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

Abstract

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 $\ell=2$ to 500. We applied two flux density cuts at $0.18$ and $0.4$mJy 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 $\ell\gtrsim250$ 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 $\sim$5.5$σ$, irrespective of flux density cut. In our theoretical modelling we considered two 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, we measured a constant galaxy bias at $0.18$mJy ($0.4$mJy) with $b_g=2.32^{+0.41}_{-0.33}$ ($2.18^{+0.17}_{-0.25}$) and a constant amplitude bias with $b_g=1.72^{+0.31}_{-0.21}$ ($1.78^{+0.22}_{-0.15}$). When $σ_8$ is a free parameter for the same models at $0.18$mJy ($0.4$mJy) with the constant model we found $σ_8=0.68^{+0.16}_{-0.14}$ ($0.82\pm0.10$), while with the constant amplitude model we measured $σ_8=0.61^{+0.18}_{-0.20}$ ($0.78^{+0.11}_{-0.09}$), 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.

Figures (9)

• Figure 1: The normalised redshift distributions of radio continuum galaxies as estimated from the simulations SKADS (blue) and T-RECS (red) at the flux density cuts 0.18mJy (solid) and 0.4mJy (dashed).
• Figure 2: A list of maps that was used in our work. Top left: The weights mask for Selavy. Top right: The galaxy overdensity map for Selavy. Middle left: The weights mask for PyBDSF. Middle right: The galaxy overdensity map for PyBDSF. Bottom: The CMB convergence map. All the galaxy maps here are for the flux density cut at $0.18$ mJy, while for the cut at $0.4$ mJy, they look similar. In the overdensities and convergence panels, the mask is shown with grey color.
• Figure 3: The auto-correlation $\tilde{C}^{gg}_\ell$ for the flux density cut at 0.18mJy (top left panel) and 0.4mJy (top right panel). Red and blue points along with their 1$\sigma$ uncertainties, correspond to the Selavy and PyBDSF catalogues. Their corresponding fitted theory models are denoted with orange and green curves, respectively, which are estimated assuming the Planck best-fit values Planck2020, the SKADS redshift distribution and HALOFIT power spectrum. The colourful horizonal dashed lines are shot noise estimates for the two catalogues, and the grey shaded area (top left panel) denotes the scale cut at $\ell=250$ for the flux density cut at 0.18mJy. The bottom panel shows the cross-correlation of galaxies with the CMB lensing convergence $\tilde{C}^{g\kappa}_\ell$ at the flux density cut 0.18mJy.
• Figure 4: Left: The best-fit values along with their 68% confidence intervals on the galaxy bias parameter $b_g$ for the auto-correlation $\tilde{C}^{gg}$, the cross-correlation $\tilde{C}^{g\kappa}$ and their combination $\tilde{C}^{gg}+\tilde{C}^{g\kappa}$, assuming the redshift distribution SKADS, a linear (denoted with 'lin') and HALOFIT power spectrum (denoted with 'nl'), and fixing the cosmology to the fiducial values. Blue (orange) errorbars correspond to the flux density cut 0.18 (0.4) mJy and solid (dashed) lines to the constant bias model (constant amplitude model). Right: Same as in the left panel but now for the $\sigma_8$ constraints on the combined spectra. The bottom lines present the PlanckPlanck2020, DES Abbott21 and KiDS Heymans2021 measurements with red, magenta and green color, respectively.
• Figure 5: Best-fit values along with the 68% confidence interval constraints on the constant bias (green and blue) and constant amplitude (magenta and red) model for the combined spectra $\tilde{C}^{gg}+\tilde{C}^{g\kappa}$ assuming a SKADS distribution, a HALOFIT (filled intervals) as well as a linear (empty intervals) spectrum and a flux density cut at 0.18mJy. The errorbars with the different marker styles represent galaxy bias measurements from different radio galaxy surveys in the literature. Grey and blue triangular markers correspond to AGN and SFG constraints as from H18 Hale18 while the black triangular marker to the combined sample in the same work. The rest of the different shape black markers show mixed populations from the works Nusser15Hale18Alonso2021Hale24Nakoneczny24.The vertical dashed line is the median redshift of the sample.