2009/02/14 by Ariel Zandivarez, A. Zandivarez, Hector J. Martinez +1
Physics and Astronomy · #Correlation function (quantum field theory) #Cosmology #Cosmology and Gravitation Theories #Dimensionless quantity #Galaxies: Formation, Evolution, Phenomena #Observable #Quasar #Redshift #Scale (ratio) #Sky #Statistical Mechanics and Entropy #Universe #astro-ph.CO
paper · pdf · doi:10.1051/0004-6361/200811360
10 pages, 8 figures, accepted for publication in Astronomy & Astrophysics
arxiv created 2009/02/14 · openalex publication_date 2009/02/18 · arxiv updated 2015/05/12 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
<i>Aims. <i/>We search for the most suitable set of cosmological parameters that describes the observable universe. The search includes the possibility of quintessential flat universes, i.e., the analysis is restricted to the determination of the dimensionless matter density and the quintessential parameters, and <i>w<i/><sub>Q<sub/>, respectively.<i>Methods. <i/>Our study is focused on 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 field fluctuations at large scales using a large and homogeneous sample of quasars (~38 000 objects with 0.3 <i>≲<i/> <i>z<i/> <i>≤<i/> 2.4 and a median <i>z<i/> = 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 done by quantifying the amount of overlap among the quasar correlation functions at different times using a cross-correlation technique. <i>Results. <i/>The most likely cosmological model is = 0.21<i>±<i/>0.02 and <i>w<i/><sub>Q<sub/> = -0.93<i>±<i/>0.04, in agreement with previous studies. These constraints are the result of a good overall agreement of the correlation function at different redshifts over scales ~100–300 <i>h<i/><sup>-1<sup/> Mpc.<i>Conclusions. <i/>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 to tighten the constraints upon cosmological parameters.