Optimising large galaxy surveys for ISW detection

TL;DR

This paper analyzes how future large-scale surveys can optimize the detection of the ISW effect to better understand dark energy, highlighting survey parameters and potential constraints from upcoming projects like DUNE.

Contribution

It identifies optimal survey properties for ISW detection and evaluates the potential of DUNE to constrain dark energy parameters through cross-correlation analysis.

Findings

Survey should cover >35% of sky for >4 sigma detection

DUNE can improve dark energy constraints via cross-correlation

Constraints are complementary to other probes like weak lensing

Abstract

We report on investigations of the power of next generation cosmic microwave background and large scale structure surveys in constraining the nature of dark energy through the cross-correlation of the Integrated Sachs Wolfe effect and the galaxy distribution. First we employ a signal to noise analysis to find the most appropriate properties of a survey in order to detect the correlated signal at a level of more than 4 sigma: such a survey should cover more than 35% of the sky, the galaxy distribution should be probed with a median redshift higher than 0.8, and the number of galaxies detected should be higher than a few per squared arcmin. We consider the forthcoming surveys DUNE, LSST, SNAP, PanSTARRS. We then compute the constraints that the DUNE survey can put on the nature of dark energy (through different parametrizations of its equation of state) with a standard Fisher matrix analysis. We confirm that, with respect to pure CMB constraints, cross-correlation constraints help in breaking degeneracies among the dark energy and the cosmological parameters. Naturally, the constraining capability is not independent of the choice of the dark energy model. Despite being weaker than some other probes (like Gravitational Weak-Lensing), these constraints are complementary to them, being sensitive to the high-redshift behaviour of the dark energy.