Browsing by Author "Reichard, TA"

Now showing 1 - 5 of 5
  • No Thumbnail Available
    Item
    A catalog of broad absorption line quasars from the Sloan Digital Sky Survey Early Data Release
    (2003) Reichard, TA; Richards, GT; Schneider, DP; Hall, PB; Tolea, A; Krolik, JH; Tsvetanov, Z; Vanden Berk, DE; York, DG; Knapp, GR; Gunn, JE; Brinkmann, J
    We present a catalog of 224 broad absorption line quasars (BALQSOs) from the Sloan Digital Sky Survey's Early Data Release Quasar Catalog, including a relatively complete and homogeneous subsample of 131 BALQSOs. Since the identification of BALQSOs is subject to considerable systematic uncertainties, we attempt to create a complete sample of SDSS BALQSOs by combining the results of two automated selection algorithms and a by-eye classification scheme. One of these automated algorithms finds broad absorption line troughs by comparing with a composite quasar spectrum. We present the details of this algorithm and compare this method with one that uses a power-law fit to the continuum. The BALQSOs in our sample are further classified as high-ionization BALQSOs (HiBALs), low-ionization BALQSOs (LoBALs), and BALQSOs with excited iron absorption features (FeLoBALs); composite spectra of each type are presented. We further present a study of the properties of the BALQSOs in terms of the balnicity distribution, which rises with decreasing balnicity. This distribution of balnicities suggests that the fraction of quasars with intrinsic outflows may be significantly underestimated.
  • No Thumbnail Available
    Item
    Broad emission-line shifts in quasars: An orientation measure for radio-quiet quasars?
    (2002) Richards, GT; Berk, DEV; Reichard, TA; Hall, PB; Schneider, DP; SubbaRao, M; Thakar, AR; York, DG
    Using a sample of 3814 quasars from the Early Data Release of the Sloan Digital Sky Survey, we confirm that high-ionization, broad emission lines, such as C IV are significantly blueshifted with respect to low-ionization, broad emission lines, such as Mg II which are thought to be close to the systemic redshift. We examine the velocity shifts of the Mg II and C iv emission lines with respect to [O III and Mg II respectively. C iv emission-line peaks have a range of shifts from a redshift of 500 km s(-1) to blueshifts well in excess of 2000 km s(-1) as compared with Mg II We confirm previous results that suggest an anticorrelation between the shift of the C iv emission-line peak and the rest equivalent width of the C iv emission line. Furthermore, by creating composite quasar spectra as a function of C iv shift, we are able to study in detail the profiles of the line as a function of velocity shift. We find that the apparent shift of the C iv emission-line peak is not a shift so much as it is a lack of flux in the red wing for the composite with the largest apparent shift. This observation should strongly constrain models for the broad emission-line region in quasars. The emission-line blueshift and equivalent width of C iv are also discussed in light of the well-known anticorrelation between the equivalent width of C iv emission and continuum luminosity, otherwise known as the Baldwin effect. We further discuss the C iv emission-line shift as a function of other quasar properties, such as spectral index, radio and X-ray detection. We find a possible correlation between the C iv emission-line shifts and the radio properties of the quasars, which is suggestive of orientation as the cause of the C iv velocity shifts. Finally, we explore whether the C iv emission-line blueshifts correlate with the presence of broad absorption line absorption troughs or with narrow, associated absorption, and how these might be related to orientation.
  • No Thumbnail Available
    Item
    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.
  • No Thumbnail Available
    Item
    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.
  • No Thumbnail Available
    Item
    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.