Access to Astronomical Catalogues

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
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:

       FileName      Lrecl  Records   Explanations

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


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

   Bytes Format Units   Label   Explanations

   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
  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

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)
    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)
      U = Unknown


History:
    From electronic version of the journal

References:
    Richards et al., Paper I. 2004ApJS..155..257R, Cat. J/ApJS/155/257
(End)                 Greg Schwarz [AAS], Emmanuelle Perret [CDS]    06-Oct-2009