J/ApJ/728/23 GALEX UV-bright high-redshift quasars (Worseck+, 2011)
GALEX far-ultraviolet color selection of UV-bright high-redshift quasars. Worseck G., Prochaska J.X. <Astrophys. J., 728, 23 (2011)> =2011ApJ...728...23W
ADC_Keywords: Photometry, ultraviolet ; Photometry, SDSS ; Redshifts ; QSOs ; Surveys Keywords: diffuse radiation - intergalactic medium - quasars: absorption lines - surveys - techniques: photometric - ultraviolet: galaxies Abstract: We study the small population of high-redshift (zem>2.7) quasars detected by the Galaxy Evolution Explorer(GALEX), whose far-UV emission is not extinguished by intervening HI Lyman limit systems. We correlate almost all verified zem>2.7 quasars to the GALEX GR4 source catalog covering ∼25000deg2, yielding 304 sources detected at signal-to-noise ratio (S/N)>3. However, ∼50% of these are only detected in the GALEX NUV band, signaling the truncation of the FUV flux by low-redshift optically thick Lyman limit systems. We regard 52 quasars detected at S/N>3 to be most promising for Hubble Space Telescope follow-up, with an additional 114 quasars if we consider S/N>2 detections in the FUV. Combining the statistical properties of HI absorbers with the Sloan Digital Sky Survey (SDSS) quasar luminosity function, we predict a large all-sky population of ∼200 quasars with zem>2.7 and i≲19 that should be detectable at the HeII edge at m304<21. However, SDSS provides just half of the NUV-bright quasars that should have been detected by SDSS and GALEX. With mock quasar photometry we revise the SDSS quasar selection function, finding that SDSS systematically misses quasars with blue u-g≲2 colors at 3≲zem≲3.5 due to overlap with the stellar locus in color space. Description: We compiled a list of practically all known quasars at zem≥2.7 from four quasar samples (SDSS-DR5 quasar catalog (Cat. VII/252; superseded by Cat. VII/260), SDSS photometric catalogs -DR6 (Cat. II/282) and -DR7 (Cat. II/294) and Veron-Cetty et al. 2006, Cat. VII/248; superseded by Cat. VII/258). We removed all misidentified SDSS sources and all quasar candidates without unambiguous redshifts from follow-up spectroscopy, but only after cross-correlating the initial quasar sample to the GALEX GR4 source catalog. We cross-correlated our initial quasar list to the available GALEX GR4 source catalogs using a maximum match radius of 4.8" around the optical quasar position. The match radius approximately corresponds to the typical GALEX FWHM. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table3.dat 82 52 *Promising targets to search for HeII (GALEX S/N>3 and (FUV-NUV)<1mag) table4.dat 82 114 *Further quasars with potential FUV flux (GALEX S/N(FUV)>2)
Note on table3.dat: Thirty-nine of the 41 zem>2.78 quasars were previously suggested as candidate HeII quasars by Syphers et al. (2009, Cat. J/ApJS/185/20). Note on table4.dat: Seventy-six of the 87 zem>2.78 quasars were previously suggested as candidate HeII quasars by Syphers et al. (2009, Cat. J/ApJS/185/20).
See also: VII/260 : The SDSS-DR7 quasar catalog (Schneider+, 2010) VII/258 : Quasars and Active Galactic Nuclei (13th Ed.) (Veron+ 2010) II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009) J/ApJS/193/28 : Galaxy survey around 20 UV-bright quasars (Prochaska+, 2011) J/MNRAS/399/728 : UV-bright sources behind M31 halo (Fittingoff+, 2009) J/AJ/137/3761 : Ultraviolet quasi-stellar objects (Bianchi+, 2009) J/ApJS/185/20 : Additional HeII quasar sightlines (Syphers+, 2009) J/ApJ/690/1181 : UV-bright quasars (Syphers+, 2009) J/MNRAS/383/1513 : 2MASS, SDSS and FIRST fluxes of QSOs (Labita+, 2008) J/AJ/133/1780 : GALEX/SDSS quasar catalog (Trammell+, 2007) J/ApJ/664/53 : UV photometry of GALEX QSO candidates (Atlee+, 2007) J/ApJS/134/35 : Large Bright Quasar Survey emission lines (Forster+, 2001) J/A+AS/111/169 : UV-excess quasar candidates (Moreau+, 1995) http://www.sdss.org/ : SDSS home page http://galex.stsci.edu/GR4/ : GALEX GR4/GR5 at MAST Byte-by-byte Description of file: table.dat
Bytes Format Units Label Explanations
1- 16 A16 --- Name Object designation 18- 19 I2 h RAh Optical hour of right ascension (J2000) 21- 22 I2 min RAm Optical minute of right ascension (J2000) 24- 28 F5.2 s RAs Optical second of right ascension (J2000) 30 A1 --- DE- Optical sign of declination (J2000) 31- 32 I2 deg DEd Optical degree of declination (J2000) 34- 35 I2 arcmin DEm Optical arcminute of declination (J2000) 37- 40 F4.1 arcsec DEs Optical arcsecond of declination (J2000) 42- 46 F5.3 --- zem [2.702/5.037] Emission redshift 48- 52 F5.2 mag mag [15.48/24.1] Optical magnitude in Filt 54- 56 A3 --- Filt Filter (BVR, b_J or r) (1) 58- 62 F5.2 mag FUV GALEX GR4 FUV (∼1350-1780Å) AB magnitude 64- 68 F5.2 mag NUV ? GALEX GR4 NUV (∼1770-2830Å) AB magnitude 70 I1 --- Lim [0/2] Limit flag on UV detections (2) 72- 75 F4.1 --- F.S/N Signal-to-noise ration in FUV 77- 80 F4.1 --- N.S/N ? Signal-to-noise ration in NUV 82 I1 --- Nf [0/3] Neighbor flag (3)
Note (1): SDSS r AB magnitude if the filter is r, otherwise Vega magnitude in the given filter. Note (2): GALEX limit flag as follows: 0 = formal two-band detection, 1 = 1σ lower limit in FUV, 2 = 1σ lower limit in NUV. Note (3): Neighbor flag as follows: 0 = no SDSS source within r<5" of the quasar, 1 = sufficiently red SDSS source within r<5" of the quasar, 2 = quasar not imaged in SDSS DR7, 3 = potential source confusion (Deep Imaging Survey detection).
History: * 31-Aug-2012: From electronic version of the journal * 03-Sep-2012: In table 4, correction of the sign of declination for SDSS J1241+2719.
(End) Emmanuelle Perret [CDS] 31-Aug-2012
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