(An)isotropy measurement with gravitational wave observations

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