J/ApJS/180/67 Photometric selection of quasars from SDSS. II. (Richards+, 2009)
Efficient photometric selection of quasars from the Sloan Digital Sky Survey.
II. ∼1,000,000 quasars from Data Release 6.
Richards G.T., Myers A.D., Gray A.G., Riegel R.N., Nichol R.C.,
Brunner R.J., Szalay A.S., Schneider D.P., Anderson S.F.
<Astrophys. J. Suppl. Ser., 180, 67-83 (2009)>
=2009ApJS..180...67R 2009ApJS..180...67R
ADC_Keywords: Photometry, SDSS ; QSOs ; Redshifts ; Spectroscopy
Keywords: catalogs - quasars: general
Abstract:
We present a catalog of 1172157 quasar candidates selected from the
photometric imaging data of the Sloan Digital Sky Survey (SDSS). The
objects are all point sources to a limiting magnitude of i=21.3 from
8417deg2 of imaging from SDSS Data Release 6 (DR6). This sample
extends our previous catalog by using the latest SDSS public release
data and probing both ultraviolet (UV)-excess and high-redshift
quasars. While the addition of high-redshift candidates reduces the
overall efficiency (quasars:quasar candidates) of the catalog to ∼80%,
it is expected to contain no fewer than 850000 bona fide quasars,
which is ∼8 times the number of our previous sample and ∼10 times the
size of the largest spectroscopic quasar catalog. Cross-matching
between our photometric catalog and spectroscopic quasar catalogs from
both the SDSS and 2dF survey yields 88879 spectroscopically confirmed
quasars. For judicious selection of the most robust UV-excess sources
(∼500000 objects in all), the efficiency is nearly 97% -more than
sufficient for detailed statistical analyses. The catalog's
completeness to type 1 (broad-line) quasars is expected to be no worse
than 70%, with most missing objects occurring at z<0.7 and 2.5<z<3.0.
In addition to classification information, we provide photometric
redshift estimates (typically good to Δz±0.3[2σ]) and
cross-matching with radio, X-ray, and proper-motion catalogs. Finally,
we consider the catalog's utility for determining the optical
luminosity function of quasars and are able to confirm the flattening
of the bright-end slope of the quasar luminosity function at z∼4 as
compared to z∼2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 271 1015082 Nonparametric Bayes classifier kernel density
estimate (NBC KDE) quasar candidate catalog
table3.dat 271 157075 Rejected quasar candidates
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See also:
VII/241 : The 2dF QSO Redshift Survey (Croom+ 2004)
VII/252 : SDSS-DR5 quasar catalog (Schneider+, 2007)
II/282 : The SDSS Photometric Catalog, Release 6 (Adelman-McCarthy+, 2007)
II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
J/ApJS/155/257 : NBC Quasar Candidate Catalog (Richards+, 2004)
http://www.sdss.org : SDSS Home Page
Byte-by-byte Description of file: table[13].dat
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Bytes Format Units Label Explanations
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1- 7 I7 --- Seq Unique catalog number
9- 26 A18 --- SDSS SDSS name (JHHMMSS.ss+DDMMSS.s)
28- 39 F12.7 deg RAdeg Right Ascension in decimal degrees (J2000)
41- 51 F11.7 deg DEdeg Declination in decimal degrees (J2000)
54- 72 A19 --- objID SDSS object identification
74- 80 F7.3 --- zph Photometric redshift; see Weinstein et al.,
2004ApJS..155..243W 2004ApJS..155..243W
82- 87 F6.3 --- zph.L Lower limit of zphot
89- 94 F6.3 --- zph.U Upper limit of zphot
96-101 F6.3 --- zpprob Photometric redshift range probability
103-109 F7.3 mag umag u band PSF ubercalibrated asinh magnitude (1)
111-116 F6.3 mag gmag g band PSF ubercalibrated asinh magnitude (1)
118-123 F6.3 mag rmag r band PSF ubercalibrated asinh magnitude (1)
125-130 F6.3 mag imag i band PSF ubercalibrated asinh magnitude (1)
132-137 F6.3 mag zmag z band PSF ubercalibrated asinh magnitude (1)
139-144 F6.3 mag e_umag Error in umag
146-150 F5.3 mag e_gmag Error in gmag
152-156 F5.3 mag e_rmag Error in rmag
158-162 F5.3 mag e_imag Error in imag
164-168 F5.3 mag e_zmag Error in zmag
170-176 F7.3 mag E(B-V) The (B-V) extinction (2)
178-184 F7.3 mag c Concentration for star/galaxy separation (3)
186-193 F8.2 mJy F20cm ?=-1.0 the 20cm (1.5GHz) flux density
195-201 F7.4 ct/s FX ?=-9.0 RASS full-band count rate (0.1-2keV)
203-210 F8.2 mas/yr pm ?=-1.0 Proper motion
212-213 I2 --- mov [-1/1] Flag to indicate possible moving
object (4)
216 I1 --- fz [0/1] Full z range flag, 95% star prior
218 I1 --- lz [0/1] Low z range flag (z≤2.2), 98% star prior
220 I1 --- mz [0/1] Mid z range flag (2.2<z<3.5), 98% star
prior
222 I1 --- hz [0/1] High z range flag (z≥3.5), 98% star
prior
224 I1 --- uv [0/1] UV-excess flag, 88% star prior;
see Paper I, Cat. J/ApJS/155/257
226-234 F9.3 [-] log(q) Kernel density estimate (KDE) quasar probability
236-243 F8.3 [-] log(s) Kernel density estimate (KDE) star probability
246-247 I2 --- good [-6/6] Quality flag (5)
249-264 A16 --- Class Previous catalog object classification (6)
266-271 F6.3 --- z ?=-1.0 Previous catalog object redshift
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Note (1): Corrected for Galactic extinction.
Note (2): Au, Ag, Ar, Ai, and Az=(5.155, 3.793, 2.751, 2.086, and
1.479)*E(B-V).
Note (3): Equal to PSFMagi-modelMagi.
Note (4): Equal to 1 if moving.
Note (5): Where 6 is most robust and -6 is least robust.
Objects with good<0 are in table3 (rejected quasar candidates)
Note (6): Previous catalog classification from sources:
2SLAQ = SDSS-2dF LRG and QSO Survey (2SLAQ) Early Data Release quasar catalog
(Croom et al., 2009MNRAS.392...19C 2009MNRAS.392...19C)
DR5 = DR5 quasar catalog (Schneider et al., 2007, Cat. VII/252)
2QZ = 2QZ quasar catalog (Croom et al., 2004, Cat. VII/241)
DR6 = SDSS-DR6 spectroscopic database (Adelman-McCarthy et al.,
2008ApJS..175..297A 2008ApJS..175..297A)
U = Unknown
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History:
From electronic version of the journal
References:
Richards et al., Paper I. 2004ApJS..155..257R 2004ApJS..155..257R, Cat. J/ApJS/155/257
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 06-Oct-2009