PUB - Publikationen an der Universität Bielefeld

Aims. We combined the LOw-Frequency ARray (LOFAR) Two-metre Sky Survey (LoTSS) second data release (DR2) catalogue with gravitational lensing maps from the cosmic microwave background (CMB) to place constraints on the bias evolution of LoTSS-detected radio galaxies, and on the amplitude of matter perturbations. Methods. We constructed a flux-limited catalogue from LoTSS DR2, and analysed its harmonic-space cross-correlation with CMB lensing maps from Planck, C-& ell;(g kappa), as well as its auto-correlation, C-gg(& ell;). We explored the models describing the redshift evolution of the large-scale radio galaxy bias, discriminating between them through the combination of both C-g kappa( & ell;) and C-gg (& ell; ). Fixing the bias evolution, we then used these data to place constraints on the amplitude of large-scale density fluctuations, parametrised by sigma 8. Results. We report the significance of the C-& ell;(g kappa) signal at a level of 26.6 sigma. We determined that a linear bias evolution of the form b(g)(z) = bg,D/D(z), where D(z) is the growth rate, is able to provide a good description of the data, and we measured bg,D = 1.41 +/- 0.06 for a sample that is flux limited at 1.5 mJy, for scales & ell; <250 for C-& ell;(gg), and & ell; <500 for C-& ell;(g kappa ). At the sample's median redshift, we obtained b(z = 0.82) = 2.34 +/- 0.10. Using sigma 8 as a free parameter, while keeping other cosmological parameters fixed to the Planck values, we found fluctuations of sigma 8 = 0.75+0.05 -0.04. The result is in agreement with weak lensing surveys, and at 1 sigma difference with Planck CMB constraints. We also attempted to detect the late-time-integrated Sachs-Wolfe effect with LOFAR data; however, with the current sky coverage, the cross-correlation with CMB temperature maps is consistent with zero. Our results are an important step towards constraining cosmology with radio continuum surveys from LOFAR and other future large radio surveys.