A 3D maximum likelihood analysis for studying highly extended sources in VERITAS data

Abstract

Imaging Atmospheric Cherenkov Telescopes have provided insights into many astrophysical phenomena including particle acceleration in SNR, studies of the extragalactic background light, and high energy emission from pulsars. However, current techniques for analyzing IACT data are poorly suited to studying emission greater than a few tenths of a degree. This thesis outlines a new analysis technique, known as the 3D MLM, designed to enhance the sensitivity of the VERITAS IACT array to sources from 0.5◦ to greater than 2◦ in radius. This analysis employs a maximum likelihood technique which models the expected distribution of events in the VERITAS data in two dimensions analogous to sky coordinates. Additionally a third dimension based on mean scaled width, a known gamma/hadron discrimination parameter, im- proves the sensitivity of the 3D MLM to such highly extended sources. Simulated VERITAS observations of 2FHL J0431.2+5553e, a 1.27◦ radius Fermi-LAT source, demonstrate the potential superior performance of this new technique over the standard ring background model analysis

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