An Isotropy Measurement with Gravitational Wave Observations

Kavli Affiliate: Daniel E. Holz

| First 5 Authors: Reed Essick, Will M. Farr, Maya Fishbach, Daniel E. Holz, Erik Katsavounidis

| Summary:

We constrain the distribution of merging compact binaries across the
celestial sphere using the GWTC-3 catalog from the LIGO-Virgo-KAGRA
Collaborations’ (LVK) third observing run. With 63 confident detections from
O3, we constrain the relative variability (standard deviation) of the rate
density across the sky to be $lesssim 16%$ at 90% confidence assuming the
logarithm of the rate density is described by a Gaussian random field with
correlation length $geq 10^circ$. This tightens to $lesssim 3.5%$ when the
correlation length is $geq 20^circ$. While the new O3 data provides the
tightest constraints on anisotropies available to-date, we do not find
overwhelming evidence in favor of isotropy, either. A simple counting
experiment favors an isotropic distribution by a factor of
$mathcal{B}^mathrm{iso}_mathrm{ani} = 3.7$, which is nonetheless an
improvement of more than a factor of two compared to analogous analyses based
on only the first and second observing runs of the LVK.

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