Cross-correlating the EMU Pilot Survey 1 with CMB lensing: constraints on cosmology and galaxy bias with harmonic-space power spectra

We measured the harmonic-space power spectrum of galaxy clustering auto-correlation from the Evolutionary Map of the Universe Pilot Survey 1 data (EMU PS1) and its cross-correlation with the lensing convergence map of cosmic microwave background (CMB) from Planck Public Release 4 at the linear scale range from ℓ = 2 to 500. We applied two flux density cuts at 0.18 and 0.4mJy on the radio galaxies observed at 944MHz and considered two source detection algorithms. We found the auto-correlation measurements from the two algorithms at the 0.18mJy cut to deviate for ℓ ≥ 250 due to the different criteria assumed on the source detection and decided to ignore data above this scale. We report a cross-correlation detection of EMU PS1 with CMB lensing at ∼5.5σ, irrespective of flux density cut. In our theoretical modelling we considered the SKADS and T-RECS redshift distribution simulation models that yield consistent results, a linear and a non-linear matter power spectrum, and two linear galaxy bias models. That is a constant redshift-independent galaxy bias b(z) = b_g and a constant amplitude galaxy bias b(z) = b_g/D(z). By fixing a cosmology model and considering a non-linear matter power spectrum with SKADS, we measured a constant galaxy bias at 0.18mJy (0.4mJy) with b_g = 2.32_-0.33^+0.41 (2.18_-0.25^+0.17) and a constant amplitude bias with b_g = 1.72_-0.21^+0.31 (1.78_-0.15^+0.22). When σ₈ is a free parameter for the same models at 0.18mJy (0.4mJy) with the constant model we found σ₈ = 0.68_-0.14^+0.16 (0.82 ±0.10), while with the constant amplitude model we measured σ₈ = 0.61_-0.20^+0.18 (0.78_-0.09^+0.11), respectively. Our results agree at 1σ with the measurements from Planck CMB and the weak lensing surveys and also show the potential of cosmology studies with future radio continuum survey data.