An Isotropy Measurement with Gravitational Wave Observations

Reed Essick, Will M. Farr, Maya Fishbach, Daniel E. Holz, Erik Katsavounidis

Submitted on 12 July 2022


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 16% at 90\% confidence assuming the logarithm of the rate density is described by a Gaussian random field with correlation length 10. This tightens to 3.5% when the correlation length is 20. 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 Baniiso=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.


Comment: main text: 12 pages, 6 figures, 2 tables

Subject: Astrophysics - High Energy Astrophysical Phenomena