Projects per year
We use a sample of about 22 000 galaxies at 0.65 <z <1.2 from the VIMOS Public Extragalactic Redshift Survey (VIPERS) Public Data Release 1 (PDR-1) catalogue, to constrain the cosmological model through a measurement of the galaxy clustering ratio eta(g,R). This statistic has favourable properties, which is defined as the ratio of two quantities characterizing the smoothed density field in spheres of a given radius R: the value of its correlation function on a multiple of this scale, xi(nR), and its variance sigma(2)(R). For sufficiently large values of R, this is a universal number, which captures 2-point clustering information independently of the linear bias and linear redshift-space distortions of the specific galaxy tracers. In this paper, we discuss how to extend the application of eta(g,R) to quasi-linear scales and how to control and remove observational selection effects, which are typical of redshift surveys as VIPERS, in detail. We verify the accuracy and efficiency of these procedures using mock catalogues that match the survey selection process. These results show the robustness of eta(g,R) to non-linearities and observational effects, which is related to its very definition as a ratio of quantities that are similarly affected. At an effective redshift z = 0.93, we measured the value eta(g,R)(15) = 0.141 +/- 0.013 at R = 5 h(-1) Mpc. Within a flat Lambda CDM cosmology and by including the best available priors on H-0, n(s) and baryon density, we obtain a matter density parameter at the current epoch Omega(m,0) = 0.270(-0.025)(+0.029). In addition to the great precision achieved on our estimation of Omega(m) using VIPERS PDR-1, this result is remarkable because it appears to be in good agreement with a recent estimate at z similar or equal to 0.3, which was obtained by applying the same technique to the SDSS-LRG catalogue. It, therefore, supports the robustness of the present analysis. Moreover, the combination of these two measurements at z similar to 0.3 and z similar to 0.9 provides us with a very precise estimate of Omega(m,0) = 0.274 +/- 0.017, which highlights the great consistency between our estimation and other cosmological probes, such as baryonic acoustic oscillations, cosmic microwave background, and supernovae.
- cosmological parameters
- dark matter
- large-scale structure of Universe