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 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superseded by Cat.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VII/248; superseded by Cat.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:
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FileName Lrecl Records Explanations
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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)
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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).
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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[34].dat
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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)
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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).
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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