break galaxies (LBGs) at z ~ 3 are selected, which are used to measure the rest-frame UV luminosity function (LF). The large sample size and survey area reduce the LF uncertainties due to Poisson statistics and cosmic variance by >=3 compared to previous studies. At the bright end, the LF shows excess power compared to the best-fit Schechter function, which can be attributed to the contribution of z ~ 3 quasars. We compute the rest-frame near-infrared LF and stellar mass function (SMF) of z ~ 3 LBGs based on the R-band and [4.5 μm]-band flux relation. We investigate the evolution of the UV LFs and SMFs between z ~ 7 and z ~ 3, which supports a rising star formation history in the LBGs. We study the spatial correlation function of two bright LBG samples and estimate their average host halo mass. We find a tight relation between the host halo mass and the galaxy star formation rate (SFR), which follows the trend predicted by the baryonic accretion rate onto the halo, suggesting that the star formation in LBGs is fueled by baryonic accretion through the cosmic web. By comparing the SFRs with the total baryonic accretion rates, we find that cosmic star formation efficiency is about 5%-20% and it does not evolve significantly with redshift, halo mass, or galaxy luminosity. Based on data acquired using the Large Binocular Telescope (LBT). The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are: The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University, and The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota, and University

  9. The race between stars and quasars in reionizing cosmic hydrogen

    International Nuclear Information System (INIS)

    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 declines sharply, implying that cosmic hydrogen was reionized by stars instead. Here, we explain the physical origin of the transition between the dominance of stars and quasars as a generic feature of structure formation in the concordance ΛCDM cosmology. At early times, the fraction of baryons in galaxies grows faster than the maximum (Eddington-limited) growth rate possible for quasars. As a result, quasars were not able to catch up with the rapid early growth of stellar mass in their host galaxies

  10. The SCUBA-2 Cosmology Legacy Survey: ALMA resolves the bright-end of the sub-millimeter number counts

    CERN Document Server

    Simpson, James; Swinbank, Mark; Chapman, Scott; Geach, James; Ivison, Rob; Thomson, Alasdair; Aretxaga, Itziar; Blain, Andrew; Cowley, Will; Chen, Chian-Chou; Coppin, Kristen; Dunlop, Jim; Edge, Alastair; Farrah, Duncan; Ibar, Edo; Karim, Alex; Knudsen, Kirsten; Meijerink, Rowin; Michalowski, Michal; Scott, Douglas; Spanns, Marco; van der Werf, Paul

    2015-01-01

    We present high-resolution 870-um ALMA continuum maps of 30 bright sub-millimeter sources in the UKIDSS UDS field. These sources are selected from deep, 1-square degrees 850-um maps from the SCUBA--2 Cosmology Legacy Survey, and are representative of the brightest sources in the field (median SCUBA2 flux S_850=8.7+/-0.4 mJy). We detect 52 sub-millimeter galaxies (SMGs) at >4-sigma significance in our 30 ALMA maps. In 61+/-17% of the ALMA maps the single-dish source comprises a blend of >=2 SMGs, where the secondary SMGs are Ultra--Luminous Infrared Galaxies (ULIRGs) with L_IR>10^12 Lo. The brightest SMG contributes on average 80+/-4% of the single-dish flux density, and in the ALMA maps containing >=2 SMGs the secondary SMG contributes 25+/-3% of the integrated ALMA flux. We construct source counts and show that multiplicity boosts the apparent single-dish cumulative counts by 20% at S_870>7.5mJy, and by 60% at S_870>12mJy. We combine our sample with previous ALMA studies of fainter SMGs and show that the cou...

  11. Microlensing variability in time-delay quasars

    CERN Document Server

    Paraficz, D; Burud, I; Jakobsson, P; Eliasdottir, A

    2006-01-01

    We have searched for microlensing variability in the light curves of five gravitationally lensed quasars with well-determined time delays: SBS 1520+530, FBQ 0951+2635, RX J0911+0551, B1600+434 and HE 2149-2745. By comparing the light curve of the leading image with a suitably time offset light curve of a trailing image we find that two (SBS 1520+530 and FBQ 0951+2635) out of the five quasars have significant long-term (years) and short-term (100 days) brightness variations that may be attributed to microlensing.The short-term variations may be due to nanolenses, relativistic hot or cold spots in the quasar accretion disks, or coherent microlensing at large optical depth.

  12. Extremely Red Quasars in BOSS

    CERN Document Server

    Hamann, Fred; Ross, Nicholas; Paris, Isabelle; Alexandroff, Rachael M; Villforth, Carolin; Richards, Gordon T; Herbst, Hanna; Brandt, W Niel; Cook, Ben; Denney, Kelly D; Greene, Jenny E; Schneider, Donald P; Strauss, Michael A

    2016-01-01

    Red quasars are candidate young objects in an early transition stage of massive galaxy evolution. Our team recently discovered a population of extremely red quasars (ERQs) in the Baryon Oscillation Spectroscopic Survey (BOSS) that has a suite of peculiar emission-line properties including large rest equivalent widths (REWs), unusual "wingless" line profiles, large NV/Lya, NV/CIV, SiIV/CIV and other flux ratios, and very broad and blueshifted [OIII] 5007. Here we present a new catalog of CIV and NV emission-line data for 216,188 BOSS quasars to characterize the ERQ line properties further. We show that they depend sharply on UV-to-mid-IR color, secondarily on REW(CIV), and not at all on luminosity or the Baldwin Effect. We identify a "core" sample of 97 ERQs with nearly uniform peculiar properties selected via i-W3 > 4.6 (AB) and REW(CIV) > 100 A at redshifts 2.0-3.4. A broader search finds 235 more red quasars with similar unusual characteristics. The core ERQs have median luminosity log L (ergs/s) ~ 47.1, sk...

  13. An Apparent Redshift Dependence of Quasar Continuum: Implication for Cosmic Dust Extinction?

    CERN Document Server

    Xie, Xiaoyi; Shao, Zhengyi; Yin, Jun

    2015-01-01

    We investigate the luminosity and redshift dependence of the quasar continuum by means of composite spectrum using a large non-BAL radio-quiet quasar sample drawn from the Sloan Digital Sky Survey. Quasar continuum slopes in the UV-Opt band are measured at two different wavelength ranges, i.e., $\\alpha_{\

  14. The cosmological evolution of flat-spectrum quasars

    International Nuclear Information System (INIS)

    The spatial distribution and luminosity functions of a complete sample of quasars from the +- 40 declination strip of the Parkes 2.7-GHz survey have been investigated. The luminosity-volume (V/Vsub(m)) test strongly suggests that the flat-spectrum quasars which dominate the sample have an evolutionary history different from that of the steep-spectrum quasars which dominate the 3CR and 4C samples investigated previously. The bivariate luminosity function for the flat-spectrum quasars shows the same strong correlation between radio and optical luminosities exhibited by steep-spectrum quasars. The results of the luminosity-volume test considered in conjunction with radio structures, spectra, and source counts, lead to the tentative suggestion that the cosmological evolution of radio-active quasars is confined to those with extended radio structures. (author)

  15. Kinematics of the ionized gas around the quasar MR 2251-178

    NARCIS (Netherlands)

    Mulder, P.S.; Valentijn, E. A.

    1992-01-01

    O III forbidden line observations of the nearby quasar MR 2251-178 were made with the Taurus II imaging Fabry-Perot instrument. The line emission around the quasar is found to consist of several regions of high surface brightness located in two half-cones with an opening angle of about 37 deg extend

  16. Structure Function Analysis of Long Term Quasar Variability

    CERN Document Server

    De Vries, W H; White, R L; Loomis, C

    2004-01-01

    In our second paper on long-term quasar variability, we employ a much larger database of quasars than in de Vries, Becker & White. This expanded sample, containing 35165 quasars from the Sloan Digital Sky Survey Data Release 2, and 6413 additional quasars in the same area of the sky taken from the 2dF QSO Redshift Survey, allows us to significantly improve on our earlier conclusions. As before, all the historic quasar photometry has been calibrated onto the SDSS scale by using large numbers of calibration stars around each quasar position. We find the following: (1) the outbursts have an asymmetric light-curve profile, with a fast-rise, slow-decline shape; this argues against a scenario in which micro-lensing events along the line-of-sight to the quasars are dominating the long-term variations in quasars; (2) there is no turnover in the Structure Function of the quasars up to time-scales of ~40 years, and the increase in variability with increasing time-lags is monotonic and constant; and consequently, (3...

  17. High-redshift SDSS Quasars with Weak Emission Lines

    DEFF Research Database (Denmark)

    Diamond-Stanic, Aleksandar M.; Fan, Xiaohui; Brandt, W. N.;

    2009-01-01

    We identify a sample of 74 high-redshift quasars (z > 3) 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. These weak emission-line quasars (WLQs) constitute a prominent...

  18. The CORALS Survey: A Review and Report on The Search for Dust Obscured Quasar Absorption Line Systems

    CERN Document Server

    Ellison, S L; Churchill, C W; Hook, I M; López, S; Rix, S A; Shaver, P; Wall, J V; Yan, L; Ellison, Sara L.; Pettini, Max; Churchill, Chris W.; Hook, Isobel M.; Lopez, Sebastian; Rix, Samantha A.; Shaver, Peter; Yan, Lin

    2003-01-01

    We present a brief overview of the ongoing Complete Optical and Radio Absorption Line System (CORALS) survey. We review the results of our survey for z>2.2 damped Lyman alpha systems (DLAs) and present the preliminary results of an extended survey to lower redshifts (0.7

  19. Powerful Activity in the Bright Ages. I. A Visible/IR Survey of High Redshift 3C Radio Galaxies and Quasars

    CERN Document Server

    Hilbert, Bryan; Kotyla, JohnPaul; Tremblay, Grant R; Stanghellini, Carlo; Sparks, William B; Baum, Stefi A; Capetti, Alessandro; Macchetto, F Duccio; Miley, George K; O'Dea, Christopher P; Perlman, Eric S; Quillen, Alice C

    2016-01-01

    We present new rest frame UV and visible observations of 22 high-redshift (1 < z < 2.5) 3C radio galaxies and QSOs obtained with the Hubble Space Telescope's (HST) Wide Field Camera 3 (WFC3) instrument. Using a custom data reduction strategy in order to assure the removal of cosmic rays, persistence signal, and other data artifacts, we have produced high-quality science-ready images of the targets and their local environments. We observe targets with regions of UV emission suggestive of active star formation. In addition, several targets exhibit highly distorted host galaxy morphologies in the rest frame visible images. Photometric analyses reveals that brighter QSOs tend to be generally redder than their dimmer counterparts. Using emission line fluxes from the literature, we estimate that emission line contamination is relatively small in the rest frame UV images for the QSOs. Using archival VLA data, we have also created radio map overlays for each of our targets, allowing for analysis of the optical ...

  20. Dust Reddening in SDSS Quasars

    CERN Document Server

    Hopkins, P F; Hall, P B; Richards, G T; Cooper, A S; Schneider, D P; Vanden Berk, Daniel E; Jester, S; Brinkmann, J; Szokoly, G P; Hopkins, Philip F.; Strauss, Michael A.; Hall, Patrick B.; Richards, Gordon T.; Cooper, Ariana S.; Schneider, Donald P.; Berk, Daniel E. Vanden; Jester, Sebastian; Szokoly, Gyula P.

    2004-01-01

    We explore the form of extragalactic reddening toward quasars using a sample of 9566 quasars with redshifts 0 0.1; less than 1% have E_{B-V} > 0.2, where the extinction is relative to quasars with modal colors. Reddening is uncorrelated with the presence of intervening narrow-line absorption systems, but reddened quasars are much more likely to show narrow absorption at the redshift of the quasar than are unreddened quasars. Thus the reddening towards quasars is dominated by SMC-like dust at the quasar redshift.

  1. Seeking the epoch of maximum luminosity for dusty quasars

    International Nuclear Information System (INIS)

    Infrared luminosities νLν(7.8 μm) arising from dust reradiation are determined for Sloan Digital Sky Survey (SDSS) quasars with 1.4 Survey Explorer. Infrared luminosity does not show a maximum at any redshift z < 5, reaching a plateau for z ≳ 3 with maximum luminosity νLν(7.8 μm) ≳ 1047 erg s–1; luminosity functions show one quasar Gpc–3 having νLν(7.8 μm) > 1046.6 erg s–1 for all 2 quasars first reached their maximum luminosity has not yet been identified at any redshift below 5. The most ultraviolet luminous quasars, defined by rest frame νLν(0.25 μm), have the largest values of the ratio νLν(0.25 μm)/νLν(7.8 μm) with a maximum ratio at z = 2.9. From these results, we conclude that the quasars most luminous in the ultraviolet have the smallest dust content and appear luminous primarily because of lessened extinction. Observed ultraviolet/infrared luminosity ratios are used to define 'obscured' quasars as those having >5 mag of ultraviolet extinction. We present a new summary of obscured quasars discovered with the Spitzer Infrared Spectrograph and determine the infrared luminosity function of these obscured quasars at z ∼ 2.1. This is compared with infrared luminosity functions of optically discovered, unobscured quasars in the SDSS and in the AGN and Galaxy Evolution Survey. The comparison indicates comparable numbers of obscured and unobscured quasars at z ∼ 2.1 with a possible excess of obscured quasars at fainter luminosities.

  2. Catalog of candidates for quasars at 3 < z < 5.5 selected among X-Ray sources from the 3XMM-DR4 survey of the XMM-Newton observatory

    Science.gov (United States)

    Khorunzhev, G. A.; Burenin, R. A.; Meshcheryakov, A. V.; Sazonov, S. Yu.

    2016-05-01

    We have compiled a catalog of 903 candidates for type 1 quasars at redshifts 3 catalog (the median X-ray flux is ≈5 × 10-15 erg s-1 cm-2 in the 0.5-2 keV energy band) and located at high Galactic latitudes | b| > 20° in Sloan Digital Sky Survey (SDSS) fields with a total area of about 300 deg2. Photometric SDSS data as well infrared 2MASS and WISE data were used to select the objects. We selected the point sources from the photometric SDSS catalog with a magnitude error δ mz' library that we compiled for these purposes using the EAZY software. Based on these data, we have rejected the objects whose spectral energy distributions are better described by the templates of stars at z = 0 and obtained a sample of quasars with photometric redshift estimates 2.75 3 in the investigated fields is shown to be about 80%. The normalized median absolute deviation (Δ z = | z spec - z phot|) is σ Δ z /(1+ z spec) = 0.07, while the outlier fraction is η = 9% when Δ z/(1 + z cпek.) > 0.2. The number of objects per unit area in our sample exceeds the number of quasars in the spectroscopic SDSS sample at the same redshifts approximately by a factor of 1.5. The subsequent spectroscopic testing of the redshifts of our selected candidates for quasars at 3 < z < 5.5 will allow the purity of this sample to be estimated more accurately.

  3. GLOBAL PROPERTIES OF M31'S STELLAR HALO FROM THE SPLASH SURVEY. I. SURFACE BRIGHTNESS PROFILE

    Energy Technology Data Exchange (ETDEWEB)

    Gilbert, Karoline M. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195-1580 (United States); Guhathakurta, Puragra [UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Beaton, Rachael L.; Majewski, Steven R.; Ostheimer, James C.; Patterson, Richard J. [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325 (United States); Bullock, James; Tollerud, Erik J. [Center for Cosmology, Department of Physics and Astronomy, University of California at Irvine, Irvine, CA 92697 (United States); Geha, Marla C. [Astronomy Department, Yale University, New Haven, CT 06520 (United States); Kalirai, Jason S. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Kirby, Evan N. [California Institute of Technology, 1200 East California Boulevard, MC 249-17, Pasadena, CA 91125 (United States); Tanaka, Mikito; Chiba, Masashi, E-mail: kgilbert@astro.washington.edu [Astronomical Institute, Tohoku University, Aoba-ku, Sendai 980-8578 (Japan)

    2012-11-20

    We present the surface brightness profile of M31's stellar halo out to a projected radius of 175 kpc. The surface brightness estimates are based on confirmed samples of M31 red giant branch stars derived from Keck/DEIMOS spectroscopic observations. A set of empirical spectroscopic and photometric M31 membership diagnostics is used to identify and reject foreground and background contaminants. This enables us to trace the stellar halo of M31 to larger projected distances and fainter surface brightnesses than previous photometric studies. The surface brightness profile of M31's halo follows a power law with index -2.2 {+-} 0.2 and extends to a projected distance of at least {approx}175 kpc ({approx}2/3 of M31's virial radius), with no evidence of a downward break at large radii. The best-fit elliptical isophotes have b/a = 0.94 with the major axis of the halo aligned along the minor axis of M31's disk, consistent with a prolate halo, although the data are also consistent with M31's halo having spherical symmetry. The fact that tidal debris features are kinematically cold is used to identify substructure in the spectroscopic fields out to projected radii of 90 kpc and investigate the effect of this substructure on the surface brightness profile. The scatter in the surface brightness profile is reduced when kinematically identified tidal debris features in M31 are statistically subtracted; the remaining profile indicates that a comparatively diffuse stellar component to M31's stellar halo exists to large distances. Beyond 90 kpc, kinematically cold tidal debris features cannot be identified due to small number statistics; nevertheless, the significant field-to-field variation in surface brightness beyond 90 kpc suggests that the outermost region of M31's halo is also comprised to a significant degree of stars stripped from accreted objects.

  4. Detailed Characterization of H_beta emission line profile in low z SDSS quasars

    CERN Document Server

    Zamfir, S; Marziani, P; Dultzin, D

    2009-01-01

    We explore the properties of the H_beta emission line profile in a large, homogeneous and bright sample of N~470 low redshift quasars extracted from Sloan Digital Sky Survey (DR5). We approach the investigation from two complementary directions: composite/median spectra and a set of line diagnostic measures (asymmetry index, centroid shift and kurtosis) in individual quasars. The project is developed and presented in the framework of the so-called 4D Eigenvector 1 (4DE1) Parameter Space, with a focus on its optical dimensions, FWHM(H_beta) and the relative strength of optical FeII (R_FeII=W(FeII4434-4684)/W(H_beta)). We reenforce the conclusion that not all quasars are alike and spectroscopically they do not distribute randomly about an average typical optical spectrum. Our results give further support to the concept of two populations A and B (narrower and broader than 4000 km/s FWHM(H_beta), respectively) that emerged in the context of 4DE1 space. The broad H_beta profiles in composite spectra of Population...

  5. The real-space clustering of luminous red galaxies around z<0.6 quasars in the Sloan Digital Sky Survey

    CERN Document Server

    Padmanabhan, N; Norberg, P; Porciani, C

    2008-01-01

    We measure the clustering of a sample of photometrically selected luminous red galaxies around a low redshift (0.2~ 10^{12} h^{-1} M_sun, Eddington ratios from 0.01 to 1 and lifetimes less than 10^{7} yr. Using simple models of halo occupation, these correspond to a number density of quasar hosts greater than 10^{-3} h^{3} Mpc^{-3} and stellar masses less than 10^{11} h^{-1} M_sun. The small-scale clustering signal can be in terpreted with the aid of our mock LRG catalogs, and depends on the manner in which quasars inhabit halos. We find that our small scale measurements are inconsistent with quasar positions being randomly subsampled from halo centers above a mass threshold, requiring a satellite fraction > 25 per cent.

  6. Mapping the Galactic Halo with blue horizontal branch stars from the 2dF quasar redshift survey

    CERN Document Server

    De Propris, Roberto; Mares, Peter J; CTIO,; University, Cornell

    2010-01-01

    We use 666 blue horizontal branch (BHB) stars from the 2Qz redshift survey to map the Galactic halo in four dimensions (position, distance and velocity). We find that the halo extends to at least 100 kpc in Galactocentric distance, and obeys a single power-law density profile of index ~-2.5 in two different directions separated by 150 degrees on the sky. This suggests that the halo is spherical. Our map shows no large kinematically coherent structures (streams, clouds or plumes) and appears homogeneous. However, we find that at least 20% of the stars in the halo reside in substructures and that these substructures are dynamically young. The velocity dispersion profile of the halo appears to increase towards large radii while the stellar velocity distribution is non Gaussian beyond 60 kpc. We argue that the outer halo consists of a multitude of low luminosity overlapping tidal streams from recently accreted objects.

  7. Quasar Classification Using Color and Variability

    CERN Document Server

    Peters, Christina M; Myers, Adam D; Strauss, Michael A; Schmidt, Kasper B; Ivezić, Željko; Ross, Nicholas P; MacLeod, Chelsea L; Riegel, Ryan

    2015-01-01

    We conduct a pilot investigation to determine the optimal combination of color and variability information to identify quasars in current and future multi-epoch optical surveys. We use a Bayesian quasar selection algorithm (Richards et al. 2004) to identify 35,820 type 1 quasar candidates in a 239 square degree field of the Sloan Digital Sky Survey (SDSS) Stripe 82, using a combination of optical photometry and variability. Color analysis is performed on 5-band single- and multi-epoch SDSS optical photometry to a depth of r ~22.4. From these data, variability parameters are calculated by fitting the structure function of each object in each band with a power law model using 10 to >100 observations over timescales from ~1 day to ~8 years. Selection was based on a training sample of 13,221 spectroscopically-confirmed type-1 quasars, largely from the SDSS. Using variability alone, colors alone, and combining variability and colors we achieve 91%, 93%, and 97% quasar completeness and 98%, 98%, and 97% efficiency ...

  8. Radio structure in quasars

    International Nuclear Information System (INIS)

    In this thesis, observational attention is given to the extended extragalactic radio sources associated with quasars. The isolated compact radio sources, often identified with quasars, are only included in the discussions. Three aspects of the radio structure in quasars and their cosmic evolution are considered: a study of the parsec scale morphology in quasar cores, in relation to the extended morphologies; an investigation of possible epoch dependent hotspot properties as well as a more detailed investigation of this fine scale structure; a VLA project was carried out to obtain morphological information on scales of 0.5 arcsec on high redshift quasars and to investigate possible epoch dependent morphological properties. MERLIN observations at 0.1 arcsec resolution to supplement the VLA data were initiated. (Auth.)

  9. The density structure around quasars inferred from optical depth statistics

    CERN Document Server

    Rollinde, E; Theuns, T; Petitjean, P; Chand, H

    2005-01-01

    We present a method for studying the proximity effect and use it to investigate the density structure around QSOs. It is based on the pixel optical depth probability distribution and its redshift evolution. We validate the method using mock spectra obtained from hydrodynamical simulations, and then apply it to a sample of 12 bright quasars at redshifts 2-3 observed with UVES at the VLT-UT2 Kueyen ESO telescope. These quasars do not show signatures of associated absorption and have a mean monochromatic luminosity of 5.4 10^31 ergs/s/Hz/h^2 at the Lyman limit. The distribution of optical depths changes considerably when the proper distance to the QSO is less than 10 Mpc/h. The size of this proximity region is small given that these QSOs are very bright, which suggests that the quasars are located in regions that are overdense by factors 2-10 on scales <= 10 Mpc/h.

  10. COLD FLOWS AND THE FIRST QUASARS

    Energy Technology Data Exchange (ETDEWEB)

    Di Matteo, T.; Khandai, N.; DeGraf, C.; Feng, Y.; Croft, R. A. C. [McWilliams Center for Cosmology, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); Lopez, J. [Computer Science Department, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); Springel, V. [Heidelberg Institute for Theoretical Studies Schloss-Wolfsbrunnenweg 35, 68118 Heidelberg (Germany)

    2012-02-15

    Observations of the most distant bright quasars imply that billion solar mass supermassive black holes (SMBHs) have to be assembled within the first 800 million years. Under our standard galaxy formation scenario such fast growth implies large gas densities providing sustained accretion at critical or supercritical rates onto an initial black hole seed. It has been a long standing question whether and how such high black hole accretion rates can be achieved and sustained at the centers of early galaxies. Here we use our new MassiveBlack cosmological hydrodynamic simulation covering a volume (0.75 Gpc){sup 3} appropriate for studying the rare first quasars to show that steady high density cold gas flows responsible for assembling the first galaxies produce the high gas densities that lead to sustained critical accretion rates and hence rapid growth commensurate with the existence of {approx}10{sup 9} M{sub Sun} black holes as early as z {approx} 7. We find that under these conditions quasar feedback is not effective at stopping the cold gas from penetrating the central regions and hence cannot quench the accretion until the host galaxy reaches M{sub halo} > or approx. 10{sup 1}2{sup M}{sub Sun }. This cold-flow-driven scenario for the formation of quasars implies that they should be ubiquitous in galaxies in the early universe and that major (proto)galaxy mergers are not a requirement for efficient fuel supply and growth, particularly for the earliest SMBHs.

  11. Leveraging Spitzer's Legacy: Quasars and Feedback at High Redshift

    Science.gov (United States)

    Richards, Gordon; Anderson, Scott; Bauer, Franz; Deo, Rajesh; Fan, Xiaohui; Gallagher, Sarah; Myers, Adam; Strauss, Michael; Zakamska, Nadia

    2009-04-01

    Recent research efforts to understand the evolution of galaxies and quasars are beginning to form a consistent picture. Galaxies and their supermassive black holes grow through mergers, but with decreasing characteristic mass scales over time. Much less, however, is known about the evolution of galaxies at high redshifts and the role played by energy injection from the onset of active black hole growth. Understanding these events requires investigating a statistically significant number of high-redshift quasars and crossing the L* boundary in luminosity. To construct an appropriate data set requires both relatively wide-areas (to find these rare objects) and moderate-depth imaging (to probe below L* in luminosity). Unfortunately, existing optical and MIR surveys fail to meet both of these requirements. Furthermore, both optical and MIR quasar selection are blindest at the most crucial redshifts. Here we propose to address these gaps with targeted IRAC observations of a few hundred high-redshift quasars from the Sloan Digital Sky Survey. Such a sample will enable the construction of a proper training set for the discovery of 2.5learn how to identify high-redshift quasars in other fields over a large range in luminosity. With this knowledge, we will crack open the high-z quasar discovery space within existing IRAC legacy surveys (SWIRE, XFLS, Bootes, COSMOS). With a large sample of high-redshift quasars spanning a large range in luminosity, we can turn the quasar luminosity function and quasar clustering analysis into tools for distinguishing between different evolutionary models and feedback prescriptions. In all, we will observe 330 SDSS quasars using 307 pointings/AORs, totaling 48.5 hours of IRAC time.

  12. Discovery of Universal Elliptical Outflow Structures in Radio-Quiet Quasars

    CERN Document Server

    Lovegrove, Justin; Leiter, Darryl

    2010-01-01

    Fifty-nine quasars in the background of the Magellanic Clouds had brightness records monitored by the MACHO project during the years 1992 - 99. Because the circumpolar fields of these quasars had no seasonal sampling defects, their observation produced data sets well suited to further careful analysis. Following a preliminary report wherein we showed the existence of reverberation in the data for one of the radio-quiet quasars in this group, we now show that similar reverberations have been seen in all of the 55 radio-quiet quasars with adequate data, making possible the determination of the quasar inclination to the observer's line of sight. The reverberation signatures indicate the presence of large-scale elliptical outflow structures similar to that predicted by the Elvis (2000) and "dusty torus" models of quasars, whose characteristic sizes vary within a surprisingly narrow range of scales. More importantly the observed opening angle relative to the polar axis of the universal elliptical outflow structure...

  13. Quasar Mass Functions Across Cosmic Time

    DEFF Research Database (Denmark)

    Vestergaard, Marianne

    2010-01-01

    I present mass functions of actively accreting black holes detected in different quasar surveys which in concert cover a wide range of cosmic history. I briefly address what we learn from these mass functions. I summarize the motivation for such a study and the methods by which we determine black...... hole masses....

  14. Distinctive 21-cm structures of the first stars, galaxies and quasars

    Science.gov (United States)

    Yajima, Hidenobu; Li, Yuexing

    2014-12-01

    Observations of the redshifted 21-cm line with forthcoming radio telescopes promise to transform our understanding of the cosmic reionization. To unravel the underlying physical process, we investigate the 21-cm structures of three different ionizing sources - Population (Pop) III stars, the first galaxies and the first quasars - by using radiative transfer simulations that include both ionization of neutral hydrogen and resonant scattering of Lyα photons. We find that Pop III stars and quasars produce a smooth transition from an ionized and hot state to a neutral and cold state, because of their hard spectral energy distribution with abundant ionizing photons, in contrast to the sharp transition in galaxies. Furthermore, Lyα scattering plays a dominant role in producing the 21-cm signal because it determines the relation between hydrogen spin temperature and gas kinetic temperature. This effect, also called Wouthuysen-Field coupling, depends strongly on the ionizing source. It is strongest around galaxies, where the spin temperature is highly coupled to that of the gas, resulting in extended absorption troughs in the 21-cm brightness temperature. However, in the case of Pop III stars, the 21-cm signal shows both emission and absorption regions around a small H II bubble. For quasars, a large emission region in the 21-cm signal is produced, and the absorption region decreases as the size of the H II bubble becomes large due to the limited travelling time of photons. We predict that future surveys from large radio arrays, such as the Murchison Widefield Array, the Low Frequency Array and the Square Kilometre Array, might be able to detect the 21-cm signals of primordial galaxies and quasars, but possibly not those of Pop III stars, because of their small angular diameters.

  15. Helium Reionization Simulations. I. Modeling Quasars as Radiation Sources

    Science.gov (United States)

    La Plante, Paul; Trac, Hy

    2016-09-01

    We introduce a new project to understand helium reionization using fully coupled N-body, hydrodynamics, and radiative transfer simulations. This project aims to capture correctly the thermal history of the intergalactic medium as a result of reionization and make predictions about the Lyα forest and baryon temperature–density relation. The dominant sources of radiation for this transition are quasars, so modeling the source population accurately is very important for making reliable predictions. In this first paper, we present a new method for populating dark matter halos with quasars. Our set of quasar models includes two different light curves, a lightbulb (simple on/off) and symmetric exponential model, and luminosity-dependent quasar lifetimes. Our method self-consistently reproduces an input quasar luminosity function given a halo catalog from an N-body simulation, and propagates quasars through the merger history of halo hosts. After calibrating quasar clustering using measurements from the Baryon Oscillation Spectroscopic Survey, we find that the characteristic mass of quasar hosts is {M}h∼ 2.5× {10}12 {h}-1 {M}ȯ for the lightbulb model, and {M}h∼ 2.3× {10}12 {h}-1 {M}ȯ for the exponential model. In the latter model, the peak quasar luminosity for a given halo mass is larger than that in the former, typically by a factor of 1.5–2. The effective lifetime for quasars in the lightbulb model is 59 Myr, and in the exponential case, the effective time constant is about 15 Myr. We include semi-analytic calculations of helium reionization, and discuss how to include these quasars as sources of ionizing radiation for full hydrodynamics with radiative transfer simulations in order to study helium reionization.

  16. Helium Reionization Simulations. I. Modeling Quasars as Radiation Sources

    Science.gov (United States)

    La Plante, Paul; Trac, Hy

    2016-09-01

    We introduce a new project to understand helium reionization using fully coupled N-body, hydrodynamics, and radiative transfer simulations. This project aims to capture correctly the thermal history of the intergalactic medium as a result of reionization and make predictions about the Lyα forest and baryon temperature-density relation. The dominant sources of radiation for this transition are quasars, so modeling the source population accurately is very important for making reliable predictions. In this first paper, we present a new method for populating dark matter halos with quasars. Our set of quasar models includes two different light curves, a lightbulb (simple on/off) and symmetric exponential model, and luminosity-dependent quasar lifetimes. Our method self-consistently reproduces an input quasar luminosity function given a halo catalog from an N-body simulation, and propagates quasars through the merger history of halo hosts. After calibrating quasar clustering using measurements from the Baryon Oscillation Spectroscopic Survey, we find that the characteristic mass of quasar hosts is {M}h˜ 2.5× {10}12 {h}-1 {M}⊙ for the lightbulb model, and {M}h˜ 2.3× {10}12 {h}-1 {M}⊙ for the exponential model. In the latter model, the peak quasar luminosity for a given halo mass is larger than that in the former, typically by a factor of 1.5-2. The effective lifetime for quasars in the lightbulb model is 59 Myr, and in the exponential case, the effective time constant is about 15 Myr. We include semi-analytic calculations of helium reionization, and discuss how to include these quasars as sources of ionizing radiation for full hydrodynamics with radiative transfer simulations in order to study helium reionization.

  17. Low Surface Brightness Galaxies selected from the 40% sky area of the ALFALFA HI survey.I.Sample and statistical properties

    CERN Document Server

    Du, Wei; Lam, Man I; Zhu, Yinan; Lei, Fengjie; Zhou, Zhimin

    2015-01-01

    The population of Low Surface Brightness (LSB) galaxies is crucial for understanding the extremes of galaxy formation and evolution of the universe. As LSB galaxies are mostly rich in gas (HI), the alpha.40-SDSS DR7 sample is absolutely one of the best survey combinations to select a sample of them in the local Universe. Since the sky backgrounds are systematically overestimated for galaxy images by the SDSS photometric pipeline, particularly for luminous galaxies or galaxies with extended low surface brightness outskirts, in this paper, we above all estimated the sky backgrounds of SDSS images in the alpha.40-SDSS DR7 sample, using a precise method of sky subtraction. Once subtracting the sky background, we did surface photometry with the Kron elliptical aperture and fitted geometric parameters with an exponential profile model for each galaxy image. Basing on the photometric and geometric results, we further calculated the B-band central surface brightness, mu_{0}(B), for each galaxy and ultimately defined ...

  18. Weak Hard X-Ray Emission from Two Broad Absorption Line Quasars Observed with NuStar: Compton-Thick Absorption or Intrinsic X-Ray Weakness?

    Science.gov (United States)

    Luo, B.; Brandt, W. N.; Alexander, D. M.; Harrison, F. A.; Stern, D.; Bauer, F. E.; Boggs, S. E.; Christensen, F. E.; Comastri, A.; Craig, W. W..; Fabian, A. C.; Farrah, D.; Fiore, F.; Fuerst, F.; Grefenstette, B. W.; Hailey, C. J.; Hickox, R.; Madsen, K. K.; Matt, G.; Ogle, P.; Risaliti, G.; Saez, C.; Teng, S. H.; Walton, D. J.; Zhang, W. W.

    2013-01-01

    We present Nuclear Spectroscopic Telescope Array (NuSTAR) hard X-ray observations of two X-ray weak broad absorption line (BAL) quasars, PG 1004+130 (radio loud) and PG 1700+518 (radio quiet). Many BAL quasars appear X-ray weak, probably due to absorption by the shielding gas between the nucleus and the accretion-disk wind. The two targets are among the optically brightest BAL quasars, yet they are known to be significantly X-ray weak at rest-frame 2-10 keV (16-120 times fainter than typical quasars). We would expect to obtain approx. or equal to 400-600 hard X-ray (is greater than or equal to 10 keV) photons with NuSTAR, provided that these photons are not significantly absorbed N(sub H) is less than or equal to 10(exp24) cm(exp-2). However, both BAL quasars are only detected in the softer NuSTAR bands (e.g., 4-20 keV) but not in its harder bands (e.g., 20-30 keV), suggesting that either the shielding gas is highly Compton-thick or the two targets are intrinsically X-ray weak. We constrain the column densities for both to be N(sub H) 7 × 10(exp 24) cm(exp-2) if the weak hard X-ray emission is caused by obscuration from the shielding gas. We discuss a few possibilities for how PG 1004+130 could have Compton-thick shielding gas without strong Fe Ka line emission; dilution from jet-linked X-ray emission is one likely explanation. We also discuss the intrinsic X-ray weakness scenario based on a coronal-quenching model relevant to the shielding gas and disk wind of BAL quasars. Motivated by our NuSTAR results, we perform a Chandra stacking analysis with the Large Bright Quasar Survey BAL quasar sample and place statistical constraints upon the fraction of intrinsically X-ray weak BAL quasars; this fraction is likely 17%-40%.

  19. The 2QDES Pilot : the luminosity and redshift dependence of quasar clustering.

    OpenAIRE

    Chehade, B.; Shanks, T.; Findlay, J.; Metcalfe, N.; Sawangwit, U.; Irwin, M; González-Solares, E.; Fine, S.; Drinkwater, M. J.; Croom, S.; Jurek, R. J.; Parkinson, D.; Bielby, R.

    2016-01-01

    We present a new redshift survey, the 2dF Quasar Dark Energy Survey pilot (2QDESp), which consists of ${\\approx}10000$ quasars from ${\\approx}150$ deg$^2$ of the southern sky, based on VST-ATLAS imaging and 2dF/AAOmega spectroscopy. Combining our optical photometry with the WISE (W1,W2) bands we can select essentially contamination free quasar samples with $0.8{

  20. Black-hole masses of distant quasars

    DEFF Research Database (Denmark)

    Vestergaard, Marianne

    2011-01-01

    A brief overview of the methods commonly used to determine or estimate the black hole mass in quiescent or active galaxies is presented and it is argued that the use of mass-scaling relations is both a reliable and the preferred method to apply to large samples of distant quasars. The method uses...... that the black hole masses are very large, of order 1 to 10 billion solar masses, even at the highest redshifts of 4 to 6. The black holes must build up their mass very fast in the early universe. Yet they do not grow much larger than that: a maximum mass of about 10 billion solar masses is also observed....... Preliminary mass functions of active black holes are presented for several quasar samples, including the Sloan Digital Sky Survey. Finally, common concerns related to the application of the mass scaling relations, especially for high redshift quasars, are briefly discussed....

  1. The UV Properties of SDSS Selected Quasars

    CERN Document Server

    Trammell, G B; Schneider, D P; Richards, G T; Hall, P B; Anderson, S F; Brinkmann, J; Trammell, George B.; Berk, Daniel E. Vanden; Schneider, Donald P.; Richards, Gordon T.; Hall, Patrick B.; Anderson, Scott F.

    2006-01-01

    We present an analysis of the broadband UV/optical properties of z<3.4 quasars matched in the Galaxy Evolution Explorer (GALEX) General Data Release 1 (GR1) and the Sloan Digital Sky Survey Data Release 3 (SDSS DR3). Of the 6371 DR3 quasars covered by 204 GR1 tiles, 5380 have near-UV detections, while 3034 have both near-UV and far-UV detections using a matching radius of 7". Most of the DR3 sample quasars are detected in the near-UV until z~1.7, with the near-UV detection fraction dropping to ~50% by z~2. Statistical tests performed on the distributions of non-detections indicate that the optically-selected quasars missed in the UV tend to be optically faint or at high redshift. The GALEX positions are shown to be consistent with the SDSS astrometry to within an rms scatter of 0.6-0.7" in each coordinate, and empirically determined photometric errors from multi-epoch GALEX observations significantly exceed the Poissonian errors quoted in the GR1 object catalogs. The UV-detected quasars are well separated ...

  2. Relativistic redshifts in quasar broad lines

    CERN Document Server

    Tremaine, Scott; Liu, Xin; Loeb, Abraham

    2014-01-01

    The broad emission lines commonly seen in quasar spectra have velocity widths of a few per cent of the speed of light, so special- and general-relativistic effects have a significant influence on the line profile. We have determined the redshift of the broad H-beta line in the quasar rest frame (determined from the core component of the [OIII] line) for over 20,000 quasars from the Sloan Digital Sky Survey DR7 quasar catalog. The mean redshift as a function of line width is approximately consistent with the relativistic redshift that is expected if the line originates in a randomly oriented Keplerian disk that is obscured when the inclination of the disk to the line of sight exceeds ~30-45 degrees, consistent with simple AGN unification schemes. This result also implies that the net line-of-sight inflow/outflow velocities in the broad-line region are much less than the Keplerian velocity when averaged over a large sample of quasars with a given line width.

  3. AN X-RAY AND MULTIWAVELENGTH SURVEY OF HIGHLY RADIO-LOUD QUASARS AT z > 4: JET-LINKED EMISSION IN THE BRIGHTEST RADIO BEACONS OF THE EARLY UNIVERSE

    International Nuclear Information System (INIS)

    We present a systematic study of the X-ray and multiwavelength properties of a sample of 17 highly radio-loud quasars (HRLQs) at z > 4 with sensitive X-ray coverage from new Chandra and archival Chandra, XMM-Newton, and Swift observations. Eight of the new and archival observations are reported in this work for the first time. New Chandra observations of two moderately radio-loud and highly optically luminous quasars at z ∼> 4 are also reported. Our HRLQ sample represents the top ∼5% of radio-loud quasars (RLQs) in terms of radio loudness. We found that our HRLQs have an X-ray emission enhancement over HRLQs at lower redshifts (by a typical factor of ≈3), and this effect, after controlling for several factors which may introduce biases, has been solidly estimated to be significant at the 3σ-4σ level. HRLQs at z = 3-4 are also found to have a similar X-ray emission enhancement over z H ∼ 1023 cm–2) may be present. Our z > 4 HRLQs generally have higher X-ray luminosities than those for the composite broadband spectral energy distributions of HRLQs at lower redshift, which further illustrates and supports the X-ray emission enhancement of z > 4 HRLQs. Some of our HRLQs also show an excess of mid-infrared emission which may originate from the synchrotron emission of the relativistic jets. None of our z > 4 HRLQs is detected by the Fermi-LAT two-year survey, which provides constraints on jet-emission models.

  4. QUASAR SELECTION BASED ON PHOTOMETRIC VARIABILITY

    International Nuclear Information System (INIS)

    We develop a method for separating quasars from other variable point sources using Sloan Digital Sky Survey (SDSS) Stripe 82 light-curve data for ∼ 10,000 variable objects. To statistically describe quasar variability, we use a damped random walk model parametrized by a damping timescale, τ, and an asymptotic amplitude (structure function), SF∞. With the aid of an SDSS spectroscopically confirmed quasar sample, we demonstrate that variability selection in typical extragalactic fields with low stellar density can deliver complete samples with reasonable purity (or efficiency, E). Compared to a selection method based solely on the slope of the structure function, the inclusion of the τ information boosts E from 60% to 75% while maintaining a highly complete sample (98%) even in the absence of color information. For a completeness of C = 90%, E is boosted from 80% to 85%. Conversely, C improves from 90% to 97% while maintaining E = 80% when imposing a lower limit on τ. With the aid of color selection, the purity can be further boosted to 96%, with C = 93%. Hence, selection methods based on variability will play an important role in the selection of quasars with data provided by upcoming large sky surveys, such as Pan-STARRS and the Large Synoptic Survey Telescope (LSST). For a typical (simulated) LSST cadence over 10 years and a photometric accuracy of 0.03 mag (achieved at i ∼ 22), C is expected to be 88% for a simple sample selection criterion of >100 days. In summary, given an adequate survey cadence, photometric variability provides an even better method than color selection for separating quasars from stars.

  5. Extragalactic Extinction Laws and Quasar Structure from Color differences Between Images of Lensed Quasars

    Science.gov (United States)

    Mediavilla, Evencio

    2011-11-01

    The action of the mean gravitational field of an intervening galaxy sufficiently aligned with a distant quasar can form several images of this object (multiple imaged quasar). Random fluctuations of the gravitational field induced by the highly inhomogeneous granulation of stars or in dark matter clumps of the lens galaxy mass distribution can subdivide the images in scales of microarcsecs (microlensing by stars) or miliarcsecs (mililensing by dark matter clumps). Anomalies induced by microlensing in the flux brightness of the images can be very strong for small sources or be averaged out by sufficiently large sources. Thus, microlensing magnification of the flux of a radially stratified source can be wavelength dependent (chromaticity). On the other hand, in their path through the lens galaxy the photons of the quasar images are also affected by the patchily distributed interstellar medium (dust extinction). Thus, the wavelength dependence of extinction can be obtained from the flux ratios between two images. In this work we review the use of quasar spectra to disentangle microlensing and dust extinction (based in the comparison between the continuum and emission line flux ratios for different images of the quasar) discussing the impact of the intrinsic source variability in this procedure. We will also review some results derived using this technique like the low fraction of mass in MACHOS in the dark halos of lens galaxies, the unexpected large sizes of the accretion disks present in the central region of lensed quasars or the derivation of extinction curves in the extragalactic domain that reveals a variability in dust properties similar to the one found in the Local Group of galaxies.

  6. Quasars and H II regions during reionization

    Science.gov (United States)

    Kramer, Roban Hultman

    The reionization history of the intergalactic medium (IGM) at high redshift (z ≳ 6) is just beginning to be probed by observational astronomy. In this dissertation, I discuss three projects related to the epoch of reionization. The first project explores how the evolution of the IGM neutral fraction was likely shaped by feedback processes. Because the earliest ionizing sources formed at the locations of the rare density peaks, their spatial distribution was strongly clustered. By building a semi-analytical model which includes feedback and clustering simultaneously and applying this model to the suppression of star formation in minihalos due to photoionization, I demonstrate that this clustering significantly boosts the impact of feedback processes operating at high redshift. The second project exploits the fact that high-redshift quasars drive ionization fronts (I-fronts) into the IGM, with the thickness of the front generally increasing with the hardness of the ionizing spectrum. If the thickness of the front can be measured, it can provide a novel constraint on the ionizing spectral energy distribution (SED). I simulate the propagation of an I-front into a uniform IGM, and compute its thickness for a range of possible quasar spectra and ages, and IGM neutral hydrogen densities and clumping factors. With a sufficiently high intrinsic hydrogen column density obscuring the source or a sufficiently hard power-law spectrum and some obscuration, the thickness of the front exceeds ˜ 1 physical Mpc and may be measurable from the three-dimensional morphology of its redshifted 21cm signal. In the third project, I investigate one promising method for probing the tail end of reionization, through the detection and characterization of the Gunn-Peterson damping wing absorption of the IGM in bright quasar spectra. However, the use of quasar spectra to measure the IGM damping wing requires a model of the quasar's intrinsic Lyman-alpha emission line. I quantify uncertainties

  7. The 1Quasars

    CERN Document Server

    Brown, M J I; Dey, A; Jannuzi, B T; Cool, R; Le Floc'h, E; Kochanek, C S; Armus, L; Bian, C; Higdon, J; Higdon, S; Papovich, C; Rieke, G; Rieke, M; Smith, J D; Soifer, B T; Weedman, D; Brown, Michael J. I.; Brand, Kate; Dey, Arjun; Jannuzi, Buell T.; Cool, Richard; Floc'h, Emeric Le; Kochanek, Christopher S.; Armus, Lee; Bian, Chao; Higdon, Jim; Higdon, Sarah; Papovich, Casey; Rieke, George; Rieke, Marcia; Weedman, Dan

    2006-01-01

    We determine the rest-frame 8 micron luminosity function of type I quasars over the redshift range 1survey of the NOAO Deep Wide-Field Survey Bootes field. The AGN and Galaxy Evolution Survey (AGES) has measured redshifts for 270 of the R<21.7 sources and we estimate that the contamination of the remaining 22 sources by stars and galaxies is low. We are able to select quasars missed by ultra-violet excess quasar surveys, including reddened type I quasars and 2.2quasars with optical colors similar to main sequence stars. We find reddened type I quasars comprise 20% of the type I quasar population. Nonetheless, the shape, normalization, and evolution of the rest-frame 8 micron luminosity function is comparable to that of quasars selected from optical surveys. The 8 micron luminosity function of type I quasars is well approximated by a power-law with i...

  8. An extinction curve template for intrinsically reddened quasars

    CERN Document Server

    Zafar, Tayyaba; Watson, Darach; Fynbo, Johan P U; Krogager, Jens-Kristian; Zafar, Nosheen; Saturni, Francesci G; Geier5, Stefan; Venemans, Bram P

    2015-01-01

    We analyze the near-infrared to UV data of 16 quasars with redshifts ranging from 0.71 $<$ $z$ $<$ 2.13 to investigate dust extinction properties. The sample presented in this work is obtained from the High $A_V$ Quasar (HAQ) survey. The quasar candidates were selected from the Sloan Digital Sky Survey (SDSS) and the UKIRT Infrared Deep Sky Survey (UKIDSS), and follow-up spectroscopy was carried out at the Nordic Optical Telescope (NOT) and the New Technology Telescope (NTT). To study dust extinction curves intrinsic to the quasars, from the HAQ survey we selected 16 cases where the Small Magellanic Cloud (SMC) law could not provide a good solution to the spectral energy distributions (SEDs). We derived the extinction curves using Fitzpatrick & Massa 1986 (FM) law by comparing the observed SEDs to the combined quasar template from Vanden Berk et al. 2001 and Glikman et al. 2006. The derived extinction, $A_V$, ranges from 0.2-1.0 mag. All the individual extinction curves of our quasars are steeper ($...

  9. The Extreme Ultraviolet Variability of Quasars

    Science.gov (United States)

    Punsly, Brian; Marziani, Paola; Zhang, Shaohua; Muzahid, Sowgat; O’Dea, Christopher P.

    2016-10-01

    We study the extreme ultraviolet (EUV) variability (rest frame wavelengths 500–920 Å) of high-luminosity quasars using Hubble Space Telescope (HST) (low to intermediate redshift sample) and Sloan Digital sky Survey (SDSS) (high redshift sample) archives. The combined HST and SDSS data indicates a much more pronounced variability when the sampling time between observations in the quasar rest frame is \\gt 2× {10}7 {{s}} compared to \\lt 1.5× {10}7 s. Based on an excess variance analysis, for time intervals \\lt 2× {10}7 {{s}} in the quasar rest frame, 10% of the quasars (4/40) show evidence of EUV variability. Similarly, for time intervals \\gt 2× {10}7 {{s}} in the quasar rest frame, 55% of the quasars (21/38) show evidence of EUV variability. The propensity for variability does not show any statistically significant change between 2.5× {10}7 {{s}} and 3.16× {10}7 {{s}} (1 year). The temporal behavior is one of a threshold time interval for significant variability as opposed to a gradual increase on these timescales. A threshold timescale can indicate a characteristic spatial dimension of the EUV region. We explore this concept in the context of the slim disk models of accretion. We find that for rapidly spinning black holes, the radial infall time to the plunge region of the optically thin surface layer of the slim disk that is responsible for the preponderance of the EUV flux emission (primarily within 0–7 black hole radii from the inner edge of the disk) is consistent with the empirically determined variability timescale.

  10. Toward an Understanding of Changing-look Quasars: An Archival Spectroscopic Search in SDSS

    Science.gov (United States)

    Ruan, John J.; Anderson, Scott F.; Cales, Sabrina L.; Eracleous, Michael; Green, Paul J.; Morganson, Eric; Runnoe, Jessie C.; Shen, Yue; Wilkinson, Tessa D.; Blanton, Michael R.; Dwelly, Tom; Georgakakis, Antonis; Greene, Jenny E.; LaMassa, Stephanie M.; Merloni, Andrea; Schneider, Donald P.

    2016-08-01

    The uncertain origin of the recently discovered “changing-look” quasar phenomenon—in which a luminous quasar dims significantly to a quiescent state in repeat spectroscopy over ˜10-year timescales—may present unexpected challenges to our understanding of quasar accretion. To better understand this phenomenon, we take a first step toward building a sample of changing-look quasars with a systematic but simple archival search for these objects in the Sloan Digital Sky Survey Data Release 12. By leveraging the >10-year baselines for objects with repeat spectroscopy, we uncover two new changing-look quasars and a third discovered previously. Decomposition of the multiepoch spectra and analysis of the broad emission lines suggest that the quasar accretion disk emission dims because of rapidly decreasing accretion rates (by factors of ≳2.5), while disfavoring changes in intrinsic dust extinction for the two objects where these analyses are possible. Broad emission line energetics also support intrinsic dimming of quasar emission as the origin for this phenomenon rather than transient tidal disruption events or supernovae. Although our search criteria included quasars at all redshifts and transitions from either quasar-like to galaxy-like states or the reverse, all of the clear cases of changing-look quasars discovered were at relatively low redshift (z˜ 0.2{--}0.3) and only exhibit quasar-like to galaxy-like transitions.

  11. Toward an Understanding of Changing-look Quasars: An Archival Spectroscopic Search in SDSS

    Science.gov (United States)

    Ruan, John J.; Anderson, Scott F.; Cales, Sabrina L.; Eracleous, Michael; Green, Paul J.; Morganson, Eric; Runnoe, Jessie C.; Shen, Yue; Wilkinson, Tessa D.; Blanton, Michael R.; Dwelly, Tom; Georgakakis, Antonis; Greene, Jenny E.; LaMassa, Stephanie M.; Merloni, Andrea; Schneider, Donald P.

    2016-08-01

    The uncertain origin of the recently discovered “changing-look” quasar phenomenon—in which a luminous quasar dims significantly to a quiescent state in repeat spectroscopy over ˜10-year timescales—may present unexpected challenges to our understanding of quasar accretion. To better understand this phenomenon, we take a first step toward building a sample of changing-look quasars with a systematic but simple archival search for these objects in the Sloan Digital Sky Survey Data Release 12. By leveraging the >10-year baselines for objects with repeat spectroscopy, we uncover two new changing-look quasars and a third discovered previously. Decomposition of the multiepoch spectra and analysis of the broad emission lines suggest that the quasar accretion disk emission dims because of rapidly decreasing accretion rates (by factors of ≳2.5), while disfavoring changes in intrinsic dust extinction for the two objects where these analyses are possible. Broad emission line energetics also support intrinsic dimming of quasar emission as the origin for this phenomenon rather than transient tidal disruption events or supernovae. Although our search criteria included quasars at all redshifts and transitions from either quasar-like to galaxy-like states or the reverse, all of the clear cases of changing-look quasars discovered were at relatively low redshift (z˜ 0.2{--}0.3) and only exhibit quasar-like to galaxy-like transitions.

  12. Quasar absorption spectra and the structure of the universe

    International Nuclear Information System (INIS)

    Analysis of the spacing between absorption-line systems in quasar spectra and comparison against deep optical survey data for the separation between superclusters of galaxies indicates that the absorption originates in the superclusters. Supported by analogous data on the absorbing gas in the galactic and Magellanic Cloud halos, this inference sharpens theoretical conclusions as to the properties of superclusters. The problem of the unidentified quasar absorption lines is discussed

  13. Quasar absorption spectra and the structure of the universe

    Energy Technology Data Exchange (ETDEWEB)

    Doroshkevich, A.G.

    1984-03-01

    Analysis of the spacing between absorption-line systems in quasar spectra and comparison against deep optical survey data for the separation between superclusters of galaxies indicates that the absorption originates in the superclusters. Supported by analogous data on the absorbing gas in the galactic and Magellanic Cloud halos, this inference sharpens theoretical conclusions as to the properties of superclusters. The problem of the unidentified quasar absorption lines is discussed.

  14. Measuring Lensing Magnification of Quasars by Large Scale Structure using the Variability-Luminosity Relation

    CERN Document Server

    Bauer, Anne H; Jerke, Jonathan; Scalzo, Richard; Rabinowitz, David; Ellman, Nancy; Baltay, Charles

    2011-01-01

    We introduce a technique to measure gravitational lensing magnification using the variability of type I quasars. Quasars' variability amplitudes and luminosities are tightly correlated, on average. Magnification due to gravitational lensing increases the quasars' apparent luminosity, while leaving the variability amplitude unchanged. Therefore, the mean magnification of an ensemble of quasars can be measured through the mean shift in the variability-luminosity relation. As a proof of principle, we use this technique to measure the magnification of quasars spectroscopically identified in the Sloan Digital Sky Survey, due to gravitational lensing by galaxy clusters in the SDSS MaxBCG catalog. The Palomar-QUEST Variability Survey, reduced using the DeepSky pipeline, provides variability data for the sources. We measure the average quasar magnification as a function of scaled distance (r/R200) from the nearest cluster; our measurements are consistent with expectations assuming NFW cluster profiles, particularly a...

  15. Hubble Space Telescope Images of Nearby Luminous Quasars. 2; Results for Eight Quasars and Tests of the Detection Sensitivity

    Science.gov (United States)

    Bahcall, John N.; Kirhakos, Sofia; Schneider, Donald P.

    1995-01-01

    Observations with the Wide-Field Camera of the Hubble Space Telescope (HST) are presented for eight intrinsically luminous quasars with redshifts between 0.16 and 0.29. These observations, when combined with a similar HST study of the quasar PKS 2349-014, show that luminous nearby quasars exist in a variety of environments. Seven companion galaxies brighter than M(V) = 16.5 (H(sub 0) = 100 km s(sup -1) Mpc(sup -1), Omega(sub 0) = 1.0) lie within a projected distance of 25 kpc of the quasars; three of the companions are located closer than 3'' (6 kpc projected distance) from the quasars, well within the volume that would be enclosed by a typical L* host galaxy. The observed association of quasars and companion galaxies is statistically significant and may he an important element in the luminous-quasar phenomenon. Apparent host galaxies are detected for three of the quasars: PG 1116+215, 3C 273, and PG 1444+407; the hosts have an average absolute magnitude of about 0.6 mag brighter than L*. The agreement between the previously published major-axis directions in ground-based images and in the present HST images of 3C 273 and PG 1444+407 constitutes important evidence supporting the reality of these candidate host galaxies. Upper limits are placed on the visual-band brightnesses of representative galactic hosts for all the quasars. These limits are established by placing galaxy images obtained with HST underneath the quasars and measuring at what faintness level the known galaxies are detected. On average, the HST spirals would have been detected if they were as faint as 1 mag below L*, and the early-type galaxies could have been detected down to a brightness level of about L*, where L* is the Schechter characteristic luminosity of field galaxies. Smooth, featureless galaxy models (exponential disks or de Vaucouleurs profiles) are fitted to the residual light after a best-fitting point source is subtracted from the quasar images. The results show that smooth spiral

  16. The VLT-FLAMES Tarantula survey XX. The nature of the X-ray bright emission line star VFTS 399

    CERN Document Server

    Clark, J S; Broos, P S; Townsley, L K; Taylor, W D; Walborn, N R; Bird, A J; Sana, H; de Mink, S E; Dufton, P L; Evans, C J; Langer, N; Apellániz, J Maíz; Schneider, F R N; Soszyński, I

    2015-01-01

    The stellar population of the 30 Doradus star-forming region in the Large Magellanic Cloud contains a subset of apparently single, rapidly rotating O-type stars. The physical processes leading to the formation of this cohort are currently uncertain. One member of this group, the late O-type star VFTS 399, is found to be unexpectedly X-ray bright for its bolometric luminosity - in this study we aim to determine its physical nature and the cause of this behaviour. We find VFTS 399 to be an aperiodic photometric variable with an apparent near-IR excess. Its optical spectrum demonstrates complex emission profiles in the lower Balmer series and select HeI lines - taken together these suggest an OeBe classification. The highly variable X-ray luminosity is too great to be produced by a single star, while the hard, non-thermal nature suggests the presence of an accreting relativistic companion. Finally, the detection of periodic modulation of the X-ray lightcurve is most naturally explained under the assumption that ...

  17. The SCUBA-2 Cosmology Legacy Survey: the nature of bright submm galaxies from 2 deg2 of 850-um imaging

    CERN Document Server

    Michałowski, Michał J; Koprowski, M P; Cirasuolo, M; Geach, J E; Bowler, R A A; Mortlock, A; Caputi, K I; Aretxaga, I; Arumugam, V; Chen, Chian-Chou; McLure, R J; Birkinshaw, M; Bourne, N; Farrah, D; Ibar, E; van der Werf, P; Zemcov, M

    2016-01-01

    We present physical properties [redshifts (z), star-formation rates (SFRs) and stellar masses (Mstar)] of nearly 2000 bright (S850 > 4 mJy) submm galaxies in the ~2 deg2 COSMOS and UDS fields selected with SCUBA-2 on the JCMT, representing the largest homogeneous sample of 850-um-selected sources to date. We check the reliability of our identifications, and the robustness of the SCUBA-2 fluxes by revisiting the recent ALMA follow-up. Considering > 4 mJy ALMA sources, our identification method has a completeness of ~86 per cent with a reliability of ~92 per cent, and only ~15-20 per cent of sources are significantly affected by multiplicity (when a secondary component is brighter than a third of the primary one). The impact of source blending on the 850-um source counts as determined with SCUBA-2 is modest; scaling the single-dish fluxes by ~0.9 reproduces the ALMA source counts. We find median values of z = 2.40+0.10-0.04, SFR = 287+-6 Mo yr-1, and log(Mstar/Mo) = 11.12+-0.02. These properties clearly locate ...

  18. The space density of Compton-thick AGN at z~0.8 in the zCOSMOS-Bright Survey

    CERN Document Server

    Vignali, C; Gilli, R; Comastri, A; Iwasawa, K; Zamorani, G; Mainieri, V; Bongiorno, A

    2014-01-01

    The obscured accretion phase in BH growth is a key ingredient in many models linking the AGN activity with the evolution of their host galaxy. At present, a complete census of obscured AGN is still missing. The purpose of this work is to assess the reliability of the [NeV] emission line at 3426 A to pick up obscured AGN up to z~1 by assuming that [NeV] is a reliable proxy of the intrinsic AGN luminosity and using moderately deep X-ray data to characterize the amount of obscuration. A sample of 69 narrow-line (Type 2) AGN at z=0.65-1.20 were selected from the 20k-zCOSMOS Bright galaxy sample on the basis of the presence of the [NeV] emission. The X-ray properties of these galaxies were then derived using the Chandra-COSMOS coverage of the field; the X-ray-to-[NeV] flux ratio, coupled with X-ray spectral and stacking analyses, was then used to infer whether Compton-thin or Compton-thick absorption were present in these sources. Then the [NeV] luminosity function was computed to estimate the space density of Com...

  19. Discovery of molecular gas around HD 131835 in an APEX molecular line survey of bright debris disks

    CERN Document Server

    Moór, A; Juhász, A; Ábrahám, P; Balog, Z; Kóspál, Á; Pascucci, I; Szabó, Gy M; Vavrek, R; Curé, M; Csengeri, T; Grady, C; Güsten, R; Kiss, Cs

    2015-01-01

    Debris disks are considered to be gas-poor, but recent observations revealed molecular or atomic gas in several 10-40 Myr old systems. We used the APEX and IRAM 30m radiotelescopes to search for CO gas in 20 bright debris disks. In one case, around the 16 Myr old A-type star HD 131835, we discovered a new gas-bearing debris disk, where the CO 3-2 transition was successfully detected. No other individual system exhibited a measurable CO signal. Our Herschel Space Observatory far-infrared images of HD 131835 marginally resolved the disk both at 70 and 100$\\mu$m, with a characteristic radius of ~170 au. While in stellar properties HD 131835 resembles $\\beta$ Pic, its dust disk properties are similar to those of the most massive young debris disks. With the detection of gas in HD 131835 the number of known debris disks with CO content has increased to four, all of them encircling young ($\\leq$40 Myr) A-type stars. Based on statistics within 125 pc, we suggest that the presence of detectable amount of gas in the m...

  20. Distributions of Quasar Hosts on the Galaxy Main Sequence Plane

    Science.gov (United States)

    Zhang, Zhoujian; Shi, Yong; Rieke, George H.; Xia, Xiaoyang; Wang, Yikang; Sun, Bingqing; Wan, Linfeng

    2016-03-01

    The relation between star formation rates (SFRs) and stellar masses, i.e., the galaxy main sequence, is a useful diagnostic of galaxy evolution. We present the distributions relative to the main sequence of 55 optically selected PG and 12 near-IR-selected Two Micron All Sky Survey (2MASS) quasars at z ≤ 0.5. We estimate the quasar host stellar masses from Hubble Space Telescope or ground-based AO photometry, and the SFRs through the mid-infrared aromatic features and far-IR photometry. We find that PG quasar hosts more or less follow the main sequence defined by normal star-forming galaxies while 2MASS quasar hosts lie systematically above the main sequence. PG and 2MASS quasars with higher nuclear luminosities seem to have higher specific SFRs (sSFRs), although there is a large scatter. No trends are seen between sSFRs and SMBH masses, Eddington ratios, or even morphology types (ellipticals, spirals, and mergers). Our results could be placed in an evolutionary scenario with quasars emerging during the transition from ULIRGs/mergers to ellipticals. However, combined with results at higher redshift, they suggest that quasars can be widely triggered in normal galaxies as long as they contain abundant gas and have ongoing star formation.

  1. Bayesian High-Redshift Quasar Classification from Optical and Mid-IR Photometry

    CERN Document Server

    Richards, Gordon T; Peters, Christina M; Krawczyk, Coleman M; Chase, Greg; Ross, Nicholas P; Fan, Xiaohui; Jiang, Linhua; Lacy, Mark; McGreer, Ian D; Trump, Jonathan R; Riegel, Ryan N

    2015-01-01

    We identify 885,503 type 1 quasar candidates to i3.5 than the traditional mid-IR selection "wedges" and to 2.23. This catalog paves the way for luminosity-dependent clustering investigations of large numbers of faint, high-redshift quasars and for further machine learning quasar selection using Spitzer and WISE data combined with other large-area optical imaging surveys.

  2. Quasar variability limits on cosmological density of cosmic strings

    CERN Document Server

    Tuntsov, Artem

    2010-01-01

    We put robust upper limits on the average cosmological density \\Omega_s of cosmic strings based on the variability properties of a large homogeneous sample of SDSS quasars. We search for an excess of characteristic variations of quasar brightness that are associated with string lensing and use the observed distribution of this variation to constrain the density of strings. The limits obtained do not invoke any clustering of strings, apply to both open segments and closed loops of strings, usefully extend over a wide range of tensions 10^{-13} < G\\mu/c^2 < 10^{-9} and reach down the level of \\Omega_s=0.01 and below. Further progress in this direction will depend on better understanding of quasar intrinsic variability rather than a mere increase in the volume of data.

  3. Unveiling the Intrinsic X-ray Properties of Broad Absorption Line Quasars with a Relatively Unbiased Sample

    CERN Document Server

    Morabito, Leah K; Leighly, Karen M; Sivakoff, Gregory R; Shankar, Francesco

    2013-01-01

    There is growing evidence of a higher intrinsic fraction of broad absorption line quasars (BALQSOs) than that obtained in optical surveys, on which most previous X-ray studies of BALQSOs have focused. Here we present Chandra observations of 18 BALQSOs at $z\\sim2$, selected from a near-infrared (2MASS) sample, where the BALQSO fraction is likely to be close to the intrinsic fraction. We measure photon indices using the stacked spectra of the optically-faint ($i-K_s\\geq 2.3$ mag) and optically-bright ($i-K_s < 2.3$ mag) samples to be $\\Gamma \\simeq 1.5$--2.1. We constrain their intrinsic column density by modelling the X-ray fractional hardness ratio, finding a mean column density of $3.5\\times10^{22}$ \\cmsq\\ assuming neutral absorption. We incorporate SDSS optical measurements (rest frame UV) to study the broadband spectral index between the X-ray and UV bands, and compare this to a large sample of normal quasars. We find that the optically-faint BALQSOs are X-ray weaker than the optically-bright ones, and ...

  4. Exploratory Chandra observation of the ultraluminous quasar SDSS J010013.02+280225.8 at redshift 6.30

    CERN Document Server

    Ai, Yanli; Fan, Xiaohui; Wang, Feige; Wu, Xue-Bing; Bian, Fuyan

    2016-01-01

    We report exploratory \\chandra\\ observation of the ultraluminous quasar SDSS J010013.02+280225.8 at redshift 6.30. The quasar is clearly detected by \\chandra\\ with a possible component of extended emission. The rest-frame 2-10 keV luminosity is 9.0$^{+9.1}_{-4.5}$ $\\times$ 10$^{45}$ erg s$^{-1}$ with inferred photon index of $\\Gamma$ = 3.03$^{+0.78}_{-0.70}$. This quasar is X-ray bright, with inferred X-ray-to-optical flux ratio \\aox\\ $=-1.22^{+0.07}_{-0.05}$, higher than the values found in other quasars of comparable ultraviolet luminosity. The properties inferred from this exploratory observation indicate that this ultraluminous quasar might be growing with super-Eddington accretion and probably viewed with small inclination angle. Deep X-ray observation will help to probe the plausible extended emission and better constraint the spectral features for this ultraluminous quasar.

  5. Low Surface Brightness Galaxies Selected from the 40% Sky Area of the ALFALFA H I Survey. I. Sample and Statistical Properties

    Science.gov (United States)

    Du, Wei; Wu, Hong; Lam, Man I.; Zhu, Yinan; Lei, Fengjie; Zhou, Zhimin

    2015-06-01

    The population of low surface brightness (LSB) galaxies, which are objects with central surface brightnesses at least one magnitude fainter than the night sky, is crucial for understanding the extremes of galactic formation and evolution of the universe. As LSB galaxies are mostly rich in gas (H i), the α.40 Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) sample is one of the best survey combinations to select a sample of them in the local universe. Since the sky backgrounds are systematically overestimated for galactic images by the SDSS photometric pipeline, particularly for luminous galaxies or galaxies with extended LSB outskirts, in this paper, we above all estimated the sky backgrounds of SDSS images accurately in both the g and r bands for each galaxy in the α.40 SDSS DR7 sample, using a precise method of sky subtraction. Once subtracting the sky background, we did surface photometry with the Kron elliptical aperture using the SExtractor software and fitted geometric parameters with an exponential profile model using the Galfit software for each galactic image in the α.40 SDSS DR7 sample. Based on the photometric and geometric results, we further calculated the B-band central surface brightness, {{μ }0}(B), for each galaxy and ultimately defined a sample of LSB galaxies consisting of 1129 galaxies with {{μ }0}(B) > 22.5 mag arcsec-2 and the axis ratio b/a > 0.3 from the 12,423 α.40 SDSS DR7 galaxies. This H i-selected sample of LSB galaxies is a relatively unbiased sample of gas-rich and disk-dominated LSB galaxies, which is complete both in H i observation and the optical magnitude within the limit of the SDSS DR7 photometric survey. This LSB galactic sample spans from 22.5 to 28.3 in {{μ }0}(B) with a fraction of 4% fainter than 25.0 mag arcsec-2 in B-band central surface brightness and distributes from -27.0 to -12.3 mag in absolute magnitude in the B band (M(B)), including the 43 faintest galaxies (M(B) > -17.3 mag). This sample is a blue LSB

  6. Low Surface Brightness Galaxies Selected from the 40% Sky Area of the ALFALFA H I Survey. I. Sample and Statistical Properties

    Science.gov (United States)

    Du, Wei; Wu, Hong; Lam, Man I.; Zhu, Yinan; Lei, Fengjie; Zhou, Zhimin

    2015-06-01

    The population of low surface brightness (LSB) galaxies, which are objects with central surface brightnesses at least one magnitude fainter than the night sky, is crucial for understanding the extremes of galactic formation and evolution of the universe. As LSB galaxies are mostly rich in gas (H i), the α.40 Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) sample is one of the best survey combinations to select a sample of them in the local universe. Since the sky backgrounds are systematically overestimated for galactic images by the SDSS photometric pipeline, particularly for luminous galaxies or galaxies with extended LSB outskirts, in this paper, we above all estimated the sky backgrounds of SDSS images accurately in both the g and r bands for each galaxy in the α.40 SDSS DR7 sample, using a precise method of sky subtraction. Once subtracting the sky background, we did surface photometry with the Kron elliptical aperture using the SExtractor software and fitted geometric parameters with an exponential profile model using the Galfit software for each galactic image in the α.40 SDSS DR7 sample. Based on the photometric and geometric results, we further calculated the B-band central surface brightness, {{μ }0}(B), for each galaxy and ultimately defined a sample of LSB galaxies consisting of 1129 galaxies with {{μ }0}(B) > 22.5 mag arcsec‑2 and the axis ratio b/a > 0.3 from the 12,423 α.40 SDSS DR7 galaxies. This H i-selected sample of LSB galaxies is a relatively unbiased sample of gas-rich and disk-dominated LSB galaxies, which is complete both in H i observation and the optical magnitude within the limit of the SDSS DR7 photometric survey. This LSB galactic sample spans from 22.5 to 28.3 in {{μ }0}(B) with a fraction of 4% fainter than 25.0 mag arcsec‑2 in B-band central surface brightness and distributes from ‑27.0 to ‑12.3 mag in absolute magnitude in the B band (M(B)), including the 43 faintest galaxies (M(B) > ‑17.3 mag). This sample is

  7. Polarization structure of 12 gamma-ray quasars at 5 and 15 GHz

    Science.gov (United States)

    Vetukhnovskaya, Yu. N.; Gabuzda, D. C.

    2012-12-01

    The results of dual-frequency polarization observations of 12 gamma-ray quasars are presented (as a continuation of a study of six blazars carried out earlier). The observations were obtained with the American Very Long Baseline Array. The distributions of intensity and polarization were obtained at 5 and 15 GHz. The degrees of polarization in the cores and jets of the 18 gamma-ray quasars do not stand out from those of other quasars. The brightness temperatures of the core components do not strongly exceed 1012 K.

  8. Resolving the Structure at the Heart of BAL Quasars Through Microlensing Induced Polarisation Variability

    CERN Document Server

    Hales, C A; Hales, Christopher A.; Lewis, Geraint F.

    2007-01-01

    While amongst the most luminous objects in the universe, many details regarding the inner structure of quasars remain unknown. One such area is the mechanism promoting increased polarisation in the broad absorption line troughs of certain quasars. This study shows how microlensing can be used to differentiate between two popular models that explain such polarisation through a realistic computational analysis. By examining a statistical ensemble of correlation data between two observables (namely image brightness and polarisation of the flux coming from the quasar), it was found that through spectropolarimetric monitoring it would be possible to discern between a model with an external scattering region and a model without one.

  9. Optical Microlensing and Accretion Disk Structure in the Lensed Quasar SDSS 1520+530

    Science.gov (United States)

    Manickam, Vigneshwar; Grinaski, Ian; MacLeod, Chelsea; Morgan, Christopher W.; Harris, Hugh C.; Kennington, James

    2015-01-01

    We analyze uncorrelated variability in seven seasons of SDSS r-band monitoring data from the doubly-imaged gravitationally lensed quasar SBS 1520+530 to yield a measurement of the size of the near-UV continuum emission region in this quasar. Photometry in the SBS 1520+530 system is complicated significantly by the proximity of a very bright star whose diffraction spike blends with the the lens, so we employed a mirror-flip subtraction technique to correct for this contamination. We conclude by testing our accretion disk measurement against the Quasar Accretion Disk Size - Black Hole Mass Relation.

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

    Science.gov (United States)

    Wu, Jianfeng; Brandt, W. N.; Anderson, Scott F.; Diamond-Stanic, Aleksandar M.; Hall, Patrick B.; Plotkin, Richard M.; Schneider, Donald P.; Shemmer, Ohad

    2012-03-01

    We report 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 (SDSS) with redshift z = 0.4-2.5. Our sample was selected from the Plotkin et al. catalog of radio-quiet, weak-featured active galactic nuclei (AGNs). The distribution of relative X-ray brightness for our low-redshift weak-line quasar (WLQ) candidates is significantly different from that of typical radio-quiet quasars, having an excess of X-ray weak sources, but it is consistent with that of high-redshift WLQs. Over half of the low-redshift WLQ candidates are X-ray weak by a factor of >~ 5, compared to a typical SDSS quasar with similar UV/optical luminosity. These X-ray weak sources generally show similar UV emission-line properties to those of the X-ray weak quasar PHL 1811 (weak and blueshifted high-ionization lines, weak semiforbidden lines, and strong UV Fe emission); they may belong to the notable class of PHL 1811 analogs. The average X-ray spectrum of these sources is somewhat harder than that of typical radio-quiet quasars. Several other low-redshift WLQ candidates have normal ratios of X-ray-to-optical/UV flux, and their average X-ray spectral properties are also similar to those of typical radio-quiet quasars. The X-ray weak and X-ray normal WLQ candidates may belong to the same subset of quasars having high-ionization "shielding gas" covering most of the wind-dominated broad emission-line region, but be viewed at different inclinations. The mid-infrared-to-X-ray spectral energy distributions (SEDs) of these sources are generally consistent with those of typical SDSS quasars, showing that they are not likely to be BL Lac objects with relativistically boosted continua and diluted emission lines. The mid-infrared-to-UV SEDs of most radio-quiet weak-featured AGNs without sensitive X-ray coverage (34 objects) are also consistent with those of typical SDSS quasars. However, one source in our X

  11. Cosmology with AGN: can we use quasars as standard candles?

    Science.gov (United States)

    Risaliti, G.

    2016-06-01

    The non-linear relation between X-ray and UV luminosity in quasars can be used to estimate their distance. Recently, we have shown that despite the large dispersion of the relation, a Hubble Diagram made of large samples of quasars can provide unique constraints on cosmology at high redshift. Furthermore, the dispersion of the relation is heavily affected by measurement errors: until now we have used serendipitous X-ray observations, but dedicated observations would significantly increase the precision of the distance estimates. I discuss the future role of XMM in this new field, showing (1) the fundamental contribution of the Serendipitous Source Catalogue and of large surveys, and (2) the breakthrough advancements we may achieve with the observation of a large number of SDSS quasars at high redshift: every 12-15 quasars observed at z~3 would be equivalent to discovering a supernova at that redshift.

  12. An HST/WFPC2 survey of bright young clusters in M31. IV. Ages and mass estimates

    CERN Document Server

    Perina, S; Barmby, P; Beasley, M A; Bellazzini, M; Brodie, J P; Federici, L; Pecci, F Fusi; Galleti, S; Hodge, P W; Huchra, J P; Kissler-Patig, M; Puzia, T H; Strader, J

    2009-01-01

    {Aims.} We present the main results of an imaging survey of possible young massive clusters (YMC) in M31 performed with the Wide Field and Planetary Camera2 (WFPC2) on the Hubble Space Telescope (HST). We present the images and color magnitude diagrams (CMDs) of all of our targets. {Methods.} The reddening, age and, metallicity of the clusters were estimated by comparing the observed CMDs and luminosity functions with theoretical models. Stellar masses were estimated by comparison with theoretical models in the log(Age) vs. absolute integrated magnitude plane. {Results.} Nineteen of the twenty surveyed candidates were confirmed to be real star clusters. Three of the clusters were found not to be good YMC candidates from newly available integrated spectroscopy and were in fact found to be old from their CMD. Of the remaining sixteen clusters, fourteen have ages between 25 Myr and 280 Myr, two have older ages than 500 Myr (lower limits). By including ten other YMC with HST photometry from the literature we have...

  13. Hα Surface Brightness Profiles of Star-Forming Galaxies and Dependence on Halo Mass Using the HAGGIS Survey

    Science.gov (United States)

    Kulkarni, S.; Wilman, D.; Erwin, P.; Koppenhöfer, J.; Gutierrez, L.; Beckman, J.; Saglia, R.; Bender, R.

    2014-03-01

    We present the first results from the Hα Galaxy Groups Imaging Survey (HAGGIS), a narrow-band imaging survey of SDSS groups at z Issac Newton Telescope (INT). In total, we observed 100 galaxy groups with a wide range of halo mass (1012 - 1014 M⊙) in pairs of narrow-band filters selected to get continuum subtracted rest-frame Hα images for each galaxy. The excellent data allows us to detect Hα down to the 10-18 ergs/s/cm2/arcsec2 level. Here, we examine the role played by halo mass and galaxy stellar mass in deciding the overall star formation activity in star forming disks by comparing stacked Hα profiles of galaxies in different halo mass and stellar mass bins. With this preliminary study, we have found that the star-formation activity in star-forming galaxies decreases in larger halos compared to the field galaxies. Using median equivalent width profiles, we can infer how environmental processes affect star-forming galaxies differently at different radii.

  14. Galaxy Zoo : 'Hanny's Voorwerp', a quasar light echo?

    CERN Document Server

    Lintott, Chris; Keel, William; van Arkel, Hanny; Bennert, Nicola; Edmondson, Edward; Thomas, Daniel; Smith, Daniel; Herbert, Peter; Jarvis, Matt; Virani, Shanil; Andreescu, Dan; Bamford, Steven; Land, Kate; Murray, Phil; Nichol, Robert; Raddick, Jordan; Slosar, Anze; Szalay, Alex; Vandenberg, Jan

    2009-01-01

    We report the discovery of an unusual object near the spiral galaxy IC 2497, discovered by visual inspection of the Sloan Digital Sky Survey (SDSS) as part of the Galaxy Zoo project. The object, known as Hanny's Voorwerp, is bright in the SDSS g band due to unusually strong OIII 4959-5007 emission lines. We present the results of the first targeted observations of the object in the optical, UV and X-ray, which show that the object contains highly ionized gas. Although the line ratios are similar to extended emission-line regions near luminous AGN, the source of this ionization is not apparent. The emission-line properties, and lack of x-ray emission from IC 2497, suggest either a highly obscured AGN with a novel geometry arranged to allow photoionization of the object but not the galaxy's own circumnuclear gas, or, as we argue, the first detection of a quasar light echo. In this case, either the luminosity of the central source has decreased dramatically or else the obscuration in the system has increased wit...

  15. The apparently normal galaxy hosts for two luminous quasars

    CERN Document Server

    Bahcall, J N; Bahcall, John N; Schneider, Donald P

    1995-01-01

    HST images (with WFPC2) of PHL~909\\ (z = 0.171) and PG~0052+251\\ (z = 0.155) show that these luminous radio-quiet quasars each occur in an apparently normal host galaxy. The host galaxy of PHL~909 is an elliptical galaxy (\\sim E4) and the host of PG~0052+251 is a spiral (\\sim~Sb). Both host galaxies are several tenths of a magnitude brighter than L^*, the characteristic Schechter luminosity of field galaxies. The images of PHL~909 and PG~0052+251, when compared with HST images of other objects in our sample of 20 luminous, small-redshift (z \\leq 0.30) quasars, show that luminous quasars occur in a variety of environments. The local environments of the luminous quasars range from luminous ellipticals, to apparently normal host galaxies, to complex systems of interacting components, to faint (and as yet undetected) hosts. The bright HII regions of the host galaxy of PG~0052+251 provide an opportunity to measure directly the metallicity of the host of a luminous quasar, to establish an upper limit to the mass of...

  16. The intrinsic quasar luminosity function: Accounting for accretion disk anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    DiPompeo, M. A.; Myers, A. D.; Brotherton, M. S. [University of Wyoming, Department of Physics and Astronomy 3905, 1000 East University, Laramie, WY 82071 (United States); Runnoe, J. C. [Penn State University, Department of Astronomy and Astrophysics, 413 Davey Lab, University Park, PA 16802 (United States); Green, R. F. [Large Binocular Telescope Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)

    2014-05-20

    Quasar luminosity functions are a fundamental probe of the growth and evolution of supermassive black holes. Measuring the intrinsic luminosity function is difficult in practice, due to a multitude of observational and systematic effects. As sample sizes increase and measurement errors drop, characterizing the systematic effects is becoming more important. It is well known that the continuum emission from the accretion disk of quasars is anisotropic—in part due to its disk-like structure—but current luminosity function calculations effectively assume isotropy over the range of unobscured lines of sight. Here, we provide the first steps in characterizing the effect of random quasar orientations and simple models of anisotropy on observed luminosity functions. We find that the effect of orientation is not insignificant and exceeds other potential corrections such as those from gravitational lensing of foreground structures. We argue that current observational constraints may overestimate the intrinsic luminosity function by as much as a factor of ∼2 on the bright end. This has implications for models of quasars and their role in the universe, such as quasars' contribution to cosmological backgrounds.

  17. Quasars : The Observational Perspectives

    NARCIS (Netherlands)

    D'Onofrio, Mauro; Marziani, Paola; Sulentic, Jack W.; Shields, Greg; Gaskell, Martin; Boroson, Todd; Laor, Ari; Hawkins, Michael; Pronik, Vladimir; Sergeev, Sergey; Dultzin, Deborah; Grupe, Dirk; Richards, Gordon; Morganti, Raffaella; Volvach, Aleksander; Zamfir, Sebastian; Falcke, Heino; Körding, Elmar; Elvis, Martin; Turner, Tracey Jane; Kembhavi, Ajit; Foschini, Luigi; Neshpor, Yuri; Franceschini, Alberto

    2012-01-01

    The empirical basis of quasar astronomy can be overawing especially in the twenty-first century. A first source of intricacy involves the nomenclature that has evolved to label the multifold phenomenological manifestations now united under the umbrella of active galactic nuclei (AGNs). A further com

  18. The ESO key-programme "a homogeneous bright QSO survey"; 1, the methods and the "deep" fields

    CERN Document Server

    Cristiani, S; Andreani, P; Gemmo, A; Goldschmidt, P; Miller, L; Vio, R; Barbieri, C; Bodini, L; Iovino, A; Lazzarin, M; Clowes, R G; MacGillivray, H T; Gouiffes, C; Lissandrini, C; Savage, A

    1995-01-01

    This is the first paper in a series aimed at defining a statistically significant sample of QSOs in the range 15 < B < 18.75 and 0.3 < z < 2.2. The selection is carried out using direct plates obtained at the ESO and UK Schmidt Telescopes, scanned with the COSMOS facility and searched for objects with an ultraviolet excess. Follow-up spectroscopy, carried out at ESO La Silla, is used to classify each candidate. In this initial paper, we describe the scientific objectives of the survey; the selection and observing techniques used. We present the first sample of 285 QSOs (M_B < -23) in a 153 deg^2 area, covered by the six ``deep'' fields, intended to obtain significant statistics down B \\simeq 18.75 with unprecedented photometric accuracy. From this database, QSO counts are determined in the magnitude range 17 < B < 18.75.

  19. The Hamburg Quasar Monitoring Program (HQM) at Calar Alto. I. Low amplitude variability in quasars

    OpenAIRE

    Borgeest, U.; Schramm, K. -J.

    1994-01-01

    HQM is an optical broad-band photometric monitoring program carried out since Sept.~1988. Our main intention is to search for indications of microlensing in a sample of $\\sim$\\,100 selected quasars; however, we also want to study the intrinsic variability. We use a CCD camera equipped to the MPIA 1.2$\\,$m telescope. Fully automatic photometric reduction relative to stars in the frame is done within a few minutes after each exposure, thus interesting brightness changes can be followed in detai...

  20. Bright Transients discovered by PSST

    Science.gov (United States)

    Smith, K. W.; Wright, D.; Smartt, S. J.; Young, D. R.; Huber, M.; Chambers, K. C.; Flewelling, H.; Willman, M.; Primak, N.; Schultz, A.; Gibson, B.; Magnier, E.; Waters, C.; Tonry, J.; Wainscoat, R. J.; Foley, R. J.; Jha, S. W.; Rest, A.; Scolnic, D.

    2016-08-01

    Six bright transients have been discovered as part of the Pan-STARRS Survey for Transients (PSST). Information on all objects discovered by the Pan-STARRS Survey for Transients is available at http://star.pst.qub.ac.uk/ps1threepi/ (see Huber et al. ATel #7153).

  1. Large scale correlations of quasar polarisation vectors: Hints of extreme scale structures?

    CERN Document Server

    Cabanac, R A; Sluse, D; Lamy, H; Cabanac, Remi A.; Hutsemekers, Damien; Sluse, Dominique; Lamy, Herve

    2005-01-01

    A survey measuring quasar polarization vectors has been started in two regions towards the North and South Galactic Poles. Here, We review the discovery of significant correlations of orientations of polarization vectors over huge angular distances. We report new results including a larger sample of the quasars confirming the existence of coherent orientations at redshifts z>1.

  2. Quasar-Galaxy Clustering through Projected Galaxy Counts at z=0.6-1.2

    OpenAIRE

    Zhang, Shao-hua; Wang, Ting-Gui; Wang, Hui-Yuan; Zhou, Hongyan

    2013-01-01

    We investigate the spatial clustering of galaxies around quasars at redshifts from 0.6 to 1.2 using the photometric data from Sloan Digital Sky Survey (SDSS) Stripe 82. The quasar and galaxy cross-correlation functions are measured through the projected galaxy number density n(r_p) on scales $0.05

  3. NuSTAR observations of heavily obscured quasars at z ~ 0.5

    DEFF Research Database (Denmark)

    Lansbury, G. B.; Alexander, D. M.; Del Moro, A.;

    2014-01-01

    We present NuSTAR hard X-ray observations of three Type 2 quasars at z ≈ 0.4-0.5, optically selected from the Sloan Digital Sky Survey. Although the quasars show evidence for being heavily obscured, Compton-thick systems on the basis of the 2-10 keV to [O III] luminosity ratio and multiwavelength...

  4. FAR-INFRARED PROPERTIES OF TYPE 1 QUASARS

    International Nuclear Information System (INIS)

    We use the Spitzer Space Telescope Enhanced Imaging Products and the Spitzer Archival Far-InfraRed Extragalactic Survey to study the spectral energy distributions (SEDs) of spectroscopically confirmed type 1 quasars selected from the Sloan Digital Sky Survey (SDSS). By combining the Spitzer and SDSS data with the Two Micron All Sky Survey, we are able to construct a statistically robust rest-frame 0.1-100 μm type 1 quasar template. We find that the quasar population is well-described by a single power-law SED at wavelengths less than 20 μm, in good agreement with previous work. However, at longer wavelengths, we find a significant excess in infrared luminosity above an extrapolated power-law, along with significant object-to-object dispersion in the SED. The mean excess reaches a maximum of 0.8 dex at rest-frame wavelengths near 100 μm.

  5. The bright end of the z ~ 7 UV Luminosity Function from a wide and deep HAWK-I survey

    CERN Document Server

    Castellano, M; Paris, D; Grazian, A; Pentericci, L; Boutsia, K; Santini, P; Testa, V; Dickinson, M; Giavalisco, M; Bouwens, R; Cuby, J -G; Mannucci, F; Clément, B; Cristiani, S; Fiore, F; Gallozzi, S; Giallongo, E; Maiolino, R; Menci, N; Moorwood, A; Nonino, M; Renzini, A; Rosati, P; Salimbeni, S; Vanzella, E

    2010-01-01

    (Abridged) We present here the second half of an ESO Large Programme, which exploits the unique combination of area and sensitivity provided in the near-IR by the camera Hawk-I at the VLT. We have obtained - 30 observing hours with Hawk-I in the Y-band of two high galactic latitude fields. We combined the Y-band data with deep J and K Hawk-I observations, and with FORS1/FORS2 U, B, V, R, I, and Z observations to select z-drop galaxies having Z - Y > 1, no optical detection and flat Y - J and Y - K colour terms. We detect 8 high-quality candidates in the magnitude range Y = 25.5 - 26.5 that we add to the z-drop candidates selected in two Hawk-I pointings over the GOODS-South field. We use this full sample of 15 objects found in -161 arcmin^2 of our survey to constrain the average physical properties and the evolution of the number density of z ~ 7 LBGs. A stacking analysis yields a best-fit SED with photometric redshift z= 6.85 +0.20 -0.15 and an E(B-V)=0.05 +0.15 -0.05. We compute a binned estimate of the z ~...

  6. A spectroscopic survey of the youngest field stars in the solar neighbourhood. I. The optically bright sample

    CERN Document Server

    Guillout, P; Frasca, A; Ferrero, R Freire; Marilli, E; Mignemi, G; Biazzo, K; Bouvier, J; Monier, R; Motch, C; Sterzik, M

    2009-01-01

    We present the first results of a ground-based programme conducted on 1-4m class telescopes. Our sample consists of 1097 active and presumably young stars, all of them being optical counterparts of RASS X-ray sources in the northern hemisphere. We concentrate on the 704 optically brightest (V_Ticho<=9.5 mag) candidates. We acquired high-res spectroscopy in the Halpha/Li spectral regions for 426 of such stars without relevant literature data. We describe the sample and the observations and we start to discuss its physical properties. We used a cross-correlation technique and other tools to derive accurate radial/rotational velocities and to perform a spectral classification for both single and SB2 stars. The spectral subtraction technique was used to derive chromospheric activity levels and Li abundances. We estimated the fraction of young single stars and multiple systems in stellar soft X-ray surveys and the contamination by more evolved systems, like RS CVn's. We classified stars on the basis of Li abund...

  7. DOUBLE QUASARS: PROBES OF BLACK HOLE SCALING RELATIONSHIPS AND MERGER SCENARIOS

    International Nuclear Information System (INIS)

    We analyze the available sample of double quasars, and investigate their physical properties. Our sample comprises 85 pairs, selected from the Sloan Digital Sky Survey (SDSS). We derive physical parameters for the engine and the host, and model the dynamical evolution of the pair. First, we compare different scaling relationships between massive black holes and their hosts (bulge mass, velocity dispersion, and their possible redshift dependences), and discuss their consistency. We then compute dynamical friction timescales for the double quasar systems to investigate their frequency and their agreement with the merger drivenscenario for quasar triggering. In optical surveys, such as the SDSS, N double,qso/N qso ∼ 0.1%. Comparing typical merging timescales to expected quasar lifetimes, the fraction of double quasars should be roughly a factor of 10 larger than observed. Additionally, we find that, depending on the correlations between black holes and their hosts, the occurrence of double quasars could be redshift dependent. Comparison of our models to the SDSS quasar catalog suggests that double quasars should be more common at high redshift. We compare the typical separations at which double quasars are observed to the predictions of merger simulations. We find that the distribution of physical separations peaks at ∼30 kpc, with a tail at larger separations (∼100-200 kpc). The peak of the distribution is roughly consistent with the first episode of quasar activity found in equal mass mergers simulations. The tail of the quasar pairs distribution at large separations is instead inconsistent with any quasar activity predicted by published simulations. These large separation pairs are instead consistent with unequal mass mergers where gas is dynamically perturbed during the first pericentric passage, but the gas reaches the black hole only at the next apocenter, where the pair is observed.

  8. Towards an Understanding of Changing-Look Quasars With a Statistical Sample: An Archival Spectroscopic Search in SDSS

    CERN Document Server

    Ruan, John J; Cales, Sabrina L; Eracleous, Michael; Green, Paul J; Morganson, Eric; Runnoe, Jessie C; Shen, Yue; Wilkinson, Tessa D; Blanton, Michael R; Dwelly, Tom; Georgakakis, Antonis; Greene, Jenny E; LaMassa, Stephanie M; Merloni, Andrea; Schneider, Donald P

    2015-01-01

    The uncertain origin of the recently-discovered 'changing-looking' quasar phenomenon - in which a luminous quasar dims significantly to a quiescent state in repeat spectroscopy over ~10 year timescales - may present unexpected challenges to our understanding of quasar accretion. To better understand this phenomenon, we take a first step to building a statistical sample of changing-look quasars with a systematic but simple archival search for these objects in the Sloan Digital Sky Survey Data Release 12. By leveraging the >10 year baselines for objects with repeat spectroscopy, we uncover two new changing-look quasars. Decomposition of the multi-epoch spectra and analysis of the broad emission lines suggest that the quasar accretion disk emission dims due to rapidly decreasing accretion rates, while disfavoring changes in intrinsic dust extinction. Narrow emission line energetics also support intrinsic dimming of quasar emission as the origin for this phenomenon rather than transient tidal disruption events. A...

  9. Optical Monitoring of Quasars; 1, Variability

    CERN Document Server

    García, A; Jablonski, F J; Terlevich, R J

    1999-01-01

    We present an analysis of quasar variability from data collected during a photometric monitoring of 50 objects carried out at CNPq/Laboratorio Nacional de Astrofisica, Brazil, between March 1993 and July 1996. A distinctive feature of this survey is its photometric accuracy, ~ 0.02 V mag, achieved through differential photometry with CCD detectors, what allows the detection of faint levels of variability. We find that the relative variability, delta = sigma / L, observed in the V band is anti-correlated with both luminosity and redshift, although we have no means of discovering the dominant relation, given the strong coupling between luminosity and redshift for the objects in our sample.We introduce a model for the dependence of quasar variability on frequency that is consistent with multi-wavelength observations of the nuclear variability of the Seyfert galaxy NGC 4151. We show that correcting the observed variability for this effect slightly increases the significance of the trends of variability with lumin...

  10. Dissecting the Quasar Main Sequence: Insight from Host Galaxy Properties

    Science.gov (United States)

    Sun, Jiayi; Shen, Yue

    2015-05-01

    The diverse properties of broad-line quasars appear to follow a well-defined main sequence along which the optical Fe ii strength increases. It has been suggested that this sequence is mainly driven by the Eddington ratio (L/LEdd) of the black hole (BH) accretion. Shen & Ho demonstrated with quasar clustering analysis that the average BH mass decreases with increasing Fe ii strength when quasar luminosity is fixed, consistent with this suggestion. Here we perform an independent test by measuring the stellar velocity dispersion σ* (hence, the BH mass via the M-σ* relation) from decomposed host spectra in low-redshift Sloan Digital Sky Survey quasars. We found that at fixed quasar luminosity, σ* systematically decreases with increasing Fe ii strength, confirming that the Eddington ratio increases with Fe ii strength. We also found that at fixed luminosity and Fe ii strength, there is little dependence of σ* on the broad Hβ FWHM. These new results reinforce the framework that the Eddington ratio and orientation govern most of the diversity seen in broad-line quasar properties.

  11. DISSECTING THE QUASAR MAIN SEQUENCE: INSIGHT FROM HOST GALAXY PROPERTIES

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Jiayi [Tsinghua Center for Astrophysics, Department of Physics, Tsinghua University, Beijing 100084 (China); Shen, Yue [Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)

    2015-05-01

    The diverse properties of broad-line quasars appear to follow a well-defined main sequence along which the optical Fe ii strength increases. It has been suggested that this sequence is mainly driven by the Eddington ratio (L/L{sub Edd}) of the black hole (BH) accretion. Shen and Ho demonstrated with quasar clustering analysis that the average BH mass decreases with increasing Fe ii strength when quasar luminosity is fixed, consistent with this suggestion. Here we perform an independent test by measuring the stellar velocity dispersion σ{sub *} (hence, the BH mass via the M–σ{sub *} relation) from decomposed host spectra in low-redshift Sloan Digital Sky Survey quasars. We found that at fixed quasar luminosity, σ{sub *} systematically decreases with increasing Fe ii strength, confirming that the Eddington ratio increases with Fe ii strength. We also found that at fixed luminosity and Fe ii strength, there is little dependence of σ{sub *} on the broad Hβ FWHM. These new results reinforce the framework that the Eddington ratio and orientation govern most of the diversity seen in broad-line quasar properties.

  12. Eight new quasars discovered by LAMOST in one extragalactic field

    CERN Document Server

    Wu, Xue-Bing; Chen, Zhaoyu; Zuo, Wenwen; Zhao, Yongheng; Luo, Ali; Bai, Zhongrui; Chen, Jianjun; Zhang, Haotong; Yan, Hongliang; Ren, Juanjuan; Sun, Shiwei; Wu, Hong; Zhang, Yong; Li, Yeping; Lu, Qishuai; Wang, You; Ni, Jijun; Wang, Hai; Kong, Xu; Shen, Shiyin

    2010-01-01

    We report the discovery of eight new quasars in one extragalactic field (five degree centered at RA=$08^h58^m08.2^s$, Dec=$01^o32'29.7''$) with the LAMOST commissioning observations on December 18, 2009. These quasars, with $i$ magnitudes from 16.21 to 19.13 and redshifts from 0.898 to 2.773, have optical colors quite similar as stars and were not targeted in the SDSS spectroscopic survey. Seven of them were selected as quasar candidates by a newly proposed criterion involving both near-IR and optical colors. Two of them were found in the 'redshift desert' for quasars ($z$ from 2.2 to 3), indicating that the new criterion is efficient for recovering the missing quasars with similar optical colors as stars. Although LAMOST met many problems including the the low accuracy of fiber positioning and poor dom seeing condition during the commissioning observations, we were still able to identify other 38 known SDSS quasars in this field, with $i$ magnitudes from 16.24 to 19.10 and redshifts from 0.297 to 4.512. Our ...

  13. The soft x-ray properties of a complete sample of optically selected quasars. 1: First results

    Science.gov (United States)

    Laor, Ari; Fiore, Fabrizio; Elvis, Martin; Wilkes, Belinda J.; Mcdowell, Jonathan C.

    1994-01-01

    We present the results of ROSAT position sensitive proportional counter (PSPC) observations of 10 quasars. These objects are part of our ROSAT program to observe a complete sample of optically selected quasars. This sample includes all 23 quasars from the bright quasar survey with a redshift z less than or = 0.400 and a Galactic H I column density N(sup Gal sub H I) less than 1.9 x 10(exp 20)/sq cm. These selection criteria, combined with the high sensitivity and improved energy resolution of the PSPC, allow us to determine the soft (approximately 0.2-2 keV) X-ray spectra of quasars with about an order of magnitude higher precision compared with earlier soft X-ray observations. The following main results are obtained: Strong correlations are suggested between the soft X-ray spectral slope alpha(sub x) and the following emission line parameters: H beta Full Width at Half Maximum (FWHM), L(sub O III), and the Fe II/H beta flux ratio. These correlations imply the following: (1) The quasar's environment is likely to be optically thin down to approximately 0.2 keV. (2) In most objects alpha(sub x) varies by less than approximately 10% on timescales shorter than a few years. (3) alpha(sub x) might be a useful absolute luminosity indicator in quasars. (4) The Galactic He I and H I column densities are well correlated. Most spectra are well characterized by a simple power law, with no evidence for either significant absorption excess or emission excess at low energies, to within approximately 30%. We find mean value of alpha(sub x) = -1.50 +/- 0.40, which is consistent with other ROSAT observations of quasars. However, this average is significantly steeper than suggested by earlier soft X-ray observations of the Einstein IPC. The 0.3 keV flux in our sample can be predicted to better than a factor of 2 once the 1.69 micrometer(s) flux is given. This implies that the X-ray variability power spectra of quasars flattens out between f approximately 10(exp -5) and f

  14. Unveiling the intrinsic X-ray properties of broad absorption line quasars with a relatively unbiased sample

    Energy Technology Data Exchange (ETDEWEB)

    Morabito, Leah K.; Dai, Xinyu; Leighly, Karen M. [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019 (United States); Sivakoff, Gregory R. [Department of Physics, University of Alberta, CCIS 4-183 Edmonton, AB T6G 2E1 (Canada); Shankar, Francesco [School of Physics and Astronomy, University of Southampton, Southampton SO17 IBJ (United Kingdom)

    2014-05-01

    There is growing evidence of a higher intrinsic fraction of broad absorption line quasars (BALQSOs) than that obtained in optical surveys, on which most previous X-ray studies of BALQSOs have focused. Here we present Chandra observations of 18 BALQSOs at z ∼ 2, selected from a near-infrared (Two Micron All Sky Survey) sample, where the BALQSO fraction is likely to be close to the intrinsic fraction. We measure photon indices using the stacked spectra of the optically faint (i – K{sub s} ≥ 2.3 mag) and optically bright (i – K{sub s} < 2.3 mag) samples to be Γ ≅ 1.5-2.1. We constrain their intrinsic column density by modeling the X-ray fractional hardness ratio, finding a mean column density of 3.5 × 10{sup 22} cm{sup –2} assuming neutral absorption. We incorporate Sloan Digital Sky Survey optical measurements (rest frame UV) to study the broadband spectral index between the X-ray and UV bands, and compare this to a large sample of normal quasars. We estimate that the optically faint BALQSOs are X-ray weaker than the optically bright ones, and the entire sample of BALQSOs are intrinsically X-ray weak when compared to normal active galactic nuclei (AGNs). Correcting for magnification of X-ray emission via gravitational lensing by the central black hole viewed at large inclination angles makes these BALQSOs even more intrinsically X-ray weak. Finally, we estimate AGN kinetic feedback efficiencies of a few percent for an X-ray wind of 0.3c in high-ionization BALQSOs. Combined with energy carried by low-ionization BALQSOs and UV winds, the total kinetic energy in BALQSOs can be sufficient to provide AGN kinetic feedback required to explain the co-evolution between black holes and host galaxies.

  15. CARMA Survey Toward Infrared-bright Nearby Galaxies (STING). III. The Dependence of Atomic and Molecular Gas Surface Densities on Galaxy Properties

    CERN Document Server

    Wong, Tony; Bolatto, Alberto D; Leroy, Adam K; Blitz, Leo; Rosolowsky, Erik; Bigiel, Frank; Fisher, David B; Ott, Jürgen; Rahman, Nurur; Vogel, Stuart N; Walter, Fabian

    2013-01-01

    We investigate the correlation between CO and HI emission in 18 nearby galaxies from the CARMA Survey Toward IR-Bright Nearby Galaxies (STING) at sub-kpc and kpc scales. Our sample, spanning a wide range in stellar mass and metallicity, reveals evidence for a metallicity dependence of the HI column density measured in regions exhibiting CO emission. Such a dependence is predicted by the equilibrium model of McKee & Krumholz, which balances H_2 formation and dissociation. The observed HI column density is often smaller than predicted by the model, an effect we attribute to unresolved clumping, although values close to the model prediction are also seen. We do not observe HI column densities much larger than predicted, as might be expected were there a diffuse HI component that did not contribute to H_2 shielding. We also find that the H_2 column density inferred from CO correlates strongly with the stellar surface density, suggesting that the local supply of molecular gas is tightly regulated by the stella...

  16. Galaxies in X-ray Selected Clusters and Groups in Dark Energy Survey Data: Stellar Mass Growth of Bright Central Galaxies Since z~1.2

    CERN Document Server

    Zhang, Y; Mckay, T; Rooney, P; Evrard, A E; Romer, A K; Perfecto, R; Song, J; Desai, S; Mohr, J; Wilcox, H; Bermeo, A; Jeltema, T; Hollowood, D; Bacon, D; Capozzi, D; Collins, C; Das, R; Gerdes, D; Hennig, C; Hilton, M; Hoyle, B; Kay, S; Liddle, A; Mann, R G; Mehrtens, N; Nichol, R C; Papovich, C; Sahlén, M; Soares-Santos, M; Stott, J; Viana, P T; Abbott, T; Abdalla, F B; Banerji, M; Bauer, A H; Benoit-Lévy, A; Bertin, E; Brooks, D; Buckley-Geer, E; Burke, D L; Rosell, A Carnero; Castander, F J; Diehl, H T; Doel, P; Cunha, C E; Eifler, T F; Neto, A Fausti; Fernandez, E; Flaugher, B; Fosalba, P; Frieman, J; Gaztanaga, E; Gruen, D; Gruendl, R A; Honscheid, K; James, D; Kuehn, K; Kuropatkin, N; Lahav, O; Maia, M A G; Makler, M; Marshall, J L; Martini, Paul; Miquel, R; Ogando, R; Plazas, A A; Roodman, A; Rykoff, E S; Sako, M; Sanchez, E; Scarpine, V; Schubnell, M; Sevilla, I; Smith, R C; Sobreira, F; Suchyta, E; Swanson, M E C; Tarle, G; Thaler, J; Tucker, D; Vikram, V; Da Costa, L N

    2015-01-01

    Using the science verification data of the Dark Energy Survey (DES) for a new sample of 106 X-Ray selected clusters and groups, we study the stellar mass growth of Bright Central Galaxies (BCGs) since redshift 1.2. Compared with the expectation in a semi-analytical model applied to the Millennium Simulation, the observed BCGs become under-massive/under-luminous with decreasing redshift. We incorporate the uncertainties associated with cluster mass, redshift, and BCG stellar mass measurements into analysis of a redshift-dependent BCG-cluster mass relation, $m_{*}\\propto(\\frac{M_{200}}{1.5\\times 10^{14}M_{\\odot}})^{0.24\\pm 0.08}(1+z)^{-0.19\\pm0.34}$, and compare the observed relation to the simulation prediction. We estimate the average growth rate since z = 1.0 for BCGs hosted by clusters of $M_{200, z}=10^{13.8}M_{\\odot}$, at $z=1.0$: $m_{*, BCG}$ appears to have grown by $0.13\\pm0.11$ dex, in tension at $\\sim 2.5 \\sigma$ significance level with the 0.4 dex growth rate expected in the simulation. We show that...

  17. The XMM deep survey in the CDF-S. IX. An X-ray outflow in a luminous obscured quasar at z~1.6

    CERN Document Server

    Vignali, C; Comastri, A; Gilli, R; Lanzuisi, G; Ranalli, P; Cappelluti, N; Mainieri, V; Georgantopoulos, I; Carrera, F J; Fritz, J; Brusa, M; Brandt, W N; Bauer, F E; Fiore, F; Tombesi, F

    2015-01-01

    In active galactic nuclei (AGN)-galaxy co-evolution models, AGN winds and outflows are often invoked to explain why super-massive black holes and galaxies stop growing efficiently at a certain phase of their lives. They are commonly referred to as the leading actors of feedback processes. Evidence of ultra-fast (v>0.05c) outflows in the innermost regions of AGN has been collected in the past decade by sensitive X-ray observations for sizable samples of AGN, mostly at low redshift. Here we present ultra-deep XMM-Newton and Chandra spectral data of an obscured (Nh~2x10^{23} cm^-2), intrinsically luminous (L2-10keV~4x10^{44} erg/s) quasar (named PID352) at z~1.6 (derived from the X-ray spectral analysis) in the Chandra Deep Field-South. The source is characterized by an iron emission and absorption line complex at observed energies of E~2-3 keV. While the emission line is interpreted as being due to neutral iron (consistent with the presence of cold absorption), the absorption feature is due to highly ionized ir...

  18. New quasars behind the Magellanic Clouds. Spectroscopic confirmation of near-infrared selected candidates

    CERN Document Server

    Ivanov, Valentin D; Bekki, Kenji; de Grijs, Richard; Emerson, Jim; Gibson, Brad K; Kamath, Devika; van Loon, Jacco Th; Piatti, Andres E; For, Bi-Qing

    2015-01-01

    Quasi--stellar objects (quasars) located behind nearby galaxies provide an excellent absolute reference system for astrometric studies, but they are difficult to identify because of fore- and background contamination. Deep wide--field, high angular resolution surveys spanning the entire area of nearby galaxies are needed to obtain a complete census of such quasars. We embarked on a program to expand the quasar reference system behind the Large and the Small Magellanic Clouds, the Magellanic Bridge, and the Magellanic Stream, connecting the Clouds with the Milky Way. Hundreds of quasar candidates were selected based on their near--infrared colors and variability properties from the ongoing public ESO VISTA Magellanic Clouds survey. A subset of 49 objects was followed up with optical spectroscopy. We confirmed the quasar nature of 37 objects (34 new identifications), four are low redshift objects, three are probably stars, and the remaining three lack prominent spectral features for a secure classification; bon...

  19. Dust reddened quasars in first and UKIDSS: Beyond the tip of the iceberg

    Energy Technology Data Exchange (ETDEWEB)

    Glikman, Eilat [Department of Physics, Middlebury College, Middlebury, VT 05753 (United States); Urrutia, Tanya [Leibniz Institut fr Astrophysik, An der Sternwarte 16, D-14482 Potsdam (Germany); Lacy, Mark [National Radio Astronomy Observatory, Charlottesville, VA (United States); Djorgovski, S. G.; Mahabal, Ashish; Graham, Matthew [California Institute of Technology, Pasadena, CA 91125 (United States); Urry, Meg [Department of Physics and Yale Center for Astronomy and Astrophysics, Yale University, P.O. Box 208121, New Haven, CT 06520-8121 (United States); Croom, Scott [Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, NSW 2006 (Australia); Schneider, Donald P. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Ge, Jian, E-mail: eglikman@middlebury.edu [Astronomy Department, University of Florida, 211 Bryant Space Science Center, P.O. Box 112055, Gainesville, FL 32611 (United States)

    2013-12-01

    We present the results of a pilot survey to find dust-reddened quasars by matching the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) radio catalog to the UKIDSS near-infrared survey and using optical data from Sloan Digital Sky Survey to select objects with very red colors. The deep K-band limit provided by UKIDSS allows for finding more heavily reddened quasars at higher redshifts as compared with previous work using FIRST and Two Micron All Sky Survey (2MASS). We selected 87 candidates with K ≤ 17.0 from the UKIDSS Large Area Survey (LAS) First Data Release (DR1), which covers 190 deg{sup 2}. These candidates reach up to ∼1.5 mag below the 2MASS limit and obey the color criteria developed to identify dust-reddened quasars. We have obtained 61 spectroscopic observations in the optical and/or near-infrared, as well as classifications in the literature, and have identified 14 reddened quasars with E(B – V) > 0.1, including 3 at z > 2. We study the infrared properties of the sample using photometry from the Wide-Field Infrared Survey Explorer and find that infrared colors improve the efficiency of red quasar selection, removing many contaminants in an infrared-to-optical color-selected sample alone. The highest-redshift quasars (z ≳ 2) are only moderately reddened, with E(B – V) ∼ 0.2-0.3. We find that the surface density of red quasars rises sharply with faintness, comprising up to 17% of blue quasars at the same apparent K-band flux limit. We estimate that to reach more heavily reddened quasars (i.e., E(B – V) ≳ 0.5) at z > 2 and a depth of K = 17, we would need to survey at least ∼2.5 times more area.

  20. The EUVE bright source list

    Science.gov (United States)

    Stroozas, B.; Mcdonald, K.; Antia, B.; Mcdonald, J.; Wiercigroch, A.

    1993-01-01

    Initial results for bright extreme ultraviolet sources discovered during the EUVE all-sky and deep ecliptic surveys have been published as a Bright Source List (BSL) and released to the astronomical community with a recent NASA research announcement (NRA 93-OSS-02, Appendix F). This paper describes the data processing software, the EUVE survey data set, and the production of the BSL at the Center for EUV Astrophysics. The contents, format, and selection criteria for sources, the data processing strategy, some problems encountered, and a summary of the BSL results are presented.

  1. Bayesian High-redshift Quasar Classification from Optical and Mid-IR Photometry

    Science.gov (United States)

    Richards, Gordon T.; Myers, Adam D.; Peters, Christina M.; Krawczyk, Coleman M.; Chase, Greg; Ross, Nicholas P.; Fan, Xiaohui; Jiang, Linhua; Lacy, Mark; McGreer, Ian D.; Trump, Jonathan R.; Riegel, Ryan N.

    2015-08-01

    We identify 885,503 type 1 quasar candidates to i≲ 22 using the combination of optical and mid-IR photometry. Optical photometry is taken from the Sloan Digital Sky Survey-III: Baryon Oscillation Spectroscopic Survey (SDSS-III/BOSS), while mid-IR photometry comes from a combination of data from the Wide-field Infrared Survey Explorer (WISE) “AllWISE” data release and several large-area Spitzer Space Telescope fields. Selection is based on a Bayesian kernel density algorithm with a training sample of 157,701 spectroscopically confirmed type 1 quasars with both optical and mid-IR data. Of the quasar candidates, 733,713 lack spectroscopic confirmation (and 305,623 are objects that we have not previously classified as photometric quasar candidates). These candidates include 7874 objects targeted as high-probability potential quasars with 3.5\\lt z\\lt 5 (of which 6779 are new photometric candidates). Our algorithm is more complete to z\\gt 3.5 than the traditional mid-IR selection “wedges” and to 2.2\\lt z\\lt 3.5 quasars than the SDSS-III/BOSS project. Number counts and luminosity function analysis suggest that the resulting catalog is relatively complete to known quasars and is identifying new high-z quasars at z\\gt 3. This catalog paves the way for luminosity-dependent clustering investigations of large numbers of faint, high-redshift quasars and for further machine-learning quasar selection using Spitzer and WISE data combined with other large-area optical imaging surveys.

  2. Spectral Energy Distributions and Multiwavelength Selection of Type 1 Quasars

    CERN Document Server

    Richards, G T; Budavari, T; Fan, X; Gallagher, S C; Hall, P B; Hines, D C; Jester, S; Lacy, M; Papovich, C; Schneider, D P; Storrie-Lombardi, L J; Szalay, A S; Trammell, G B; Vanden Berk, Daniel E; Vestergaard, M; York, D G; Anderson, Scott F.; Berk, Daniel E. Vanden; Budavari, Tamas; Fan, Xiaohui; Hall, Patrick B.; Hines, Dean C.; Jester, Sebastian; Lacy, Mark; Papovich, Casey; Richards, Gordon T.; Schneider, Donald P.; Storrie-Lombardi, Lisa J.; Szalay, Alexander S.; Trammell, George B.; Vestergaard, Marianne; York, Donald G.

    2006-01-01

    We present an analysis of the mid-infrared (MIR) and optical properties of type 1 (broad-line) quasars detected by the Spitzer Space Telescope. The MIR color-redshift relation is characterized to z=3, with predictions to z=7. We demonstrate how combining MIR and optical colors can yield even more efficient selection of active galactic nuclei (AGN) than MIR or optical colors alone. Composite spectral energy distributions (SEDs) are constructed for 259 quasars with both Sloan Digital Sky Survey and Spitzer photometry, supplemented by near-IR, GALEX, VLA and ROSAT data where available. We discuss how the spectral diversity of quasars influences the determination of bolometric luminosities and accretion rates; assuming the mean SED can lead to errors as large as a factor of 2 for individual quasars. Finally, we show that careful consideration of the shape of the mean quasar SED and its redshift dependence leads to a lower estimate of the fraction of reddened/obscured AGNs missed by optical surveys as compared to ...

  3. Quasars in the Cosmic Environment

    NARCIS (Netherlands)

    D'Onofrio, Mauro; Marziani, Paola; Sulentic, Jack W.; Dultzin, Deborah; Richards, Gordon; Knapen, Johan; Shlosman, Isaac; Morganti, Raffaella; Falomo, Renato; Hawkins, Mike; Cavaliere, Alfonso; McLure, Ross; Shields, Greg; Netzer, Hagai; Proga, Daniel; Franceschini, Alberto; Fan, Xiaoui; Elvis, Martin

    2012-01-01

    We now consider the environment of quasars in the widest possible sense, from the circumnuclear regions to very large scales of hundreds of kiloparsecs. The circumgalactic environment of nearby quasars has been widely studied since the late 1960s in an attempt to test its influence on the triggering

  4. Decline of the space density of quasars between z=2 and z=4

    CERN Document Server

    Vigotti, M; Benn, C R; De Zotti, G; Fanti, R; Serrano, J I G; Mack, K H; Holt, J

    2003-01-01

    We define a new complete sample of 13 optically-luminous radio quasars M_AB(1450 Angstrom) 25.7 with redshift 3.8 < z < 4.5, obtained by cross-correlating the FIRST radio survey and the APM catalogue of POSS-I. We measure the space density to be 1.0 +/- 0.3 /Gpc^3, a factor 1.9 +/- 0.7 smaller than the space density of similar quasars at z=2. Using a new measurement of the radio-loud fraction of quasars we find that at z=4 the total space density of quasars with M_AB(1450 Angstrom) < -26.9 is 7.4 +/- 2.6/Gpc^3. This is a factor 1.8 +/- 0.8 less than the space density at z=2, found by the 2dF quasar survey. This (z=2)/(z=4) ratio, consistent with that of the radio-loud quasars, is significantly different from the ratio of about 10 found for samples including lower-luminosity quasars. This suggests that the decline of the space density beyond z=2 is slower for optically-luminous quasars than for less-luminous ones.

  5. Microlensing as a possible probe of event-horizon structure in quasars

    CERN Document Server

    Tomozeiu, Mihai; Rabold, Manuel; Saha, Prasenjit; Wambsganss, Joachim

    2016-01-01

    In quasars which are lensed by galaxies, the point-like images sometimes show sharp and uncorrelated brightness variations (microlensing). These brightness changes are associated with the innermost region of the quasar passing through a complicated pattern of caustics produced by the stars in the lensing galaxy. In this paper, we study whether the universal properties of optical caustics could enable extraction of shape information about the central engine of quasars. We present a toy model with a crescent-shaped source crossing a fold caustic. The silhouette of a black hole over an accretion disk tends to produce roughly crescent sources. When a crescent-shaped source crosses a fold caustic, the resulting light curve is noticeably different from the case of a circular luminosity profile or Gaussian source. With good enough monitoring data, the crescent parameters, apart from one degeneracy, can be recovered.

  6. Quasars Probing Quasars VI. Excess HI Absorption Within One Proper Mpc of z~2 Quasars

    CERN Document Server

    Prochaska, J Xavier; Lee, Khee-Gan; Cantalupo, Sebastiano; Bovy, Jo; Djorgovski, S G; Ellison, Sara L; Lau, Marie Wingyee; Martin, Crystal L; Myers, Adam; Rubin, Kate H R; Simcoe, Robert A

    2013-01-01

    With close pairs of quasars at different redshifts, a background quasar sightline can be used to study a foreground quasar's environment in absorption. We use a sample of 650 projected quasar pairs to study the HI Lya absorption transverse to luminous, z~2 quasars at proper separations of 30kpc 17.3) at separations R<200kpc, which decreases to ~20% at R~1Mpc, but still represents a significant excess over the cosmic average. This excess of optically thick absorption can be described by a quasar-absorber cross-correlation function xi_QA(r) = (r/r_0)^gamma with a large correlation length r_0 = 12.5+2.7-1.4 Mpc/h (comoving) and gamma = 1.68+0.14-0.30. The HI absorption measured around quasars exceeds that of any previously studied population, consistent with quasars being hosted by massive dark matter halos Mhalo~10^12.5 Msun at z~2.5. The environments of these massive halos are highly biased towards producing optically thick gas, and may even dominate the cosmic abundance of Lyman limit systems and hence th...

  7. Investigation of the angular structure of the quasar 3C196 radio emission

    International Nuclear Information System (INIS)

    The angular dimensions and spectral characteristics are determined for the components of the preferrable brightness distribution model of the quasar 3C196 at decameter and shorter wavelengths. The physical processes are discussed that might be responsible for the extended region of radio emission that has been detected in 3C196 at decameter wavelengths

  8. Improved Spectrophotometric Calibration of the SDSS-III BOSS Quasar Sample

    OpenAIRE

    Margala, Daniel; Kirkby, David; Dawson, Kyle; Bailey, Stephen; Blanton, Michael; Schneider, Donald P.

    2015-01-01

    We present a model for spectrophotometric calibration errors in observations of quasars from the third generation of the Sloan Digital Sky Survey (SDSS-III) Baryon Oscillation Spectroscopic Survey (BOSS) and describe the correction procedure we have developed and applied to this sample. Calibration errors are primarily due to atmospheric differential refraction and guiding offsets during each exposure. The corrections potentially reduce the systematics for any studies of BOSS quasars, includi...

  9. NuSTAR J033202-2746.8: Direct constraints on the Compton reflection in a heavily obscured quasar at z ≈ 2

    Energy Technology Data Exchange (ETDEWEB)

    Del Moro, A.; Mullaney, J. R.; Alexander, D. M.; Aird, J. A.; Gandhi, P. [Department of Physics, Durham University, South Road, Durham, DH1 3LE (United Kingdom); Comastri, A.; Vignali, C.; Gilli, R. [INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy); Bauer, F. E. [Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, 306, Santiago 22 (Chile); Treister, E. [Departamento de Astronomía, Universidad de Concepción, Casilla 160-C, Concepción (Chile); Stern, D. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Mail Stop 169-221, Pasadena, CA 91109 (United States); Civano, F. [Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, NH 03755 (United States); Ranalli, P. [National Observatory of Athens, Institute of Astronomy, Astrophysics, Space Applications and Remote Sensing, Metaxa and Pavlou St., 15236 Penteli (Greece); Ballantyne, D. R. [Center for Relativistic Astrophysics, School of Physics, Georgia Institute of Technology, Atlanta, GA 30332 (United States); Baloković, M. [Cahill Center for Astrophysics, 1216 East California Boulevard, California Institute of Technology, Pasadena, CA 91125 (United States); Boggs, S. E. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Brandt, W. N. [Department of Astronomy and Astrophysics, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802 (United States); Christensen, F. E. [DTU Space-National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark); Craig, W. W. [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Hailey, C. J., E-mail: agnese.del-moro@durham.ac.uk [Columbia Astrophysics Laboratory, 550 W 120th Street, Columbia University, NY 10027 (United States); and others

    2014-05-01

    We report Nuclear Spectroscopic Telescope Array (NuSTAR) observations of NuSTAR J033202-2746.8, a heavily obscured, radio-loud quasar detected in the Extended Chandra Deep Field-South, the deepest layer of the NuSTAR extragalactic survey (∼400 ks, at its deepest). NuSTAR J033202-2746.8 is reliably detected by NuSTAR only at E > 8 keV and has a very flat spectral slope in the NuSTAR energy band (Γ=0.55{sub −0.64}{sup +0.62}; 3-30 keV). Combining the NuSTAR data with extremely deep observations by Chandra and XMM-Newton (4 Ms and 3 Ms, respectively), we constrain the broad-band X-ray spectrum of NuSTAR J033202-2746.8, indicating that this source is a heavily obscured quasar (N{sub H}=5.6{sub −0.8}{sup +0.9}×10{sup 23} cm{sup –2}) with luminosity L {sub 10-40} {sub keV} ≈ 6.4 × 10{sup 44} erg s{sup –1}. Although existing optical and near-infrared (near-IR) data, as well as follow-up spectroscopy with the Keck and VLT telescopes, failed to provide a secure redshift identification for NuSTAR J033202-2746.8, we reliably constrain the redshift z = 2.00 ± 0.04 from the X-ray spectral features (primarily from the iron K edge). The NuSTAR spectrum shows a significant reflection component (R=0.55{sub −0.37}{sup +0.44}), which was not constrained by previous analyses of Chandra and XMM-Newton data alone. The measured reflection fraction is higher than the R ∼ 0 typically observed in bright radio-loud quasars such as NuSTAR J033202-2746.8, which has L {sub 1.4} {sub GHz} ≈ 10{sup 27} W Hz{sup –1}. Constraining the spectral shape of active galactic nuclei (AGNs), including bright quasars, is very important for understanding the AGN population, and can have a strong impact on the modeling of the X-ray background. Our results show the importance of NuSTAR in investigating the broad-band spectral properties of quasars out to high redshift.

  10. The ISO View of Palomar-Green Quasars

    Science.gov (United States)

    Haas, M.; Klaas, U.; Mueller, S. A. H.; Bertoldi, F.; Camenzind, M.; Chini, R.; Krause, O.; Lemke, D.; Meisenheimer; Richards, P. J.

    2003-01-01

    Mining the ISO data archive we provide the complete ISO view of PG quasars containing 64 infrared spectral energy distributions between 5 and 200 mu m. About half of the sample was supplemented by MAMBO and SCUBA (sub-)millimeter data. Since the PG quasars were selected optically, the high infrared detection rate of more than 80% suggests that every quasar possesses luminous to hyper-luminous dust emission with dust masses comparable to Seyferts and ultra-luminous IR galaxies (ULIRGs). The gas to-dust mass ratio (of those sources where CO measurements are available in the literature) is consistent with the galactic value providing further evidence for the thermal nature of the IR emission of radio quiet quasars. The SEDs represent templates of unprecedented detail and sensitivity. We suggest that the diversity of the SEDs reflects largely the evolution of the dust distribution, and we propose a classification of the SED shapes as well as an evolutionary scheme in which this variety can be understood. During the evolution the surrounding dust redistributes, settling more and more into a torus/disk like configuration, while the SEDs show an initial FIR bump, then an increasing MIR emission and a steeper near- to mid-infrared slope, both of which finally also decrease. Regarding cosmic evolution, our hyper-luminous quasars in the "local" universe at z=l do not show the hyper-luminous (LFIR >? 10(exp 13) L(sub sun)) starburst activity inferred for z=4 quasars detected in several (sub-)millimeter surveys. In view of several caveats this difference should be established further, but it already suggests that in the early dense universe stronger merger events led to more powerful starbursts accompanying the quasar phenomenon, while at later cosmic epochs any coeval starbursts obviously do not reach that high power and are outshone by the AGN. Additional information is included in the original extended abstract.

  11. The complex evolutionary paths of local infrared bright galaxies: a high angular resolution mid-infrared view

    CERN Document Server

    Alonso-Herrero, A; Roche, P F; Hernan-Caballero, A; Aretxaga, I; Martinez-Paredes, M; Almeida, C Ramos; Pereira-Santaella, M; Diaz-Santos, T; Levenson, N A; Packham, C; Colina, L; Esquej, P; Gonzalez-Martin, O; Ichikawa, K; Imanishi, M; Espinosa, J M Rodriguez; Telesco, C

    2016-01-01

    We investigate the evolutionary connection between local IR-bright galaxies ($\\log L_{\\rm IR}\\ge 11.4\\,L_\\odot$) and quasars. We use high angular resolution ($\\sim$ 0.3-0.4 arcsec $\\sim$ few hundred parsecs) $8-13\\,\\mu$m ground-based spectroscopy to disentangle the AGN mid-IR properties from those of star formation. The comparison between the nuclear $11.3\\,\\mu$m PAH feature emission and that measured with Spitzer/IRS indicates that the star formation is extended over a few kpc in the IR-bright galaxies. The AGN contribution to the total IR luminosity of IR-bright galaxies is lower than in quasars. Although the dust distribution is predicted to change as IR-bright galaxies evolve to IR-bright quasars and then to optical quasars, we show that the AGN mid-IR emission of all the quasars in our sample is not significantly different. In contrast, the nuclear emission of IR-bright galaxies with low AGN contributions appears more heavily embedded in dust although there is no clear trend with the interaction stage or...

  12. Absorption spectra of quasars and the structure of the Universe

    International Nuclear Information System (INIS)

    The analysis of the distribution of the distances between the systems of absorption lines in the quasars' spectra and the comparison of this distribution with the distribution of the distances between superclusters in the deep optical surveys are carried out. It is shown that the systems of absorption lines are connected with superclusters of galaxies. The comparison of the absorbing gas parameters with the data for coronae of the Galaxy and of the Magellanic Clouds confirms this connection and permits to revise conclusions of the theory on the properties of superclusters. The problem of unidentified absorption lines in the quasars spectra is discussed

  13. Parsec-scale radio structures in Quasars

    Science.gov (United States)

    Coldwell, G.; Paragi, Z.; Gurvits, L.

    Very Long Baseline Interferometry (VLBI) con su nueva extensión para el radio telescopio orbital, VSOP/HALCA, ofrece una incomparable resolución angular alcanzando escalas de milisegundos y submilisegundos de arco a longitudes de onda de centímetros. En este trabajo presentamos observaciones y análisis de estructuras en radio, en escalas de parsec, para 3 radio fuentes extragalácticas de la muestra de VSOP Survey y 1 quasar, 1442+101, del proyecto `VSOP High Redshift'.

  14. How Similar are the Properties of Quasars with Nearly Identical Ultraviolet Spectra?

    CERN Document Server

    Rochais, Thomas; Chick, William; Maithil, Jaya; Sutter, Jessica; Brotherton, Michael; Shang, Zhouhui

    2016-01-01

    The spectrum of a quasar contains important information about its properties. Thus, it can be expected that two quasars with similar spectra will have similar properties, but just how similar has not before been quantified. Here we compare the ultraviolet spectra of a sample of 5553 quasars from Data Release 7 of the Sloan Digital Sky Survey, focusing on the $1350$ \\AA \\ $\\leq \\lambda \\leq 2900$ \\AA \\ rest-frame region which contains prominent emission lines from \\SiIV, O IV], \\CIV, \\CIII, and \\MgII\\ species. We use principal component analysis to determine the dominant components of spectral variation, as well as to quantitatively measure spectral similarity. As suggested by both the Baldwin effect and modified Baldwin effect, quasars with similar spectra have similar properties: bolometric luminosity, Eddington fraction, and black hole mass. The latter two quantities are calculated from the luminosity in conjunction with spectral features, and the variation between quasars with virtually identical spectra (...

  15. SDSS J115517.35+634622.0: A Newly Discovered Gravitationally Lensed Quasar

    CERN Document Server

    Pindor, B; Inada, N; Gregg, M D; Becker, R H; Brinkmann, J; Burles, S; Frieman, J A; Johnston, D E; Richards, G T; Schneider, D P; Scraton, R; Sekiguchi, M; Turner, E L; York, D G; Pindor, Bart; Eisenstein, Daniel J.; Inada, Naohisa; Gregg, Michael D.; Becker, Robert H.; Brinkmann, Jon; Burles, Scott; Frieman, Joshua A.; Johnston, David E.; Richards, Gordon T.; Schneider, Donald P.; Scraton, Ryan; Sekiguchi, Maki; Turner, Edwin L.; York, Donald G.

    2003-01-01

    We report the discovery of SDSSJ115517.35+634622.0, a previously unknown gravitationally lensed quasar. The lens system exhibits two images of a $z = 2.89$ quasar, with an image separation of $1{\\farcs}832 \\pm 0.007$ . Near-IR imaging of the system reveals the presence of the lensing galaxy between the two quasar images. Based on absorption features seen in the Sloan Digital Sky Survey (SDSS) spectrum, we determine a lens galaxy redshift of $z = 0.1756$. The lens is rather unusual in that one of the quasar images is only $0{\\farcs}22\\pm0{\\farcs}07$ ($\\sim 0.1 R_{\\rm eff}$) from the center of the lens galaxy and photometric modeling indicates that this image is significantly brighter than predicted by a SIS model. This system was discovered in the course of an ongoing search for strongly lensed quasars in the dataset from the SDSS.

  16. The Road to Quasars

    CERN Document Server

    Kellermann, K I

    2014-01-01

    Although the extragalactic nature of 3C 48 and other quasi stellar radio sources was discussed as early as 1960 by John Bolton and others, it was rejected largely because of preconceived ideas about what appeared to be unrealistically high radio and optical luminosities. Not until the 1962 occultations of the strong radio source 3C 273 at Parkes, which led Maarten Schmidt to identify 3C 273 with an apparent stellar object at a redshift of 0.16, was the true nature understood. Successive radio and optical measurements quickly led to the identification of other quasars with increasingly large redshifts and the general, although for some decades not universal, acceptance of quasars as the very luminous nuclei of galaxies. Curiously, 3C 273, which is one of the strongest extragalactic sources in the sky, was first cataloged in 1959 and the magnitude 13 optical counterpart was observed at least as early as 1887. Since 1960, much fainter optical counterparts were being routinely identified using accurate radio inte...

  17. Absorption lines and the radio structure of quasars

    International Nuclear Information System (INIS)

    High angular resolution radio observations at lambda6cm of 20 quasars are presented, all but two of which have been selected from a sample used by previous authors for a survey of absorption lines. The additional two, 1246-057 and 1333 + 286, are quasars with broad absorption lines and appear to be radio quiet. The radio structures for the entire sample of 66 sources of the previous authors are summarized and an investigation is made of whether the radio structure might provide clues on understanding the origin of the absorption lines in the range Zsub(em)-Zsub(ab) approx. 3000-18000 kms-1. The frequency of occurrence of absorption lines appears to be similar for both radio and optically selected quasars. (author)

  18. Photometric Classification of quasars from RCS-2 using Random Forest

    CERN Document Server

    Carrasco, D; Pichara, K; Anguita, T; Murphy, D N A; Gilbank, D G; Gladders, M D; Yee, H K C; Hsieh, B C; López, S

    2014-01-01

    We describe the construction of a quasar catalog containing 91,842 candidates derived from analysis of imaging data with a Random Forest algorithm. Using spectroscopically-confirmed stars and quasars from the SDSS as a training set, we blindly search the RCS-2 (~750 deg^2) imaging survey. From a source catalogue of 1,863,970 RCS-2 point sources, our algorithm identifies putative quasars from broadband magnitudes (g, r, i, z) and colours. Exploiting NUV GALEX measurements available for a subset 16,898 of these objects, we refine the classifier by adding NUV-optical colours to the algorithm's search. An additional subset (comprising 13% of the source catalog) features WISE coverage; we explore the effect of including W1 and W2 bands on the performance of the algorithm. Upon analysing all RCS-2 point sources, the algorithm identified 85,085 quasar candidates, with a training-set-derived precision (the fraction of true positives within the group assigned quasar status) of 90.4% and a recall (the fraction of true ...

  19. Dissecting the quasar main sequence: insight from host galaxy properties

    CERN Document Server

    Sun, Jiayi

    2015-01-01

    The diverse properties of broad-line quasars appear to follow a well-defined main sequence along which the optical FeII strength increases. It has been suggested that this sequence is mainly driven by the Eddington ratio (L/L_Edd) of the black hole (BH) accretion. Shen & Ho demonstrated with quasar clustering analysis that the average BH mass decreases with increasing FeII strength when quasar luminosity is fixed, consistent with this suggestion. Here we perform an independent test by measuring the stellar velocity dispersion sigma* (hence the BH mass via the M-sigma* relation) from decomposed host spectra in low-redshift Sloan Digital Sky Survey quasars. We found that at fixed quasar luminosity, sigma* systematically decreases with increasing FeII strength, confirming that Eddington ratio increases with FeII strength. We also found that at fixed luminosity and FeII strength, there is little dependence of sigma* on the broad Hbeta FWHM. These new results reinforce the framework put forward by Shen & H...

  20. Time Variability of Quasars: the Structure Function Variance

    Science.gov (United States)

    MacLeod, C.; Ivezić, Ž.; de Vries, W.; Sesar, B.; Becker, A.

    2008-12-01

    Significant progress in the description of quasar variability has been recently made by employing SDSS and POSS data. Common to most studies is a fundamental assumption that photometric observations at two epochs for a large number of quasars will reveal the same statistical properties as well-sampled light curves for individual objects. We critically test this assumption using light curves for a sample of ~2,600 spectroscopically confirmed quasars observed about 50 times on average over 8 years by the SDSS stripe 82 survey. We find that the dependence of the mean structure function computed for individual quasars on luminosity, rest-frame wavelength and time is qualitatively and quantitatively similar to the behavior of the structure function derived from two-epoch observations of a much larger sample. We also reproduce the result that the variability properties of radio and X-ray selected subsamples are different. However, the scatter of the variability structure function for fixed values of luminosity, rest-frame wavelength and time is similar to the scatter induced by the variance of these quantities in the analyzed sample. Hence, our results suggest that, although the statistical properties of quasar variability inferred using two-epoch data capture some underlying physics, there is significant additional information that can be extracted from well-sampled light curves for individual objects.

  1. Red quasars not so dusty

    CERN Document Server

    Benn, C R; Carballo, R; González-Serrano, J I; Sánchez, S F

    1997-01-01

    Webster et al (1995) claimed that up to 80% of QSOs may be obscured by dust. They inferred the presence of this dust from the remarkably broad range of B-K optical-infrared colours of a sample of flat-spectrum PKS radio QSOs. If such dust is typical of QSOs, it will have rendered invisible most of those which would otherwise been have detected by optical surveys. We used the William Herschel Telescope on La Palma to obtain K infrared images of 54 B3 radio quasars selected at low frequency (mainly steep-spectrum), and we find that although several have very red optical-infrared colours, most of these can be attributed to an excess of light in K rather than a dust-induced deficit in B. We present evidence that some of the infrared excess comes from the light of stars in the host galaxy (some, as previously suggested, comes from synchrotron radiation associated with flat-spectrum radio sources). The B-K colours of the B3 QSOs provide no evidence for a large reddened population. Either the Webster et al QSOs are ...

  2. Constraining quasar host halo masses with the strength of nearby Lyman-alpha forest absorption

    CERN Document Server

    Kim, Y R; Kim, Young-Rae; Croft, Rupert

    2006-01-01

    Using cosmological hydrodynamic simulations we measure the mean transmitted flux in the Lyman alpha forest for quasar sightlines that pass near a foreground quasar. We find that the trend of absorption with pixel-quasar separation distance can be fitted using a simple power law form including the usual correlation function parameters r_{0} and \\gamma so that ( = \\sum exp(-tau_eff*(1+(r/r_{0})^(-\\gamma)))). From the simulations we find the relation between r_{0} and quasar mass and formulate this as a way to estimate quasar host dark matter halo masses, quantifying uncertainties due to cosmological and IGM parameters, and redshift errors. With this method, we examine data for ~3000 quasars from the Sloan Digital Sky Survey (SDSS) Data Release 3, assuming that the effect of ionizing radiation from quasars (the so-called transverse proximity effect) is unimportant (no evidence for it is seen in the data.) We find that the best fit host halo mass for SDSS quasars with mean redshift z=3 and absolute G band magnitu...

  3. Herschel-ATLAS: Far-infrared properties of radio-loud and radio-quiet quasars

    CERN Document Server

    Kalfountzou, E; Jarvis, M J; Hardcastle, M J; Smith, D J B; Bourne, N; Dunne, L; Ibar, E; Eales, S; Ivison, R J; Maddox, S; Smith, M W L; Valiante, E; de Zotti, G

    2014-01-01

    We have constructed a sample of radio-loud and radio-quiet quasars from the Faint Im- ages Radio Sky at Twenty-one centimetres (FIRST) and the Sloan Digital Sky Survey Data Release 7 (SDSS DR7), over the H-ATLAS Phase 1 Area (9h, 12h and 14.5h). Using a stacking analysis we find a significant correlation between the far-infrared luminosity and 1.4-GHz luminosity for radio-loud quasars. Partial correlation analysis confirms the intrinsic correlation after removing the redshift contribution while for radio-quiet quasars no partial correlation is found. Using a single-temperature grey-body model we find a general trend of lower dust temperatures in the case of radio-loud quasars comparing to radio-quiet quasars. Also, radio-loud quasars are found to have almost constant mean values of dust mass along redshift and optical luminosity bins. In addition, we find that radio-loud quasars at lower optical luminosities tend to have on average higher FIR and 250-micron luminosity with respect to radio-quiet quasars with ...

  4. First Measurement of the Clustering Evolution of Photometrically-Classified Quasars

    CERN Document Server

    Myers, A D; Richards, G T; Nichol, R C; Schneider, D P; Vanden Berk, Daniel E; Scranton, R; Gray, A G; Brinkmann, J; Myers, Adam D.; Brunner, Robert J.; Richards, Gordon T.; Nichol, Robert C.; Schneider, Donald P.; Berk, Daniel E. Vanden; Scranton, Ryan; Gray, Alexander G.; Brinkmann, Jon

    2006-01-01

    We present new measurements of the quasar autocorrelation from a sample of \\~80,000 photometrically-classified quasars taken from SDSS DR1. We find a best-fit model of $\\omega(\\theta) = (0.066\\pm^{0.026}_{0.024})\\theta^{-(0.98\\pm0.15)}$ for the angular autocorrelation, consistent with estimates from spectroscopic quasar surveys. We show that only models with little or no evolution in the clustering of quasars in comoving coordinates since z~1.4 can recover a scale-length consistent with local galaxies and Active Galactic Nuclei (AGNs). A model with little evolution of quasar clustering in comoving coordinates is best explained in the current cosmological paradigm by rapid evolution in quasar bias. We show that quasar biasing must have changed from b_Q~3 at a (photometric) redshift of z=2.2 to b_Q~1.2-1.3 by z=0.75. Such a rapid increase with redshift in biasing implies that quasars at z~2 cannot be the progenitors of modern L* objects, rather they must now reside in dense environments, such as clusters. Simil...

  5. Capability of Quasar Selection by Combining the SCUSS and SDSS Observations

    CERN Document Server

    Zou, Hu; Zhou, Xu; Wang, Shu; Jiang, Linhua; Fan, Xiaohui; Fan, Zhou; Jiang, Zhaoji; Jing, Yipeng; Lesser, Michael; Li, Cheng; Ma, Jun; Nie, Jundan; Shen, Shiyin; Wang, Jiali; Wu, Zhenyu; Zhang, Tianmeng; Zhou, Zhimin

    2015-01-01

    The South Galactic Cap $u$-band Sky Survey (SCUSS) provides a deep $u$-band imaging of about 5000 deg$^2$ in south Galactic cap. It is about 1.5 mag deeper than the SDSS $u$-band. In this paper we evaluate the capability of quasar selection using both SCUSS and SDSS data, based on considerations of the deep SCUSS $u$-band imaging and two-epoch $u$-band variability. We find that the combination of the SCUSS $u$-band and the SDSS $griz$ band allows us to select more faint quasars and more quasars at redshift around 2.2 than the selection only with the SDSS $ugriz$ data. Quasars have significant $u$-band variabilities. The fraction of quasars with large two-epoch variability is much higher than that of stars. The selection by variability can select both low-redshift quasars with ultraviolet excess and mid-redshift ($2 < z <3.5$) quasars where quasar selection by optical colors is inefficient. The above two selections are complementary and make full use of the SCUSS u-band advantages.

  6. Bright and Faint Ends of Ly$\\alpha$ Luminosity Functions at $\\textit{z} = 2$ Determined by the Subaru Survey: Implications for AGN, Magnification Bias, and ISM HI Evolution

    CERN Document Server

    Konno, Akira; Nakajima, Kimihiko; Duval, Florent; Kusakabe, Haruka; Ono, Yoshiaki; Shimasaku, Kazuhiro

    2015-01-01

    We present the Lya luminosity functions (LFs) derived by our deep Subaru narrowband survey that identifies a total of 3,137 Lya emitters (LAEs) at $z = 2.2$ in five independent blank fields. The sample of these LAEs is the largest, to date, and covers a very wide Lya luminosity range of $\\log L_{Ly\\alpha} = 41.7-44.4$ erg s$^{-1}$. We determine the Lya LF at $z = 2.2$ with unprecedented accuracies, and obtain the best-fit Schechter parameters of $L^{*}_{Ly\\alpha} = 5.29^{+1.67}_{-1.13} \\times 10^{42}$ erg s$^{-1}$, $\\phi^{*}_{Ly\\alpha} = 6.32^{+3.08}_{-2.31} \\times 10^{-4}$ Mpc$^{-3}$, and $\\alpha = -1.75^{+0.10}_{-0.09}$ showing a steep faint-end slope. We identify a significant hump at the LF bright end ($\\log L_{Ly\\alpha} > 43.4$ erg s$^{-1}$). Because all of the LAEs in the bright-end hump have (a) bright counterpart(s) either in the X-ray, UV, or radio data, this bright-end hump is not made by gravitational lensing magnification bias but AGNs. These AGNs allow us to derive the AGN UV LF at $z \\sim 2$ dow...

  7. Quasars Probing Quasars. VI. Excess H I Absorption within One Proper Mpc of z ~ 2 Quasars

    Science.gov (United States)

    Prochaska, J. Xavier; Hennawi, Joseph F.; Lee, Khee-Gan; Cantalupo, Sebastiano; Bovy, Jo; Djorgovski, S. G.; Ellison, Sara L.; Lau, Marie Wingyee; Martin, Crystal L.; Myers, Adam; Rubin, Kate H. R.; Simcoe, Robert A.

    2013-10-01

    With close pairs of quasars at different redshifts, a background quasar sightline can be used to study a foreground quasar's environment in absorption. We use a sample of 650 projected quasar pairs to study the H I Lyα absorption transverse to luminous, z ~ 2 quasars at proper separations of 30 kpc line-of-sight, regions transverse to quasars exhibit enhanced H I Lyα absorption and a larger variance than the ambient intergalactic medium, with increasing absorption and variance toward smaller scales. Analysis of composite spectra reveals excess absorption characterized by a Lyα equivalent width profile W = 2.3 Å (R /100 kpc)-0.46. We also observe a high (sime 60%) covering factor of strong, optically thick H I absorbers (H I column N_{H\\,\\scriptsize{I}}>10^{17.3}\\, cm^{-2}) at separations R dark matter halos M halo ≈ 1012.5 M ⊙ at z ~ 2.5. The environments of these massive halos are highly biased toward producing optically thick gas, and may even dominate the cosmic abundance of Lyman limit systems and hence the intergalactic opacity to ionizing photons at z ~ 2.5. The anisotropic absorption around quasars implies the transverse direction is much less likely to be illuminated by ionizing radiation than the line-of-sight.

  8. A Glimpse at Quasar Host Galaxy Far-UV Emission Using Damped Lyα's as Natural Coronagraphs

    Science.gov (United States)

    Cai, Zheng; Fan, Xiaohui; Noterdaeme, Pasquier; Wang, Ran; McGreer, Ian; Carithers, Bill; Bian, Fuyan; Miralda-Escudé, Jordi; Finley, Hayley; Pâris, Isabelle; Schneider, Donald P.; Zakamska, Nadia L.; Ge, Jian; Petitjean, Patrick; Slosar, Anze

    2014-10-01

    In merger-driven models of massive galaxy evolution, the luminous quasar phase is expected to be accompanied by vigorous star formation in quasar host galaxies. In this paper, we use high column density damped Lyα (DLA) systems along quasar sight lines as natural coronagraphs to directly study the far-UV (FUV) radiation from the host galaxies of luminous background quasars. We have stacked the spectra of ~2000 DLA systems (N H I > 1020.6 cm-2) with a median absorption redshift langzrang = 2.6 selected from quasars observed in the SDSS-III Baryon Oscillation Spectroscopic Survey. We detect residual flux in the dark troughs of the composite DLA spectra. The level of this residual flux significantly exceeds systematic errors in the Sloan Digital Sky Survey fiber sky subtraction; furthermore, the residual flux is strongly correlated with the continuum luminosity of the background quasar, while uncorrelated with DLA column density or metallicity. We conclude that the flux could be associated with the average FUV radiation from the background quasar host galaxies (with medium redshift langzrang = 3.1) that is not blocked by the intervening DLA. Assuming that all of the detected flux originates from quasar hosts, for the highest quasar luminosity bin (langLrang = 2.5 × 1013 L ⊙), the host galaxy has an FUV intensity of 1.5 ± 0.2 × 1040 erg s-1 Å-1 this corresponds to an unobscured UV star formation rate of 9 M ⊙ yr-1.

  9. A Structure for Quasars

    CERN Document Server

    Elvis, Martin

    2009-01-01

    This paper proposes a simple, empirically derived, unifying structure for the inner regions of quasars. This structure is constructed to explain the broad absorption line (BAL) regions, the narrow `associated' ultraviolet and X-ray warm absorbers (NALs); and is also found to explain the broad emission line regions (BELR), and several scattering features, including a substantial fraction of the broad X-ray Iron-K emission line, and the bi-conical extended narrow emission line region (ENLR) structures seen on large kiloparsec scales in Seyfert images. Small extensions of the model to allow luminosity dependent changes in the structure may explain the UV and X-ray Baldwin effects and the greater prevalence of obscuration in low luminosity AGN.

  10. 'Round the Clock Observations of the Q0957+561 A,B Gravitationally Lensed Quasar

    CERN Document Server

    Colley, W N; Abajas, C; Alcalde, D; Aslan, Z; Barrena, R; Dudinov, V; Khamitov, I; Kjernsmo, K; Lee, H J; Lee, J; Lee, M G; Licandro, J; Maoz, D; Mediavilla, E; Motta, V; Muñoz, J; Oscoz, A; Serra-Ricart, M; Sinelnikov, I; Stabell, R; Teuber, J; Zheleznyak, A T; Colley, Wesley N.; Schild, Rudolph E.; Abajas, Cristina; Alcalde, David; Aslan, Zeki; Barrena, Rafael; Dudinov, Vladimir; Khamitov, Irek; Kjernsmo, Kjetil; Lee, Hyun Ju; Lee, Jonghwan; Lee, Myung Gyoon; Licandro, Javier; Maoz, Dan; Mediavilla, Evencio; Motta, Veronica; Munoz, Jose; Oscoz, Alex; Serra-Ricart, Miquel; Sinelnikov, Igor; Stabell, Rolf; Teuber, Jan; Zheleznyak, Alexander

    2001-01-01

    An observing campaign with 10 participating observatories has undertaken to monitor the optical brightness of the Q0957 gravitationally lensed quasar for 10 consecutive nights in January 2000. The resulting A image brightness curve has significant brightness fluctuations and makes a photometric prediction for the B image light curve for a second campaign planned for 12-21 March 2001. The ultimate purpose is to determine the gravitational lens time delay to a fraction of an hour, and to seek evidence for rapid microlensing.

  11. THE HIGH A{sub V} Quasar Survey: Reddened Quasi-Stellar Objects selected from optical/near-infrared photometry. II

    Energy Technology Data Exchange (ETDEWEB)

    Krogager, J.-K.; Fynbo, J. P. U.; Vestergaard, M. [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø (Denmark); Geier, S. [Instituto de Astrofísica de Canarias (IAC), E-38205 La Laguna, Tenerife (Spain); Venemans, B. P. [Max-Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Ledoux, C. [European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago 19 (Chile); Møller, P. [European Southern Observatory, Karl-Schwarzschildstrasse 2, D-85748 Garching bei München (Germany); Noterdaeme, P. [Institut d’Astrophysique de Paris, CNRS-UPMC, UMR7095, 98bis bd Arago, F-75014 Paris (France); Kangas, T.; Pursimo, T.; Smirnova, O. [Nordic Optical Telescope, Apartado 474, E-38700 Santa Cruz de La Palma (Spain); Saturni, F. G. [Tuorla Observatory, Department of Physics and Astronomy, University of Turku, Väisäläntie 20, 21500 Piikkiö (Finland)

    2015-03-15

    Quasi-stellar objects (QSOs) whose spectral energy distributions (SEDs) are reddened by dust either in their host galaxies or in intervening absorber galaxies are to a large degree missed by optical color selection criteria like the ones used by the Sloan Digital Sky Survey (SDSS). To overcome this bias against red QSOs, we employ a combined optical and near-infrared (near-IR) color selection. In this paper, we present a spectroscopic follow-up campaign of a sample of red candidate QSOs which were selected from the SDSS and the UKIRT Infrared Deep Sky Survey (UKIDSS). The spectroscopic data and SDSS/UKIDSS photometry are supplemented by mid-infrared photometry from the Wide-field Infrared Survey Explorer. In our sample of 159 candidates, 154 (97%) are confirmed to be QSOs. We use a statistical algorithm to identify sightlines with plausible intervening absorption systems and identify nine such cases assuming dust in the absorber similar to Large Magellanic Cloud sightlines. We find absorption systems toward 30 QSOs, 2 of which are consistent with the best-fit absorber redshift from the statistical modeling. Furthermore, we observe a broad range in SED properties of the QSOs as probed by the rest-frame 2 μm flux. We find QSOs with a strong excess as well as QSOs with a large deficit at rest-frame 2 μm relative to a QSO template. Potential solutions to these discrepancies are discussed. Overall, our study demonstrates the high efficiency of the optical/near-IR selection of red QSOs.

  12. Measuring Lensing Magnification of Quasars by Large Scale Structure Using the Variability-Luminosity Relation

    Science.gov (United States)

    Bauer, Anne H.; Seitz, Stella; Jerke, Jonathan; Scalzo, Richard; Rabinowitz, David; Ellman, Nancy; Baltay, Charles

    2011-05-01

    We introduce a technique to measure gravitational lensing magnification using the variability of type I quasars. Quasars' variability amplitudes and luminosities are tightly correlated, on average. Magnification due to gravitational lensing increases the quasars' apparent luminosity, while leaving the variability amplitude unchanged. Therefore, the mean magnification of an ensemble of quasars can be measured through the mean shift in the variability-luminosity relation. As a proof of principle, we use this technique to measure the magnification of quasars spectroscopically identified in the Sloan Digital Sky Survey (SDSS), due to gravitational lensing by galaxy clusters in the SDSS MaxBCG catalog. The Palomar-QUEST Variability Survey, reduced using the DeepSky pipeline, provides variability data for the sources. We measure the average quasar magnification as a function of scaled distance (r/R 200) from the nearest cluster; our measurements are consistent with expectations assuming Navarro-Frenk-White cluster profiles, particularly after accounting for the known uncertainty in the clusters' centers. Variability-based lensing measurements are a valuable complement to shape-based techniques because their systematic errors are very different, and also because the variability measurements are amenable to photometric errors of a few percent and to depths seen in current wide-field surveys. Given the volume data of the expected from current and upcoming surveys, this new technique has the potential to be competitive with weak lensing shear measurements of large-scale structure.

  13. MEASURING LENSING MAGNIFICATION OF QUASARS BY LARGE SCALE STRUCTURE USING THE VARIABILITY-LUMINOSITY RELATION

    International Nuclear Information System (INIS)

    We introduce a technique to measure gravitational lensing magnification using the variability of type I quasars. Quasars' variability amplitudes and luminosities are tightly correlated, on average. Magnification due to gravitational lensing increases the quasars' apparent luminosity, while leaving the variability amplitude unchanged. Therefore, the mean magnification of an ensemble of quasars can be measured through the mean shift in the variability-luminosity relation. As a proof of principle, we use this technique to measure the magnification of quasars spectroscopically identified in the Sloan Digital Sky Survey (SDSS), due to gravitational lensing by galaxy clusters in the SDSS MaxBCG catalog. The Palomar-QUEST Variability Survey, reduced using the DeepSky pipeline, provides variability data for the sources. We measure the average quasar magnification as a function of scaled distance (r/R200) from the nearest cluster; our measurements are consistent with expectations assuming Navarro-Frenk-White cluster profiles, particularly after accounting for the known uncertainty in the clusters' centers. Variability-based lensing measurements are a valuable complement to shape-based techniques because their systematic errors are very different, and also because the variability measurements are amenable to photometric errors of a few percent and to depths seen in current wide-field surveys. Given the volume data of the expected from current and upcoming surveys, this new technique has the potential to be competitive with weak lensing shear measurements of large-scale structure.

  14. Structure of the Seyfert galaxy NGC 1275 and the quasar 3C 345 nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Matveenko, L.I.; Paulini-Tos, I.K.; Kostenko, V.I.; Romni, Dzh.D.; Bot, L.B.

    1985-06-01

    Structure of the quasar 3C 345 and the Seyfert galaxy NGC 1275 has been studied with a global radio interference network at 18 cm wavelength. The quasar has a nucleus and a compact feature, both sizing to approximately 0.3 mas, and a fine jet, the brightness of which decreases with the distance from the nucleus, its position angle changing too. The central compact feature of NGC 1275, which has been observed at shorter wavelengths, is absent at 18 cm. This is likely due to reabsorption and absorption of synchrotron emission by the ionized gas surrounding the nucleus.

  15. Structure of the Seyfert galaxy NGC 1275 and the quasar 3C 345 nuclei

    International Nuclear Information System (INIS)

    Structure of the quasar 3C 345 and the Seyfert galaxy NGC 1275 has been studied with a global radio interference network at 18 cm wavelength. Quasar has a nucleus and a compact feature, both sizing to approximately 0.3 mas, and a fine jet, the brightness of which decreases with the distance from the nucleus, its position angle changing too. The central compact feature of NGC 1275, which has been observed at shorter wavelengths, is absent at 18 cm. This is likely due to reabsorption and absorption of synchrotron emission by the ionized gas surrounding the nucleus

  16. A study of the 15 micron quasars in the ELAIS N1 and N2 fields

    CERN Document Server

    Afonso-Luis, A; González-Solares, E A; Hatziminaoglou, E; Montenegro-Montes, F M; Hernan-Caballero, A; Serjeant,; Rowan-Robinson, M; Lari, C; Vaccari, M; Oliver, S

    2004-01-01

    This paper discusses properties of the European Large Area ISO Survey 15 micron quasars and tries to establish a robust method of quasar selection for future use within the Spitzer Wide-Area Infrared Extragalactic Survey (SWIRE) framework. The importance of good quality ground-based optical data is stressed, both for the candidates selection and for the photometric redshifts estimates. Colour-colour plots and template fitting are used for these purposes. The properties of the 15 micron quasars sample are studied, including variability and black hole masses and compared to the properties of other quasars that lie within the same fields but have no mid-infrared counterparts. The two subsamples do not present substantial differences and are believed to come from the same parent population.

  17. Environments of strong/ultrastrong, ultraviolet Fe II emitting quasars

    Science.gov (United States)

    Clowes, Roger G.; Raghunathan, Srinivasan; Söchting, Ilona K.; Graham, Matthew J.; Campusano, Luis E.

    2013-08-01

    We have investigated the strength of ultraviolet (UV) Fe II emission from quasars within the environments of large quasar groups (LQGs) in comparison with quasars elsewhere, for 1.1 ≤ zLQG ≤ 1.7, using the DR7QSO catalogue of the Sloan Digital Sky Survey. We use the Weymann et al. W2400 equivalent width, defined between the rest-frame continuum windows 2240-2255 and 2665-2695 Å, as the measure of the UV Fe II emission. We find a significant shift of the W2400 distribution to higher values for quasars within LQGs, predominantly for those LQGs with 1.1 ≤ zLQG ≤ 1.5. There is a tentative indication that the shift to higher values increases with the quasar i magnitude. We find evidence that within LQGs the ultrastrong emitters with W2400 ≥ 45 Å (more precisely, ultrastrong plus with W2400 ≥ 44 Å) have preferred nearest-neighbour separations of ˜30-50 Mpc to the adjacent quasar of any W2400 strength. No such effect is seen for the ultrastrong emitters that are not in LQGs. The possibilities for increasing the strength of the Fe II emission appear to be iron abundance, Lyα fluorescence and microturbulence, and probably all of these operate. The dense environment of the LQGs may have led to an increased rate of star formation and an enhanced abundance of iron in the nuclei of galaxies. Similarly, the dense environment may have led to more active blackholes and increased Lyα fluorescence. The preferred nearest-neighbour separation for the stronger emitters would appear to suggest a dynamical component, such as microturbulence. In one particular LQG, the Huge-LQG (the largest structure known in the early Universe), six of the seven strongest emitters very obviously form three pairings within the total of 73 members.

  18. The high-z quasar Hubble Diagram

    Energy Technology Data Exchange (ETDEWEB)

    Melia, Fulvio, E-mail: fmelia@email.arizona.edu [Department of Physics, the Applied Math Program, and Steward Observatory, The University of Arizona, Tucson, AZ 85721 (United States)

    2014-01-01

    Two recent discoveries have made it possible for us to begin using high-z quasars as standard candles to construct a Hubble Diagram (HD) at z > 6. These are (1) the recognition from reverberation mapping that a relationship exists between the optical/UV luminosity and the distance of line-emitting gas from the central ionizing source. Thus, together with a measurement of the velocity of the line-emitting gas, e.g., via the width of BLR lines, such as Mg II, a single observation can therefore in principle provide a determination of the black hole's mass; and (2) the identification of quasar ULAS J1120+0641 at z = 7.085, which has significantly extended the redshift range of these sources, providing essential leverage when fitting theoretical luminosity distances to the data. In this paper, we use the observed fluxes and Mg II line-widths of these sources to show that one may reasonably test the predicted high-z distance versus redshift relationship, and we assemble a sample of 20 currently available high-z quasars for this exercise. We find a good match between theory and observations, suggesting that a more complete, high-quality survey may indeed eventually produce an HD to complement the highly-detailed study already underway (e.g., with Type Ia SNe, GRBs, and cosmic chronometers) at lower redshifts. With the modest sample we have here, we show that the R{sub h} = ct Universe and ΛCDM both fit the data quite well, though the smaller number of free parameters in the former produces a more favorable outcome when we calculate likelihoods using the Akaike, Kullback, and Bayes Information Criteria. These three statistical tools result in similar probabilities, indicating that the R{sub h} = ct Universe is more likely than ΛCDM to be correct, by a ratio of about 85% to 15%.

  19. CARMA Survey Toward Infrared-bright Nearby Galaxies (STING) II: Molecular Gas Star Formation Law and Depletion Time Across the Blue Sequence

    CERN Document Server

    Rahman, Nurur; Xue, Rui; Wong, Tony; Leroy, Adam K; Walter, Fabian; Bigiel, Frank; Rosolowsky, Erik; Fisher, David B; Vogel, Stuart N; Blitz, Leo; West, Andrew A; Ott, Juergen

    2011-01-01

    We present an analysis of the relationship between molecular gas and current star formation rate surface density at sub-kpc and kpc scales in a sample of 14 nearby star-forming galaxies. Measuring the relationship in the bright, high molecular gas surface density ($\\Shtwo\\gtrsim$20 \\msunpc) regions of the disks to minimize the contribution from diffuse extended emission, we find an approximately linear relation between molecular gas and star formation rate surface density, $\

  20. Quasar Structure from Microlensing in Gravitationally Lensed Quasars

    Science.gov (United States)

    Morgan, Christopher W.

    2007-12-01

    I investigate microlensing in gravitationally lensed quasars and discuss the use of its signal to probe quasar structure on small angular scales. I describe our lensed quasar optical monitoring program and RETROCAM, the optical camera I built for the 2.4m Hiltner telescope to monitor lensed quasars. I use the microlensing variability observed in 11 gravitationally lensed quasars to show that the accretion disk size at 2500Å is related to the black hole mass by log(R2500/cm) = (15.70±0.16) + (0.64±0.18)log(MBH/109M⊙). This scaling is consistent with the expectation from thin disk theory (R ∝ MBH2/3), but it implies that black holes radiate with relatively low efficiency, log(η) = -1.54±0.36 + log(L/LE) where η=L/(Mdotc2). With one exception, these sizes are larger by a factor of 4 than the size needed to produce the observed 0.8µm quasar flux by thermal radiation from a thin disk with the same T ∝ R-3/4 temperature profile. More sophisticated disk models are clearly required, particularly as our continuing observations improve the precision of the measurements and yield estimates of the scaling with wavelength and accretion rate. This research made extensive use of a Beowulf computer cluster obtained through the Cluster Ohio program of the Ohio Supercomputer Center. Support for program HST-GO-9744 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS-5-26666.

  1. Quasars as a tracer of large-scale structures in the distant universe

    CERN Document Server

    Song, Hyunmi; Lietzen, Heidi; Einasto, Maret

    2016-01-01

    We study the dependence of the number density and properties of quasars on the background galaxy density using the currently largest spectroscopic datasets of quasars and galaxies. We construct a galaxy number density field smoothed over the variable smoothing scale of between approximately 10 and $20\\,h^{-1}$Mpc over the redshift range of $0.46Survey (SDSS) Data Release 12 (DR12) Constant MASS (CMASS) galaxies. The quasar sample is prepared from the SDSS I/II DR7. We examine the correlation of incidence of quasars with the large-scale background density and dependence of quasar properties such as bolometric luminosity, black hole mass, and Eddington ratio on the large-scale density. We find a monotonic correlation between the quasar number density and large-scale galaxy number density, which is fitted well with a power law relation, $n_Q\\propto\\rho_G^{0.618}$. We detect weak dependences of quasar properties on the large-scale density such as a positive correlation b...

  2. Low redshift quasars in the SDSS Stripe 82. Host galaxy colors and close environment

    CERN Document Server

    Bettoni, D; Kotilainen, J K; Karhunen, K; Uslenghi, M

    2015-01-01

    We present a photometrical and morphological multicolor study of the properties of low redshift (z<0.3) quasar hosts based on a large and homogeneous dataset of quasars derived from the Sloan Digital Sky Survey (DR7). We used quasars that were imaged in the SDSS Stripe82 that is up to 2 mag deeper than standard Sloan images. This sample is part of a larger dataset of ~400 quasars at z<0.5 for which both the host galaxies and their galaxy environments were studied (Falomo et al. 2014,Karhunen et al. 2014). For 52 quasars we undertake a study of the color of the host galaxies and of their close environments in u,g,r,i and z bands. We are able to resolve almost all the quasars in the sample in the filters g,r,i and z and also in $u$ for about 50% of the targets. We found that the mean colors of the QSO host galaxy (g-i=0.82+-0.26; r-i=0.26+-0.16 and u-g=1.32+-0.25) are very similar to the values of a sample of inactive galaxies matched in terms of redshift and galaxy luminosity with the quasar sample. Ther...

  3. Evidence for large temperature fluctuations in quasar accretion disks from spectral variability

    Energy Technology Data Exchange (ETDEWEB)

    Ruan, John J.; Anderson, Scott F.; Agol, Eric [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Dexter, Jason, E-mail: jruan@astro.washington.edu [Departments of Physics and Astronomy, University of California, Berkeley, CA 94720 (United States)

    2014-03-10

    The well-known bluer-when-brighter trend observed in quasar variability is a signature of the complex processes in the accretion disk and can be a probe of the quasar variability mechanism. Using a sample of 604 variable quasars with repeat spectra in the Sloan Digital Sky Survey-I/II (SDSS), we construct difference spectra to investigate the physical causes of this bluer-when-brighter trend. The continuum of our composite difference spectrum is well fit by a power law, with a spectral index in excellent agreement with previous results. We measure the spectral variability relative to the underlying spectra of the quasars, which is independent of any extinction, and compare to model predictions. We show that our SDSS spectral variability results cannot be produced by global accretion rate fluctuations in a thin disk alone. However, we find that a simple model of an inhomogeneous disk with localized temperature fluctuations will produce power-law spectral variability over optical wavelengths. We show that the inhomogeneous disk will provide good fits to our observed spectral variability if the disk has large temperature fluctuations in many independently varying zones, in excellent agreement with independent constraints from quasar microlensing disk sizes, their strong UV spectral continuum, and single-band variability amplitudes. Our results provide an independent constraint on quasar variability models and add to the mounting evidence that quasar accretion disks have large localized temperature fluctuations.

  4. Peculiar Broad Absorption Line Quasars found in DPOSS

    CERN Document Server

    Brunner, R J; Djorgovski, S G; Gal, R R; Mahabal, A A; Lopes, P A A; De Carvalho, R R; Odewahn, S C; Castro, S; Thompson, D; Chaffee, F; Darling, J; Desai, V; Brunner, Robert J.; Hall, Patrick B.

    2003-01-01

    With the recent release of large (i.e., > hundred million objects), well-calibrated photometric surveys, such as DPOSS, 2MASS, and SDSS, spectroscopic identification of important targets is no longer a simple issue. In order to enhance the returns from a spectroscopic survey, candidate sources are often preferentially selected to be of interest, such as brown dwarfs or high redshift quasars. This approach, while useful for targeted projects, risks missing new or unusual species. We have, as a result, taken the alternative path of spectroscopically identifying interesting sources with the sole criterion being that they are in low density areas of the g - r and r - i color-space defined by the DPOSS survey. In this paper, we present three peculiar broad absorption line quasars that were discovered during this spectroscopic survey, demonstrating the efficacy of this approach. PSS J0052+2405 is an Iron LoBAL quasar at a redshift z = 2.4512 with very broad absorption from many species. PSS J0141+3334 is a reddened...

  5. Radio structures of a complete sample of quasars from the 4C catalog

    International Nuclear Information System (INIS)

    Radio observations are reported for 57 quasars. Included are all of the quasars of Schmidt's 1974 complete sample from the 4C catalog. The observations were made with the Green Bank interferometer at 2.7 and 8.1 GHz, with baselines ranging from 300 m to 35 km. Model brightness distributions are presented, consisting of one to four elliptical Gaussian components. Angular sizes range from <0.2 to 77 arcsec. Of 38 well-resolved sources 21 contain a compact central component coincident with the optical object. The quasar 4C32. 69=2349+328 appears to exhibit a jetlike structure connecting the central component to one of the outer lobes

  6. Vanishing Absorption and Blueshifted Emission in FeLoBAL Quasars

    CERN Document Server

    Rafiee, Alireza; Hall, Patrick B; Galati, Natalee; Rogerson, Jesse; Ameri, Abtin

    2016-01-01

    We study the dramatic decrease in iron absorption strength in the iron low-ionization broad absorption line quasar SDSS J084133.15+200525.8. We report on the continued weakening of absorption in the prototype of this class of variable broad absorption line quasar, FBQS J140806.2+305448. We also report a third example of this class, SDSS J123103.70+392903.6; unlike the other two examples, it has undergone an increase in observed continuum brightness (at 3000~\\AA\\ rest-frame) as well as a decrease in iron absorption strength. These changes could be caused by absorber transverse motion or by ionization variability. We note that the \\mgii\\ and UV \\feii\\ lines in several FeLoBAL quasars are blueshifted by thousands of \\kms\\ relative to the \\Hb\\ emission line peak. We suggest that such emission arises in the outflowing winds normally seen only in absorption.

  7. The time-delay of the gravitationally lensed double quasar UM 673

    CERN Document Server

    Akhunov, T A; Burkhonov, O; Gaynullina, E R; Gottlöber, S; Mirtadjieva, K; Nuritdinov, S N; Tadjibaev, I; Wambsganss, J; Wisotzki, L; Bruevich, V V; Gusev, A S; Sergeyev, A; Smirnov, G

    2008-01-01

    We present the results of a monitoring campaign of the gravitational double quasar UM 673 at Maydanak observatory from August 2001 to December 2006. We obtained light curves in the V-filter (101 nights) and the R-filter (208 nights), split up into five observing seasons. We find brightness variations and V-R colour variations of the quasar on time scales of several years. The observing conditions at the telescope limited individual observing seasons to less than 150 days, which makes the estimation of the time-delay between the two lensed images by light curve correlation difficult. To overcome this problem we introduce a novel technique to measure the time-delay from the variation of the V-R colour of the quasar, and use this to obtain a time-delay Delta t=(106.8 days\\pm 17.0) days at 68 per cent confidence (image A leading).

  8. A Population of Short-Period Variable Quasars from PTF as Supermassive Black Hole Binary Candidates

    CERN Document Server

    Charisi, M; Haiman, Z; Price-Whelan, A M; Graham, M J; Bellm, E C; Laher, R R; Marka, S

    2016-01-01

    Supermassive black hole binaries (SMBHBs) at sub-parsec separations should be common in galactic nuclei, as a result of frequent galaxy mergers. Hydrodynamical simulations of circumbinary discs predict strong periodic modulation of the mass accretion rate on time-scales comparable to the orbital period of the binary. As a result, SMBHBs may be recognized by the periodic modulation of their brightness. We conducted a statistical search for periodic variability in a sample of 35,383 spectroscopically confirmed quasars in the photometric database of the Palomar Transient Factory (PTF). We analysed Lomb-Scargle periodograms and assessed the significance of our findings by modeling each individual quasar's variability as a damped random walk (DRW). We identified 50 quasars with significant periodicity beyond the DRW model, typically with short periods of a few hundred days. We find 33 of these to remain significant after a re-analysis of their periodograms including additional optical data from the intermediate-PT...

  9. MEAN SPECTRAL ENERGY DISTRIBUTIONS AND BOLOMETRIC CORRECTIONS FOR LUMINOUS QUASARS

    Energy Technology Data Exchange (ETDEWEB)

    Krawczyk, Coleman M.; Richards, Gordon T.; Mehta, Sajjan S.; Vogeley, Michael S. [Department of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Gallagher, S. C. [Department of Physics and Astronomy, The University of Western Ontario, London, ON N6A 3K7 (Canada); Leighly, Karen M. [Homer L. Dodge Department of Physics and Astronomy, The University of Oklahoma, 440 W. Brooks Street, Norman, OK 73019 (United States); Ross, Nicholas P. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Schneider, Donald P. [Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States)

    2013-05-01

    We explore the mid-infrared (mid-IR) through ultraviolet (UV) spectral energy distributions (SEDs) of 119,652 luminous broad-lined quasars with 0.064 < z < 5.46 using mid-IR data from Spitzer and WISE, near-infrared data from the Two Micron All Sky Survey and UKIDSS, optical data from the Sloan Digital Sky Survey, and UV data from the Galaxy Evolution Explorer. The mean SED requires a bolometric correction (relative to 2500 A) of BC{sub 2500A} =2.75 {+-} 0.40 using the integrated light from 1 {mu}m-2 keV, and we further explore the range of bolometric corrections exhibited by individual objects. In addition, we investigate the dependence of the mean SED on various parameters, particularly the UV luminosity for quasars with 0.5 {approx}< z {approx}< 3 and the properties of the UV emission lines for quasars with z {approx}> 1.6; the latter is a possible indicator of the strength of the accretion disk wind, which is expected to be SED-dependent. Luminosity-dependent mean SEDs show that, relative to the high-luminosity SED, low-luminosity SEDs exhibit a harder (bluer) far-UV spectral slope ({alpha}{sub UV}), a redder optical continuum, and less hot dust. Mean SEDs constructed instead as a function of UV emission line properties reveal changes that are consistent with known Principal Component Analysis trends. A potentially important contribution to the bolometric correction is the unseen extreme UV (EUV) continuum. Our work suggests that lower-luminosity quasars and/or quasars with disk-dominated broad emission lines may require an extra continuum component in the EUV that is not present (or much weaker) in high-luminosity quasars with strong accretion disk winds. As such, we consider four possible models and explore the resulting bolometric corrections. Understanding these various SED-dependent effects will be important for accurate determination of quasar accretion rates.

  10. Insights into Quasar UV Spectra Using Unsupervised Clustering Analysis

    CERN Document Server

    Tammour, Aycha; Daley, Mark; Richards, Gordon T

    2016-01-01

    Machine learning can provide powerful tools to detect patterns in multi-dimensional parameter space. We use K-means -a simple yet powerful unsupervised clustering algorithm which picks out structure in unlabeled data- to study a sample of quasar UV spectra from the Quasar Catalog of the 10th Data Release of the Sloan Digital Sky Survey of Paris et al. (2014). Detecting patterns in large datasets helps us gain insights into the physical conditions and processes giving rise to the observed properties of quasars. We use K-means to find clusters in the parameter space of the equivalent width (EW), the blue- and red-half-width at half-maximum (HWHM) of the Mg II 2800 A line, the C IV 1549 A line, and the C III] 1908 A blend in samples of Broad Absorption-Line (BAL) and non-BAL quasars at redshift 1.6-2.1. Using this method, we successfully recover correlations well-known in the UV regime such as the anti-correlation between the EW and blueshift of the C IV emission line and the shape of the ionizing Spectra Energy...

  11. Time Variability of Quasars: the Structure Function Variance

    CERN Document Server

    MacLeod, C; De Vries, W; Sesar, B; Becker, A

    2008-01-01

    Significant progress in the description of quasar variability has been recently made by employing SDSS and POSS data. Common to most studies is a fundamental assumption that photometric observations at two epochs for a large number of quasars will reveal the same statistical properties as well-sampled light curves for individual objects. We critically test this assumption using light curves for a sample of $\\sim$2,600 spectroscopically confirmed quasars observed about 50 times on average over 8 years by the SDSS stripe 82 survey. We find that the dependence of the mean structure function computed for individual quasars on luminosity, rest-frame wavelength and time is qualitatively and quantitatively similar to the behavior of the structure function derived from two-epoch observations of a much larger sample. We also reproduce the result that the variability properties of radio and X-ray selected subsamples are different. However, the scatter of the variability structure function for fixed values of luminosity...

  12. Low-ionization Outflows in High Eddington Ratio Quasars

    Science.gov (United States)

    Marziani, Paola; Sulentic, Jack W.; Plauchu-Frayn, Ilse; del Olmo, Ascensión

    2013-02-01

    The broad Mg II λ2800 doublet has been frequently studied in connection with its potentially important role as a virial estimator of black hole mass in high-redshift quasars. An important task, therefore, is the identification of any line components that are likely related to broadening by non-virial motions. High signal-to-noise median composite spectra (binned in the "four-dimensional eigenvector 1" context of Sulentic et al.) were constructed for the brightest 680 Sloan Digital Sky Survey Data Release 7 quasars in the 0.4 radiators in the sample. In the median spectra of these sources, FWHM Mg II λ2800 is equal to or greater than FWHM(Hβ) and shows a significant blueshift relative to Hβ. We interpret the Mg II λ2800 blueshift as the signature of a radiation-driven wind or outflow in the highest accreting quasars. In this interpretation, the Mg II λ2800 line width—affected by blueshifted emission—is unsuitable for virial mass estimation in ≈10% of quasars.

  13. Selecting Quasar Candidates by a SVM Classification System

    CERN Document Server

    Peng, Nanbo; Zhao, Yongheng; Wu, Xuebing

    2012-01-01

    We develop and demonstrate a classification system constituted by several Support Vector Machines (SVM) classifiers, which can be applied to select quasar candidates from large sky survey projects, such as SDSS, UKIDSS, GALEX. How to construct this SVM classification system is presented in detail. When the SVM classification system works on the test set to predict quasar candidates, it acquires the efficiency of 93.21% and the completeness of 97.49%. In order to further prove the reliability and feasibility of this system, two chunks are randomly chosen to compare its performance with that of the XDQSO method used for SDSS-III's BOSS. The experimental results show that the high faction of overlap exists between the quasar candidates selected by this system and those extracted by the XDQSO technique in the dereddened i-band magnitude range between 17.75 and 22.45, especially in the interval of dereddened i-band magnitude < 20.0. In the two test areas, 57.38% and 87.15% of the quasar candidates predicted by ...

  14. The discovery of timescale-dependent color variability of quasars

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yu-Han; Wang, Jun-Xian; Chen, Xiao-Yang [CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei, Anhui 230026 (China); Zheng, Zhen-Ya, E-mail: sunyh92@mail.ustc.edu.cn, E-mail: jxw@ustc.edu.cn [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States)

    2014-09-01

    Quasars are variable on timescales from days to years in UV/optical and generally appear bluer while they brighten. The physics behind the variations in fluxes and colors remains unclear. Using Sloan Digital Sky Survey g- and r-band photometric monitoring data for quasars in Stripe 82, we find that although the flux variation amplitude increases with timescale, the color variability exhibits the opposite behavior. The color variability of quasars is prominent at timescales as short as ∼10 days, but gradually reduces toward timescales up to years. In other words, the variable emission at shorter timescales is bluer than that at longer timescales. This timescale dependence is clearly and consistently detected at all redshifts from z = 0 to 3.5; thus, it cannot be due to contamination to broadband photometry from emission lines that do not respond to fast continuum variations. The discovery directly rules out the possibility that simply attributes the color variability to contamination from a non-variable redder component such as the host galaxy. It cannot be interpreted as changes in global accretion rate either. The thermal accretion disk fluctuation model is favored in the sense that fluctuations in the inner, hotter region of the disk are responsible for short-term variations, while longer-term and stronger variations are expected from the larger and cooler disk region. An interesting implication is that one can use quasar variations at different timescales to probe disk emission at different radii.

  15. Quasar Variability in the Mid-Infrared

    Science.gov (United States)

    Kozłowski, Szymon; Kochanek, Christopher S.; Ashby, Matthew L. N.; Assef, Roberto J.; Brodwin, Mark; Eisenhardt, Peter R.; Jannuzi, Buell T.; Stern, Daniel

    2016-02-01

    The Decadal IRAC Boötes Survey is a mid-IR variability survey of the ˜9 sq. deg. of the NDWFS Boötes Field and extends the time baseline of its predecessor, the Spitzer Deep, Wide-Field Survey (SDWFS), from 4 to 10 years. The Spitzer Space Telescope visited the field five times between 2004 and 2014 at 3.6 and 4.5 μm. We provide the difference image analysis photometry for a half a million mostly extragalactic sources. In mid-IR color-color plane, sources with quasar colors constitute the largest variability class (75%), 16% of the variable objects have stellar colors and the remaining 9% have the colors of galaxies. Adding the fifth epoch doubles the number of variable active galactic nuclei (AGNs) for the same false positive rates as in SDWFS, or increases the number of sources by 20% while decreasing the false positive rates by factors of 2-3 for the same variability amplitude. We quantify the ensemble mid-IR variability of ˜1500 spectroscopically confirmed AGNs using single power-law structure functions (SFs), which we find to be steeper (index γ ≈ 0.45) than in the optical (γ ≈ 0.3), leading to much lower amplitudes at short time-lags. This provides evidence for large emission regions, smoothing out any fast UV/optical variations, as the origin of infrared quasar variability. The mid-IR AGN SF slope γ seems to be uncorrelated with both the luminosity and rest-frame wavelength, while the amplitude shows an anti-correlation with the luminosity and a correlation with the rest-frame wavelength.

  16. Quasar Structure and Cosmological Feedback

    CERN Document Server

    Elvis, M

    2006-01-01

    Feedback from quasars and AGNs is being invoked frequently in several cosmological settings. Currently, order of magnitude, or more, uncertainties in the structure of both the wind and the 'obscuring torus' make predictions highly uncertain. To make testable models of this 'cosmological feedback' it is essential to understand the detailed structure of AGNs sufficiently well to predict their properties for the whole quasar population, at all redshifts. Progress in both areas is rapid, and I describe the near-term prospects for reducing these uncertainties for 'slow' (non-relativistic) AGN winds and the obscuring torus.

  17. Direct determination of quasar redshifts

    CERN Document Server

    De Bruijne, J H J; Perryman, M; Peacock, A; Favata, F; Rando, N; Martin, D; Verhoeve, P; Christlieb, N; Bruijne, Jos de; Reynolds, Alastair P; Perryman, Michael; Peacock, Anthony; Favata, Fabio; Rando, Nicola; Martin, Didier; Verhoeve, Peter; Christlieb, Norbert

    2001-01-01

    We present observations of 11 quasars, selected in the range z = 2.2-4.1, obtained with ESA's Superconducting Tunnel Junction (STJ) camera on the WHT. Using a single template quasar spectrum, we show that we can determine the redshifts of these objects to about 1%. A follow-up spectroscopic observation of one QSO for which our best-fit redshift (z = 2.976) differs significantly from the tentative literature value (z ~ 2.30) confirms that the latter was incorrect.

  18. Bright Metal-Poor Stars from the Hamburg/ESO Survey. I. Selection and Follow-up Observations from 329 Fields

    CERN Document Server

    Frebel, A; Norris, J E; Beers, T C; Bessell, M S; Rhee, J; Fechner, C; Marsteller, B; Rossi, S; Thom, C; Wisotzki, L; Reimers, D

    2006-01-01

    We present a sample of 1777 bright (91.0) metal-poor ([Fe/H]20%) and higher values with increasing distance from the Galactic plane. Although the numbers of stars at low metallicity are falling rapidly at the lowest metallicities, there is evidence that the fraction of carbon-enhanced metal-poor stars is increasing rapidly as a function of declining metallicity. For ~60 objects, high-resolution data have already been obtained; one of these, HE 1327-2326, is the new record holder for the most iron-deficient star known.

  19. The VLT-FLAMES Tarantula survey. XX. The nature of the X-ray bright emission-line star VFTS 399

    OpenAIRE

    Clark, J. S.; Bartlett, E. S.; Broos, P. S.; Townsley, L. K.; Taylor, W.D.; N. R. Walborn; Bird, A. J.; Sana, H.; Mink, de, S.E.; Dufton, P. L.; Evans, C J; Langer, N.; Maíz Apellániz, J; Schneider, F.R.N.; Soszyński, I.

    2015-01-01

    Context. The stellar population of the 30 Doradus star-forming region in the Large Magellanic Cloud contains a subset of apparently single, rapidly rotating O-type stars. The physical processes leading to the formation of this cohort are currently uncertain. Aims. One member of this group, the late O-type star VFTS 399, is found to be unexpectedly X-ray bright for its bolometric luminosity − in this study we aim to determine its physical nature and the cause of this behaviour. Methods...

  20. CONSTRAINING SUB-PARSEC BINARY SUPERMASSIVE BLACK HOLES IN QUASARS WITH MULTI-EPOCH SPECTROSCOPY. I. THE GENERAL QUASAR POPULATION

    International Nuclear Information System (INIS)

    We perform a systematic search for sub-parsec binary supermassive black holes (BHs) in normal broad-line quasars at z BLR, where RBLR ∼ 0.01-0.1 pc is the BLR size. We search for the expected line-of-sight acceleration of the broad-line velocity from binary orbital motion by cross-correlating SDSS spectra from two epochs separated by up to several years in the quasar rest frame. Out of ∼700 pairs of spectra for which we have good measurements of the velocity shift between two epochs (1σ error ∼40 km s–1), we detect 28 systems with significant velocity shifts in broad Hβ, among which 7 are the best candidates for the hypothesized binaries, 4 are most likely due to broad-line variability in single BHs, and the rest are ambiguous. Continued spectroscopic observations of these candidates will easily strengthen or disprove these claims. We use the distribution of the observed accelerations (mostly non-detections) to place constraints on the abundance of such binary systems among the general quasar population. Excess variance in the velocity shift is inferred for observations separated by longer than 0.4 yr (quasar rest frame). Attributing all the excess to binary motion would imply that most of the quasars in this sample must be in binaries, that the inactive BH must be on average more massive than the active one, and that the binary separation is at most a few times the size of the BLR. However, if this excess variance is partly or largely due to long-term broad-line variability, the requirement of a large population of close binaries is much weakened or even disfavored for massive companions. Future time-domain spectroscopic surveys of normal quasars can provide vital prior information on the structure function of stochastic velocity shifts induced by broad-line variability in single BHs. Such surveys with improved spectral quality, increased time baseline, and more epochs can greatly improve the statistical constraints of this method on the general binary

  1. A Quasar-Galaxy Mixing Diagram: Quasar Spectral Energy Distribution Shapes in the Optical to Near-Infrared

    CERN Document Server

    Hao, Heng; Kelly, Brandon C; Civano, Francesca; Bongiorno, Angela; Zamorani, Gianni; Celotti, Annalisa; Ho, Luis C; Merloni, Andrea; Jahnke, Knud; Comastri, Andrea; Trump, Jonathan R; Mainieri, Vincenzo; Salvato, Mara; Brusa, Marcella; Impey, Chris D; Koekemoer, Anton M; Lanzuisi, Giorgio; Vignali, Cristian; Silverman, John D; Urry, C Megan; Schawinski, Kevin

    2012-01-01

    We define the quasar-galaxy mixing diagram by the slopes of the spectral energy distribution (SED) of quasars from $1\\mu m$ to 3000 \\AA\\ and from $1\\mu m$ to 3 $\\mu m$ in the rest frame. The mixing diagram can easily distinguish among quasar-dominated, galaxy-dominated and reddening-dominated SED shapes. By studying the position of the 413 XMM selected Type 1 AGN in the wide-field "Cosmic Evolution Survey" (COSMOS) in the mixing diagram, we find that a combination of the Elvis et al. (1994, hereafter E94) quasar SED with various contributions from galaxy emission and some dust reddening is remarkably effective in describing the SED shape near $1\\mu m$ for large ranges of redshift, luminosity, black hole mass and Eddington ratio of type 1 AGN. In particular, the location in the mixing diagram of the highest luminosity AGN is very close (within 1$\\sigma$) to that expected on the basis of the E94 SED. The mixing diagram can also be used to estimate the host galaxy fraction and reddening in the SED. We also show ...

  2. Stars, Galaxies and Quasars

    Directory of Open Access Journals (Sweden)

    Patrick Das Gupta

    2009-05-01

    Full Text Available This article provides a brief introduction to the basics of stars, galaxies and Quasi-stellar objects (QSOs. In stars, the central pressure and temperature must be high in order to halt the stellar gravitational collapse. High temperature leads to thermonuclear fusion in the stellar core, releasing thereby enormous amount of nuclear energy, making the star shine brilliantly. On the other hand, the QSOs are very bright nuclei lying in the centres of some galaxies. Many of these active galactic nuclei, which appear star-like when observed through a telescope and  whose power output are more than 1011 times that of the Sun, exhibit rapid time variability in their X-ray emissions.  Rapid variability along with the existence of a maximum speed limit, c, provide a strong argument in favour of a compact central engine model for QSOs in which a thick disc of hot gas going around a supermassive blackhole is what makes a QSO appear like a bright point source. Hence, unlike stars, QSOs are powered by gravitational potential energy.

  3. Probable Bright Supernova discovered by PSST

    Science.gov (United States)

    Smith, K. W.; Wright, D.; Smartt, S. J.; Young, D. R.; Huber, M.; Chambers, K. C.; Flewelling, H.; Willman, M.; Primak, N.; Schultz, A.; Gibson, B.; Magnier, E.; Waters, C.; Tonry, J.; Wainscoat, R. J.; Foley, R. J.; Jha, S. W.; Rest, A.; Scolnic, D.

    2016-09-01

    A bright transient, which is a probable supernova, has been discovered as part of the Pan-STARRS Survey for Transients (PSST). Information on all objects discovered by the Pan-STARRS Survey for Transients is available at http://star.pst.qub.ac.uk/ps1threepi/ (see Huber et al. ATel #7153).

  4. Broad absorption line (BAL) quasars as a class of low luminosity AGNs

    CERN Document Server

    Kunert-Bajraszewska, M; Roskowinski, C; Gawronski, M

    2015-01-01

    Broad absorption lines seen in some quasars prove the existence of ionized plasma outflows from the accretion disk. Outflows together with powerful jets are important feedback processes. Understanding physics behind BAL outflows might be a key to comprehend Galaxy Evolution as a whole. First radio-loud BAL quasar was discovered in 1997 and this discovery has opened new possibilities for studies of the BAL phenomena, this time on the basis of radio emission. However, information about the radio structures, orientation and age of BAL quasars is still very limited due to weak radio emission and small sizes of these objects. Our high-resolution radio survey of a sample of BAL quasars aims to increase our knowledge about these objects. In this article, we present some conclusions arising from our research.

  5. Galaxy evolution. Quasar quartet embedded in giant nebula reveals rare massive structure in distant universe.

    Science.gov (United States)

    Hennawi, Joseph F; Prochaska, J Xavier; Cantalupo, Sebastiano; Arrigoni-Battaia, Fabrizio

    2015-05-15

    All galaxies once passed through a hyperluminous quasar phase powered by accretion onto a supermassive black hole. But because these episodes are brief, quasars are rare objects typically separated by cosmological distances. In a survey for Lyman-α emission at redshift z ≈ 2, we discovered a physical association of four quasars embedded in a giant nebula. Located within a substantial overdensity of galaxies, this system is probably the progenitor of a massive galaxy cluster. The chance probability of finding a quadruple quasar is estimated to be ∼10(-7), implying a physical connection between Lyman-α nebulae and the locations of rare protoclusters. Our findings imply that the most massive structures in the distant universe have a tremendous supply (≃10(11) solar masses) of cool dense (volume density ≃ 1 cm(-3)) gas, which is in conflict with current cosmological simulations. PMID:25977547

  6. Quasar quartet embedded in giant nebula reveals rare massive structure in distant universe

    Science.gov (United States)

    Hennawi, Joseph F.; Prochaska, J. Xavier; Cantalupo, Sebastiano; Arrigoni-Battaia, Fabrizio

    2015-05-01

    All galaxies once passed through a hyperluminous quasar phase powered by accretion onto a supermassive black hole. But because these episodes are brief, quasars are rare objects typically separated by cosmological distances. In a survey for Lyman-α emission at redshift z ≈ 2, we discovered a physical association of four quasars embedded in a giant nebula. Located within a substantial overdensity of galaxies, this system is probably the progenitor of a massive galaxy cluster. The chance probability of finding a quadruple quasar is estimated to be ˜10-7, implying a physical connection between Lyman-α nebulae and the locations of rare protoclusters. Our findings imply that the most massive structures in the distant universe have a tremendous supply (≃1011 solar masses) of cool dense (volume density ≃ 1 cm-3) gas, which is in conflict with current cosmological simulations.

  7. Quasar Quartet Embedded in Giant Nebula Reveals Rare Massive Structure in Distant Universe

    CERN Document Server

    Hennawi, Joseph F; Cantalupo, Sebastiano; Arrigoni-Battaia, Fabrizio

    2015-01-01

    All galaxies once passed through a hyperluminous quasar phase powered by accretion onto a supermassive black hole. But because these episodes are brief, quasars are rare objects typically separated by cosmological distances. In a survey for Lyman-alpha emission at redshift z ~ 2, we discovered a physical association of four quasars embedded in a giant nebula. Located within a substantial overdensity of galaxies, this system is probably the progenitor of a massive galaxy cluster. The chance probability of finding a quadruple quasar is estimated to be ~10^-7, implying a physical connection between Lyman-alpha nebulae and the locations of rare protoclusters. Our findings imply that the most massive structures in the distant universe have a tremendous supply (~ 10^11 solar masses) of cool dense (volume density ~1 cm^-3) gas, which is in conflict with current cosmological simulations.

  8. Clustering on very small scales from a large, complete sample of confirmed quasar pairs

    Science.gov (United States)

    Eftekharzadeh, Sarah; Myers, Adam D.; Djorgovski, Stanislav G.; Graham, Matthew J.; Hennawi, Joseph F.; Mahabal, Ashish A.; Richards, Gordon T.

    2016-06-01

    We present by far the largest sample of spectroscopically confirmed binaryquasars with proper transverse separations of 17.0 ≤ Rprop ≤ 36.6 h-1 kpc. Our sample, whichis an order-of-magnitude larger than previous samples, is selected from Sloan Digital Sky Survey (SDSS) imaging over an area corresponding to the SDSS 6th data release (DR6). Our quasars are targeted using a Kernel Density Estimation technique (KDE), and confirmed using long-slit spectroscopy on a range of facilities.Our most complete sub-sample of 44 binary quasars with g<20.85, extends across angular scales of 2.9" < Δθ < 6.3", and is targeted from a parent sample that would be equivalent to a full spectroscopic survey of nearly 300,000 quasars.We determine the projected correlation function of quasars (\\bar Wp) over proper transverse scales of 17.0 ≤ Rprop ≤ 36.6 h-1 kpc, and also in 4 bins of scale within this complete range.To investigate the redshift evolution of quasar clustering on small scales, we make the first self-consistent measurement of the projected quasar correlation function in 4 bins of redshift over 0.4 ≤ z ≤ 2.3.

  9. Calibrating the Galaxy Halo - Black Hole Relation Based on the Clustering of Quasars

    CERN Document Server

    Wyithe, S; Wyithe, Stuart; Loeb, Abraham

    2004-01-01

    The observed number counts of quasars may be explained either by long-lived activity within rare massive hosts, or by short-lived activity within smaller, more common hosts. It has been argued that quasar lifetimes may therefore be inferred from their clustering length, which determines the typical mass of the quasar host. Here we point out that the relationship between the mass of the black-hole and the circular velocity of its host dark-matter halo is more fundamental to the determination of the clustering length. In particular, the clustering length observed in the 2dF quasar redshift survey is consistent with the galactic halo - black-hole relation observed in local galaxies, provided that quasars shine at ~10-100% of their Eddington luminosity. The slow evolution of the clustering length with redshift inferred in the 2dF quasar survey favors a black-hole mass whose redshift-independent scaling is with halo circular velocity, rather than halo mass. These results are independent from observations of the nu...

  10. A Description of Quasar Variability Measured Using Repeated SDSS and POSS Imaging

    CERN Document Server

    MacLeod, Chelsea L; Sesar, Branimir; de Vries, Wim; Kochanek, Christopher S; Kelly, Brandon C; Becker, Andrew C; Lupton, Robert H; Hall, Patrick B; Richards, Gordon T; Anderson, Scott F; Schneider, Donald P

    2011-01-01

    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 34,727 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. The observed time lags span the range from a day to almost 10 years, and constrain quasar variability at rest-frame time lags of up to 4 years, and at rest-frame wavelengths from 1000A to 6000A. We publicly release a user-friendly catalog of quasars from the SDSS Data Release 7 that have been observed at least twice in SDSS or once in both SDSS and the Palomar Observatory Sky Survey, and we use it to analyze the ensemble properties of quasar variability. Based on a damped random walk (DRW) model defined by a characteristic time scale and an asymptotic variabilit...

  11. Counting quasar--radio source pairs to derive the millijansky radio luminosity function and clustering strength to z=3.5

    CERN Document Server

    Fine, S; Johnston, R; Jarvis, M J; Mauch, T

    2015-01-01

    We apply a cross-correlation technique to infer the $S>3$mJy radio luminosity function (RLF) from the NRAO VLA sky survey (NVSS) to $z\\sim3.5$. We measure $\\Sigma$ the over density of radio sources around spectroscopically confirmed quasars. $\\Sigma$ is related to the space density of radio sources at the distance of the quasars and the clustering strength between the two samples, hence knowledge of one constrains the other. Under simple assumptions we find $\\Phi\\propto (1+z)^{3.7\\pm0.7}$ out to $z\\sim2$. Above this redshift the evolution slows and we constrain the evolution exponent to $<1.01$ ($2\\sigma$). This behaviour is almost identical to that found by previous authors for the bright end of the RLF potentially indicating that we are looking at the same population. This suggests that the NVSS is dominated by a single population; most likely radio sources associated with high-excitation cold-mode accretion. Inversely, by adopting a previously modelled RLF we can constrain the clustering of high-redshif...

  12. Measuring the dark energy with quasar clustering

    CERN Document Server

    Calvão, M O; Waga, I

    2002-01-01

    We show, through Monte Carlo simulations, that the Alcock-Pazynski test, as applied to quasar clustering, is a powerful tool to probe the cosmological density and equation of state parameters, Omega_{m0}, Omega_{x0} and w. By taking into account peculiar velocity corrections to the correlation function we obtain, for the Two-Degree Field QSO Redshift Survey (2QZ), the predicted 1\\sigma and 2\\sigma confidence contours. It turns out that the test is competitive with future supernova and galaxy number count ones, besides being complementary to them, for fixed curvature. In particular, we find out that it is especially sensitive to the difference Omega_{m0}-Omega_{Lambda 0}, thus being ideal to combine with CMB results.

  13. Burkina Faso - BRIGHT II

    Data.gov (United States)

    Millenium Challenge Corporation — Millennium Challenge Corporation hired Mathematica Policy Research to conduct an independent evaluation of the BRIGHT II program. The three main research questions...

  14. Flamingos 2 Spectroscopy of Obscured and Unobscured Quasars

    Science.gov (United States)

    Ridgway, Susan; Lacy, Mark; Urrutia, Tanya; Petric, Andreea

    2013-08-01

    We will use Flamingos-2 to obtain spectra of luminous AGN and quasars selected in the mid-infrared. Mid-infrared selection is much less biased with respect to obscuration than optical and X-ray techniques, and hence allows for finding obscured (Type-2) quasars as well as Type-1 quasars. Our survey so far has been very successful and has provided an unique opportunity to construct luminosity functions for both Type-1 and Type-2 quasars selected in the same way and covering similar redshifts and luminosities. We have quantifed the change in the obscured fraction with luminosity and redshift for the first time, and find interesting indications that at high redshift the obscured fraction rises, consistent with models for the joint formation of the galaxy and black hole populations. Our samples are, however, still quite incomplete at low fluxes (and therefore lower luminosities at a given redshift), particularly in the southern hemisphere. Near-infrared spectroscopy, such as that we have previously obtained with NIRI at Gemini N, offers us the best possibility of bringing these southern samples to a reasonable completeness level, and will greatly increase the number of high z quasars in our sample. This will allow us to better judge our tantalizing initial results on the redshift evolution of the obscured fraction. In addition, these southern targets can be followed up with ALMA and GEMS/GSAOI to study the morphologies and star-formation properties of the hosts, allowing further exploration of the relationship between the formation of massive bulges and supermassive blackholes in the early universe.

  15. The 2QDES Pilot : The luminosity and redshift dependence of quasar clustering

    CERN Document Server

    Chehade, Ben; Findlay, J; Metcalfe, N; Sawangwit, U; Irwin, M; González-Solares, E; Fine, S; Drinkwater, M J; Croom, S; Jurek, R J; Parkinson, D; Bielby, R

    2016-01-01

    We present a new redshift survey, the 2dF Quasar Dark Energy Survey pilot (2QDESp), which consists of ${\\approx}10000$ quasars from ${\\approx}150$ deg$^2$ of the southern sky, based on VST-ATLAS imaging and 2dF/AAOmega spectroscopy. Combining our optical photometry with the WISE (W1,W2) bands we can select essentially contamination free quasar samples with $0.8{<}z{<}2.5$ and $g{<}20.5$. At fainter magnitudes, optical UVX selection is still required to reach our $g{\\approx}22.5$ limit. Using both these techniques we observed quasar redshifts at sky densities up to $90$ deg$^{-2}$. By comparing 2QDESp with other surveys (SDSS, 2QZ and 2SLAQ) we find that quasar clustering is approximately luminosity independent, with results for all four surveys consistent with a correlation scale of $r_{0}{=}6.1{\\pm}0.1 \\: h^{-1}$Mpc, despite their decade range in luminosity. We find a significant redshift dependence of clustering, particularly when BOSS data with $r_{0}{=}7.3{\\pm}0.1 \\: h^{-1}$Mpc are included at $z...

  16. An X-ray and Multiwavelength Survey of Highly Radio-Loud Quasars at z > 4: Jet-Linked Emission in the Brightest Radio Beacons of the Early Universe

    CERN Document Server

    Wu, Jianfeng; Miller, Brendan P; Garmire, Gordon P; Schneider, Donald P; Vignali, Cristian

    2013-01-01

    (Abridged) We present a systematic study of the X-ray and multiwavelength properties of a sample of 17 highly radio-loud quasars (HRLQs) at z > 4 with sensitive X-ray coverage from new Chandra and archival Chandra, XMM-Newton, and Swift observations. Eight of the new and archival observations are reported in this work for the first time. New Chandra observations of two moderately radio-loud and highly optically luminous quasars at z > 4 are also reported. Our HRLQ sample represents the top ~5% of radio-loud quasars in terms of radio loudness. We found that our HRLQs have an X-ray emission enhancement over HRLQs at lower redshifts (by a typical factor of ~3), and this effect, after controlling for several factors which may introduce biases, has been solidly estimated to be significant at the 3-4 sigma level. HRLQs at z=3-4 are also found to have a similar X-ray emission enhancement over z < 3 HRLQs, which supports further the robustness of our results. We discuss models for the X-ray enhancement's origin in...

  17. CARMA SURVEY TOWARD INFRARED-BRIGHT NEARBY GALAXIES (STING). II. MOLECULAR GAS STAR FORMATION LAW AND DEPLETION TIME ACROSS THE BLUE SEQUENCE

    Energy Technology Data Exchange (ETDEWEB)

    Rahman, Nurur; Bolatto, Alberto D.; Fisher, David B.; Vogel, Stuart N. [Department of Astronomy, University of Maryland, College Park, MD (United States); Xue Rui; Wong, Tony [Department of Astronomy, University of Illinois, Urbana-Champaign, IL (United States); Leroy, Adam K. [National Radio Astronomy Observatory, Charlottesville, VA (United States); Walter, Fabian [Max-Planck-Institute fur Astronomie, Heidelberg (Germany); Bigiel, Frank [Institut fuer Theoretische Astrophysik, Universitaet Heidelberg, D-69120 Heidelberg (Germany); Rosolowsky, Erik [I. K. Barber School of the Arts and Science, University of British-Columbia, Kelowna, BC (Canada); Blitz, Leo [Department of Astronomy, University of California, Berkeley, CA (United States); West, Andrew A. [Department of Astronomy, Boston University, Boston, MA (United States); Ott, Juergen, E-mail: nurur@astro.umd.edu [National Radio Astronomy Observatory, Socorro, NM (United States)

    2012-02-01

    We present an analysis of the relationship between molecular gas and current star formation rate surface density at sub-kiloparsec and kiloparsec scales in a sample of 14 nearby star-forming galaxies. Measuring the relationship in the bright, high molecular gas surface density ({Sigma}{sub H{sub 2}}{approx}>20 M{sub Sun} pc{sup -2}) regions of the disks to minimize the contribution from diffuse extended emission, we find an approximately linear relation between molecular gas and star formation rate surface density, N{sub mol} {approx} 0.96 {+-} 0.16, with a molecular gas depletion time, {tau}{sup mol}{sub dep} {approx} 2.30 {+-} 1.32 Gyr. We show that in the molecular regions of our galaxies there are no clear correlations between {tau}{sup mol}{sub dep} and the free-fall and effective Jeans dynamical times throughout the sample. We do not find strong trends in the power-law index of the spatially resolved molecular gas star formation law or the molecular gas depletion time across the range of galactic stellar masses sampled (M{sub *} {approx} 10{sup 9.7}-10{sup 11.5} M{sub Sun }). There is a trend, however, in global measurements that is particularly marked for low-mass galaxies. We suggest that this trend is probably due to the low surface brightness CO J = 1-0, and it is likely associated with changes in CO-to-H{sub 2} conversion factor.

  18. The double quasar 0957 + 561 AB as a probe of quasar structure

    International Nuclear Information System (INIS)

    If the individual components of the double quasar exhibit uncorrelated time-variations, it will become possible to estimate the size and number of clouds in the region of the quasar in which the emission lines are formed. (author)

  19. The DESI Experiment Part I: Science,Targeting, and Survey Design

    CERN Document Server

    Aghamousa, Amir; Ahlen, Steve; Alam, Shadab; Allen, Lori E; Prieto, Carlos Allende; Annis, James; Bailey, Stephen; Balland, Christophe; Ballester, Otger; Baltay, Charles; Beaufore, Lucas; Bebek, Chris; Beers, Timothy C; Bell, Eric F; Bernal, José Luis; Besuner, Robert; Beutler, Florian; Blake, Chris; Bleuler, Hannes; Blomqvist, Michael; Blum, Robert; Bolton, Adam S; Briceno, Cesar; Buckley-Geer, Elizabeth; Burden, Angela; Burtin, Etienne; Busca, Nicolas G; Cahn, Robert N; Cai, Yan-Chuan; Carlberg, Raymond G; Carton, Pierre-Henri; Casas, Ricard; Castander, Francisco J; Claybaugh, Todd M; Close, Madeline; Coker, Carl T; Cole, Shaun; Cooper, Andrew P; Cousinou, M -C; Crocce, Martin; Cuby, Jean-Gabriel; Cunningham, Daniel P; Davis, Tamara; Dawson, Kyle S; de la Macorra, Axel; De Vicente, Juan; Delubac, Timothée; Derwent, Mark; Dey, Arjun; Dhungana, Govinda; Ding, Zhejie; Duan, Yutong T; Ealet, Anne; Edelstein, Jerry; Eftekharzadeh, Sarah; Eisenstein, Daniel J; Elliott, Ann; Escoffier, Stephanie; Evatt, Matthew; Fagrelius, Parker; Fan, Xiaohui; Fanning, Kevin; Farahi, Arya; Favole, Ginevra; Feng, Yu; Fernandez, Enrique; Findlay, Joseph R; Finkbeiner, Douglas P; Fitzpatrick, Michael J; Flaugher, Brenna; Flender, Samuel; Font-Ribera, Andreu; Forero-Romero, Jaime E; Fosalba, Pablo; Frenk, Carlos S; Fumagalli, Michele; Garcia-Bellido, Juan; Gaztanaga, Enrique; Gershkovich, Irina; Gillet, Denis; Gonzalez-de-Rivera, Guillermo; Gonzalez-Perez, Violeta; Gott, Shelby; Graur, Or; Gutierrez, Gaston; Guy, Julien; Habib, Salman; Heetderks, Henry; Heetderks, Ian; Heitmann, Katrin; Hellwing, Wojciech A; Herrera, David A; Ho, Shirley; Honscheid, Klaus; Huff, Eric; Hutchinson, Timothy A; Huterer, Dragan; Hwang, Ho Seong; Laguna, Joseph Maria Illa; Ishikawa, Yuzo; Jacobs, Dianna; Jeffrey, Niall; Jelinsky, Patrick; Jiang, Linhua; Jimenez, Jorge; Johnson, Jennifer; Joyce, Richard; Jullo, Eric; Juneau, Stephanie; Kama, Sami; Karcher, Armin; Karkar, Sonia; Kehoe, Robert; Kennamer, Noble; Kent, Stephen; Kilbinger, Martin; Kim, Alex G; Kirkby, David; Kisner, Theodore; Kitanidis, Ellie; Kneib, Jean-Paul; Koposov, Sergey; Kovacs, Eve; Kremin, Anthony; Kron, Richard; Kronig, Luzius; Kueter-Young, Andrea; Lacey, Cedric G; Lafever, Robin; Lahav, Ofer; Lambert, Andrew; Landriau, Martin; Lang, Dustin; Name, Publication; Lauer, Tod R; Goff, Jean-Marc Le; Guillou, Laurent Le; Van Suu, Auguste Le; Lee, Jae Hyeon; Lee, Su-Jeong; Leitner, Daniela; Levi, Michael E; L'Huillier, Benjamin; Li, Baojiu; Liang, Ming; Lin, Huan; Linder, Eric; Loebman, Sarah R; Lukić, Zarija; MacCrann, Niall; Magneville, Christophe; Makarem, Laleh; Manera, Marc; Manser, Christopher J; Marshall, Robert; Martini, Paul; Massey, Richard; Matheson, Thomas; McCauley, Jeremy; McDonald, Patrick; McGreer, Ian D; Meisner, Aaron; Metcalfe, Nigel; Miller, Timothy N; Miquel, Ramon; Moustakas, John; Myers, Adam; Naik, Milind; Newman, Jeffrey; Nichol, Robert C; Nicola, Andrina; da Costa, Luiz Nicolati; Niz, Gustavo; Norberg, Peder; Nord, Brian; Norman, Dara; Nugent, Peter; O'Brien, Thomas; Oh, Minji; Olsen, Knut A G; Padilla, Cristobal; Padmanabhan, Hamsa; Padmanabhan, Nikhil; Palanque-Delabrouille, Nathalie; Palmese, Antonella; Pappalardo, Daniel; Park, Changbom; Patej, Anna; Peacock, John A; Peiris, Hiranya V; Percival, Will J; Perruchot, Sandrine; Pieri, Matthew M; Pogge, Richard; Poppett, Claire; Probst, Ronald G; Rabinowitz, David; Ree, Chang Hee; Refregier, Alexandre; Regal, Xavier; Reid, Beth; Reil, Kevin; Rezaie, Mehdi; Rockosi, Connie; Roe, Natalie; Ronayette, Samuel; Roodman, Aaron; Ross, Ashley J; Ross, Nicholas P; Rossi, Graziano; Rozo, Eduardo; Ruhlmann-Kleider, Vanina; Rykoff, Eli; Sabiu, Cristiano; Samushia, Lado; Sanchez, Javier; Schlegel, David J; Schneider, Michael; Schubnell, Michael; Secroun, Aurélia; Seljak, Uros; Seo, Hee-Jong; Serrano, Santiago; Shafieloo, Arman; Shan, Huanyuan; Sholl, Michael J; Shourt, William V; Silber, Joseph H; Silva, David R; Sirk, Martin M; Slosar, Anze; Smith, Alex; Smoot, George; Som, Debopam; Song, Yong-Seon; Sprayberry, David; Staten, Ryan; Stefanik, Andy; Tarle, Gregory; Tie, Suk Sien; Tinker, Jeremy L; Tojeiro, Rita; Valdes, Francisco; Valenzuela, Octavio; Valluri, Monica; Vargas-Magana, Mariana; Verde, Licia; Walker, Alistair R; Wang, Yuting; Weaver, Benjamin A; Weaverdyck, Curtis; Wechsler, Risa; Weinberg, David H; White, Martin; Yang, Qian; Yeche, Christophe; Zhao, Gong-Bo; Zheng, Yi; Zhu, Yaling; Zou, Hu; Zu, Ying

    2016-01-01

    DESI (Dark Energy Spectroscopic Instrument) is a Stage IV ground-based dark energy experiment that will study baryon acoustic oscillations (BAO) and the growth of structure through redshift-space distortions with a wide-area galaxy and quasar redshift survey. To trace the underlying dark matter distribution, spectroscopic targets will be selected in four classes from imaging data. We will measure luminous red galaxies up to $z=1.0$. To probe the Universe out to even higher redshift, DESI will target bright [O II] emission line galaxies up to $z=1.7$. Quasars will be targeted both as direct tracers of the underlying dark matter distribution and, at higher redshifts ($ 2.1 < z < 3.5$), for the Ly-$\\alpha$ forest absorption features in their spectra, which will be used to trace the distribution of neutral hydrogen. When moonlight prevents efficient observations of the faint targets of the baseline survey, DESI will conduct a magnitude-limited Bright Galaxy Survey comprising approximately 10 million galaxie...

  20. A systematic search for changing-look quasars in SDSS

    Science.gov (United States)

    MacLeod, Chelsea L.; Ross, Nicholas P.; Lawrence, Andy; Goad, Mike; Horne, Keith; Burgett, William; Chambers, Ken C.; Flewelling, Heather; Hodapp, Klaus; Kaiser, Nick; Magnier, Eugene; Wainscoat, Richard; Waters, Christopher

    2016-03-01

    We present a systematic search for changing-look quasars based on repeat photometry from Sloan Digital Sky Survey (SDSS) and Pan-STARRS1, along with repeat spectra from SDSS and SDSS-III Baryon Oscillation Spectroscopic Survey. Objects with large, |Δg| > 1 mag photometric variations in their light curves are selected as candidates to look for changes in broad emission line (BEL) features. Out of a sample of 1011 objects that satisfy our selection criteria and have more than one epoch of spectroscopy, we find 10 examples of quasars that have variable and/or `changing-look' BEL features. Four of our objects have emerging BELs, five have disappearing BELs, and one object shows tentative evidence for having both emerging and disappearing BELs. With redshifts in the range 0.20 15 per cent of strongly variable luminous quasars display changing-look BEL features on rest-frame time-scales of 8 to 10 yr. Plausible time-scales for variable dust extinction are factors of 2-10 too long to explain the dimming and brightening in these sources, and simple dust reddening models cannot reproduce the BEL changes. On the other hand, an advancement such as disc reprocessing is needed if the observed variations are due to accretion rate changes.

  1. Decoding quasars: gravitationally redshifted spectral lines !

    CERN Document Server

    Kantharia, Nimisha G

    2016-01-01

    Further investigation of data on quasars, especially in the ultraviolet band, yields an amazingly coherent narrative which we present in this paper. Quasars are characterised by strong continuum emission and redshifted emission and absorption lines which includes the famous Lyman $\\alpha$ forest. We present irrefutable evidence in support of (1) the entire line spectrum arising in matter located inside the quasar system, (2) the range of redshifts shown by the lines being due to the variable contribution of the gravitational redshift in the observed line velocity, (3) existence of rotating black holes and of matter inside its ergosphere, (4) quasars located within cosmological redshifts $\\sim 3$, (5) $\\gamma$ ray bursts being explosive events in a quasar. These results are significant and a game-changer when we realise that the absorbing gas has been postulated to exist along the line-of-sight to the quasar and observations have accordingly been interpreted. In light of these definitive results which uniquely...

  2. Herschel observed Stripe 82 quasars and their host galaxies: connections between the AGN activity and the host galaxy star formation

    CERN Document Server

    Dong, Xiaoyi

    2016-01-01

    In this work, we present a study of 207 quasars selected from the Sloan Digital Sky Survey quasar catalogs and the Herschel Stripe 82 survey. Quasars within this sample are high luminosity quasars with a mean bolometric luminosity of $10^{46.4}$ erg s$^{-1}$. The redshift range of this sample is within $z<4$, with a mean value of $1.5\\pm0.78$. Because we only selected quasars that have been detected in all three Herschel-SPIRE bands, the quasar sample is complete yet highly biased. Based on the multi-wavelength photometric observation data, we conducted a spectral energy distribution (SED) fitting through UV to FIR. Parameters such as active galactic nucleus (AGN) luminosity, FIR luminosity, stellar mass, as well as many other AGN and galaxy properties are deduced from the SED fitting results. The mean star formation rate (SFR) of the sample is 419 $M_{\\odot}$ yr$^{-1}$ and the mean gas mass is $\\sim 10^{11.3}$ $M_{\\odot}$. All these results point to an IR luminous quasar system. Comparing with star format...

  3. Discovery of universal outflow structures above and below the accretion disc plane in radio-quiet quasars

    Science.gov (United States)

    Lovegrove, Justin; Schild, Rudolph E.; Leiter, Darryl

    2011-04-01

    59 quasars in the background of the Magellanic Clouds had brightness records monitored by the MACHO project during the years 1992-99. Because the circumpolar fields of these quasars had no seasonal sampling defects, their observation produced data sets well suited to further careful analysis. Following a preliminary report wherein we showed the existence of reverberation in the data for one of the radio-quiet quasars in this group, we now show that similar reverberations have been seen in all of the 55 radio-quiet quasars with adequate data, making possible the determination of the quasar inclination to the observer's line of sight. The reverberation signatures indicate the presence of large-scale elliptical outflow structures similar to that predicted by the Elvis and 'dusty torus' models of quasars, whose characteristic sizes vary within a surprisingly narrow range of scales. More importantly, the observed opening angle relative to the polar axis of the universal elliptical outflow structure present was consistently found to be on the order of 78°.

  4. Constraining the lifetime and opening angle of quasars using fluorescent Ly a emission: the case of Q0420-388

    CERN Document Server

    Borisova, Elena; Cantalupo, Sebastiano; Prochaska, J Xavier; Rakic, Olivera; Worseck, Gabor

    2015-01-01

    A toy model is developed to understand how the spatial distribution of fluorescent emitters in the vicinity of bright quasars could be affected by the geometry of the quasar bi-conical radiation field and by the quasar lifetime. We then compare the predictions of this model to a sample of high equivalent width Ly a emitters (EW0 > 100 A) that were identified in a deep narrow-band 36x36 arcmin2 image centered on the luminous quasar Q0420-388. These are identified to the edge of the field and show some evidence of an azimuthal asymmetry on the sky of the type expected if the quasar is radiating in a bipolar cone. If these sources are being fluorescently illuminated by the quasar, then the two most distant sources require a lifetime of at least 15 Myr for an opening angle of 60 degrees or more, increasing to more than 40 Myr if the opening angle is reduced to a minimum 30 degrees. The overall distribution of all of the sources across the field gives best fit lifetimes in the range 20 < t < 50 Myr for openi...

  5. Radio Structures of Compact Quasars with Broad Absorption Lines

    Science.gov (United States)

    Kunert-Bajraszewska, Magdalena; Gawroński, Marcin P.

    2010-05-01

    Broad absorption lines (BALs), seen in a small fraction of both the radio-quiet and radio-loud quasar populations, are probably caused by the outflow of gas with high velocities and are part of the accretion process. The presence of BALs is due to a geometrical effect and/or it is connected with the quasar evolution. Using the final release of FIRST survey combined with a catalog of BAL QSOs from SDSS/DR3, we have constructed a new sample of compact radio-loud BAL QSOs, which constitutes the majority of radio-loud BAL QSOs. The main goal of this project is to study the origin of BALs by analysis of the BAL QSOs radio morphology, orientation, and jet evolution using the European VLBI Network (EVN) at 1.6 GHz and the Very Long Baseline Array (VLBA) at 5 and 8.4 GHz.

  6. The UVX quasar optical luminosity function and its evolution

    CERN Document Server

    Goldschmidt, P; Goldschmidt, Pippa; Miller, Lance

    1997-01-01

    The recently-finished Edinburgh UVX quasar survey at B < 18 is used together with other complete samples to estimate the shape and evolution of the optical luminosity function in the redshift range 0.3 < z < 2.2. There is a significantly higher space density of quasars at high luminosity and low redshift than previously found in the PG sample of Schmidt \\& Green (1983), with the result that the shape of the luminosity function at low redshifts (z < 1) is seen to be consistent with a single power-law. At higher redshifts the slope of the power-law at high luminosities appears to steepen significantly. There does not appear to be any consistent break feature which could be used as a tracer of luminosity evolution in the population.

  7. TYPE 1 AND TYPE 2 QUASARS IN THE MID-INFRARED

    Directory of Open Access Journals (Sweden)

    S. E. Ridgway

    2009-01-01

    Full Text Available Type 2 or \\obscured" AGN have long been identi ed at low AGN luminosities (e.g. Seyfert 2s or through their radio luminosities (e.g. radio galaxies. But radio-quiet quasars (RQQs are many times more common than radio-loud quasars, and it's therefore unsurprising that recent searches have revealed that radio-quiet quasar 2s also form a signi cant population. Finding the numbers, properties, and redshift distribution of quasar 2s will be very important to resolving questions about the formation and co-evolution of black holes and galaxies. We have selected a sample of Type 2 and Type 1 quasars matched in their mid-infrared luminosity from the Spitzer First Look Survey by selecting on their mid-infrared dust emission properties (as measured by Spitzer IRAC photometry. This emission provides a distinctive signature of AGN activity but should not be a cted by orientation or torus opening angle. We have obtained mid-infrared IRS spectroscopy of these samples to study star formation activity in the host galaxies and the dust environments of the AGN, using measurements of the PAH features, the shape of the mid-infrared SED, and the equivalent width of the silicate features at 10 microns. We nd that the quasar 2s have more diverse mid-IR spectral properties, and that obscuration of the AGN is linked to star formation activity in the host.

  8. The Link Between UV and X-ray Emission in Quasars

    Science.gov (United States)

    Coffey, D.; Salvato, M.; Merloni, A.; Boller, T.; Nandra, K.

    2016-08-01

    Quasars are well known to exhibit a non-linear relationship between the UV emission from their accretion disks and the X-ray emission from the surrounding corona. This relationship has recently been used to include quasars as standard candles in a Hubble diagram in order to estimate the cosmological parameters ΩM and ΩΛ (Risaliti and Lusso 2015). This project aims to improve this method by adding a large sample of quasars detected by ROSAT. These sources have been matched to UV and IR counterparts using GALEX and WISE data, and have optical spectra available from the Sloan Digital Sky Survey, which resulted in a catalogue of 5500 sources in the redshift range 0 ≤ z ≤ 2. This project will investigate whether the L(X-ray) - L(UV) relationship is universal to quasars of all types. Optical spectra and spectral energy distribution fitting will be used to test the L(X-ray) - L(UV) relationship for signs of evolution with quasar properties such as redshift, black hole mass, and Eddington ratio. A large number of sources from this sample will be added to the Hubble diagram in the redshift range currently populated by type 1a supernovae (z ≤ 1.4). This will allow the cosmological parameter results obtained from quasars to be compared directly with those obtained from supernovae.

  9. SDSSJ102111.02+491330.4: A Newly Discovered Gravitationally Lensed Quasar

    CERN Document Server

    Pindor, B; Gregg, M D; Becker, R H; Inada, N; Oguri, M; Hall, P B; Johnston, D E; Richards, G T; Schneider, D P; Turner, E L; Brasi, G; Hinz, P M; Kenworthy, M A; Miller, D; Barentine, J C; Brewington, H J; Brinkmann, J; Harvanek, M; Kleinman, S J; Krzesínski, J; Long, D; Neilsen, E H; Newman, P R; Nitta, A; Snedden, S A; York, D G; Pindor, Bart; Eisenstein, Daniel J.; Gregg, Michael D.; Becker, Robert H.; Inada, Naohisa; Oguri, Masamune; Hall, Patrick B.; Johnston, David E.; Richards, Gordon T.; Schneider, Donald P.; Turner, Edwin L.; Brasi, Guido; Hinz, Philip M.; Kenworthy, Matthew A.; Miller, Doug; Brewington, Howard J.; Harvanek, Michael; Krzesinski, Jurek; Long, Dan; Neilsen, Eric H.; Newman, Peter R.; Nitta, Atsuko; Snedden, Stephanie A.; York, Donald G.

    2006-01-01

    We report follow-up observations of two gravitational lens candidates identified in the Sloan Digital Sky Survey (SDSS) dataset. We have confirmed that SDSS J102111.02+491330.4 is a previously unknown gravitationally lensed quasar. This lens system exhibits two images of a $z = 1.72$ quasar, with an image separation of $1{\\farcs}14 \\pm 0.04$. Optical and near-IR imaging of the system reveals the presence of the lensing galaxy between the two quasar images. Observations of SDSS J112012.12+671116.0 indicate that it is more likely a binary quasar than a gravitational lens. This system has two quasars at a redshift of $z = 1.49$, with an angular separation of $1{\\farcs}49 \\pm 0.02$. However, the two quasars have markedly different SEDs and no lens galaxy is apparent in optical and near-IR images of this system. We also present a list of 31 SDSS lens candidates which follow-up observations have confirmed are \\textit{not} gravitational lenses.

  10. A Glimpse at Quasar Host Galaxy Far-UV Emission, Using DLAs as Natural Coronagraphs

    CERN Document Server

    Cai, Zheng; Noterdaeme, Pasquier; Wang, Ran; McGreer, Ian; Carithers, Bill; Bian, Fuyan; Escude, Jordi Miralda; Finley, Hayley; Paris, Isabelle; Schneider, Donald P; Zakamska, Nadia L; Ge, Jian; Petitjean, Patrick; Slosar, Anze

    2014-01-01

    In merger-driven models of massive galaxy evolution, the luminous quasar phase is expected to be accompanied by vigorous star formation in quasar host galaxies. In this paper, we use high column density Damped Lyman Alpha (DLA) systems along quasar sight lines as natural coronagraphs to directly study the far-UV (FUV) radiation from the host galaxies of luminous background quasars. We have stacked the spectra of $\\sim$2,000 DLA systems (N_HI>10^{20.6} cm^{-2}) with a median absorption redshift = 2.6 selected from quasars observed in the SDSS-III Baryon Oscillation Spectroscopic Survey. We detect residual flux in the dark troughs of the composite DLA spectra. The level of this residual flux significantly exceeds systematic errors in the SDSS fiber sky subtraction; furthermore, the residual flux is strongly correlated with the continuum luminosity of the background quasar, while uncorrelated with DLA column density or metallicity. We conclude that the flux could be associated with the average FUV radiation fro...

  11. SDSS J102111.02+491330.4: A Newly discovered gravitationally lensed quasar

    Energy Technology Data Exchange (ETDEWEB)

    Pindor, Bart; Eisenstein, Daniel J.; Gregg, Michael D.; Becker, Robert H.; Inada, Naohisa; Oguri, Masamune; Hall, Patrick B.; Johnston, David E.; Richards, Gordon T.; Schneider, Donald P.; Turner, Edwin L.; Brasi, Guido; Hinz, Philip M.; Kenworthy, Matthew A.; Miller, Doug; Barentine, J.C.; Brewington, Howard J.; Brinkmann, J.; Harvanek,; Kleinman, S.J.; Krzesinski, Jurek; /Toronto U., Astron. Dept. /Arizona U., Astron. Dept. - Steward Observ. /UC, Davis /LLNL, Livermore /Tokyo U., Inst. Astron. /Tokyo U.

    2005-09-01

    We report follow-up observations of two gravitational lens candidates identified in the Sloan Digital Sky Survey (SDSS) dataset. We have confirmed that SDSS J102111.02+491330.4 is a previously unknown gravitationally lensed quasar. This lens system exhibits two images of a z = 1.72 quasar, with an image separation of 1.14'' {+-} 0.04''. Optical and near-IR imaging of the system reveals the presence of the lensing galaxy between the two quasar images. Observations of SDSS J112012.12+671116.0 indicate that it is more likely a binary quasar than a gravitational lens. This system has two quasars at a redshift of z = 1.49, with an angular separation of 1.49'' {+-} 0.02''. However, the two quasars have markedly different SEDs and no lens galaxy is apparent in optical and near-IR images of this system. We also present a list of 31 SDSS lens candidates which follow-up observations have confirmed are not gravitational lenses.

  12. SDSSJ102111.02+491330.4: A Newly Discovered Gravitationally Lensed Quasar

    Energy Technology Data Exchange (ETDEWEB)

    Pindor, B; Eisenstein, D J; Gregg, M D; Becker, R H; Inada, N; Oguri, M; Hall, P B; Johnston, D E; Richards, G T; Schneider, D P; Turner, E L; Brasi, G; Hinz, P M; Kenworthy, M A; Miller, D; Barentine, J C; Brewington, H J; Brinkmann, J; Harvanek, M; Kleinman, S J; Krzesinski, J; Long, D; Neilsen Jr., E H; Newman, P R; Nitta, A; Snedden, S A; York, D G

    2005-11-10

    We report follow-up observations of two gravitational lens candidates identified in the Sloan Digital Sky Survey (SDSS) dataset. We have confirmed that SDSS J102111.02+491330.4 is a previously unknown gravitationally lensed quasar. This lens system exhibits two images of a z = 1.72 quasar, with an image separation of 1''.14 {+-} 0.04. Optical and near-IR imaging of the system reveals the presence of the lensing galaxy between the two quasar images. Observations of SDSS J112012.12+671116.0 indicate that it is more likely a binary quasar than a gravitational lens. This system has two quasars at a redshift of z = 1.49, with an angular separation of 1''.49 {+-} 0.02. However, the two quasars have markedly different SEDs and no lens galaxy is apparent in optical and near-IR images of this system. We also present a list of 31 SDSS lens candidates which follow-up observations have confirmed are not gravitational lenses.

  13. Various Approaches for Targeting Quasar Candidates

    Science.gov (United States)

    Zhang, Y.; Zhao, Y.

    2015-09-01

    With the establishment and development of space-based and ground-based observational facilities, the improvement of scientific output of high-cost facilities is still a hot issue for astronomers. The discovery of new and rare quasars attracts much attention. Different methods to select quasar candidates are in bloom. Among them, some are based on color cuts, some are from multiwavelength data, some rely on variability of quasars, some are based on data mining, and some depend on ensemble methods.

  14. Orbital and physical parameters of eclipsing binaries from the All-Sky Automated Survey catalogue - VI. AK Fornacis - a rare, bright K-type eclipsing binary

    CERN Document Server

    Hełminiak, K G; Ratajczak, M; Espinoza, N; Jordán, A; Konacki, M; Rabus, M

    2014-01-01

    We present the results of the combined photometric and spectroscopic analysis of a bright (V=9.14), nearby (d=31 pc), late-type detached eclipsing binary AK Fornacis. This P=3.981 d system has not been previously recognised as a double-lined spectroscopic binary, and this is the first full physical model of this unique target. With the FEROS, CORALIE and HARPS spectrographs we collected a number of high-resolution spectra in order to calculate radial velocities of both components of the binary. Measurements were done with our own disentangling procedure and the TODCOR technique, and were later combined with the photometry from the ASAS and SuperWASP archives. We also performed an atmospheric analysis of the component spectra with the Spectroscopy Made Easy (SME) package. Our analysis shows that AK For consists of two active, cool dwarfs having masses of $M_1=0.6958 \\pm 0.0010$ and $M_2=0.6355 \\pm 0.0007$ M$_\\odot$ and radii of $R_1=0.687 \\pm 0.020$ and $R_2=0.609 \\pm 0.016$ R$_\\odot$, slightly less metal abun...

  15. Chandra Finds Well-Established Black Holes In Distant Quasars

    Science.gov (United States)

    2002-03-01

    Pushing further back toward the first generation of objects to form in the universe, NASA's Chandra X-ray Observatory has observed the three most distant known quasars and found them to be prodigious producers of X-rays. This indicates that the supermassive black holes powering them were already in place when the Universe was only about one billion years old. "Chandra's superb sensitivity has allowed the detection of X-rays from the dawn of the modern universe, when the first massive black holes and galaxies were forming," said Niel Brandt of Penn State University, leader of one the teams involved. "These results indicate that future X-ray surveys should be able to detect the first black holes to form in the Universe." The three quasars were recently discovered at optical wavelengths by the Sloan Digital Sky Survey and are 13 billion light years from Earth, making them the most distant known quasars. The X-rays Chandra detected were emitted when the universe was only a billion years old, about 7 percent of the present age of the Universe. Since X-rays reveal conditions in the immediate vicinity of supermassive black holes, Brandt proposed that Chandra look at these objects in three snapshots of about two hours each to see if they were different from their older counterparts. The observations on January 29, 2002 were made public immediately and the four different teams quickly went to work on them. Brandt's team concluded that the quasars looked similar to ones that were at least twice as old, so the conditions around the central black hole had not changed much in that time, contrary to some theoretical expectations. A team led by Smita Mathur of Ohio State University reached a similar conclusion. "These young quasars do not appear to be any different from their older cousins, based upon our current understanding and assumptions," said Mathur. "Perhaps the most remarkable thing about them may be that they are so absolutely unremarkable." Jill Bechtold of the

  16. How Similar are the Properties of Quasars with Nearly Identical Ultraviolet Spectra?

    Science.gov (United States)

    Rochais, Thomas; Singh, Vikram; Chick, William; Maithil, Jaya; Sutter, Jessica; Brotherton, Michael S.; Shang, Zhaohui

    2016-09-01

    The spectrum of a quasar contains important information about its properties. Thus, it can be expected that two quasars with similar spectra will have similar properties, but just how similar has not before been quantified. Here we compare the ultraviolet spectra of a sample of 5553 quasars from Data Release 7 of the Sloan Digital Sky Survey, focusing on the 1350 Å ≤λ ≤ 2900 Å rest-frame region which contains prominent emission lines from Si IV, O IV], C IV, C III], and Mg II species. We use principal component analysis to determine the dominant components of spectral variation, as well as to quantitatively measure spectral similarity. As suggested by both the Baldwin effect and modified Baldwin effect, quasars with similar spectra have similar properties: bolometric luminosity, Eddington fraction, and black hole mass. The latter two quantities are calculated from the luminosity in conjunction with spectral features, and the variation between quasars with virtually identical spectra (which we call doppelgangers) is driven by the variance in the luminosity plus measurement uncertainties. In the doppelgangers the luminosity differences show 1σ uncertainties of 57% (or 0.63 magnitudes) and ˜70% 1σ uncertainties for mass and Eddington fraction. Much of the difference in luminosities may be attributable to time lags between the spectral lines and the continuum. Furthermore, we find that suggestions that the mostly highly accreting quasars should be better standard candles than other quasars are not bourne out for doppelgangers. Finally, we discuss the implications for using quasars as cosmological probes and the nature of the first two spectral principal components.

  17. Sunspot Bright Points

    CERN Document Server

    Choudhary, Debi Prasad

    2010-01-01

    We used the flux calibrated images through the Broad Band Filter Imager and Stokes Polarimeter data obtained with the Solar Optical Telescope onboard the Hinode spacecraft to study the properties of bright points in and around the sunspots. The well isolated bright points were selected and classified as umbral dot, peripheral umbral dot, penumbral grains and G-band bright point depending on their location. Most of the bright points are smaller than about 150 km. The larger points are mostly associated with the penumbral features. The bright points are not uniformly distributed over the umbra but preferentially located around the penumbral boundary and in the fast decaying parts of umbra. The color temperature of the bright points, derived using the continuum irradiance, are in the range of 4600 K to 6600 K with cooler ones located in the umbra. The temperature increases as a function of distance from the center to outside. The G-band, CN-band and CaII H flux of the bright points as a function of their blue ba...

  18. Quasar Variability in the Mid-Infrared

    CERN Document Server

    Kozlowski, Szymon; Ashby, Matthew L N; Assef, Roberto J; Brodwin, Mark; Eisenhardt, Peter R; Jannuzi, Buell T; Stern, Daniel

    2015-01-01

    The Decadal IRAC Bootes Survey (DIBS) is a mid-IR variability survey of the ~9 sq. deg. of the NDWFS Bootes Field and extnds the time baseline of its predecessor, the Spitzer Deep, Wide-Field Survey (SDWFS), from 4 to 10 years. The Spitzer Space Telescope visited the field five times between 2004 and 2014 at 3.6 and 4.5 microns. We provide the difference image analysis photometry for a half a million mostly extragalactic sources. In the mid-IR color-color plane, sources with quasar colors constitute the largest variability class (75%), 16% of the variable objects have stellar colors and the remaining 9% have the colors of galaxies. Adding the fifth epoch doubles the number of variable AGNs for the same false positive rates as in SDWFS, or increases the number of sources by 20% while decreasing the false positive rates by factors of 2-3 for the same variability amplitude. We quantify the ensemble mid-IR variability of ~1500 spectroscopically confirmed AGNs using single power-law structure functions, which we f...

  19. Quasars Probing Quasars VII. The Pinnacle of the Cool Circumgalactic Medium Surrounds Massive z~2 Galaxies

    CERN Document Server

    Prochaska, J Xavier; Hennawi, Joseph F

    2014-01-01

    We survey the incidence and absorption strength of the metal-line transitions CII 1334 and CIV from the circumgalactic medium (CGM) surrounding z~2 quasars, which act as signposts for massive dark matter halos M_halo~10^12.5 Msun. On scales of the virial radius (Mvir~160kpc), we measure a high covering fraction fC=0.73+/-0.10 to strong CII absorption (rest equivalent width W1334>0.2A), implying a massive reservoir of cool (T~10^4K) metal enriched gas. We conservatively estimate a metal mass exceeding 10^8 Msun. We propose these metals trace enrichment of the incipient intragroup/intracluster medium that these halos eventually inhabit. This cool CGM around quasars is the pinnacle amongst galaxies observed at all epochs, as regards covering fraction and average equivalent width of HI Lya and low-ion metal absorption. We argue that the properties of this cool CGM primarily reflect the halo mass, and that other factors such as feedback, star-formation rate, and accretion from the intergalactic medium are secondar...

  20. Comparing Simple Quasar Demographics Models

    CERN Document Server

    Veale, Melanie; Conroy, Charlie

    2014-01-01

    This paper explores several simple model variations for the connections among quasars, galaxies, and dark matter halos for redshifts 1 < z < 6. A key component of these models is that we enforce a self-consistent black hole (BH) history by tracking both BH mass and BH growth rate at all redshifts. We connect objects across redshift with a simple constant-number-density procedure, and choose a fiducial model with a relationship between BH and galaxy growth rates that is linear and evolves in a simple way with redshift. Within this fiducial model, we find the quasar luminosity function (QLF) by calculating an "intrinsic" luminosity based on either the BH mass or BH growth rate, and then choosing a model of quasar variability with either a lognormal or truncated power-law distribution of instantaneous luminosities. This gives four model variations, which we fit to the observed QLF at each redshift. With the best-fit models in hand, we undertake a detailed comparison of the four fiducial models, and explore...

  1. Functional Regression for Quasar Spectra

    CERN Document Server

    Ciollaro, Mattia; Freeman, Peter; Genovese, Christopher; Lei, Jing; O'Connell, Ross; Wasserman, Larry

    2014-01-01

    The Lyman-alpha forest is a portion of the observed light spectrum of distant galactic nuclei which allows us to probe remote regions of the Universe that are otherwise inaccessible. The observed Lyman-alpha forest of a quasar light spectrum can be modeled as a noisy realization of a smooth curve that is affected by a `damping effect' which occurs whenever the light emitted by the quasar travels through regions of the Universe with higher matter concentration. To decode the information conveyed by the Lyman-alpha forest about the matter distribution, we must be able to separate the smooth `continuum' from the noise and the contribution of the damping effect in the quasar light spectra. To predict the continuum in the Lyman-alpha forest, we use a nonparametric functional regression model in which both the response and the predictor variable (the smooth part of the damping-free portion of the spectrum) are function-valued random variables. We demonstrate that the proposed method accurately predicts the unobserv...

  2. [Galaxy/quasar classification based on nearest neighbor method].

    Science.gov (United States)

    Li, Xiang-Ru; Lu, Yu; Zhou, Jian-Ming; Wang, Yong-Jun

    2011-09-01

    With the wide application of high-quality CCD in celestial spectrum imagery and the implementation of many large sky survey programs (e. g., Sloan Digital Sky Survey (SDSS), Two-degree-Field Galaxy Redshift Survey (2dF), Spectroscopic Survey Telescope (SST), Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) program and Large Synoptic Survey Telescope (LSST) program, etc.), celestial observational data are coming into the world like torrential rain. Therefore, to utilize them effectively and fully, research on automated processing methods for celestial data is imperative. In the present work, we investigated how to recognizing galaxies and quasars from spectra based on nearest neighbor method. Galaxies and quasars are extragalactic objects, they are far away from earth, and their spectra are usually contaminated by various noise. Therefore, it is a typical problem to recognize these two types of spectra in automatic spectra classification. Furthermore, the utilized method, nearest neighbor, is one of the most typical, classic, mature algorithms in pattern recognition and data mining, and often is used as a benchmark in developing novel algorithm. For applicability in practice, it is shown that the recognition ratio of nearest neighbor method (NN) is comparable to the best results reported in the literature based on more complicated methods, and the superiority of NN is that this method does not need to be trained, which is useful in incremental learning and parallel computation in mass spectral data processing. In conclusion, the results in this work are helpful for studying galaxies and quasars spectra classification. PMID:22097877

  3. A comparison of the structures of 3CR quasars and blank field radio sources

    International Nuclear Information System (INIS)

    The purpose of this communication is to update our knowledge of the radio structural properties of quasars and blank field radio sources (blank field = any radio source without an identification on the Palomar Sky Survey prints). The quasar sample consists of all sources (25) with angular sizes greater than 10 arcsec in the list of Jodrell Bank quasars observed by Owen, Porcas and Neff (1978). The blank fields consist of 16 3CR sources also with structures > 10 arcsec based on Cambridge 5 km telescope observations. The sources were selected in low-frequency surveys; their emission at γ < 1 GHz is dominated by extended components with steep spectra. Thus, both samples should be oriented randomly in space except for a slight bias to be in the plane of the sky. (Auth.)

  4. Automated physical classification in the SDSS DR10. A catalogue of candidate Quasars

    CERN Document Server

    Brescia, Massimo; Longo, Giuseppe

    2015-01-01

    We discuss whether modern machine learning methods can be used to characterize the physical nature of the large number of objects sampled by the modern multi-band digital surveys. In particular, we applied the MLPQNA (Multi Layer Perceptron with Quasi Newton Algorithm) method to the optical data of the Sloan Digital Sky Survey - Data Release 10, investigating whether photometric data alone suffice to disentangle different classes of objects as they are defined in the SDSS spectroscopic classification. We discuss three groups of classification problems: (i) the simultaneous classification of galaxies, quasars and stars; (ii) the separation of stars from quasars; (iii) the separation of galaxies with normal spectral energy distribution from those with peculiar spectra, such as starburst or starforming galaxies and AGN. While confirming the difficulty of disentangling AGN from normal galaxies on a photometric basis only, MLPQNA proved to be quite effective in the three-class separation. In disentangling quasars ...

  5. A glimpse at quasar host galaxy far-UV emission using damped Lyα's as natural coronagraphs

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Zheng; Fan, Xiaohui; Wang, Ran; McGreer, Ian, E-mail: caize@arizona.edu [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Noterdaeme, Pasquier; Finley, Hayley; Petitjean, Patrick [Institut d' Astrophysique de Paris, CNRS-UPMC, UMR7095, 98bis bd Arago, F-75014 Paris (France); Carithers, Bill [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA (United States); Bian, Fuyan [Research School of Astronomy and Astrophysics, Australian National University, Canberra, Weston Creek, ACT, 2611 (Australia); Miralda-Escudé, Jordi [Institució Catalana de Recerca i Estudis Avançats, Barcelona (Spain); Pâris, Isabelle [Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago (Chile); Schneider, Donald P. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Zakamska, Nadia L. [Department of Physics and Astronomy, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218 (United States); Ge, Jian [Department of Astronomy, University of Florida, Gainesville, FL (United States); Slosar, Anze [Brookhaven National Laboratory, Upton, NY 11973 (United States)

    2014-10-01

    In merger-driven models of massive galaxy evolution, the luminous quasar phase is expected to be accompanied by vigorous star formation in quasar host galaxies. In this paper, we use high column density damped Lyα (DLA) systems along quasar sight lines as natural coronagraphs to directly study the far-UV (FUV) radiation from the host galaxies of luminous background quasars. We have stacked the spectra of ∼2000 DLA systems (N {sub H} {sub I} > 10{sup 20.6} cm{sup –2}) with a median absorption redshift (z) = 2.6 selected from quasars observed in the SDSS-III Baryon Oscillation Spectroscopic Survey. We detect residual flux in the dark troughs of the composite DLA spectra. The level of this residual flux significantly exceeds systematic errors in the Sloan Digital Sky Survey fiber sky subtraction; furthermore, the residual flux is strongly correlated with the continuum luminosity of the background quasar, while uncorrelated with DLA column density or metallicity. We conclude that the flux could be associated with the average FUV radiation from the background quasar host galaxies (with medium redshift (z) = 3.1) that is not blocked by the intervening DLA. Assuming that all of the detected flux originates from quasar hosts, for the highest quasar luminosity bin ((L) = 2.5 × 10{sup 13} L {sub ☉}), the host galaxy has an FUV intensity of 1.5 ± 0.2 × 10{sup 40} erg s{sup –1} Å{sup –1}; this corresponds to an unobscured UV star formation rate of 9 M {sub ☉} yr{sup –1}.

  6. The identification of z-dropouts in Pan-STARRS1: three quasars at 6.5

    CERN Document Server

    Venemans, B P; Decarli, R; Farina, E P; Walter, F; Chambers, K C; Fan, X; Rix, H-W; Schlafly, E; McMahon, R G; Simcoe, R; Stern, D; Burgett, W S; Draper, P W; Flewelling, H; Hodapp, K W; Kaiser, N; Magnier, E A; Metcalfe, N; Morgan, J S; Price, P A; Tonry, J L; Waters, C; AlSayyad, Y; Banerji, M; Chen, S S; González-Solares, E A; Greiner, J; Mazzucchelli, C; McGreer, I; Miller, D R; Reed, S; Sullivan, P W

    2015-01-01

    Luminous distant quasars are unique probes of the high redshift intergalactic medium (IGM) and of the growth of massive galaxies and black holes in the early universe. Absorption due to neutral Hydrogen in the IGM makes quasars beyond a redshift of z~6.5 very faint in the optical $z$-band, thus locating quasars at higher redshifts require large surveys that are sensitive above 1 micron. We report the discovery of three new z>6.5 quasars, corresponding to an age of the universe of 6.5 quasars from 4 to 7. The quasars have redshifts of z=6.50, 6.52, and 6.66, and include the brightest z-dropout quasar reported to date, PSO J036.5078+03.0498 with M_1450=-27.4. We obtained near-infrared spectroscopy for the quasars and from the MgII line we estimate that the central black holes have masses between 5x10^8 and 4x10^9 M_sun, and are accreting close to the Eddington limit (L_Bol/L_Edd=0.13-1.2). We investigate the ionized regions around the quasars and find near zone radii of R_NZ=1.5-5.2 proper Mpc, confirming the t...

  7. The VLT-FLAMES Tarantula survey. XX. The nature of the X-ray bright emission-line star VFTS 399

    Science.gov (United States)

    Clark, J. S.; Bartlett, E. S.; Broos, P. S.; Townsley, L. K.; Taylor, W. D.; Walborn, N. R.; Bird, A. J.; Sana, H.; de Mink, S. E.; Dufton, P. L.; Evans, C. J.; Langer, N.; Maíz Apellániz, J.; Schneider, F. R. N.; Soszyński, I.

    2015-07-01

    Context. The stellar population of the 30 Doradus star-forming region in the Large Magellanic Cloud contains a subset of apparently single, rapidly rotating O-type stars. The physical processes leading to the formation of this cohort are currently uncertain. Aims: One member of this group, the late O-type star VFTS 399, is found to be unexpectedly X-ray bright for its bolometric luminosity - in this study we aim to determine its physical nature and the cause of this behaviour. Methods: To accomplish this we performed a time-resolved analysis of optical, infrared and X-ray observations. Results: We found VFTS 399 to be an aperiodic photometric variable with an apparent near-IR excess. Its optical spectrum demonstrates complex emission profiles in the lower Balmer series and select He i lines - taken together these suggest an OeBe classification. The highly variable X-ray luminosity is too great to be produced by a single star, while the hard, non-thermal nature suggests the presence of an accreting relativistic companion. Finally, the detection of periodic modulation of the X-ray lightcurve is most naturally explained under the assumption that the accretor is a neutron star. Conclusions: VFTS 399 appears to be the first high-mass X-ray binary identified within 30 Dor, sharing many observational characteristics with classical Be X-ray binaries. Comparison of the current properties of VFTS 399 to binary-evolution models suggests a progenitor mass ≳25 M⊙ for the putative neutron star, which may host a magnetic field comparable in strength to those of magnetars. VFTS 399 is now the second member of the cohort of rapidly rotating "single" O-type stars in 30 Dor to show evidence of binary interaction resulting in spin-up, suggesting that this may be a viable evolutionary pathway for the formation of a subset of this stellar population. Based on observations collected at the European Southern Observatory under program ID 182.D-0222.

  8. The space density of Compton-thick AGN at z ≈ 0.8 in the zCOSMOS-Bright Survey

    Science.gov (United States)

    Vignali, C.; Mignoli, M.; Gilli, R.; Comastri, A.; Iwasawa, K.; Zamorani, G.; Mainieri, V.; Bongiorno, A.

    2014-11-01

    Context. The obscured accretion phase in black hole growth is a crucial ingredient in many models linking the active galactic nuclei (AGN) activity with the evolution of their host galaxy. At present, a complete census of obscured AGN is still missing, although several attempts in this direction have been carried out recently, mostly in the hard X-rays and at mid-infrared wavelengths. Aims: The purpose of this work is to assess whether the [Ne v] emission line at 3426 Å can reliably pick up obscured AGN up to z ≈ 1 by assuming that it is a reliable proxy of the intrinsic AGN luminosity and using moderately deep X-ray data to characterize the amount of obscuration. Methods: A sample of 69 narrow-line (Type 2) AGN at z ≈ 0.65-1.20 were selected from the 20k-zCOSMOS Bright galaxy sample on the basis of the presence of the [Ne v]3426 Å emission. The X-ray properties of these galaxies were then derived using the Chandra-COSMOS coverage of the field; the X-ray-to-[Ne v] flux ratio, coupled with X-ray spectral and stacking analyses, was then used to infer whether Compton-thin or Compton-thick absorption is present in these sources. Then the [Ne v] luminosity function was computed to estimate the space density of Compton-thick AGN at z ≈ 0.8. Results: Twenty-three sources were detected by Chandra, and their properties are consistent with moderate obscuration (on average, ≈a few × 1022 cm-2). The X-ray properties of the remaining 46 X-ray undetected Type 2 AGN (among which we expect to find the most heavily obscured objects) were derived using X-ray stacking analysis. Current data, supported by Monte Carlo simulations, indicate that a fraction as high as ≈40% of the present sample is likely to be Compton thick. The space density of Compton-thick AGN with logL2-10 keV> 43.5 at z = 0.83 is ΦThick = (9.1 ± 2.1) × 10-6 Mpc-3, in good agreement with both X-ray background model expectations and the previously measured space density for objects in a similar

  9. The Composite Spectrum of BOSS Quasars Selected for Studies of the Lyα Forest

    Science.gov (United States)

    Harris, David W.; Jensen, Trey W.; Suzuki, Nao; Bautista, Julian E.; Dawson, Kyle S.; Vivek, M.; Brownstein, Joel R.; Ge, Jian; Hamann, Fred; Herbst, H.; Jiang, Linhua; Moran, Sarah E.; Myers, Adam D.; Olmstead, Matthew D.; Schneider, Donald P.

    2016-06-01

    The Baryon Oscillation Spectroscopic Survey (BOSS) has collected more than 150,000 2.1 ≤ z ≤ 3.5 quasar spectra since 2009. Using this unprecedented sample, we create a composite spectrum in the rest-frame of 102,150 quasar spectra from 800-3300 Å at a signal-to-noise ratio close to 1000 per pixel (Δv of 69 km s-1). Included in this analysis is a correction to account for flux calibration residuals in the BOSS spectrophotometry. We determine the spectral index as a function of redshift of the full sample, warp the composite spectrum to match the median spectral index, and compare the resulting spectrum to Sloan Digital Sky Survey (SDSS) photometry used in target selection. The quasar composite matches the color of the quasar population to 0.02 mag in g - r, 0.03 mag in r - i, and 0.01 mag in i - z over the redshift range 2.2 < z < 2.6. The composite spectrum deviates from the imaging photometry by 0.05 mag around z = 2.7, likely due to differences in target selection as the quasar colors become similar to the stellar locus at this redshift. Finally, we characterize the line features in the high signal-to-noise composite and identify nine faint lines not found in the previous composite spectrum from SDSS.

  10. Observations Supporting the Existence of an Intrinsic Magnetic Moment Inside the Central Compact Object Within the Quasar Q0957+561

    CERN Document Server

    Schild, R E; Robertson, S L; Schild, Rudolph E.; Leiter, Darryl J.; Robertson, Stanley L.

    2005-01-01

    Recent auto-correlation and fluctuation analysis of time series data in the brightness curves and micro-lensing size scales seen in Q0957+561 A,B has produced important information about the existence and characteristic physical dimensions of a new non-standard internal structure contained within this quasar. We find that the new internal quasar structure, which we shall call the Schild-Vakulik Structure, can be consistently explained in terms of a new calss of gravitationally collapsing solutions to the Einstein field equations which describe highly redshifted, Eddington limited, Magnetospheric Eternally Collapsing Objects (MECO) that contain intrinsic magnetic moments. Since observation of the Schild-Vakulik structure within Q0957+561 implies that this quasar contains an observable intrinsic magnetic moment, this represents strong evidence that this quasar does not have an event horizon

  11. Quasars - powerhouses at the edge of time

    Science.gov (United States)

    Gavin, M.

    2000-06-01

    1999 was the 70th anniversary of Edwin Hubble's seminal publication1 showing a cosmological redshift in galaxies. More recent discoveries of quasars have extended the universe's boundaries back in time nearer to the Big Bang. Some amateur spectrograms of quasars are presented showing a cosmological redshift.

  12. Chandra and XMM-Newton observations of the first quasars X-rays from the age of cosmic enlightenment

    CERN Document Server

    Vignali, C; Schneider, D P; Anderson, S F; Fan, X; Gunn, J E; Kaspi, S; Richards, G T; Strauss, M A; Strauss, Michael A.

    2003-01-01

    We report on Chandra and XMM-Newton observations of a sample of 13 quasars at z~4.7-5.4 mostly taken from the Sloan Digital Sky Survey (SDSS). The present sample complements previous X-ray studies of z>4 quasars, in which the majority of the objects are optically more luminous and at lower redshifts. All but two of our quasars have been detected in the X-ray band, thus doubling the number of z>4.8 X-ray detected quasars. The two non-detections are likely to be due to a short exposure time and to the presence of intrinsic absorption. We confirm and extend to the highest redshifts the presence of a correlation between AB1450(1+z) magnitude and soft X-ray flux for z>4 quasars, and the presence of a steeper optical-to-X-ray spectral energy distribution (parameterized by aox) for high-luminosity, high-redshift quasars than for lower-luminosity, lower-redshift quasars. The second effect is likely due to the known anti-correlation between aox and rest-frame 2500 Angstrom luminosity, whose significance is confirmed v...

  13. Quasar Evolution Driven by Galaxy Encounters in Hierarchical Structures

    CERN Document Server

    Menci, N; Fontana, A; Giallongo, E; Poli, F; Vittorini, V

    2003-01-01

    We link the evolution of the galaxies in the hierarchical clustering scenario with the changing accretion rates of cold gas onto the central massive black holes that power the quasars. We base on galaxy interactions as main triggers of accretion; the related scaling laws are taken up from Cavaliere & Vittorini (2000), and grafted to a semi-analytic code for galaxy formation. As a result, at high $z$ the protogalaxies grow rapidly by hierarchical merging; meanwhile, much fresh gas is imported and also destabilized, so the holes are fueled at their full Eddington rates. At lower $z$ the galactic dynamical events are mostly encounters in hierarchically growing groups; now the refueling peters out, as the residual gas is exhausted while the destabilizing encounters dwindle. So, with no parameter tuning other than needed for stellar observables, our model uniquely produces at $z>3$ a rise, and at $z\\lesssim 2.5 $ a decline of the bright quasar population as steep as observed. In addition, our results closely f...

  14. The Neutrino Ball Model of a Quasar

    CERN Document Server

    Manka, R; Karczewska, D

    1993-01-01

    It is suggested that the nonorthodox model of a quasar as a neutrino ball described in terms of the standard model extended by adding right-handed neutrinos and the Majorana scalar field can be presented in order to explain a quasar as a body of weak interacting neutrinos. Neutrino interaction with the scalar Majorana field violates the lepton number and produces the mass splitting of the neutrino due to the sea-saw mechanism. In this model a quasar is an object which appears in the result of the first order cosmological phase transition. In this interpretation a quasar may be regarded as a ball filled with Dirac neutrinos and can be treated as a remnant of phase transition with unbroken global lepton symmetry. In this paper we study the macroscopic parameters of such a configuration. In the result the mass-radius curve M(R) for the quasar is obtained.

  15. The Mass Budget of Merging Quasars

    CERN Document Server

    Menou, K

    2004-01-01

    Two spectacular results emerging from recent studies of nearby dead quasars and distant active quasars are (i) the existence of tight relations between the masses of black holes (BHs) and the properties of their host galaxies (spheroid luminosity or velocity dispersion, galaxy mass), and (ii) a consistency between the local mass density in BHs and that expected by summing up the light received from distant active quasars. These results are partly shaped by successive galactic mergers and BH coalescences, since mergers redistribute the population of BHs in galaxies and BH binary coalescences reduce the mass density in BHs through losses to gravitational waves. Here, we isolate and quantify these effects by following the cosmological merger history of a population of massive BHs representing the quasar population between z = 3 and z =0. Our results suggest that the relation between BH mass and host galaxy properties, and inferences on the global efficiency of BH accretion during active quasar phases, could be i...

  16. Insights into quasar UV spectra using unsupervised clustering analysis

    Science.gov (United States)

    Tammour, A.; Gallagher, S. C.; Daley, M.; Richards, G. T.

    2016-06-01

    Machine learning techniques can provide powerful tools to detect patterns in multidimensional parameter space. We use K-means - a simple yet powerful unsupervised clustering algorithm which picks out structure in unlabelled data - to study a sample of quasar UV spectra from the Quasar Catalog of the 10th Data Release of the Sloan Digital Sky Survey (SDSS-DR10) of Paris et al. Detecting patterns in large data sets helps us gain insights into the physical conditions and processes giving rise to the observed properties of quasars. We use K-means to find clusters in the parameter space of the equivalent width (EW), the blue- and red-half-width at half-maximum (HWHM) of the Mg II 2800 Å line, the C IV 1549 Å line, and the C III] 1908 Å blend in samples of broad absorption line (BAL) and non-BAL quasars at redshift 1.6-2.1. Using this method, we successfully recover correlations well-known in the UV regime such as the anti-correlation between the EW and blueshift of the C IV emission line and the shape of the ionizing spectra energy distribution (SED) probed by the strength of He II and the Si III]/C III] ratio. We find this to be particularly evident when the properties of C III] are used to find the clusters, while those of Mg II proved to be less strongly correlated with the properties of the other lines in the spectra such as the width of C IV or the Si III]/C III] ratio. We conclude that unsupervised clustering methods (such as K-means) are powerful methods for finding `natural' binning boundaries in multidimensional data sets and discuss caveats and future work.

  17. Extreme Ultraviolet Explorer Bright Source List

    Science.gov (United States)

    Malina, Roger F.; Marshall, Herman L.; Antia, Behram; Christian, Carol A.; Dobson, Carl A.; Finley, David S.; Fruscione, Antonella; Girouard, Forrest R.; Hawkins, Isabel; Jelinsky, Patrick

    1994-01-01

    Initial results from the analysis of the Extreme Ultraviolet Explorer (EUVE) all-sky survey (58-740 A) and deep survey (67-364 A) are presented through the EUVE Bright Source List (BSL). The BSL contains 356 confirmed extreme ultraviolet (EUV) point sources with supporting information, including positions, observed EUV count rates, and the identification of possible optical counterparts. One-hundred twenty-six sources have been detected longward of 200 A.

  18. Adaptive optics imaging of low and intermediate redshift quasars

    CERN Document Server

    Márquez, I; Theodore, B; Bremer, M; Monnet, G; Beuzit, J L

    2001-01-01

    We present the results of adaptive-optics imaging in the H and K bands of 12 low and intermediate redshift (z15.0) themselves as reference for the correction, have typical spatial resolution of FWHM~0.3 arcsec before deconvolution. The deconvolved H-band image of PG1700+514 has a spatial resolution of 0.16 arcsec and reveals a wealth of details on the companion and the host-galaxy. Four out of the twelve quasars have close companions and obvious signs of interactions. The two-dimensional images of three of the host-galaxies unambiguously reveal bars and spiral arms. The morphology of the other objects are difficult to determine from one dimensional surface brightness profile and deeper images are needed. Analysis of mocked data shows that elliptical galaxies are always recognized as such, whereas disk hosts can be missed for small disk scale lengths and large QSO contributions.

  19. Spitzer observations of a gravitationally lensed quasar, QSO 2237+0305

    CERN Document Server

    Agol, Eric; Gorjian, Varoujan; Kimball, Amy; 10.1088/0004-637X/697/2/1010

    2009-01-01

    The four-image gravitationally lensed quasar QSO 2237+0305 is microlensed by stars in the lens galaxy. The amplitude of microlensing variability can be used to infer the relative size of the quasar as a function of wavelength; this provides a test of quasar models. Toward this end, we present Spitzer Space Telescope Infrared Spectrograph and Infrared Array Camera (IRAC) observations of QSO 2237+0305, finding the following. (1) The infrared (IR) spectral energy distribution (SED) is similar to that of other bright radio-quiet quasars, contrary to an earlier claim. (2) A dusty torus model with a small opening angle fits the overall shape of the IR SED well, but the quantitative agreement is poor due to an offset in wavelength of the silicate feature. (3) The flux ratios of the four lensed images can be derived from the IRAC data despite being unresolved. We find that the near-IR fluxes are increasingly affected by microlensing toward shorter wavelengths. (4) The wavelength dependence of the IRAC flux ratios is ...

  20. The Impact of Dust in Host Galaxies on Quasar Luminosity Functions

    CERN Document Server

    Shirakata, H; Enoki, M; Nagashima, M; Kobayashi, M A R; Ishiyama, T; Makiya, R

    2014-01-01

    We have investigated effects of dust attenuation on quasar luminosity functions using a semi-analytic galaxy formation model combined with a large cosmological N-body simulation. We estimate the dust attenuation of quasars self-consistently with that of galaxies by considering the dust in their host bulges.We find that the luminosity of the bright quasars is strongly dimmed by the dust attenuation, about 2 mag in the B-band, and that the faint end slope of the luminosity function is steepened. We also study for the first time the case in which gas fueling to a central black hole starts some time after the beginning of the starburst induced by a major merger. In this case, nuclei are less attenuated by the dust since the cold gas in the bulges is consumed by the starbursts and expelled by the stellar feedback. In order to make the dust attenuation of the quasars negligible, the accretion has to be delayed at least five times the dynamical timescale of their host bulges.

  1. Tracing dark energy with quasars

    CERN Document Server

    Średzińska, J; Bilicki, M; Hryniewicz, K; Krupa, M; Kurcz, A; Marziani, P; Pollo, A; Pych, W; Udalski, A

    2016-01-01

    The nature of dark energy, driving the accelerated expansion of the Universe, is one of the most important issues in modern astrophysics. In order to understand this phenomenon, we need precise astrophysical probes of the universal expansion spanning wide redshift ranges. Quasars have recently emerged as such a probe, thanks to their high intrinsic luminosities and, most importantly, our ability to measure their luminosity distances independently of redshifts. Here we report our ongoing work on observational reverberation mapping using the time delay of the Mg II line, performed with the South African Large Telescope (SALT).

  2. Occurrence and Global Properties of Narrow CIV lambda 1549 Absorption Lines in Moderate-Redshift Quasars

    DEFF Research Database (Denmark)

    Vestergaard, Marianne

    2003-01-01

    is that the most strongly absorbed radio quasars have the largest radio source extent. This result is in stark contrast to a recent study of the low-frequency selected Molonglo survey in which a connection between the strength of the narrow absorbers and the (young) age of the radio source has been proposed...

  3. The XMM-Newton/2dF survey - II. The nature of X-ray faint optically bright X-ray sources

    CERN Document Server

    Georgakakis, A; Vallbe, M; Kolokotronis, V G; Basilakos, S; Plionis, M; Stewart, G C; Shanks, T; Boyle, B J

    2004-01-01

    In this paper we investigate the properties of low X-ray-to-optical flux ratio sources detected in a wide area (2.5deg^2) shallow (f(0.5-8keV)~10e-14cgs) XMM-Newton survey. We find a total of 26 sources (5% of the total X-ray selected population) with log f_X/f_{opt}<-0.9 to the above flux limit. Optical spectroscopy is available for 20 of these low X-ray-to-optical flux ratio objects. Most of them are found to be associated with Galactic stars (total of 8) and broad line AGNs (total of 8).We also find two sources with optical spectra showing absorption and/or narrow emission lines and X-ray/optical properties suggesting AGN activity. Another two sources are found to be associated with low redshift galaxies with narrow emission line optical spectra, X-ray luminosities L_X(0.5-8keV)~10e41cgs and logf_X/f_opt ~ -2 suggesting `normal' star-forming galaxies. Despite the small number statistics the sky density of `normal' X-ray selected star-forming galaxies at the flux limit of the present sample is low consis...

  4. The Galactic O-Star Spectroscopic Survey. I. Classification System and Bright Northern Stars in the Blue-Violet at R~2500

    CERN Document Server

    Sota, A; Walborn, N R; Alfaro, E J; Barbá, R H; Morrell, N I; Gamen, R C; Arias, J I

    2011-01-01

    We present the first installment of a massive spectroscopic survey of Galactic O stars, based on new, high signal-to-noise ratio, R~2500 digital observations from both hemispheres selected from the Galactic O-Star Catalog of Ma\\'iz Apell\\'aniz et al. (2004) and Sota et al. (2008). The spectral classification system is rediscussed and a new atlas is presented, which supersedes previous versions. Extensive sequences of exceptional objects are given, including types Ofc, ON/OC, Onfp, Of?p, Oe, and double-lined spectroscopic binaries. The remaining normal spectra bring this first sample to 184 stars, which is close to complete to B=8 and north of delta = -20 and includes all of the northern objects in Ma\\'iz Apell\\'aniz et al. (2004) that are still classified as O stars. The systematic and random accuracies of these classifications are substantially higher than previously attainable, because of the quality, quantity, and homogeneity of the data and analysis procedures. These results will enhance subsequent invest...

  5. Orbital and physical parameters of eclipsing binaries from the All-Sky Automated Survey catalogue - VII. V1200 Centauri: a bright triple in the Hyades moving group

    CERN Document Server

    Coronado, J; Vanzi, L; Espinoza, N; Brahm, R; Jordán, A; Catelán, M; Ratajczak, M; Konacki, M

    2015-01-01

    We present the orbital and physical parameters of the detached eclipsing binary V1200~Centauri (ASAS~J135218-3837.3) from the analysis of spectroscopic observations and light curves from the \\textit{All Sky Automated Survey} (ASAS) and SuperWASP database. The radial velocities were computed from the high-resolution spectra obtained with the OUC 50-cm telescope and PUCHEROS spectrograph and with 1.2m Euler telescope and CORALIE spectrograph using the cross-correlation technique \\textsc{todcor}. We found that the absolute parameters of the system are $M_1= 1.394\\pm 0.030$ M$_\\odot$, $M_2= 0.866\\pm 0.015$ M$_\\odot$, $R_1= 1.39\\pm 0.15$ R$_\\odot$, $R_2= 1.10\\pm 0.25$ R$_\\odot$. We investigated the evolutionary status and kinematics of the binary and our results indicate that V1200~Centauri is likely a member of the Hyades moving group, but the largely inflated secondary's radius may suggest that the system may be even younger, around 30 Myr. We also found that the eclipsing pair is orbited by another, stellar-mas...

  6. Quasars can be used to verify the parallax zero-point of the Tycho-Gaia Astrometric Solution

    Science.gov (United States)

    Michalik, Daniel; Lindegren, Lennart

    2016-02-01

    Context. The Gaia project will determine positions, proper motions, and parallaxes for more than one billion stars in our Galaxy. It is known that Gaia's two telescopes are affected by a small but significant variation of the basic angle between them. Unless this variation is taken into account during data processing, e.g. using on-board metrology, it causes systematic errors in the astrometric parameters, in particular a shift in the parallax zero-point. Previously, we suggested an early reduction of Gaia data for the subset of Tycho-2 stars (Tycho-Gaia Astrometric Solution; TGAS). Aims: We investigate whether quasars can be used to independently verify the parallax zero-point in early data reductions. This is not trivially possible as the observation interval is too short to disentangle parallax and proper motion for the quasar subset. Methods: We repeat TGAS simulations but additionally include simulated Gaia observations of quasars from ground-based surveys. All observations are simulated with basic angle variations. To obtain a full astrometric solution for the quasars in TGAS we explore the use of prior information for their proper motions. Results: It is possible to determine the parallax zero-point for the quasars with a few μas uncertainty, and it agrees to a similar precision with the zero-point for the Tycho-2 stars. The proposed strategy is robust even for quasars exhibiting significant spurious proper motion due to a variable source structure, or when the quasar subset is contaminated with stars misidentified as quasars. Conclusions: Using prior information about quasar proper motions we could provide an independent verification of the parallax zero-point in early solutions based on less than one year of Gaia data.

  7. HST images of FeLoBAL quasars: Testing quasar-galaxy evolution models

    Science.gov (United States)

    Herbst, Hanna; Hamann, Fred; Villforth, Carolin; Caselli, Paola; Koekemoer, Anton M.; Veilleux, Sylvain

    2016-01-01

    We present preliminary results from an HST imaging study of FeLoBAL quasars, which have extremely low-ionization Broad Absorption Line (BAL) outflows and might be a young quasar population based on their red colors, large far-IR luminosities (suggesting high star formation rates), and powerful outflows. Some models of quasar - host galaxy evolution propose a triggering event, such as a merger, to fuel both a burst of star formation and the quasar/AGN activity. These models suggest young quasars are initially obscured inside the dusty starburst until a "blowout" phase, driven by the starburst or quasar outflows like FeLoBALs, ends the star formation and reveals the visibly luminous quasar. Despite the popularity of this evolution scheme, there is little observational evidence to support the role of mergers in triggering AGN or the youth of dust-reddened quasars (such as FeLoBALs) compared to normal blue quasars.Our Cycle 22 HST program is designed to test the youth of FeLoBAL quasars and the connection of FeLoBALs to mergers. We obtain WFC3/IR F160W images of 10 FeLoBAL quasars at redshift z~0.9 (covering ~8500A in the quasar rest frame). We will compare the host galaxy morphologies and merger signatures of FeLoBALs with normal blue quasars (which are older according to the evolution model) and non-AGN galaxies matched in redshift and stellar mass. If FeLoBAL quasars are indeed in a young evolutionary state, close in time to the initial merging event, they should have stronger merger features compared to blue quasars and non-AGN galaxies. Preliminary results suggest that this is not the case - FeLoBAL quasars appear to reside in faint, compact hosts with weak or absent merger signatures. We discuss the implications of these results for galaxy evolution models and other studies of dust-reddened quasar populations.

  8. MusE GAs FLOw and Wind (MEGAFLOW) I: First MUSE results on background quasars

    OpenAIRE

    Schroetter, Ilane; Bouché, Nicolas; Wendt, Martin; Contini, Thierry; Finley, Hayley; Pello, Roser; Bacon, Roland; Cantalupo, Sebastiano; Marino, Raffaella; Richard, Johan,; Lilly, Simon; Schaye, Joop; Soto, Kurt; Steinmetz, Matthias; Straka, Lorrie A.

    2016-01-01

    The physical properties of galactic winds are one of the keys to understand galaxy formation and evolution. These properties can be constrained thanks to background quasar lines of sight (LOS) passing near star-forming galaxies (SFGs). We present the first results of the MusE GAs FLOw and Wind (MEGAFLOW) survey obtained of 2 quasar fields which have 8 MgII absorbers of which 3 have rest-equivalent width greater than 0.8 \\AA. With the new Multi Unit Spectroscopic Explorer (MUSE) spectrograph o...

  9. Tentative Detection of Quasar Feedback from WMAP and SDSS Cross-Correlation

    OpenAIRE

    Chatterjee, Suchetana; Ho, Shirley; Newman, Jeffrey A.; Kosowsky, Arthur

    2009-01-01

    We perform a cross-correlation analysis of microwave data from Wilkinson Microwave Anisotropy Probe and photometric quasars from the Sloan Digital Sky Survey, testing for Sunyaev-Zeldovich (SZ) effect from quasars. A statistically significant (2.5 $\\sigma$) temperature decrement exists in the 41 GHz microwave band. A two-component fit to the cross-correlation spectrum incorporating both dust emission and SZ yields a best-fit $y$ parameter of $(7.0 \\pm 3.4)\\times 10^{-7}$. A similar cross-corr...

  10. A unique UV flare in the optical light curve of the quasar J004457.9+412344

    Directory of Open Access Journals (Sweden)

    Hatzidimitriou D.

    2012-12-01

    Full Text Available We found that the nova candidate J004457.9+412344 is a radio-quiet quasar at z ∼ 2. Its optical long-term light curve, covering more than half a century, shows quasar typical flux variations superimposed by a spectacular single flare lasting more than one year (observer frame. We could not find comparable light curves among the several thousand catalogued radio-quiet quasars in the stripe 82 of the Sloan Digital Sky Survey. The decreasing part of the flare light curve roughly follows a power law t−5/3. The quasar spectrum, the total energy of the flare, and the decline of the light curve are consistent with the tidal disruption of a ∼10 Mʘ giant star by a supermassive black hole of a few 108 Mʘ. We argue that the alternative explanation by gravitational microlensing is less likely, though it cannot be definitely excluded.

  11. Discovery of a z=0.65 Post-Starburst BAL Quasar in the DES Supernova Fields

    CERN Document Server

    Mudd, Dale; Tie, Suk Sien; Lidman, Chris; McMahon, Richard; Banerji, Manda; Davis, Tamara; Peterson, Bradley; Sharp, Rob; Childress, Michael; Lewis, Geraint; Tucker, Brad; Yuan, Fang; Abbot, Tim; Abdalla, Filipe; Allam, Sahar; Benoit-Levy, Aurelien; Bertin, Emmanuel; Brooks, David; Rosell, A Camero; Kind, Matias Carrasco; Carretero, Jorge; da Costa, Luiz N; Desai, Shantanu; Diehl, Thomas; Eifler, Tim; Finley, David; Flaugher, Brenna; Glazebrook, Karl; Gruen, Daniel; Gruendl, Robert; Gutierrez, Gaston; Hinton, Samuel; Honscheid, Klaus; James, David; Kuehn, Kyler; Kuropatkin, Nikolav; Macaulay, Edward; Maia, M A G; Miquel, Ramon; Ogando, Ricardo; Plazas, Andres; Riel, Kevin; Sanchez, Eusebio; Santiago, Basillio; Schubnell, Michael; Sevilla-Noarbe, Ignacio; Smith, R C; Soares-Santos, Marcelle; Sobreira, Flavia; Suchyta, Eric; Swanson, Molly; Tarle, Gregory; Thomas, Daniel; Uddin, Sved; Walker, Alistair; Zhang, Bonnie

    2016-01-01

    We present the discovery of a z=0.65 low-ionization broad absorption line (LoBAL) quasar in a post-starburst galaxy in data from the Dark Energy Survey (DES) and spectroscopy from the Australian Dark Energy Survey (OzDES). LoBAL quasars are a minority of all BALs, and rarer still is that this object also exhibits broad FeII (an FeLoBAL) and Balmer absorption. This is the first BAL quasar that has signatures of recently truncated star formation, which we estimate ended about 40 Myr ago. The characteristic signatures of an FeLoBAL require high column densities, which could be explained by the emergence of a young quasar from an early, dust-enshrouded phase, or by clouds compressed by a blast wave. The age of the starburst component is comparable to estimates of the lifetime of quasars, so if we assume the quasar activity is related to the truncation of the star formation, this object is better explained by the blast wave scenario.

  12. The environment of Low Surface Brightness Galaxies

    OpenAIRE

    Rosenbaum, S. D.; Bomans, D. J.

    2004-01-01

    Using the Early Data Release of the Sloan Digital Sky Survey (SDSS) we investigated the clustering properties of Low Surface Brightness (LSB) galaxies in comparison to normal, High Surface Brightness (HSB) galaxies. We selected LSB galaxies and HSB galaxies with well measured redshifts from the SDSS data base and performed three-dimensional neighbour counting analysis within spheres of radii between 0.8 Mpc and 8.0 Mpc. As a second analysis method we used an N-th neighbour analysis with N var...

  13. Quasar Proximity Zones and Patchy Reionization

    CERN Document Server

    Lidz, A; Zaldarriaga, M; Hernquist, L; Dutta, S; Lidz, Adam; Quinn, Matthew Mc; Zaldarriaga, Matias; Hernquist, Lars; Dutta, Suvendra

    2007-01-01

    Lyman-alpha forest absorption spectra towards quasars at z ~ 6 show regions of enhanced transmission close to their source. Several authors have argued that the apparently small sizes of these regions indicate that quasar ionization fronts at z >~ 6 expand into a largely or partly neutral intergalactic medium (IGM). Assuming that the typical region in the IGM is reionized by z <= 6, as is suggested by Ly-a forest observations, we argue that at {\\em least} 50% of the volume of the IGM was reionized before the highest redshift quasars turned on. Further, even if the IGM is as much as 50% neutral at quasar turn-on, the quasars are likely born into large galaxy-generated HII regions. The HII regions during reionization are themselves clustered, and using radiative transfer simulations, we find that long skewers through the IGM towards quasar progenitor halos pass entirely through ionized bubbles, even when the IGM is half neutral. These effects have been neglected in most previous analyses of quasar proximity ...

  14. Low redshift quasars in the SDSS Stripe 82. The local environments

    CERN Document Server

    Karhunen, K; Falomo, R; Bettoni, D

    2014-01-01

    We study the environments of low redshift (z < 0.5) quasars based on a large and homogeneous dataset from the Stripe 82 region of the Sloan Digital Sky Survey (SDSS). We have compared the < 1 Mpc scale envi- ronments of 302 quasars that were resolved in our recent study to those of 288 inactive galaxies with closely matched redshifts. Crucially, the lu- minosities of the inactive galaxies and the quasar host galaxies are also closely matched, unlike in most previous studies. The environmental overdensities were studied by measuring the num- ber density of galaxies within a projected distance of 200 kpc to 1 Mpc. The galaxy number density of the quasar environments is comparable to that of the inactive galaxies with similar luminosities, both classes of ob- jects showing significant excess compared to the background galaxy density for distances < 400 kpc. There is no significant dependence of the galaxy number density on redshift, quasar or host galaxy luminosity, black hole mass or radio loudness. Th...

  15. A Quasar Catalog with Simultaneous UV, Optical and X-ray Observations by Swift

    CERN Document Server

    Wu, Jian; Grupe, Dirk; Koch, Scott; Gelbord, Jonathan; Schneider, Donald P; Gronwall, Caryl; Wesolowski, Sarah; Porterfield, Blair L

    2012-01-01

    We have compiled a catalog of optically-selected quasars with simultaneous observations in UV/optical and X-ray bands by the Swift Gamma Ray Burst Explorer. Objects in this catalog are identified by matching the Swift pointings with the Sloan Digital Sky Survey Data Release 5 quasar catalog. The final catalog contains 843 objects, among which 637 have both UVOT and XRT observations and 354 of which are detected by both instruments. The overall X-ray detection rate is ~60% which rises to ~85% among sources with at least 10 ks of XRT exposure time. We construct the time-averaged spectral energy distribution for each of the 354 quasars using UVOT photometric measurements and XRT spectra. From model fits to these SEDs, we find that the big blue bump contributes about 0.3 dex to the quasar luminosity. We re-visit the alpha_ox-L_uv relation by selecting a clean sample with only type 1 radio-quiet quasars; the dispersion of this relation is reduced by at least 15% compared to studies that use non-simultaneous UV/opt...

  16. Evidence for the Thermal Sunyaev-Zel'dovich Effect Associated with Quasar Feedback

    Science.gov (United States)

    Crichton, Devin T.; Gralla, Megan B.; Hall, Kirsten; Marriage, Tobias; Zakamska, Nadia L.; Atacama Cosmology Telescope Collaboration

    2016-06-01

    Using a radio-quiet subsample of the Sloan Digital Sky Survey spectroscopic quasar catalog, spanning redshifts 0.5–3.5, we derive the mean millimetre and far-infrared quasar spectral energy distributions (SEDs) via a stacking analysis of Atacama Cosmology Telescope and Herschel-SPIRE data. We constrain the form of the far-infrared emission and find 3–4σ evidence for the thermal Sunyaev-Zel'dovich (SZ) effect, characteristic of a hot ionized gas component with thermal energy (6.2 ± 1.7) × 1060 erg. This amount of thermal energy is greater than expected assuming only hot gas in virial equilibrium with the dark matter haloes of (1 ‑ 5) × 1012h‑1M⊙ that these systems are expected to occupy. Modeling this signal as energy injection due to quasar feedback, our measurements are found to be consistent with a scenario in which quasars deposit up to (14.5±3.3) τ8‑1 per cent of their radiative energy into their circumgalactic environment if their typical period of quasar activity is τ8 × 108 years.

  17. MusE GAs FLOw and Wind (MEGAFLOW) I: First MUSE results on background quasars

    CERN Document Server

    Schroetter, Ilane; Wendt, Martin; Contini, Thierry; Finley, Hayley; Pello, Roser; Bacon, Roland; Cantalupo, Sebastiano; Marino, Raffaella; Richard, Johan; Lilly, Simon; Schaye, Joop; Soto, Kurt; Steinmetz, Matthias; Straka, Lorrie A; Wisotzki, Lutz

    2016-01-01

    The physical properties of galactic winds are one of the keys to understand galaxy formation and evolution. These properties can be constrained thanks to background quasar lines of sight (LOS) passing near star-forming galaxies (SFGs). We present the first results of the MusE GAs FLOw and Wind (MEGAFLOW) survey obtained of 2 quasar fields which have 8 MgII absorbers of which 3 have rest-equivalent width greater than 0.8 \\AA. With the new Multi Unit Spectroscopic Explorer (MUSE) spectrograph on the Very Large Telescope (VLT), we detect 6 (75$\\%$) MgII host galaxy candidates withing a radius of 30 arcsec from the quasar LOS. Out of these 6 galaxy--quasar pairs, from geometrical arguments, one is likely probing galactic outflows, two are classified as "ambiguous", two are likely probing extended gaseous disks and one pair seems to be a merger. We focus on the wind$-$pair and constrain the outflow using a high resolution quasar spectra from Ultraviolet and Visual Echelle Spectrograph (UVES). Assuming the metal ab...

  18. AN APPARENT REDSHIFT DEPENDENCE OF QUASAR CONTINUUM: IMPLICATION FOR COSMIC DUST EXTINCTION?

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Xiaoyi; Shen, Shiyin; Shao, Zhengyi; Yin, Jun, E-mail: ssy@shao.ac.cn [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China)

    2015-04-01

    We investigate the luminosity and redshift dependence of the quasar continuum by means of the composite spectrum using a large non-BAL radio-quiet quasar sample drawn from the Sloan Digital Sky Survey. Quasar continuum slopes in the UV-Opt band are measured at two different wavelength ranges, i.e., α{sub ν12} (1000 ∼ 2000 Å) and α{sub ν24} (2000 ∼ 4000 Å) derived from a power-law fitting. Generally, the UV spectra slope becomes harder (higher α{sub ν}) toward higher bolometric luminosity. On the other hand, when quasars are further grouped into luminosity bins, we find that both α{sub ν12} and α{sub ν24} show significant anti-correlations with redshift (i.e., the quasar continuum becomes redder toward higher redshift). We suggest that the cosmic dust extinction is very likely the cause of this observed α{sub ν} − z relation. We build a simple cosmic dust extinction model to quantify the observed reddening tendency and find an effective dust density nσ{sub v} ∼ 10{sup −5}h Mpc{sup −1} at z < 1.5. The other possibilities that could produce such a reddening effect have also been discussed.

  19. An Apparent Redshift Dependence of Quasar Continuum: Implication for Cosmic Dust Extinction?

    Science.gov (United States)

    Xie, Xiaoyi; Shen, Shiyin; Shao, Zhengyi; Yin, Jun

    2015-04-01

    We investigate the luminosity and redshift dependence of the quasar continuum by means of the composite spectrum using a large non-BAL radio-quiet quasar sample drawn from the Sloan Digital Sky Survey. Quasar continuum slopes in the UV-Opt band are measured at two different wavelength ranges, i.e., αν12 (1000 ˜ 2000 Å) and αν24 (2000 ˜ 4000 Å) derived from a power-law fitting. Generally, the UV spectra slope becomes harder (higher αν) toward higher bolometric luminosity. On the other hand, when quasars are further grouped into luminosity bins, we find that both αν12 and αν24 show significant anti-correlations with redshift (i.e., the quasar continuum becomes redder toward higher redshift). We suggest that the cosmic dust extinction is very likely the cause of this observed αν - z relation. We build a simple cosmic dust extinction model to quantify the observed reddening tendency and find an effective dust density nσv ˜ 10-5h Mpc-1 at z effect have also been discussed.

  20. The odd couple: quasars and black holes

    OpenAIRE

    Tremaine, Scott

    2014-01-01

    Quasars emit more energy than any other objects in the universe, yet are not much bigger than the solar system. We are almost certain that quasars are powered by giant black holes of up to $10^{10}$ times the mass of the Sun, and that black holes of between $10^6$ and $10^{10}$ solar masses---dead quasars---are present at the centers of most galaxies. Our own galaxy contains a black hole of $4.3\\times10^6$ solar masses. The mass of the central black hole appears to be closely related to other...

  1. Features of thin spatial structure of the quasar 3C216 at decameter lengths of waves

    Science.gov (United States)

    Megn, A. V.; Rashkovskiy, S. L.; Shepelev, V. A.; Inytin, G. A.; Vashchishin, R. V.; Brazhenko, A. I.; Koshoviy, V. V.; Lozinskiy, A. B.

    2010-01-01

    The results of interferometric researches of the quasar 3C216 have been presented. The model of brightness distribution of the quasar at frequencies of 20 and 25 MHz and spectra of its details at frequencies below 1 GHz have been refined. It was found out, that at decameter lengths the radio image of 3C216 has three components. It consists of a compact component having the size limited by scattering, an extended component with the size of 4.5'' and a halo with the size about 23''. The northeast hot spot (instead of the core, as it was supposed earlier) is the dominating compact component at decameter waves. The self-absorption effect in the northeast hot spot has been detected.

  2. Quasar host environments: The view from Planck

    Science.gov (United States)

    Verdier, Loïc; Melin, Jean-Baptiste; Bartlett, James G.; Magneville, Christophe; Palanque-Delabrouille, Nathalie; Yèche, Christophe

    2016-04-01

    We measure the far-infrared emission of the general quasar (QSO) population using Planck observations of the Baryon Oscillation Spectroscopic Survey QSO sample. By applying multi-component matched multi-filters to the seven highest Planck frequencies, we extract the amplitudes of dust, synchrotron, and thermal Sunyaev-Zeldovich (SZ) signals for nearly 300 000 QSOs over the redshift range 0.1

  3. Quasar Host Environments: The view from Planck

    CERN Document Server

    Verdier, Loïc; Bartlett, James G; Magneville, Christophe; Palanque-Delabrouille, Nathalie; Yèche, Christophe

    2015-01-01

    We measure the far-infrared emission of the general quasar (QSO) population using Planck observations of the Baryon Oscillation Spectroscopic Survey QSO sample. By applying multi-component matched multi-filters to the seven highest Planck frequencies, we extract the amplitudes of dust, synchrotron and thermal Sunyaev-Zeldovich (SZ) signals for nearly 300,000 QSOs over the redshift range $0.1

  4. Galaxies in x-ray selected clusters and groups in Dark Energy Survey Data I: Stellar mass growth of bright central galaxies since Z similar to 1.2

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Y.; Miller, C.; McKay, T.; Rooney, P.; Evrard, A. E.; Romer, A. K.; Perfecto, R.; Song, J; Desai, S.; Mohr, J. J.; Vikram, V.

    2016-01-10

    Using the science verification data of the Dark Energy Survey for a new sample of 106 X-ray selected clusters and groups, we study the stellar mass growth of bright central galaxies (BCGs) since redshift z similar to 1.2. Compared with the expectation in a semi-analytical model applied to the Millennium Simulation, the observed BCGs become under-massive/under-luminous with decreasing redshift. We incorporate the uncertainties associated with cluster mass, redshift, and BCG stellar mass measurements into an analysis of a redshift-dependent BCG-cluster mass relation, m(*) proportional to (M-200/1.5 x 10(14)M(circle dot))(0.24 +/- 0.08)(1+z)(-0.19 +/- 0.34), and compare the observed relation to the model prediction. We estimate the average growth rate since z = 1.0 for BCGs hosted by clusters of M-200,M-z = 10(13.8)M(circle dot); at z = 1.0: m(*, BCG) appears to have grown by 0.13 +/- 0.11 dex, in tension at the similar to 2.5 sigma significance level with the 0.40 dex growth rate expected from the semi-analytic model. We show that the build-up of extended intracluster light after z = 1.0 may alleviate this tension in BCG growth rates.

  5. Unveiling hidden black holes in the cosmic web: Dark matter halos of WISE quasars from Planck CMB lensing

    Science.gov (United States)

    Hickox, Ryan

    The WISE and Planck surveys have now produced groundbreaking data sets which, in concert, can be exploited to obtain revolutionary constraints on the evolution of structure in the Universe. One particularly powerful application of WISE has been to uncover millions of the previously "hidden" obscured quasars, rapidly growing supermassive black holes that are shrouded in gas and dust and so are not detectable using traditional ground-based optical and near-IR techniques. Recently, Planck has produced the most precise all-sky map to date of dark matter structures via the lensing of the cosmic microwave background (CMB). We propose to combine these data sets to obtain a uniquely powerful measurement of the link between rapidly growing black holes and their host dark matter structures, by cross-correlating the density field of WISE-selected quasars with the CMB lensing convergence maps obtained from Planck. This proposal will build on our current ADAP program (NNX12AE38G), which studies the host dark matter halos of WISE-selected quasars via spatial clustering. NNX12AE38G involves a detailed characterization of the redshifts, luminosities, and spectral energy distributions of WISE-selected quasars and uses new techniques to measure how quasars cluster around themselves. NNX12AE38G has contributed to more than 10 journal articles and 5 conference proceedings. Building on our current work, an even more complete understanding of the link between black holes and their host dark matter structures is possible if we employ an independent method for measuring the clustering bias (and thus characteristic halo mass) of the quasar population. This has recently become possible using CMB lensing maps. In the past two years, our team has conducted an initial analysis covering 2500 square degrees using WISE-selected quasars and lensing maps from the South Pole Telescope (Geach, Hickox, Myers et al., 2013), and have implemented this technique with Planck over part of the SDSS region

  6. THE XMM-NEWTON X-RAY SPECTRA OF THE MOST X-RAY LUMINOUS RADIO-QUIET ROSAT BRIGHT SURVEY-QSOs: A REFERENCE SAMPLE FOR THE INTERPRETATION OF HIGH-REDSHIFT QSO SPECTRA

    International Nuclear Information System (INIS)

    We present the broadband X-ray properties of four of the most X-ray luminous (LX ≥ 1045 erg s-1 in the 0.5-2 keV band) radio-quiet QSOs found in the ROSAT Bright Survey. This uniform sample class, which explores the extreme end of the QSO luminosity function, exhibits surprisingly homogenous X-ray spectral properties: a soft excess with an extremely smooth shape containing no obvious discrete features, a hard power law above 2 keV, and a weak narrow/barely resolved Fe Kα fluorescence line for the three high signal-to-noise ratio (S/N) spectra. The soft excess can be well fitted with only a soft power law. No signatures of warm or cold intrinsic absorbers are found. The Fe Kα centroids and the line widths indicate emission from neutral Fe (E = 6.4 keV) originating from cold material from distances of only a few light days or further out. The well-constrained equivalent widths (EW) of the neutral Fe lines are higher than expected from the X-ray Baldwin effect which has been only poorly constrained at very high luminosities. Taking into account our individual EW measurements, we show that the X-ray Baldwin effect flattens above LX ∼ 1044 erg s-1 (2-10 keV band) where an almost constant (EW) of ∼100 eV is found. We confirm the assumption of having very similar X-ray active galactic nucleus properties when interpreting stacked X-ray spectra. Our stacked spectrum serves as a superb reference for the interpretation of low S/N spectra of radio-quiet QSOs with similar luminosities at higher redshifts routinely detected by XMM-Newton and Chandra surveys.

  7. Giant Gas Cloud Made of Atoms Formed in First Stars Revealed in Universe's Most Distant Quasar

    Science.gov (United States)

    2003-07-01

    Astronomers studying the most distant quasar yet found in the Universe have discovered a massive reservoir of gas containing atoms made in the cores of some of the first stars ever formed. The carbon-monoxide gas was revealed by the National Science Foundation's Very Large Array (VLA) and the Plateau de Bure radio interferometer in Europe. The gas, along with the young galaxy containing it, is seen as it was when the Universe was only one-sixteenth its current age, just emerging from the primeval "Dark Ages" before light could travel freely through the cosmos. VLA Image of Quasar VLA Image of J1148+5251 CREDIT: NRAO/AUI/NSF (Click on Image for Larger Version) "Our discovery of this much carbon monoxide gas in such an extremely distant and young galaxy is surprising. It means that, even at a very early time in the history of the Universe, galaxies already had huge amounts of molecular gas that would eventually form new generations of stars," said Chris Carilli, of the National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico. The distant galaxy, dubbed J1148+5251, contains a bright quasar powered by a black hole at least a billion times more massive than the Sun. The galaxy is seen as it was only 870 million years after the Big Bang. The Universe now is 13.7 billion years old. J1148+5251 would have been among the first luminous objects in the Universe. The original atoms formed in the Universe within the first three minutes of the Big Bang were only hydrogen and helium. Carbon and oxygen -- the atoms making up carbon monoxide -- had to be made in the thermonuclear furnaces at the cores of the earliest stars. "The carbon and oxygen atoms in the gas we detected were made by some of the first stars ever formed, only about 650 million years after the Big Bang. In the next 200 million years or so, those stars -- probably very different stars from those we see today -- exploded as supernovae, spreading the carbon and oxygen out into space. Those atoms then cooled

  8. Mid-Infrared Selection of Brown Dwarfs and High-Redshift Quasars

    CERN Document Server

    Stern, D; Allen, L; Bian, C; Blain, A; Brand, K; Brodwin, M; Brown, M J I; Cool, R; Desai, V; Dey, A; Eisenhardt, P; González, A; Jannuzi, B T; Menendez-Delmestre, K; Smith, H A; Soifer, B T; Tiede, G P; Wright, E

    2006-01-01

    We discuss color selection of rare objects in a wide-field, multiband survey spanning from the optical to the mid-infrared. Simple color criteria simultaneously identify and distinguish two of the most sought after astrophysical sources: the coolest brown dwarfs and the most distant quasars. We present spectroscopically-confirmed examples of each class identified in the IRAC Shallow Survey of the Bootes field of the NOAO Deep Wide-Field Survey. ISS J142950.9+333012 is a T4.5 brown dwarf at a distance of approximately 42 pc, and ISS J142738.5+331242 is a radio-loud quasar at redshift z=6.12. Our selection criteria identify a total of four candidates over 8 square degrees of the Bootes field. The other two candidates are both confirmed 5.5quasars, previously reported by Cool et al. (2006). We discuss the implications of these discoveries and conclude that there are excellent prospects for extending such searches to cooler brown dwarfs and higher redshift quasars.

  9. Moon night sky brightness simulation for the Xinglong station

    International Nuclear Information System (INIS)

    Using a sky brightness monitor at the Xinglong station of National Astronomical Observatories, Chinese Academy of Sciences, we collected data from 22 dark clear nights and 90 moon nights. We first measured the sky brightness variation with time for dark nights and found a clear correlation between sky brightness and human activity. Then with a modified sky brightness model of moon nights and data from these nights, we derived the typical value for several important parameters in the model. With these results, we calculated the sky brightness distribution under a given moon condition for the Xinglong station. Furthermore, we simulated the sky brightness distribution of a moon night for a telescope with a 5° field of view (such as LAMOST). These simulations will be helpful for determining the limiting magnitude and exposure time, as well as planning the survey for LAMOST during moon nights

  10. ASERA: A Spectrum Eye Recognition Assistant for Quasar Spectra

    CERN Document Server

    Yuan, Hailong; Zhang, Yanxia; Lei, Yajuan; Dong, Yiqiao; Zhao, Yongheng

    2014-01-01

    Spectral type recognition is an important and fundamental step of large sky survey projects in the data reduction for further scientific research, like parameter measurement and statistic work. It tends out to be a huge job to manually inspect the low quality spectra produced from massive spectroscopic survey, where the automatic pipeline may not provide confident type classification results. In order to improve the efficiency and effectiveness of spectral classification, we develop a semi-automated toolkit named ASERA, A Spectrum Eye Recognition Assistant. The main purpose of ASERA is to help the user in quasar spectral recognition and redshift measurement. Furthermore it can also be used to recognize various types of spectra of stars, galaxies and AGNs (Active Galactic Nucleus). It is an interactive software allowing the user to visualize observed spectra, superimpose template spectra from the Sloan Digital Sky Survey (SDSS), and interactively access related spectral line information. It is an efficient and...

  11. Observations of feedback from radio-quiet quasars - I. Extents and morphologies of ionized gas nebulae

    Science.gov (United States)

    Liu, Guilin; Zakamska, Nadia L.; Greene, Jenny E.; Nesvadba, Nicole P. H.; Liu, Xin

    2013-04-01

    Black hole feedback - the strong interaction between the energy output of supermassive black holes and their surrounding environments - is routinely invoked to explain the absence of overly luminous galaxies, the black hole versus bulge correlations and the similarity of black hole accretion and star formation histories. Yet direct probes of this process in action are scarce and limited to small samples of active nuclei. In this paper, we present Gemini Integral Field Unit observations of the distribution of ionized gas around luminous, obscured, radio-quiet quasars at z ˜ 0.5. We detect extended ionized gas nebulae via [O III] λ5007 Å emission in every case, with a mean diameter of 28 kpc. These nebulae are nearly perfectly round, with Hβ surface brightness declining ∝R-3.5 ± 1.0. The regular morphologies of nebulae around radio-quiet quasars are in striking contrast with lumpy or elongated [O III] nebulae seen around radio galaxies at low and high redshifts. We present the uniformly measured size-luminosity relationship of [O III] nebulae around Seyfert 2 galaxies and type 2 quasars spanning six orders of magnitude in luminosity and confirm the flat slope of the correlation (R_{[O III]}∝ L_{[O III]}^{0.25± 0.02}). We propose a model of clumpy nebulae in which clouds that produce line emission transition from being ionization-bounded at small distances from the quasar to being matter-bounded in the outer parts of the nebula. The model - which has a declining pressure profile - qualitatively explains line ratio profiles and surface brightness profiles seen in our sample. It is striking that we see such smooth and round large-scale gas nebulosities in this sample, which are inconsistent with illuminated merger debris and which we suggest may be the signature of accretion energy from the nucleus reaching gas at large scales.

  12. The brightness of colour.

    Directory of Open Access Journals (Sweden)

    David Corney

    Full Text Available BACKGROUND: The perception of brightness depends on spatial context: the same stimulus can appear light or dark depending on what surrounds it. A less well-known but equally important contextual phenomenon is that the colour of a stimulus can also alter its brightness. Specifically, stimuli that are more saturated (i.e. purer in colour appear brighter than stimuli that are less saturated at the same luminance. Similarly, stimuli that are red or blue appear brighter than equiluminant yellow and green stimuli. This non-linear relationship between stimulus intensity and brightness, called the Helmholtz-Kohlrausch (HK effect, was first described in the nineteenth century but has never been explained. Here, we take advantage of the relative simplicity of this 'illusion' to explain it and contextual effects more generally, by using a simple Bayesian ideal observer model of the human visual ecology. We also use fMRI brain scans to identify the neural correlates of brightness without changing the spatial context of the stimulus, which has complicated the interpretation of related fMRI studies. RESULTS: Rather than modelling human vision directly, we use a Bayesian ideal observer to model human visual ecology. We show that the HK effect is a result of encoding the non-linear statistical relationship between retinal images and natural scenes that would have been experienced by the human visual system in the past. We further show that the complexity of this relationship is due to the response functions of the cone photoreceptors, which themselves are thought to represent an efficient solution to encoding the statistics of images. Finally, we show that the locus of the response to the relationship between images and scenes lies in the primary visual cortex (V1, if not earlier in the visual system, since the brightness of colours (as opposed to their luminance accords with activity in V1 as measured with fMRI. CONCLUSIONS: The data suggest that perceptions

  13. Optical spectra and radio properties of quasars

    International Nuclear Information System (INIS)

    Using high quality spectrophotometric scans obtained at the McDonald Observatory, and data from the literature the author shows that, for quasars, the relative strength of optical Fe II emission (the broad blended feature lambda4570) may be roughly inversely proportional to line widths (full width at half maximum, FWHM). A similar relation between the relative intensity of the UV Fe II blend between 2300 and 2600 A (the lambda2500 feature) and the widths of Mg II and Hβ is shown. She distinguishes between compact and extended radio sources and includes radio quiet quasars, Seyfert 1 galaxies and BLRG's. The quasars associated with extended radio sources have the broadest emission lines and the weakest Fe II, falling close to the region occupied by BLRG's which also have extended radio structure. Those quasars with strong Fe II and compact radio structure are most similar to the Seyfert 1 galaxies. (Auth.)

  14. Quasars as probes of cosmological reionization

    CERN Document Server

    Mortlock, Daniel J

    2015-01-01

    Quasars are the most luminous non-transient sources in the epoch of cosmological reionization (i.e., which ended a billion years after the Big Bang, corresponding to a redshift of z ~ 5), and are powerful probes of the inter-galactic medium at that time. This review covers current efforts to identify high-redshift quasars and how they have been used to constrain the reionization history. This includes a full description of the various processes by which neutral hydrogen atoms can absorb/scatter ultraviolet photons, and which lead to the Gunn-Peterson effect, dark gap and dark pixel analyses, quasar near zones and damping wing absorption. Finally, the future prospects for using quasars as probes of reionization are described.

  15. Quasars as tracers of cosmic flows

    CERN Document Server

    Modzelewska, J; Bilicki, M; Hryniewicz, K; Krupa, M; Petrogalli, F; Pych, W; Kurcz, A; Udalski, A

    2014-01-01

    Quasars, as the most luminous persistent sources in the Universe, have broad applications for cosmological studies. In particular, they can be employed to directly measure the expansion history of the Universe, similarly to SNe Ia. The advantage of quasars is that they are numerous, cover a broad range of redshifts, up to $z = 7$, and do not show significant evolution of metallicity with redshift. The idea is based on the relation between the time delay of an emission line and the continuum, and the absolute monochromatic luminosity of a quasar. For intermediate redshift quasars, the suitable line is Mg II. Between December 2012 and March 2014, we performed five spectroscopic observations of the QSO CTS C30.10 ($z = 0.900$) using the South African Large Telesope (SALT), supplemented with photometric monitoring, with the aim of determining the variability of the line shape, changes in the total line intensity and in the continuum. We show that the method is very promising.

  16. CA BrightStor

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    CA推出的BrightStor系列存储管理解决方案已经成为企业电子商务体系架构管理战略中举足轻重的组成部分。BrightStor是一整套企业级的智能化存储管理解决方案,定位在存储硬件设备和上层应用之间,通过各种集成化的产品和工具为驻留在企业任何位置的数据提供全方位的、有效的存储管理和保护。

  17. The Physical Nature of Polar Broad Absorption Line Quasars

    Science.gov (United States)

    Ghost, Kajal; Punsly, Brian

    2007-01-01

    It has been shown based on radio variability arguments that some BALQSOs (broad absorption line quasars) are viewed along the polar axis (o rthogonal to accretion disk) in the recent article of Zhou et a. Thes e arguments are based on the brightness temperature, T(sub b) exceedi ng 10(exp 12) K which leads to the well-known inverse Compton catastr ophe unless the radio jet is relativistic and is viewed along its axi s. In this letter, we expand the Zhou et al sample of polar BALQSOs u sing their techniques applied to SDSS DR5. In the process, we clarify a mistake in their calculation of brightness temperature. The expanded sample of high T(sub b) BALQSOS, has an inordinately large fraction of LoBALQSOs (low ionization BALQSOs). We consider this an important clue to understanding the nature of the polar BALQSOs. This is expec ted in the polar BALQSO analytical/numerical models of Punsly that pr edicted that LoBALQSOs occur when the line of sight is very close to the polar axis, where the outflow density is the highest.

  18. Bright Economic Prospects

    Institute of Scientific and Technical Information of China (English)

    Zhang Minqiu

    2004-01-01

    @@ India is expected to register an 8.2% growth rate for the 2003-04 fiscal year. The overall economic situation this year has been satisfactory despite the scaled down 6-6.5% growth rate for the new fiscal year due to oil price hikes, reduced monsoon volume and some 7% inflation. Judging from the following factors, bright prospects are in store for the country down the road.

  19. Balmer line shifts in quasars

    CERN Document Server

    Sulentic, J W; Del Olmo, A; Zamfir, S

    2015-01-01

    We offer a broad review of Balmer line phenomenology in type 1 active galactic nuclei, briefly sum- marising luminosity and radio loudness effects, and discussing interpretation in terms of nebular physics along the 4D eigenvector 1 sequence of quasars. We stress that relatively rare, peculiar Balmer line profiles (i.e., with large shifts with respect to the rest frame or double and multiple peaked) that start attracted attentions since the 1970s are still passable of multiple dynamical interpretation. More mainstream objects are still not fully understood as well, since competing dynamical models and geometries are possible. Further progress may come from inter-line comparison across the 4D Eigenvector 1 sequence.

  20. Quasar clustering in a galaxy and quasar formation model based on ultra high-resolution N-body simulations

    Science.gov (United States)

    Oogi, Taira; Enoki, Motohiro; Ishiyama, Tomoaki; Kobayashi, Masakazu A. R.; Makiya, Ryu; Nagashima, Masahiro

    2016-02-01

    We investigate clustering properties of quasars using a new version of our semi-analytic model of galaxy and quasar formation with state-of-the-art cosmological N-body simulations. In this study, we assume that a major merger of galaxies triggers cold gas accretion on to a supermassive black hole and quasar activity. Our model can reproduce the downsizing trend of the evolution of quasars. We find that the median mass of quasar host dark matter haloes increases with cosmic time by an order of magnitude from z = 4 (a few 1011 M⊙) to z = 1 (a few 1012 M⊙), and depends only weakly on the quasar luminosity. Deriving the quasar bias through the quasar-galaxy cross-correlation function in the model, we find that the quasar bias does not depend on the quasar luminosity, similar to observed trends. This result reflects the fact that quasars with a fixed luminosity have various Eddington ratios and thus have various host halo masses that primarily determine the quasar bias. We also show that the quasar bias increases with redshift, which is in qualitative agreement with observations. Our bias value is lower than the observed values at high redshifts, implying that we need some mechanisms that make quasars inactive in low-mass haloes and/or that make them more active in high-mass haloes.