Euclid

Abstract:

Galaxy proto-clusters are receiving increased interest since most of the processes shaping the structure of clusters of galaxies and their galaxy population happen at the early stages of their formation. The Euclid Survey will provide a unique opportunity to discover a large number of proto-clusters over a large fraction of the sky (14 500 deg2). In this paper, we explore the expected observational properties of proto-clusters in the Euclid Wide Survey by means of theoretical models and simulations. We provide an overview of the predicted proto-cluster extent, galaxy density profiles, mass-richness relations, abundance, and sky-filling as a function of redshift. Useful analytical approximations for the functions of these properties are provided. The focus is on the redshift range z = 1.5-4. In particular we discuss the density contrast with which proto-clusters can be observed against the background in the galaxy distribution if photometric galaxy redshifts are used as supplied by the ESA Euclid mission together with the ground-based photometric surveys. We show that the obtainable detection significance is sufficient to find large numbers of interesting proto-cluster candidates. For quantitative studies, additional spectroscopic follow-up is required to confirm the proto-clusters and establish their richness.

Abstract:

Context. The Euclid mission of the European Space Agency will deliver weak gravitational lensing and galaxy clustering surveys that can be used to constrain the standard cosmological model and extensions thereof. Aims. We present forecasts from the combination of the Euclid photometric galaxy surveys (weak lensing, galaxy clustering, and their cross-correlations) and its spectroscopic redshift survey with respect to their sensitivity to cosmological parameters. We include the summed neutrino mass, Σmν, and the effective number of relativistic species, Neff, in the standard Λ CDM scenario and in the dynamical dark energy (w0waCDM) scenario. Methods. We compared the accuracy of different algorithms predicting the non-linear matter power spectrum for such models. We then validated several pipelines for Fisher matrix and Markov chain Monte Carlo (MCMC) forecasts, using different theory codes, algorithms for numerical derivatives, and assumptions on the non-linear cut-off scale. Results. The Euclid primary probes alone will reach a sensitivity of σ (Σmν = 60 meV) = 56 meV in the Λ CDM+Σmν model, whereas the combination with cosmic microwave background (CMB) data from Planck is expected to achieve σ (Σmν) = 23 meV, offering evidence of a non-zero neutrino mass to at least the 2.6 σ level. This could be pushed to a 4 σ detection if future CMB data from LiteBIRD and CMB Stage-IV were included. In combination with Planck, Euclid will also deliver tight constraints on Δ Neff < 0.144 (95%CL) in the Λ CDM+Σmν+Neff model or even Δ Neff < 0.063 when future CMB data are included. When floating the dark energy parameters, we find that the sensitivity to Neff remains stable, but for Σmν, it gets degraded by up to a factor of 2, at most. Conclusions. This work illustrates the complementarity among the Euclid spectroscopic and photometric surveys and among Euclid and CMB constraints. Euclid will offer great potential in measuring the neutrino mass and excluding well-motivated scenarios with additional relativistic particles.

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 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) = bg and a constant amplitude galaxy bias b(z) = bg/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 bg = 2.32-0.33^+0.41 (2.18-0.25^+0.17) and a constant amplitude bias with bg = 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.