Oral comunication
C. Clarkson, J. Fonseca, S. Zazzera, T. Baker
Abstract
Gravitational waves (GWs) have rapidly become important cosmological probes since their first de-
tection in 2015. As the number of detected events continues to rise, upcoming instruments like
the Einstein Telescope (ET) and Cosmic Explorer (CE) will observe millions of compact binary (CB)
mergers. These detections, coupled with galaxy surveys by instruments such as DESI, Euclid, and the
Vera Rubin Observatory, will provide unique information on the large-scale structure of the universe
by cross-correlating GWs with the distribution of galaxies which host them. In this paper, we focus
on how these cross-correlations constrain the clustering bias of GWs emitted by the coalescence
of binary black holes (BBH). This parameter links BBHs to the underlying dark matter distribution,
hence informing us how they populate galaxies. Using a multi-tracer approach, we forecast the
precision of these measurements under different survey combinations. Our results indicate that cur-
rent GW detectors will have limited precision, with measurement errors as high as ∼ 50%. However,
third-generation detectors like ET, when cross-correlated with LSST data, can improve clustering
bias measurements to within 2.5%. Furthermore, we demonstrate that these cross-correlations can
enable a percent-level measurement of the magnification lensing effect on GWs. Despite this, there
is a degeneracy between magnification and evolution biases, which hinders the precision of both.
This degeneracy is most effectively addressed by assuming knowledge of one bias or targeting an
optimal redshift range of 1 < < 2.5. Our analysis opens new avenues for studying the distribution
of BBHs and testing the nature of gravity through large-scale structure.
XVII Black Holes Workshop
Aveiro, Portugal
2024 December
