Speaker
Description
We investigate the detectability of the stochastic gravitational wave background (SGWB) anisotropies by cross-correlating them with a galaxy distribution. We develop two independent and complementary approaches: galaxy-informed simulations of SGWB maps and a physically motivated analytical modelling. We implement an empirically driven method to map SGWB anisotropies by simulating compact binary mergers according to population constraints from recent LIGO–Virgo–KAGRA (LVK) observations and assigning them to host galaxies drawn from the Euclid Flagship catalogue. Consequently, we forecast that in a shot-noise limit scenario, for 10 years of observation, we can obtain a clearly detectable multi-messenger cross-correlation for any likely merger rate at a minimal angular resolution of $\ell = 28$. Moreover, for a resolution of $\ell = 44$, a signal an be detected in 1, 3 and 4.4 years of observation respectively for the LVK O4a upper, median and lower merger rate estimates. We further show that for high merger rates, the signal is maximised in a redshift range of $1.3< z < 2.5$ and that a tomographic binning of the multi-messenger cross-correlation enables to constrain the evolution of compact binary mergers. These results provide forecasts for the detectability of SGWB anisotropies and highlight the potential of multi-messenger cross-correlations to probe the large-scale structures of the Universe.