Using the large scale quasar clustering to constrain flat quintessential universes

ARIEL ZANDIVAREZ; HECTOR J. MARTINEZ

ASTRONOMY AND ASTROPHYSICS

EDP Sciences

Lugar: Paris, Francia; Año: 2009 p. 347 - 355

0004-6361

We search for the most suitable set of cosmological parameters that describes the observable universe. The seek contemplates the possibility of quintessential flat universes, i.e., the analysis is restricted to the determination of the dimensionless matter density and the quintessential parameters, $Omega_{ m M}$ and $w_{ m Q}$, respectively.Our study is focused in comparing the position of features at large scales in the density fluctuation field at different redshifts by analysing the evolution of the quasar two-point correlation function. We trace the density fluctuations field at large scales using a large and homogeneous sample of quasars ($sim$ 38000 objects with 0.3 $lesssim$ z $le$ 2.4 and a median $z=1.45$) drawn from the Sloan Digital Sky Survey Data Release Six. The analysis relies on the assumption that, in the linear regime, the length scale of a particular feature should remain fixed at different times of the universe for the proper cosmological model. Our study does not assume any particular comoving length scale at which a feature should be found, but intends to perform a comparison for a wide range of scales instead. This is performed by quantifying the amountof overlap among the quasar correlation functions at different times using a cross-correlation technique.The most likely cosmological model is $Omega_{ m M}=0.21pm 0.02$ and $w_{ m Q}=-0.93pm0.04$, in agreement with previous studies. These constraints are the result of a good overall agreement of the correlation function at different redshifts over scales $sim 100-300mpc$.Under the assumption of a flat cosmological model, our results indicate that we are living in a low density universe with a quintessential parameter greater than the one corresponding to a cosmological constant. This work also demonstrates that a large homogeneous quasar sample can be used for tightening the constraints upon cosmological parameters.