[Paper Review] Euclid & SKA Synergies

T. Kitching, David Bacon+8 more|arXiv (Cornell University)|Jan 16, 2015

Radio Astronomy Observations and Technology4 citations

TL;DR

This paper proposes that the Euclid space mission and the Square Kilometre Array (SKA) radio telescope will deliver transformative cosmological insights through synergistic cross-correlation of their data, leveraging complementary redshift coverage, wavelength regimes, and systematic error control. The combination enhances constraints on dark energy, modified gravity, and neutrino masses beyond what either mission could achieve alone.

ABSTRACT

Over the past few years two of the largest and highest fidelity experiments conceived have been approved for construction: Euclid is an ESA M-Class mission that will map three-quarters of the extra galactic sky with Hubble Space Telescope resolution optical and NIR imaging, and NIR spectroscopy, its scientific aims (amongst others) are to create a map of the dark Universe and to determine the nature of dark energy. The Square Kilometre Array (SKA) has similar scientific aims (and others) using radio wavelength observations. The two experiments are synergistic in several respects, both through the scientific objectives and through the control of systematic effects. SKA Phase-1 and Euclid will be commissioned on similar timescales offering an exciting opportunity to exploit synergies between these facilities.

Motivation & Objective

• To identify and quantify the scientific synergies between the Euclid space mission and the Square Kilometre Array (SKA) in cosmology and astrophysics.
• To demonstrate how cross-correlation of weak lensing, galaxy clustering, and 21cm intensity mapping data from both facilities can improve cosmological parameter constraints.
• To reduce systematic errors in weak lensing measurements by exploiting differing instrumental systematics between the optical/NIR (Euclid) and radio (SKA) domains.
• To enable more accurate redshift calibration and intrinsic alignment modeling through joint analysis of shape and flux measurements.
• To support the development of shared data analysis methodologies, including compressive sensing and sparsity-based techniques, for handling peta-scale datasets from both missions.

Proposed method

• Utilize cross-correlation statistics between Euclid’s weak lensing and galaxy clustering data and SKA’s 21cm intensity mapping and radio source catalogs to extract cosmological information.
• Apply sparsity-based compressive sensing techniques to reconstruct 3D density fields from weak lensing and interferometric radio data, leveraging wavelet transforms and convex optimization.
• Cross-calibrate shape systematics and intrinsic alignment effects by comparing ellipticity measurements from Euclid (optical/NIR) and SKA (radio) at the same sky locations.
• Use 21cm line redshifts from SKA to provide precise photometric redshifts for Euclid sources, improving tomographic weak lensing and clustering analyses.
• Integrate data from Planck (CMB, SZ, ISW) with Euclid and SKA to enhance constraints on dark energy and growth of structure through multi-probe cross-correlations.
• Develop shared numerical pipelines and simulation frameworks for N-body and hydrodynamical simulations to model non-linear clustering and baryonic feedback effects.

Experimental results

Research questions

• RQ1 How can the combination of Euclid and SKA improve constraints on the dark energy equation of state and its redshift evolution?
• RQ2 In what ways can cross-correlation of weak lensing data from Euclid and SKA reduce sensitivity to shape measurement systematics?
• RQ3 To what extent can SKA’s 21cm redshift measurements improve photometric redshift accuracy for Euclid’s source galaxies?
• RQ4 How do joint analyses of intrinsic alignment and lensing data from both missions enhance cosmological parameter estimation?
• RQ5 What methodological synergies exist in data analysis, particularly in compressive sensing and sparsity-based imaging, for handling peta-scale datasets from both missions?

Key findings

• The combination of Euclid and SKA is expected to exceed the individual Figure of Merit for dark energy (≥400) and improve the accuracy of the growth index γ to 0.02.
• Cross-correlation of weak lensing data from Euclid and SKA can significantly reduce shape measurement biases due to differing systematics in optical and radio domains.
• SKA’s 21cm line observations provide precise redshifts that enhance the tomographic resolution of Euclid’s weak lensing and clustering measurements.
• Joint analysis enables improved constraints on modified gravity and neutrino mass, with enhanced sensitivity to signatures in the matter power spectrum across linear and quasi-non-linear scales.
• Sparsity-based methods such as compressive sensing can be applied uniformly to both Euclid and SKA data, enabling shared algorithms and codebases for image reconstruction and inverse problem solving.
• The synergy extends beyond science to infrastructure, with shared simulation needs and data analysis pipelines expected to reduce resource burden and accelerate discovery.