Browsing by Author "Burles, S"

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    An initial survey of white dwarfs in the Sloan Digital Sky Survey
    (2003) Harris, HC; Liebert, J; Kleinman, SJ; Nitta, A; Anderson, SF; Knapp, GR; Krzesinski, J; Schmidt, G; Strauss, MA; Berk, DV; Eisenstein, D; Hawley, S; Margon, B; Munn, JA; Silvestri, NM; Smith, JA; Szkody, P; Collinge, MJ; Dahn, CC; Fan, XH; Hall, PB; Schneider, DP; Brinkmann, J; Burles, S; Gunn, JE; Hennessy, GS; Hindsley, R; Ivezic, Z; Kent, S; Lamb, DQ; Lupton, RH; Nichol, RC; Pier, JR; Schlegel, DJ; SubbaRao, M; Uomoto, A; Yanny, B; York, DG
    An initial assessment is made of white dwarf and hot subdwarf stars observed in the Sloan Digital Sky Survey. In a small area of sky ( 190 square degrees), observed much like the full survey will be, 269 white dwarfs (WDs) and 56 hot subdwarfs are identified spectroscopically where only 44 white dwarfs and five hot subdwarfs were known previously. Most are ordinary DA ( hydrogen atmosphere) and DB ( helium) types. In addition, in the full survey to date, a number of WDs have been found with uncommon spectral types. Among these are blue DQ stars displaying lines of atomic carbon; red DQ stars showing molecular bands of C-2 with a wide variety of strengths; DZ stars where Ca and occasionally Mg, Na, and/or Fe lines are detected; and magnetic WDs with a wide range of magnetic field strengths in DA, DB, DQ, and ( probably) DZ spectral types. Photometry alone allows identification of stars hotter than 12,000 K, and the density of these stars for 15 < g < 20 is found to be similar to2.2 deg(-2) at Galactic latitudes of 29degrees - 62degrees. Spectra are obtained for roughly half of these hot stars. The spectra show that for 15 < g < 17, 40% of hot stars are WDs, and the fraction of WDs rises to similar to90% at g = 20. The remainder are hot sdB and sdO stars.
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    Composite quasar spectra from the Sloan Digital Sky Survey
    (2001) Vanden Berk, DE; Richards, GT; Bauer, A; Strauss, MA; Schneider, DP; Heckman, TM; York, DG; Hall, PB; Fan, XH; Knapp, GR; Anderson, SF; Annis, J; Bahcall, NA; Bernardi, M; Briggs, JW; Brinkmann, J; Brunner, R; Burles, S; Carey, L; Castander, FJ; Connolly, AJ; Crocker, JH; Csabai, I; Doi, M; Finkbeiner, D; Friedman, S; Frieman, JA; Fukugita, M; Gunn, JE; Hennessy, GS; Ivezic, Z; Kent, S; Kunszt, PZ; Lamb, DQ; Leger, RF; Long, DC; Loveday, J; Lupton, RH; Meiksin, A; Pier, JR; Pope, A; Rockosi, CM; Schlegel, DJ; Siegmund, WA; Smee, S; Snir, Y; Stoughton, C; Stubbs, C; SubbaRao, M; Szalay, AS; Szokoly, GP; Tremonti, C; Uomoto, A; Waddell, P; Yanny, B; Zheng, W
    We have created a variety of composite quasar spectra using a homogeneous data set of over 2200 spectra from the Sloan Digital Sky Survey (SDSS). The quasar sample spans a redshift range of 0.044 less than or equal to z less than or equal to 4.789 and an absolute r' magnitude range of -18.0 to -26.5. The input spectra cover an observed wavelength range of 3800-9200 Angstrom at a resolution of 1800. The median composite covers a rest-wavelength range from 800 to 8555 Angstrom and reaches a peak signal-to-noise ratio of over 300 per 1 Angstrom resolution element in the rest frame. We have identified over 80 emission-line features in the spectrum. Emission-line shifts relative to nominal laboratory wavelengths are seen for many of the ionic species. Peak shifts of the broad permitted and semiforbidden lines are strongly correlated with ionization energy, as previously suggested, but we find that the narrow forbidden lines are also shifted by amounts that are strongly correlated with ionization energy. The magnitude of the forbidden line shifts is less than or similar to 100 km s(-1), compared with shifts of up to 550 km s(-1) for some of the permitted and semiforbidden lines. At wavelengths longer than the Ly alpha emission, the continuum of the geometric mean composite is well fitted by two power laws, with a break at approximate to 5000 Angstrom. The frequency power-law index, alpha (v), is -0.44 from approximate to 1300 to 5000 and -2.45 redward of approximate to 5000 The abrupt change in slope can be accounted for partly by host-galaxy contamination at low redshift. Stellar absorption lines, including higher order Balmer lines, seen in the composites suggest that young or intermediate-age stars make a significant contribution to the light of the host galaxies. Most of the spectrum is populated by blended emission lines, especially in the range 1500-3500 Angstrom, which can make the estimation of quasar continua highly uncertain unless large ranges in wavelength are observed. An electronic table of the median quasar template is available.
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    Photometric redshifts of quasars
    (2001) Richards, GT; Weinstein, MA; Schneider, DP; Fan, XH; Strauss, MA; Vanden Berk, DE; Annis, J; Burles, S; Laubacher, EM; York, DG; Frieman, JA; Johnston, D; Scranton, R; Gunn, JE; Nichol, RC; Ivezic, Z; Nichol, RC; Budavári, T; Csabai, I; Szalay, AS; Connolly, AJ; Szokoly, GP; Bahcall, NA; Benítez, N; Brinkmann, J; Brunner, R; Fukugita, M; Hall, PB; Hennessy, GS; Knapp, GR; Kunszt, PZ; Lamb, DQ; Munn, JA; Newberg, HJ; Stoughton, C
    We demonstrate that the design of the Sloan Digital Sky Survey (SDSS) filter system and the quality of the SDSS imaging data are sufficient for determining accurate and precise photometric redshifts of quasars. Using a sample of 2625 quasars, we show that "photo-z" determination is even possible for z less than or equal to2.2 despite the lack of a strong continuum break, which robust photo-z techniques normally require. We find that, using our empirical method on our sample of objects known to be quasars, approximately 70% of the photometric redshifts are correct to within Deltaz = 0.2; the fraction of correct photometric redshifts is even better for z >3. The accuracy of quasar photometric redshifts does not appear to be dependent upon magnitude to nearly 21st magnitude in i'. Careful calibration of the color-redshift relation to 21st magnitude may allow for the discovery of similar to 10(6) quasar candidates in addition to the 10(5) quasars that the SDSS will confirm spectroscopically. We discuss the efficient selection of quasar candidates from imaging data for use with the photometric redshift technique and the potential scientific uses of a large sample of quasar candidates with photometric redshifts.
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    SDSS J092455.87+021924.9: An interesting gravitationally lensed quasar from the Sloan Digital Sky Survey
    (2003) Inada, N; Becker, RH; Burles, S; Castander, FJ; Eisenstein, D; Hall, PB; Johnston, DE; Pindor, B; Richards, GT; Schechter, PL; Sekiguchi, M; White, RL; Brinkmann, J; Frieman, JA; Kleinman, SJ; Krzesinski, J; Long, DC; Neilsn, EH; Newman, PR; Nitta, A; Schneider, DP; Snedden, S; York, DG
    We report the discovery of a new gravitationally lensed quasar from the Sloan Digital Sky Survey, SDSS J092455.87+021924.9 (SDSS J0924+0219). This object was selected from among known SDSS quasars by an algorithm that was designed to select another known SDSS lensed quasar (SDSS J1226-0006A,B). Five separate components, three of which are unresolved, are identified in photometric follow-up observations obtained with the Magellan Consortium's 6.5 m Walter Baade Telescope at Las Campanas Observatory. Two of the unresolved components (designated A and B) are confirmed to be quasars with z = 1.524; the velocity difference is less than 100 km s(-1) according to spectra taken with the W. M. Keck Observatory's Keck II Telescope at Mauna Kea, Hawaii. A third stellar component, designated C, has the colors of a quasar with redshift similar to components A and B. The maximum separation of the point sources is 1."78. The other two sources, designated G and D, are resolved. Component G appears to be the best candidate for the lensing galaxy. Although component D is near the expected position of the fourth lensed component in a four-image lens system, its properties are not consistent with being the image of a quasar at z similar to 1.5. Nevertheless, the identical redshifts of components A and B and the presence of component C strongly suggest that this object is a gravitational lens. Our observations support the idea that a foreground object reddens the fourth lensed component and that another unmodeled effect (such as micro- or millilensing) demagnifies it, but we cannot rule out the possibility that SDSS J0924+0219 is an example of the relatively rare class of "three-component'' lens systems.
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    Sloan Digital Sky Survey
    (2002) Stoughton, C; Lupton, RH; Bernardi, M; Blanton, MR; Burles, S; Castander, FJ; Connolly, AJ; Eisenstein, DJ; Frieman, JA; Hennessy, GS; Hindsley, RB; Ivezic, Z; Kent, S; Kunszt, PZ; Lee, BC; Meiksin, A; Munn, JA; Newberg, HJ; Nichol, RC; Nicinski, T; Pier, JR; Richards, GT; Richmond, MW; Schlegel, DJ; Smith, JA; Strauss, MA; SubbaRao, M; Szalay, AS; Thakar, AR; Tucker, DL; Vanden Berk, DE; Yanny, B; Adelman, JK; Anderson, JE; Anderson, SF; Annis, J; Bahcall, NA; Bakken, JA; Bartelmann, M; Bastian, S; Bauer, A; Berman, E; Böhringer, H; Boroski, WN; Bracker, S; Briegel, C; Briggs, JW; Brinkmann, J; Brunner, R; Carey, L; Carr, MA; Chen, B; Christian, D; Colestock, PL; Crocker, JH; Csabai, IN; Czarapata, PC; Dalcanton, J; Davidsen, AF; Davis, JE; Dehnen, W; Dodelson, S; Doi, M; Dombeck, T; Donahue, M; Ellman, N; Elms, BR; Evans, ML; Eyer, L; Fan, XH; Federwitz, GR; Friedman, S; Fukugita, M; Gal, R; Gillespie, B; Glazebrook, K; Gray, J; Grebel, EK; Greenawalt, B; Greene, G; Gunn, JE; de Haas, E; Haiman, Z; Haldeman, M; Hall, PB; Hamabe, M; Hansen, B; Harris, FH; Harris, H; Harvanek, M; Hawley, SL; Hayes, JJE; Heckman, TM; Helmi, A; Henden, A; Hogan, CJ; Hogg, DW; Holmgren, DJ; Holtzman, J; Huang, CH; Hull, C; Ichikawa, SI; Ichikawa, T; Johnston, DE; Kauffmann, G; Kim, RSJ; Kimball, T; Kinney, E; Klaene, M; Kleinman, SJ; Klypin, A; Knapp, GR; Korienek, J; Krolik, J; Kron, RG; Krzesinski, J; Lamb, DQ; Leger, RF; Limmongkol, S; Lindenmeyer, C; Long, DC; Loomis, C; Loveday, J; MacKinnon, B; Mannery, EJ; Mantsch, PM; Margon, B; McG'hee, P; Mckay, TA; McLean, B; Menou, K; Merelli, A; Mo, HJ; Monet, DG; Nakamura, O; Narayanan, VK; Nash, T; Neilsen, EH; Newman, PR; Nitta, A; Odenkirchen, M; Okada, N; Okamura, S; Ostriker, JP; Owen, R; Pauls, AG; Peoples, J; Peterson, RS; Petravick, D; Pope, A; Pordes, R; Postman, M; Prosapio, A; Quinn, TR; Rechenmacher, R; Rivetta, CH; Rix, HW; Rockosi, CM; Rosner, R; Ruthmansdorfer, K; Sandford, D; Schneider, DP; Scranton, R; Sekiguchi, M; Sergey, G; Sheth, R; Shimasaku, K; Smee, S; Snedden, SA; Stebbins, A; Stubbs, C; Szapudi, I; Szkody, P; Szokoly, GP; Tabachnik, S; Tsvetanov, Z; Uomoto, A; Vogeley, MS; Voges, W; Waddell, P; Walterbos, R; Wang, SI; Watanabe, M; Weinberg, DH; White, RL; White, SDM; Wilhite, B; Wolfe, D; Yasuda, N; York, DG; Zehavi, I; Zheng, W
    The Sloan Digital Sky Survey (SDSS) is an imaging and spectroscopic survey that will eventually cover approximately one-quarter of the celestial sphere and collect spectra of 10 6 galaxies, 100,000 quasars, 30,000 stars, and 30,000 serendipity targets. In 2001 June, the SDSS released to the general astronomical community its early data release, roughly 462 deg(2) of imaging data including almost 14 million detected objects and 54,008 follow-up spectra. The imaging data were collected in drift-scan mode in five bandpasses (u, g, r, i, and z); our 95% completeness limits for stars are 22.0, 22.2, 22.2, 21.3, and 20.5, respectively. The photometric calibration is reproducible to 5%, 3%, 3%, 3%, and 5%, respectively. The spectra are flux- and wavelength-calibrated, with 4096 pixels from 3800 to 9200 Angstrom at R approximate to 1800. We present the means by which these data are distributed to the astronomical community, descriptions of the hardware used to obtain the data, the software used for processing the data, the measured quantities for each observed object, and an overview of the properties of this data set.
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    Spectroscopic target selection in the Sloan Digital Sky Survey: The quasar sample
    (2002) Richards, GT; Fan, XH; Newberg, HJ; Strauss, MA; Berk, DEV; Schneider, DP; Yanny, B; Boucher, A; Burles, S; Frieman, JA; Gunn, JE; Hall, PB; Ivezic, Z; Kent, S; Loveday, J; Lupton, RH; Rockosi, CM; Schlegel, DJ; Stoughton, C; SubbaRao, M; York, DG
    We describe the algorithm for selecting quasar candidates for optical spectroscopy in the Sloan Digital Sky Survey. Quasar candidates are selected via their nonstellar colors in ugriz broadband photometry and by matching unresolved sources to the FIRST radio catalogs. The automated algorithm is sensitive to quasars at all redshifts lower than z similar to 5.8. Extended sources are also targeted as low-redshift quasar candidates in order to investigate the evolution of active galactic nuclei (AGNs) at the faint end of the luminosity function. Nearly 95% of previously known quasars are recovered (based on 1540 quasars in 446 deg(2)). The overall completeness, estimated from simulated quasars, is expected to be over 90%, whereas the overall efficiency (quasars/quasar candidates) is better than 65%. The selection algorithm targets ultraviolet excess quasars to i* = 19.1 and higher redshift (z greater than or similar to 3) quasars to i* = 20.2, yielding approximately 18 candidates deg(-2). In addition to selecting normal quasars, the design of the algorithm makes it sensitive to atypical AGNs such as broad absorption line quasars and heavily reddened quasars.
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    The Sloan Digital Sky Survey Quasar Catalog. I. Early data release
    (2002) Schneider, DP; Richards, GT; Fan, XH; Hall, PB; Strauss, MA; Vanden Berk, DE; Gunn, JE; Newberg, HJ; Reichard, TA; Stoughton, C; Voges, W; Yanny, B; Anderson, SF; Annis, J; Bahcall, NA; Bauer, A; Bernardi, M; Blanton, MR; Boroski, WN; Brinkmann, J; Briggs, JW; Brunner, R; Burles, S; Carey, L; Castander, FJ; Connolly, AJ; Csabai, I; Doi, M; Friedman, S; Frieman, JA; Fukugita, M; Heckman, TM; Hennessy, GS; Hindsley, RB; Hogg, DW; Ivezic, Z; Kent, S; Knapp, GR; Kunzst, PZ; Lamb, DQ; Leger, RF; Long, DC; Loveday, J; Lupton, RH; Margon, B; Meiksin, A; Merelli, A; Munn, JA; Newcomb, M; Nichol, RC; Owen, R; Pier, JR; Pope, A; Rockosi, CM; Saxe, DH; Schlegel, D; Siegmund, WA; Smee, S; Snir, Y; SubbaRao, M; Szalay, AS; Thakar, AR; Uomoto, A; Waddell, P; York, DG
    We present the first edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog. The catalog consists of the 3814 objects ( 3000 discovered by the SDSS) in the initial SDSS public data release that have at least one emission line with a full width at half-maximum larger than 1000 km s(-1), luminosities brighter than M(i*) = -23, and highly reliable redshifts. The area covered by the catalog is 494 deg(2); the majority of the objects were found in SDSS commissioning data using a multicolor selection technique. The quasar redshifts range from 0.15 to 5.03. 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 0.05 mag, radio and X-ray emission properties, and information on the morphology and selection method. Calibrated spectra of all objects in the catalog, covering the wavelength region 3800-9200 Angstrom at a spectral resolution of 1800-2100, are also available. Since the quasars were selected during the commissioning period, a time when the quasar selection algorithm was undergoing frequent revisions, the sample is not homogeneous and is not intended for statistical analysis.
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    The Sloan Digital Sky Survey Quasar Catalog. II. First data release
    (2003) Schneider, DP; Fan, XH; Hall, PB; Jester, S; Richards, GT; Stoughton, C; Strauss, MA; SubbaRao, M; Vanden Berk, DE; Anderson, SF; Brandt, WN; Gunn, JE; Gray, J; Trump, JR; Voges, W; Yanny, B; Bahcall, NA; Blanton, MR; Boroski, WN; Brinkmann, J; Brunner, R; Burles, S; Castander, FJ; Doi, M; Eisenstein, D; Frieman, JA; Fukugita, M; Heckman, TM; Hennessy, GS; Ivezic, Z; Kent, S; Knapp, GR; Lamb, DQ; Lee, BC; Loveday, J; Lupton, RH; Margon, B; Meiksin, A; Munn, JA; Newberg, HJ; Nichol, RC; Niederste-Ostholt, M; Pier, JR; Richmond, MW; Rockosi, CM; Saxe, DH; Schlegel, DJ; Szalay, AS; Thakar, AR; Uomoto, A; York, DG
    We present the second edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog. The catalog consists of the 16,713 objects in the SDSS First Data Release that have luminosities larger than M-i=-22 (in a cosmology with H-0=70 km s(-1) Mpc(-1), Omega(M)=0.3, and Omega(Lambda)=0.7), have at least one emission line with FWHM larger than 1000 km s(-1), and have highly reliable redshifts. The area covered by the catalog is approximate to1360 deg(2). The quasar redshifts range from 0.08 to 5.41, with a median value of 1.43. 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 some radio, near-infrared, and X-ray emission properties of the quasars, when available, from other large-area surveys. Calibrated digital spectra of all objects in the catalog, covering the wavelength region 3800-9200 Angstrom at a spectral resolution of 1800-2100, are available. This publication supersedes the first SDSS Quasar Catalog, which was based on material from the SDSS Early Data Release. A summary of corrections to current quasar databases is also provided. The majority of the objects were found in SDSS commissioning data using a multicolor selection technique. Since the quasar selection algorithm was undergoing testing during the entire observational period covered by this catalog, care must be taken when assembling samples from the catalog for use in statistical studies. A total of 15,786 objects (94%) in the catalog were discovered by the SDSS; 12,173 of the SDSS discoveries are reported here for the first time. Included in the new discoveries are five quasars brighter than i=16.0 and 17 quasars with redshifts larger than 4.5.