Simulating Astronomical Images One Photon at a Time
John Peterson
Purdue University



Recent work in many fields of astronomy and cosmology has increasingly required higher precision measurements. This includes measurements that utilize detailed astrometry, precision photometry, accurate shape measurements, and faint source detection. In order to achieve an even higher level of measurement precision, detailed simulations can help to mitigate subtle systematics of these methods. For that purpose, we describe a novel code to simulate astronomical images called the Photon Simulator (PhoSim). We use a photon Monte Carlo approach to construct images by sampling photons from models of astronomical source populations, and then simulating those photons through the system as they interact with the atmosphere, telescope, and camera using appropriate detailed physics. We also demonstrate that despite the physics detail, small fields can be simulated in seconds, and even the largest optical surveys can be simulated efficiently. We have extended PhoSim to a variety of current and future telescopes. PhoSim is publicly available.