Author/Authors :
Schlegel، David J. نويسنده , , Brinkmann، J. نويسنده , , Fukugita، Masataka نويسنده , , Gunn، James E. نويسنده , , Lupton، Robert H. نويسنده , , Anderson، Scott F. نويسنده , , Hall، Patrick B. نويسنده , , Loveday، Jon نويسنده , , Schneider، Donald P. نويسنده , , Strauss، Michael A. نويسنده , , Kleinman، S. J. نويسنده , , Knapp، G. R. نويسنده , , Richards، Gordon T. نويسنده , , Fan، Xiaohui نويسنده , , Brunner، Robert J. نويسنده , , Barentine، J. C. نويسنده , , Nitta، Atsuko نويسنده , , Snedden، Stephanie A. نويسنده , , York، Donald G. نويسنده , , Berk، Daniel E. Vanden نويسنده , , Jester، Sebastian نويسنده , , Stoughton، Chris نويسنده , , Gray، Jim نويسنده , , Ivezi، eljko نويسنده , , Kirkland، Margaret K. نويسنده , , Meiksin، Avery نويسنده , , Pope، Adrian نويسنده , , Szalay، Alexander S. نويسنده , , Thakar، Anirudda R. نويسنده , , Yanny، Brian نويسنده , , Brewington، Howard J. نويسنده , , Harvanek، Michael نويسنده , , Kent، Stephen M. نويسنده , , Krzesiski، Jurek نويسنده , , Long، Daniel C. نويسنده , , Nash، Thomas نويسنده , , Neilsen، Eric H. نويسنده ,
Abstract :
We determine the number counts and z = 0–5 luminosity function for a welldefined, homogeneous sample of quasars from the Sloan Digital Sky Survey (SDSS). We conservatively define the most uniform statistical sample possible, consisting of 15,343 quasars within an effective area of 1622 deg2 that was derived from a parent sample of 46,420 spectroscopically confirmed broad-line quasars in the 5282 deg2 of imaging data from SDSS Data Release 3. The sample extends from i = 15 to 19.1 at z(less-than or equivalent)3 and to i = 20.2 for z(greater-than or equivalent)3. The number counts and luminosity function agree well with the results of the Two Degree Field QSO Redshift Survey (2QZ) at redshifts and luminosities at which the SDSS and 2QZ quasar samples overlap, but the SDSS data probe to much higher redshifts than does the 2QZ sample. The number density of luminous quasars peaks between redshifts 2 and 3, although uncertainties in the selection function in this range do not allow us to determine the peak redshift more precisely. Our best-fit model has a flatter bright-end slope at high redshift than at low redshift. For z < 2.4 the data are best fit by a redshiftindependent slope of (beta)= -3.1 [(phi)(L)(infinity)L(beta)]. Above z = 2.4 the slope flattens with redshift to (beta)(greater-than or equivalent)-2.37 at z = 5. This slope change, which is significant at the 5 level, must be accounted for in models of the evolution of accretion onto supermassive black holes.
