Gravitational-Wave Background Sky Maps from Advanced LIGO O1 Data.

Abstract

We integrate the publicly available O1 LIGO time-domain data to obtain maximum-likelihood constraints on the gravitational-wave background (GWB) arising from stochastic, persistent signals. Our method produces sky maps of the strain intensity I as a function of direction on the sky at a reference frequency f_{0}. The data are integrated assuming a set of fixed power-law spectra for the signal. The maps provide upper limits on the amplitude of the GWB density Ω_{GW}(f_{0}) and any anisotropy around the background. We find 95%confidence upper limits of Ω_{GW}<4.8×10^{-7} at f_{0}=50 Hz with similar constraints on a dipole modulation for the inspiral-dominated stochastic background case.