11 research outputs found
The Sloan Digital Sky Survey Quasar Catalog IV. Fifth Data Release
We present the fourth edition of the Sloan Digital Sky Survey (SDSS) Quasar
Catalog. The catalog contains 77,429 objects; this is an increase of over
30,000 entries since the previous edition. The catalog consists of the objects
in the SDSS Fifth Data Release that have luminosities larger than M_i = -22.0
(in a cosmology with H_0 = 70 km/s/Mpc, Omega_M = 0.3, and Omega_Lambda = 0.7)
have at least one emission line with FWHM larger than 1000 km/s, or have
interesting/complex absorption features, are fainter than i=15.0, and have
highly reliable redshifts. The area covered by the catalog is 5740 sq. deg. The
quasar redshifts range from 0.08 to 5.41, with a median value of 1.48; the
catalog includes 891 quasars at redshifts greater than four, of which 36 are at
redshifts greater than five. Approximately half of the catalog quasars have i <
19; nearly all have i < 21. For each object the catalog presents positions
accurate to better than 0.2 arcsec. rms per coordinate, five-band (ugriz)
CCD-based photometry with typical accuracy of 0.03 mag, and information on the
morphology and selection method. The catalog also contains basic radio,
near-infrared, and X-ray emission properties of the quasars, when available,
from other large-area surveys. The calibrated digital spectra cover the
wavelength region 3800--9200A at a spectral resolution of ~2000. The spectra
can be retrieved from the public database using the information provided in the
catalog. The average SDSS colors of quasars as a function of redshift, derived
from the catalog entries, are presented in tabular form. Approximately 96% of
the objects in the catalog were discovered by the SDSS.Comment: 37 pages, Accepted for publication in A
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Clustering of High Redshift (z>2.9) Quasars from the Sloan Digital Sky Survey
We study the two-point correlation function of a uniformly selected sample of 4,428 optically selected luminous quasars with redshift 2.9 {le} z {le} 5.4 selected over 4041 deg{sup 2} from the Fifth Data Release of the Sloan Digital Sky Survey. We fit a power-law to the projected correlation function w{sub p}(r{sub p}) to marginalize over redshift space distortions and redshift errors. For a real-space correlation function of the form {zeta}(r) = (r/r{sub 0}){sup -{gamma}}, the fitted parameters in comoving coordinates are r{sub 0} = 15.2 {+-} 2.7 h{sup -1} Mpc and {gamma} = 2.0 {+-} 0.3, over a scale range 4 {le} r{sub p} {le} 150 h{sup -1} Mpc. Thus high-redshift quasars are appreciably more strongly clustered than their z {approx} 1.5 counterparts, which have a comoving clustering length r{sub 0} {approx} 6.5 h{sup -1} Mpc. Dividing our sample into two redshift bins: 2.9 {le} z {le} 3.5 and z {ge} 3.5, and assuming a power-law index {gamma} = 2.0, we find a correlation length of r{sub 0} = 16.9 {+-} 1.7 h{sup -1} Mpc for the former, and r{sub 0} = 24.3 {+-} 2.4 h{sup -1} Mpc for the latter. Strong clustering at high redshift indicates that quasars are found in very massive, and therefore highly biased, halos. Following Martini & Weinberg, we relate the clustering strength and quasar number density to the quasar lifetimes and duty cycle. Using the Sheth & Tormen halo mass function, the quasar lifetime is estimated to lie in the range 4 {approx} 50 Myr for quasars with 2.9 {le} z {le} 3.5; and 30 {approx} 600 Myr for quasars with z {ge} 3.5. The corresponding duty cycles are 0.004 {approx} 0.05 for the lower redshift bin and 0.03 {approx} 0.6 for the higher redshift bin. The minimum mass of halos in which these quasars reside is 2-3 x 10{sup 12} h{sup -1} M{sub {circle_dot}} for quasars with 2.9 {le} z {le} 3.5 and 4-6 x 10{sup 12} h{sup -1} M{sub {circle_dot}} for quasars with z {ge} 3.5; the effective bias factor b{sub eff} increases with redshift, e.g., b{sub eff} {approx} 8 at z = 3.0 and b{sub eff} {approx} 16 at z = 4.5
Clustering of High Redshift () Quasars from the Sloan Digital Sky Survey
(Abridged) We study the two-point correlation function of a uniformly
selected sample of 4,426 luminous optical quasars with redshift selected over 4041 deg from the Fifth Data Release of the Sloan
Digital Sky Survey. For a real-space correlation function of the form
, the fitted parameters in comoving coordinates are
Mpc and , over a scale range
Mpc. Thus high-redshift quasars are appreciably more
strongly clustered than their counterparts, which have a
comoving clustering length Mpc. Dividing our sample
into two redshift bins: and , and assuming a
power-law index , we find a correlation length of Mpc for the former, and Mpc for the
latter. Following Martini & Weinberg, we relate the clustering strength and
quasar number density to the quasar lifetimes and duty cycle. Using the Sheth &
Tormen halo mass function, the quasar lifetime is estimated to lie in the range
Myr for quasars with ; and Myr for
quasars with . The corresponding duty cycles are for
the lower redshift bin and for the higher redshift bin. The
minimum mass of halos in which these quasars reside is $2-3\times 10^{12}\
h^{-1}M_\odot2.9\le z\le 3.54-6\times 10^{12}\
h^{-1}M_\odotz\ge 3.5$.Comment: To appear in AJ; 20 emulateapj pages; supplemental materials can be
found at
http://www.astro.princeton.edu/~yshen/highz_qso_clustering/qso_clustering.ht
The Sloan Digital Sky Survey Quasar Catalog V. Seventh Data Release
We present the fifth edition of the Sloan Digital Sky Survey (SDSS) Quasar
Catalog, which is based upon the SDSS Seventh Data Release. The catalog, which
contains 105,783 spectroscopically confirmed quasars, represents the conclusion
of the SDSS-I and SDSS-II quasar survey. The catalog consists of the SDSS
objects that have luminosities larger than M_i = -22.0 (in a cosmology with H_0
= 70 km/s/Mpc Omega_M = 0.3, and Omega_Lambda = 0.7) have at least one emission
line with FWHM larger than 1000 km/s or have interesting/complex absorption
features, are fainter than i > 15.0 and have highly reliable redshifts. The
catalog covers an area of 9380 deg^2. The quasar redshifts range from 0.065 to
5.46, with a median value of 1.49; the catalog includes 1248 quasars at
redshifts greater than four, of which 56 are at redshifts greater than five.
The catalog contains 9210 quasars with i < 18; slightly over half of the
entries have i< 19. For each object the catalog presents positions accurate to
better than 0.1" rms per coordinate, five-band (ugriz) CCD-based photometry
with typical accuracy of 0.03 mag, and information on the morphology and
selection method. The catalog also contains radio, near-infrared, and X-ray
emission properties of the quasars, when available, from other large-area
surveys. The calibrated digital spectra cover the wavelength region 3800-9200
Ang. at a spectral resolution R = 2000 the spectra can be retrieved from the
SDSS public database using the information provided in the catalog. Over 96% of
the objects in the catalog were discovered by the SDSS. We also include a
supplemental list of an additional 207 quasars with SDSS spectra whose archive
photometric information is incomplete.Comment: Accepted, to appear in AJ, 7 figures, electronic version of Table 2
is available, see
http://www.sdss.org/dr7/products/value_added/qsocat_dr7.htm
A New Very Cool White Dwarf Discovered by the Sloan Digital Sky Survey
Early data taken during commissioning of the SDSS have resulted in the
discovery of a very cool white dwarf. It appears to have stronger collision
induced absorption from molecular hydrogen than any other known white dwarf,
suggesting it has a cooler temperature than any other. While its distance is
presently unknown, it has a surprisingly small proper motion, making it
unlikely to be a halo star. An analysis of white dwarf cooling times suggests
that this object may be a low-mass star with a helium core. The SDSS imaging
and spectroscopy also recovered LHS 3250, the coolest previously known white
dwarf, indicating that the SDSS will be an effective tool for identifying these
extreme objects.Comment: 15 pages, including 5 figures. Accepted for Astrophysical Journal
Letter
The SDSS Quasar Survey: Quasar Luminosity Function from Data Release Three
We determine the number counts and z=0-5 luminosity function for a
well-defined, 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 deg^2 that was
derived from a parent sample of 46,420 spectroscopically confirmed broad-line
quasars in the 5282 deg^2 of imaging data from SDSS Data Release Three. The
sample extends from i=15 to i=19.1 at z3. The number
counts and luminosity function agree well with the results of the 2dF QSO
Survey, but the SDSS data probe to much higher redshifts than does the 2dF
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 redshift-independent slope of beta = -3.1 (Phi(L) propto L^beta).
Above z=2.4 the slope flattens with redshift to beta=-2.37 at z=5. This slope
change, which is significant at a >5-sigma level, must be accounted for in
models of the evolution of accretion onto supermassive black holes.Comment: 57 pages, 21 figures (9 color); minor changes to reflect the version
accepted by AJ; higher resolution version available at
ftp://ftp.astro.princeton.edu/gtr/dr3qlf/Feb1306
The Sloan Digital Sky Survey: Technical Summary
The Sloan Digital Sky Survey (SDSS) will provide the data to support detailed
investigations of the distribution of luminous and non- luminous matter in the
Universe: a photometrically and astrometrically calibrated digital imaging
survey of pi steradians above about Galactic latitude 30 degrees in five broad
optical bands to a depth of g' about 23 magnitudes, and a spectroscopic survey
of the approximately one million brightest galaxies and 10^5 brightest quasars
found in the photometric object catalog produced by the imaging survey. This
paper summarizes the observational parameters and data products of the SDSS,
and serves as an introduction to extensive technical on-line documentation.Comment: 9 pages, 7 figures, AAS Latex. To appear in AJ, Sept 200