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NED Abstract
Copyright by American Astronomical Society.
Reproduced by permission
2007AJ....133.2222S
Clustering of HighRedshift (z >= 2.9) Quasars from the Sloan Digital Sky
Survey
Yue Shen, Michael A. Strauss, Masamune Oguri, Joseph F. Hennawi, Xiaohui
Fan, Gordon T. Richards, Patrick B. Hall, James E. Gunn, Donald P.
Schneider, Alexander S. Szalay, Anirudda R. Thakar, Daniel E. Vanden Berk,
Scott F. Anderson, Neta A. Bahcall, Andrew J. Connolly, and Gillian R.
Knapp
Abstract. We study the twopoint correlation function of a uniformly
selected sample of 4426 luminous optical quasars with redshift
2.9<=z<=5.4 selected over 4041 deg^2^ from the Fifth Data Release of the
Sloan Digital Sky Survey. We fit a powerlaw to the projected
correlation function w_p_(r_p_) to marginalize over redshiftspace
distortions and redshift errors. For a realspace correlation function
of the form {xi}(r)=(r/r_0_)^{gamma}^, the fitted parameters in
comoving coordinates are r_0_=15.2+/2.7h^1^ Mpc and {gamma}=2.0+/0.3,
over a scale range 4h^1^Mpc<=r_p_<=150h^1^Mpc. Thus highredshift
quasars are appreciably more strongly clustered than their z~1.5
counterparts, which have a comoving clustering length r_0_~6.5h^1^ Mpc.
Dividing our sample into two redshift bins, 2.9<=z<=3.5 and z >= 3.5,
and assuming a powerlaw index {gamma}=2.0, we find a correlation length
of r_0_=16.9+/1.7h^1^ Mpc for the former and r_0_=24.3+/2.4h^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  50 Myr for quasars with 2.9<=z<=3.5, and ~30 
600 Myr for quasars with z >= 3.5. The corresponding duty cycles are
~0.004  0.05 for the lower redshift bin and ~0.03  0.6 for the
higher redshift bin. The minimum mass of halos in which these quasars
reside is (2  3)x10^12^h^1^ M_sun_ for quasars with 2.9<=z<=3.5 and
(4  6)x10^12^h^1^ M_sun_ for quasars with z >= 3.5; the effective
bias factor b_eff_ increases with redshift, e.g., b_eff_~8 at z=3.0 and
b_eff_~16 at z=4.5.
Key words: Cosmology: Observations, Cosmology: LargeScale Structure of
Universe, Galaxies: Quasars: General, Surveys
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