Forecasting constraints on anisotropy in the nanohertz gravitational wave background

Pulsar timing arrays are projected to make a detection of the nanohertz gravitational wave background (GWB) in the next few years. This background is expected to be produced by inspiraling supermassive black-hole binaries (SMBHBs) in the local universe. The angular power of the background produced by these SMBHBs will be anisotropic, with the brightest binaries standing out above the background. In this work, we present a method that makes use of the measured cross-correlations between pulsars in the array to place constraints on the anisotropy of the GWB. We then use realistic simulations of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) dataset to forecast the constraints that we will be able to place on the anisotropy of the GWB in the next few years.