Fisher Forecasting for the DESC with Augur

The Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) has begun its ten-year survey of the entire visible southern hemisphere. To ensure robust cosmological measurements, computationally inexpensive investigations of modeling choices must be made to gauge the performance of proposed cosmological analyses. In this paper, we introduce the 𝙰𝚞𝚐𝚞𝚛 tool of the Dark Energy Science Collaboration (DESC), which provides Fisher forecasts for cosmological inference for the LSST using software frameworks designed for DESC science. We test the pipeline by comparing it to forecasts produced by external code and direct sampling of the posterior via nested sampling methods, finding good agreement between all methods. We additionally investigate a range of modeling and hyperparameter choices for a 3 × 2pt investigation in harmonic space, providing users with diagnostics to obtain reliable forecasts. 𝙰𝚞𝚐𝚞𝚛 will be continually updated to be compatible with the other tools in the DESC software ecosystem as additional probes and functionality become available.