Euclid

We present a new, model-independent measurement of the clustering amplitude of galaxies and the growth of cosmic large-scale structures from the Baryon Oscillation Spectroscopic Survey (BOSS) 12th data release (DR12). This is achieved by generalising harmonic-space power spectra for galaxy clustering to measure separately the magnitudes of the density and of the redshift-space distortion terms, which are respectively related to the clustering amplitude, bσ8(z), and the growth, fσ8(z). We adopt a tomographic approach with 15 redshift bins in the range z∈[0.15,0.67]. We restrict our analysis to strictly linear scales, implementing a redshift-dependent maximum multipole for each of the tomographic bins. Thus, we obtain 30 data points in total, 15 for each of the quantities bσ8(z) and fσ8(z). The measurements do not appear to suffer from any apparent systematic effect and show excellent agreement with the theoretical prediction from a concordance cosmology as from the Planck satellite. Our results also agree with previous analyses by the BOSS collaboration. Although each single datum has, in general, a larger error bar than that obtained in configuration- or Fourier-space analyses, our study provides the community with a larger number of tomographic data points that allow for a complementary tracking in redshift of the evolution of fundamental cosmological quantities.