Browsing by Author "Fan, XH"

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    A large, uniform sample of X-ray-emitting AGNs
    (2003) Anderson, SF; Voges, W; Margon, B; Trümper, J; Agüeros, MA; Boller, T; Collinge, MJ; Homer, L; Stinson, G; Strauss, MA; Annis, J; Gómez, P; Hall, PB; Nichol, RC; Richards, GT; Schneider, DP; Vanden Berk, DE; Fan, XH; Ivezic, Z; Munn, JA; Newberg, HJ; Richmond, MW; Weinberg, DH; Yanny, B; Bahcall, NA; Brinkmann, J; Fukugita, M; York, DG
    Many open questions in X-ray astronomy are limited by the relatively small number of objects in uniform optically identified and observed samples, especially when rare subclasses are considered or when subsets are isolated to search for evolution or correlations between wavebands. We describe the initial results of a new program aimed to ultimately yield similar to10(4) fully characterized X-ray source identifications-a sample about an order of magnitude larger than earlier efforts. The technique is detailed and employs X-ray data from the ROSAT All-Sky Survey (RASS) and optical imaging and spectroscopic follow-up from the Sloan Digital Sky Survey (SDSS); these two surveys prove to be serendipitously very well matched in sensitivity. As part of the SDSS software pipelines, optical objects in the SDSS photometric catalogs are automatically positionally cross-correlated with RASS X-ray sources. Then priorities for follow-on SDSS optical spectra of candidate counterparts are automatically assigned using an algorithm based on the known ratios of f(x)/f(opt) for various classes of X-ray emitters at typical RASS fluxes of similar to10(-13) ergs cm(-2) s(-1). SDSS photometric parameters for optical morphology, magnitude, and colors, plus FIRST radio information, serve as proxies for object class. Initial application of this approach to RASS/SDSS data from 1400 deg(2) of sky provides a catalog of more than 1200 spectroscopically confirmed quasars and other AGNs that are probable RASS identifications. Most of these are new identifications, and only a few percent of the AGN counterparts are likely to be random superpositions. The magnitude and redshift ranges of the counterparts are very broad, extending over 15
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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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    Broad absorption line quasars in the Sloan Digital Sky Survey with VLA first radio detections
    (2001) Menou, K; Vanden Berg, DE; Kim, RSJ; Knapp, GR; Richards, GT; Strateva, I; Fan, XH; Gunn, JE; Hall, PB; Heckman, T; Krolik, J; Lupton, RH; Schneider, DP; York, DG; Anderson, SF; Bahcall, NA; Brinkmann, J; Brunner, R; Csabai, I; Fukugita, M; Hennessy, GS; Kunszt, PZ; Lamb, DQ; Munn, JA; Nichol, RC; Szokoly, GP
    We present 13 broad absorption line (BAL) quasars, including 12 new objects, identified in the Sloan Digital Sky Survey (SDSS) and matched within 2 " to sources in the FIRST radio survey catalog. The surface density of this sample of radio-detected BAL quasars is 4.5 +/- 1.2 per 100 deg(2), i.e., approximately 4 times as high as previously found by the shallower FIRST Bright Quasar Survey (FBQS). A majority of these radio-detected BAL quasars are moderately radio-loud objects. The fraction of BAL quasars in the entire radio quasar sample, 4.8% +/- 1.3%, is comparable to the fraction of BAL quasars among the SDSS optical quasar sample (ignoring selection effects). We estimate that the true fraction of BAL quasars (mostly "HiBALs") in the radio sample is 9.2% +/- 2.6%, once selection effects are accounted for. We caution that the absorption troughs of four of the 13 radio-detected quasars considered do not strictly satisfy the standard BALnicity criteria. One or possibly two of the new radio-detected BAL quasars are of the rare "FeLoBAL" type. BAL quasars are generally redder than the median SDSS quasar at the same redshift.
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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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    Continuum and emission-line properties of broad absorption line quasars
    (2003) Reichard, TA; Richards, GT; Hall, PB; Schneider, DP; Vanden Berk, DE; Fan, XH; York, DG; Knapp, GR; Brinkmann, J
    We investigate the continuum and emission-line properties of 224 broad absorption line quasars (BALQSOs) with 0.9less than or similar tozless than or similar to4.4 drawn from the Sloan Digital Sky Survey Early Data Release, which contains 3814 bona. de quasars. We find that low-ionization BALQSOs (LoBALs) are significantly reddened as compared with normal quasars, in agreement with previous work. High-ionization BALQSOs (HiBALs) are also more reddened than the average non-BALQSO. Assuming SMC-like dust reddening at the quasar redshift, the amount of reddening needed to explain HiBALs is E(B-V)similar to0.023 and LoBALs is E( B-V)similar to0.077 (compared with the ensemble average of the entire quasar sample). We find that there are differences in the emission-line properties between the average HiBAL, LoBAL, and non-BAL quasar. These differences, along with differences in the absorption-line troughs, may be related to intrinsic quasar properties such as the slope of the intrinsic (unreddened) continuum; more extreme absorption properties are correlated with bluer intrinsic continua. Despite the differences among BALQSO subtypes and non-BALQSOs, BALQSOs appear to be drawn from the same parent population as non-BALQSOs when both are selected by their UV/optical properties. We find that the overall fraction of traditionally defined BALQSOs, after correcting for color-dependent selection effects due to different SEDs of BALQSOs and non-BALQSOs, is 13.4%+/-1.2% and shows no significant redshift dependence for 1.7less than or equal tozless than or equal to3.45. After a rough completeness correction for the effects of dust extinction, we find that approximately one in every six quasars is a BALQSO.
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    Faint high-latitude carbon stars discovered by the Sloan Digital Sky Survey: Methods and initial results
    (2002) Margon, B; Anderson, SF; Harris, HC; Strauss, MA; Knapp, GR; Fan, XH; Schneider, DP; Berk, DEV; Schlegel, DJ; Deutsch, EW; Ivezic, Z; Hall, PB; Williams, BF; Davidsen, AF; Brinkmann, J; Csabai, I; Hayes, JJE; Hennessy, G; Kinney, EK; Kleinman, SJ; Lamb, DQ; Long, D; Neilsen, EH; Nichol, R; Nitta, A; Snedden, SA; York, DG
    We report the discovery of 39 faint high-latitude carbon stars (FHLCs) from Sloan Digital Sky Survey (SDSS) commissioning data. The objects, each selected photometrically and verified spectroscopically, range over 16.6 < r* < 20.0 and show a diversity of temperatures as judged by both colors and NaD line strengths. Although a handful of these stars were previously known, these objects are, in general, too faint and too warm to be effectively identified in other modern surveys such as the Two Micron All Sky Survey, nor are their red/near-IR colors particularly distinctive. The implied surface density of FHLCs in this magnitude range is uncertain at this preliminary stage of the survey because of completeness corrections but is clearly greater than 0.05 deg(-2). At the completion of the Sloan survey, there will be many hundred homogeneously selected and observed FHLCs in this sample. We present proper-motion measures for each object, indicating that the sample is a mixture of extremely distant (greater than 100 kpc) halo giant stars, useful for constraining halo dynamics, and members of the recently recognized exotic class of very nearby dwarf carbon (dC) stars. The broadband colors of the two populations are indistinguishable. Motions, and thus dC classification, are inferred for 40%-50% of the sample, depending on the level of statistical significance invoked. The new list of dC stars presented here, although selected from only a small fraction of the final SDSS, doubles the number of such objects found by all previous methods. The observed kinematics suggest that the dwarfs occupy distinct halo and disk populations. The coolest FHLCs with detectable proper motions in our sample also display multiple CaH bands in their spectra. It may be that CaH is another long-sought, low-resolution, spectroscopic luminosity discriminant between dC's and distant faint giants, at least for the cooler stars.
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    Optical and radio properties of extragalactic sources observed by the first survey and the Sloan Digital Sky Survey
    (2002) Ivezic, Z; Menou, K; Knapp, GR; Strauss, MA; Lupton, RH; Vanden Berk, DE; Richards, GT; Tremonti, C; Weinstein, MA; Anderson, S; Bahcall, NA; Becker, RH; Bernardi, M; Blanton, M; Eisenstein, D; Fan, XH; Finkbeiner, D; Finlator, K; Frieman, J; Gunn, JE; Hall, PB; Kim, RSJ; Kinkhabwala, A; Narayanan, VK; Rockosi, CM; Schlegel, D; Schneider, DP; Strateva, I; SubbaRao, M; Thakar, AR; Voges, W; White, RL; Yanny, B; Brinkmann, J; Doi, M; Fukugita, M; Hennessy, GS; Munn, JA; Nichol, RC; York, DG
    We discuss the optical and radio properties of similar to30,000 FIRST (radio, 20 cm, sensitive to 1 mJy) sources positionally associated within 1."5 with a Sloan Digital Sky Survey (SDSS) (optical, sensitive to r*similar to22.2) source in 1230 deg(2) of sky. The matched sample represents similar to30% of the 108,000 FIRST sources and 0.1% of the 2.5x10(7) SDSS sources in the studied region. SDSS spectra are available for 4300 galaxies and 1154 quasars from the matched sample and for a control sample of 140,000 galaxies and 20, 000 quasars in 1030 deg(2) of sky. Here we analyze only core sources, which dominate the sample; the fraction of SDSS-FIRST sources with complex radio morphology is determined to be less than 10%. This large and unbiased catalog of optical identifications provides much firmer statistical footing for existing results and allows several new findings. The majority (83%) of the FIRST sources identified with an SDSS source brighter than r*=21 are optically resolved; the fraction of resolved objects among the matched sources is a function of the radio flux, increasing from similar to50% at the bright end to similar to90% at the FIRST faint limit. Nearly all optically unresolved radio sources have nonstellar colors indicative of quasars. We estimate an upper limit of similar to5% for the fraction of quasars with broadband optical colors indistinguishable from those of stars. The distribution of quasars in the radio flux optical flux plane suggests the existence of the "quasar radio dichotomy" 8%+/-1% of all quasars with i*<18.5 are radio-loud, and this fraction seems independent of redshift and optical luminosity. The radio-loud quasars have a redder median color by 0.08±0.02 mag, and show a 3 times larger fraction of objects with extremely red colors. FIRST galaxies represent 5% of all SDSS galaxies with r*<17.5, and 1% for r*<20, and are dominated by red (u*-r*>2.22) galaxies, especially those with r*>17.5. Magnitude- and redshift-limited samples show that radio galaxies have a different optical luminosity distribution than nonradio galaxies selected by the same criteria; when galaxies are further separated by their colors, this result remains valid for both blue and red galaxies. For a given optical luminosity and redshift, the observed optical colors of radio galaxies are indistinguishable from those of all SDSS galaxies selected by identical criteria. The distributions of radio-to-optical flux ratio are similar for blue and red galaxies in redshift-limited samples; this similarity implies that the difference in their luminosity functions and resulting selection effects are the dominant cause for the preponderance of red radio galaxies in flux-limited samples. The fraction of radio galaxies whose emission-line ratios indicate an AGN(30%), rather than starburst, origin is 6 times larger than the corresponding fraction for all SDSS galaxies (r*<17.5). We confirm that the AGN-to-starburst galaxy number ratio increases with radio flux and find that radio emission from AGNs is more concentrated than radio emission from starburst galaxies.
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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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    Red and reddened quasars in the Sloan Digital Sky Survey
    (2003) Richards, GT; Hall, PB; Berk, DEV; Strauss, MA; Schneider, DP; Weinstein, MA; Reichard, TA; York, DG; Knapp, GR; Fan, XH; Ivezic, Z; Brinkmann, J; Budavári, T; Csabai, I; Nichol, RC
    We investigate the overall continuum and emission-line properties of quasars as a function of their optical/ UV spectral energy distributions. Our sample consists of 4576 quasars from the Sloan Digital Sky Survey (SDSS) that were chosen using homogeneous selection criteria. Expanding on our previous work, which demonstrated that the optical/ UV color distribution of quasars is roughly Gaussian but with a red tail, here we distinguish between ( 1) quasars that have intrinsically blue ( optically. at) power-law continua, ( 2) quasars that have intrinsically red ( optically steep) power-law continua, and ( 3) quasars whose colors are inconsistent with a single power-law continuum. We find that 273 (6.0%) of the quasars in our sample fall into the latter category and appear to be redder because of SMC-like dust extinction and reddening rather than because of synchrotron emission. Even though the SDSS quasar survey is optically selected and flux-limited, we demonstrate that it is sensitive to dust reddened quasars with E( B - V) less than or similar to 0.5, assuming a classical SMC extinction curve. The color distribution of our SDSS quasar sample suggests that the population of moderately dust reddened, but otherwise normal (i.e., type 1) quasars is smaller than the population of unobscured quasars: we estimate that a further 10% of the quasar population with M(i) < - 25.61 is missing from the SDSS sample because of extinction, bringing the total fraction of dust-reddened quasars to 15% of broad-line quasars. We also investigate the emission- and absorption-line properties of these quasars as a function of color and comment on how some of these results relate to Boroson-Green- type eigenvectors. Quasars with intrinsically red ( optically steep) power-law continua tend to have narrower Balmer lines and weaker C IV, C III], He II, and 3000 angstrom bump emission as compared with bluer ( optically flatter) quasars. The change in strength of the 3000 angstrom bump appears to be dominated by the Balmer continuum and not by Fe II emission. The dust-reddened quasars have even narrower Balmer lines and weaker 3000 angstrom bumps, in addition to having considerably larger equivalent widths of [O II] and [ O III] emission. The fraction of broad absorption line quasars (BALQSOs) increases from similar to 3.4% for the bluest quasars to perhaps as large as 20% for the dust-reddened quasars, but the intrinsic color distribution will be much bluer if all BALQSOs are affected by dust reddening.
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    SDSS white dwarfs with spectra showing atomic oxygen and/or carbon lines
    (2003) Liebert, J; Harris, HC; Dahn, CC; Schmidt, GD; Kleinman, SJ; Nitta, A; Krzesinski, J; Eisenstein, D; Smith, JA; Szkody, P; Hawley, S; Anderson, SF; Brinkmann, J; Collinge, MJ; Fan, XH; Hall, PB; Knapp, GR; Lamb, DQ; Margon, B; Schneider, DP; Silvestri, N
    We discuss 18 white dwarfs, one of which (G227-5) was previously known, whose SDSS spectra show lines of neutral and/or singly ionized carbon. At least two and perhaps four show lines of neutral or singly ionized oxygen. Apart from the extremely hot "PG 1159'' stars, these are the first white dwarfs with photospheric oxygen detected in their optical spectra. The photometry strongly suggests that these stars lie in the 11,000-30,000 K temperature range of the helium-atmosphere DB white dwarfs, though only one of them shows weak neutral helium lines in the spectrum. Trigonometric parallaxes are known for G227-5 and another, previously known white dwarf (G35-26) showing atomic carbon lines, and they indicate that both are massive stars. Theoretical arguments suggest that all members of this class of rare white dwarfs are massive (similar to1 M.), and this finding could explain the paucity of massive DB white dwarfs.
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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 CIV mass density of the universe at redshift 5
    (2003) Pettini, M; Madau, P; Bolte, M; Prochaska, JX; Ellison, SL; Fan, XH
    In order to search for metals in the Lyalpha forest at redshifts z(abs) > 4, we have obtained spectra of high signal-to-noise ratio and moderately high resolution of three QSOs at z(em) > 5: 4 discovered by the Sloan Digital Sky Survey. These data allow us to probe to metal enrichment of the intergalactic medium at early times with higher sensitivity than previous studies. We find 16 C IV absorption systems with column densities log N (C IV) = 12.50-13.98 over a total redshift path DeltaX = 3.29. In the redshift interval z = 4.5-5.0, where our statistics are most reliable, we deduce a comoving mass density of C3+ ions Omega(CIV) = (4.3 +/- 2.5) x 10(-8) ( 90% confidence limits) for absorption systems with log N (C-IV) greater than or equal to 13.0 ( for an Einstein - de Sitter cosmology with h = 0.65). This value of Omega(CIV) is entirely consistent with those measured at z < 4; we confirm the earlier finding by Songaila that neither the column density distribution of C iv absorbers nor its integral show significant redshift evolution over a period of time that stretches from similar to 1.25 to similar to 4.5 Gyr after the big bang. This somewhat surprising conclusion may be an indication that the intergalactic medium was enriched in metals at z >> 5, perhaps by the sources responsible for its reionization. Alternatively, the C iv systems we see may be associated with outflow from massive star- forming galaxies at later times, while the truly intergalactic metals may reside in regions of the Ly alpha forest of lower density than those probed up to now.
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    The first data release of the Sloan Digital Sky Survey
    (2003) Abazajian, K; Adelman-McCarthy, JK; Agüeros, MA; Allam, SS; Anderson, SF; Annis, J; Bahcall, NA; Baldry, IK; Bastian, S; Berlind, A; Bernardi, M; Blanton, MR; Blythe, N; Bochanski, JJ; Boroski, WN; Brewington, H; Briggs, JW; Brinkmann, J; Brunner, RJ; Budavári, T; Carey, LN; Carr, MA; Castander, FJ; Chiu, K; Collinge, MJ; Connolly, AJ; Covey, KR; Csabai, I; Dalcanton, JJ; Dodelson, S; Doi, M; Dong, F; Eisenstein, DJ; Evans, ML; Fan, XH; Feldman, PD; Finkbeiner, DP; Friedman, SD; Frieman, JA; Fukugita, M; Gal, RR; Gillespie, B; Glazebrook, K; Gonzalez, CF; Gray, J; Grebel, EK; Grodnicki, L; Gunn, JE; Gurbani, VK; Hall, PB; Hao, L; Harbeck, D; Harris, FH; Harris, HC; Harvanek, M; Hawley, SL; Heckman, TM; Helmboldt, JF; Hendry, JS; Hennessy, GS; Hindsley, RB; Hogg, DW; Holmgren, DJ; Holtzman, JA; Homer, L; Hui, L; Ichikawa, SI; Ichikawa, T; Inkmann, JP; Ivezic, Z; Jester, S; Johnston, DE; Jordan, B; Jordan, WP; Jorgensen, AM; Juric, M; Kauffmann, G; Kent, SM; Kleinman, SJ; Knapp, GR; Kniazev, AY; Kron, RG; Krzesinski, J; Kunszt, PZ; Kuropatkin, N; Lamb, DQ; Lampeitl, H; Laubscher, BE; Lee, BC; Leger, RF; Li, N; Lidz, A; Lin, H; Loh, YS; Long, DC; Loveday, J; Lupton, RH; Malik, T; Margon, B; McGehee, PM; McKay, TA; Meiksin, A; Miknaitis, GA; Moorthy, BK; Munn, JA; Murphy, T; Nakajima, R; Narayanan, VK; Nash, T; Neilsen, EH; Newberg, HJ; Newman, PR; Nichol, RC; Nicinski, T; Nieto-Santisteban, M; Nitta, A; Odenkirchen, M; Okamura, S; Ostriker, JP; Owen, R; Padmanabhan, N; Peoples, J; Pier, JR; Pindor, B; Pope, AC; Quinn, TR; Rafikov, RR; Raymond, SN; Richards, GT; Richmond, MW; Rix, HW; Rockosi, CM; Schaye, J; Schlegel, DJ; Schneider, DP; Schroeder, J; Scranton, R; Sekiguchi, M; Seljak, U; Sergey, G; Sesar, B; Sheldon, E; Shimasaku, K; Siegmund, WA; Silvestri, NM; Sinisgalli, AJ; Sirko, E; Smith, JA; Smolcic, V; Snedden, SA; Stebbins, A; Steinhardt, C; Stinson, G; Stoughton, C; Strateva, IV; Strauss, MA; Subbarao, M; Szalay, AS; Szapudi, I; Szkody, P; Tasca, L; Tegmark, M; Thakar, AR; Tremonti, C; Tucker, DL; Uomoto, A; Vanden Berk, DE; Vandenberg, J; Vogeley, MS; Voges, W; Vogt, NP; Walkowicz, LM; Weinberg, DH; West, AA; White, SDM; Wilhite, BC; Willman, B; Xu, YZ; Yanny, B; Yarger, J; Yasuda, N; Yip, CW; Yocum, DR; York, DG; Zakamska, NL; Zehavi, I; Zheng, W; Zibetti, S; Zucker, DB
    The Sloan Digital Sky Survey (SDSS) has validated and made publicly available its First Data Release. This consists of 2099 deg(2) of five-band (u, g, r, i, z) imaging data, 186,240 spectra of galaxies, quasars, stars and calibrating blank sky patches selected over 1360 deg(2) of this area, and tables of measured parameters from these data. The imaging data go to a depth of r approximate to 22.6 and are photometrically and astrometrically calibrated to 2% rms and 100 mas rms per coordinate, respectively. The spectra cover the range 3800-9200 Angstrom, with a resolution of 1800-2100. This paper describes the characteristics of the data with emphasis on improvements since the release of commissioning data (the SDSS Early Data Release) and serves as a pointer to extensive published and on-line documentation of the survey.
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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.