Testing gravity with gravitational waves $\times$ electromagnetic probes cross-correlations

Abstract

In a General Relativistic framework, Gravitational Waves (GW) and Electromagnetic (EM) waves are expected to respond in the same way to the effects of matter perturbations between the emitter and the observer. A different behaviour might be a signature of alternative theories of gravity. In this work we study the cross-correlation of resolved GW events (from compact objects mergers detected by the Einstein Telescope, either assuming or excluding the detection of an EM counterpart) and EM signals (coming both from the Intensity Mapping of the neutral hydrogen distribution and resolved galaxies from the SKA Observatory), considering weak lensing, angular clustering and their cross term (L × C) as observable probes. Cross-correlations of these effects are expected to provide promising information on the behaviour of these two observables, hopefully shedding light on beyond GR signatures. We perform a Fisher matrix analysis with the aim of constraining the {µ 0 , η 0 , Σ 0 } parameters, either opening or keeping fixed the background parameters {w 0 , w a }. We find that, although lensing-only forecasts provide significantly unconstrained results, the combination with angular clustering and the cross-correlation of all three considered tracers (GW, IM, resolved galaxies) leads to interesting and competitive constraints. This offers a novel and alternative path to both multi-tracing opportunities for Cosmology and the Modified Gravity sector.

Prospects of testing late-time cosmology with weak lensing of gravitational waves and galaxy surveys

“…For high enough redshift sources (z 1.5), GW-WL can cause up to ∼ 5% distortion in the GW strain, posing a serious limitation to the precision with which the luminosity distance of the sources is measured [46,47]. However, it can also be exploited as an interesting signal [48], especially when cross-correlated with galaxies [49][50][51], CMB lensing [52], HI intensity mapping [53,54] and other GW probes [55,56]. Cross-correlation of the GW sources with galaxies is shown to be a powerful technique for several other science topics ranging from cosmology and astrophysics [53,[57][58][59][60][61] and its recent application on GWTC-3 [62].…”

Constraining gravity with synergies between radio and optical cosmological surveys

“…While completing this paper,[95] appeared on the ArXiv independently. While[95] investigates synergies with gravitational waves, we rather focus on cross-correlation with optical surveys.…”

“…While completing this paper,[95] appeared on the ArXiv independently. While[95] investigates synergies with gravitational waves, we rather focus on cross-correlation with optical surveys. Choices in scale cuts and non-linear assumptions are also different; we discuss our prescriptions in subsubsection 3.5.1, including the PPF formalism allowing us to reach smaller scales.…”