Matched Runs Method to Study Extended Regions of Gamma-ray Emission

Abstract

Imaging atmospheric Cherenkov telescopes, such as the Very Energetic Radiation Imaging Telescope Array System (VERITAS), are uniquely suited to resolve the detailed morphology of extended regions of gamma-ray emission. However, standard VERITAS data analysis techniques have insufficient sensitivity to gamma-ray sources spanning the VERITAS field of view (3.5°), due to difficulties with background estimation. For analysis of such spatially extended sources with 0.5° to greater than 2° radius, we developed the Matched Runs Method. This method derives background estimations for observations of extended sources using matched separate observations of known point sources taken under similar observing conditions. Our technique has been validated by application to archival VERITAS data. Here we present a summary of the Matched Runs Method and multiple validation studies on different gamma-ray sources using VERITAS data.