Constraining the dark energy equation of state using LISA observations of spinning Massive Black Hole binaries

TL;DR

This paper explores how future LISA gravitational wave observations of massive black hole mergers can constrain the dark energy equation of state by statistically analyzing host galaxy distributions, offering an independent cosmological test.

Contribution

It introduces a method to constrain dark energy parameters using gravitational wave data without requiring electromagnetic counterparts, leveraging galaxy distribution models within LISA error boxes.

Findings

Dark energy parameter w can be constrained to 4-8% (2sigma)

Method is competitive with supernovae measurements

Provides an independent test of cosmological models

Abstract

Gravitational wave signals from coalescing Massive Black Hole (MBH) binaries could be used as standard sirens to measure cosmological parameters. The future space based gravitational wave observatory Laser Interferometer Space Antenna (LISA) will detect up to a hundred of those events, providing very accurate measurements of their luminosity distances. To constrain the cosmological parameters we also need to measure the redshift of the galaxy (or cluster of galaxies) hosting the merger. This requires the identification of a distinctive electromagnetic event associated to the binary coalescence. However, putative electromagnetic signatures may be too weak to be observed. Instead, we study here the possibility of constraining the cosmological parameters by enforcing statistical consistency between all the possible hosts detected within the measurement error box of a few dozen of low redshift (z<3) events. We construct MBH populations using merger tree realizations of the dark matter hierarchy in a LambdaCDM Universe, and we use data from the Millennium simulation to model the galaxy distribution in the LISA error box. We show that, assuming that all the other cosmological parameters are known, the parameter w describing the dark energy equation of state can be constrained to a 4-8% level (2sigma error), competitive with current uncertainties obtained by type Ia supernovae measurements, providing an independent test of our cosmological model.