J/ApJ/690/1181 UV-bright quasars (Syphers+, 2009)
A high yield of new sightlines for the study of intergalactic helium:
Far-UV-Bright quasars from the SDSS, GALEX, and HST.
Syphers D., Anderson S.F., Zheng W., Haggard D., Meiksin A., Chiu K.,
Hogan C., Schneider D.P., York D.G.
<Astrophys. J., 690, 1181-1192 (2009)>
=2009ApJ...690.1181S 2009ApJ...690.1181S
ADC_Keywords: QSOs ; Photometry, ultraviolet ; Redshifts ; Surveys ;
Keywords: catalogs - galaxies: active - intergalactic medium -
quasars: general - surveys - ultraviolet: galaxies
Abstract:
Investigations of HeII Lyα (304Å rest-frame) absorption toward a
half-dozen quasars at z∼3-4 have demonstrated the great potential of
helium studies of the intergalactic medium, but the current critically
small sample size of clean sightlines for the HeII Gunn-Peterson test
limits confidence in cosmological inferences, and a larger sample is
required. Although the unobscured quasar sightlines to high redshift
are extremely rare, the Sloan Digital Sky Survey (SDSS) DR6 provides
thousands of z>2.8 quasars. We have cross-correlated these SDSS
quasars with the Galaxy Evolution Explorer (GALEX) GR2/GR3 to
establish a catalog of 200 higher-confidence (∼70% secure) cases of
quasars at z=2.8-5.1 potentially having surviving far-UV
(rest-frame) flux. We also catalog another 112 likely far-UV-bright
quasars from GALEX cross-correlation with other (non-SDSS) quasar
compilations. Reconnaissance UV prism observations with the Hubble
Space Telescope (HST) of 24 of our SDSS/GALEX candidates confirm 12 as
detected in the far-UV, with at least nine having flux extending to
very near the HeII break; with refinements our success rate is even
higher. Our SDSS/GALEX selection approach is thereby confirmed to be
an order of magnitude more efficient than previous HeII quasar
searches, more than doubles the number of spectroscopically confirmed
clean sightlines to high redshift, and provides a resource list of
hundreds of high-confidence sightlines for upcoming HeII and other
far-UV studies from the HST. Our reconnaissance HST prism spectra
suggest some far-UV diversity, confirming the need to obtain a large
sample of independent quasar sightlines across a broad redshift range
to assess such issues as the epoch(s) of helium reionization, while
averaging over individual-object pathology and/or cosmic variance.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 74 200 Catalog of candidate Far-UV-Bright SDSS/GALEX
quasars
table2.dat 62 112 Catalog of candidate Far-UV-Bright (non-SDSS)
VCV/GALEX quasars
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See also:
II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
VII/258 : Quasars and Active Galactic Nuclei (13th Ed.) (Veron+ 2010)
J/AJ/133/1780 : GALEX/SDSS quasar catalog (Trammell+, 2007)
J/ApJ/664/53 : UV photometry of GALEX QSO candidates (Atlee+, 2007)
J/ApJS/185/20 : Additional HeII quasar sightlines (Syphers+, 2009)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- --- [SDSS]
5- 23 A19 --- SDSS SDSS DR6 name (JHHMMSS.ss+DDMMSS.s)
25- 34 F10.6 deg RAdeg Right Ascension in decimal degrees (J2000)
36- 45 F10.6 deg DEdeg Declination in decimal degrees (J2000)
47- 50 F4.2 --- z SDSS pipeline redshift (photometric)
52- 56 F5.2 mag zmag SDSS z-band magnitude
58- 63 F6.3 10-19W/m2/nm NUV ? GALEX NUV flux (177-300nm)
65- 70 F6.3 10-19W/m2/nm FUV ? GALEX FUV flux (120-177nm)
72 I1 --- Insp [0/8] Inspection flag (1)
74 I1 --- Obs [0/2] Prior observation flag (G2)
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Note (1): 4-bit integer flag. These individual flags are additive for a given
object (e.g., 6 denotes a BAL with an LLS or DLA). Flags as follows:
1 = very near neighbor in the SDSS image
2 = probable LLS or DLA in the SDSS spectrum
3 = very near neighbor in the SDSS image and probable LLS or DLA
in the SDSS spectrum
4 = BAL (Broad Absorption Line)
5 = BAL with very near neighbor in the SDSS image
6 = BAL with probable LLS or DLA in the SDSS spectrum
8 = possible BAL
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- Name Veron-Cetty & Veron (VCV) name
(Cat. VII/258)
18- 25 F8.4 deg RAdeg Right Ascension in decimal degrees (J2000)
27- 34 F8.4 deg DEdeg Declination in decimal degrees (J2000)
36- 40 F5.3 --- z VCV redshift (spectroscopic)
42 A1 --- f_Vmag Flag on Vmag (1)
43- 47 F5.2 mag Vmag VCV V-band magnitude
49- 53 F5.2 10-19W/m2/nm NUV ? GALEX NUV flux (177-300nm)
55- 60 F6.2 10-19W/m2/nm FUV ? GALEX FUV flux (120-177nm)
62 I1 --- Obs [0/2] Prior observation flag (G2)
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Note (1): V magnitude unless otherwise marked as follows:
* = photographic
B = blue
R = red
I = infrared
J = infrared
K = infrared
O = photographic O-plate
J = photographic J-plate
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Global notes:
Note (G2): Flags as follows:
0 = object has not been observed with HST
1 = object has been observed with FUV (to near 304Å rest) spectroscopy
through HST cycle 16
2 = object has been observed less conclusively, i.e., NUV spectroscopy,
UV imaging, or pre-COSTAR observation
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History:
From electronic version of the journal
References:
Syphers et al., Paper II 2009ApJS..185...20S 2009ApJS..185...20S Cat. J/ApJS/185/20
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 08-Mar-2010