Clustering of luminous red galaxies – II. Small-scale redshift-space distortions |
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| Authors: | Anna Cabré Enrique Gaztañaga |
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| Institution: | Institut de Ciències de l'Espai, CSIC/IEEC, Campus UAB, F. de Ciències, Torre C5 par-2, Barcelona 08193, Spain |
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| Abstract: | This is the second paper of a series where we study the clustering of luminous red galaxies (LRG) in the recent spectroscopic Sloan Digital Sky Survey (SDSS) data release, DR6, which has 75 000 LRG covering over 1 Gpc3 h −3 for 0.15 < z < 0.47 . Here, we focus on modelling redshift-space distortions in ξ(σ, π) , the two-point correlation in separate line-of-sight and perpendicular directions, at small scales and in the line-of-sight. We show that a simple Kaiser model for the anisotropic two-point correlation function in redshift space, convolved with a distribution of random peculiar velocities with an exponential form, can describe well the correlation of LRG on all scales. We show that to describe with accuracy the so-called 'fingers-of-God' (FOG) elongations in the radial direction, it is necessary to model the scale dependence of both bias b and the pairwise rms peculiar velocity σ12 with the distance. We show how both quantities can be inferred from the ξ(σ, π) data. From r ≃ 10 Mpc h −1 to r ≃ 1 Mpc h −1 , both the bias and σ12 are shown to increase by a factor of 2: from b = 2 to 4 and from σ12= 400 to 800 km s−1 . The latter is in good agreement, within a 5 per cent accuracy in the recovered velocities, with direct velocity measurements in dark matter simulations with Ωm= 0.25 and σ8= 0.85 . |
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| Keywords: | galaxies: distances and redshifts galaxies: evolution cosmology: observations |
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