Application of Maximum Entropy Deconvolution to ${\gamma}$-ray Skymaps

TL;DR

This paper explores the use of the Maximum Entropy Algorithm for deconvolving gamma-ray skymaps from atmospheric Cherenkov telescopes, aiming to improve angular resolution despite high noise levels.

Contribution

It provides an analysis of the parameter influences on the Maximum Entropy Algorithm's effectiveness in gamma-ray skymap deconvolution.

Findings

Parameter influences on deconvolution quality analyzed

Maximum Entropy Algorithm shown to be promising for gamma-ray data

Implementation details and applicability discussed

Abstract

Skymaps measured with imaging atmospheric Cherenkov telescopes (IACTs) represent the real source distribution convolved with the point spread function of the observing instrument. Current IACTs have an angular resolution in the order of 0.1$^\circ$ which is rather large for the study of morphological structures and for comparing the morphology in $\gamma$-rays to measurements in other wavelengths where the instruments have better angular resolutions. Serendipitously it is possible to approximate the underlying true source distribution by applying a deconvolution algorithm to the observed skymap, thus effectively improving the instruments angular resolution. From the multitude of existing deconvolution algorithms several are already used in astronomy, but in the special case of $\gamma$-ray astronomy most of these algorithms are challenged due to the high noise level within the measured data. One promising algorithm for the application to $\gamma$-ray data is the Maximum Entropy Algorithm. The advantages of this algorithm are the possibility to take a priori knowledge into account and that it is an independent approach to previous work, e.g., Heinz et al. (2012) who applied the Richardson Lucy Algorithm to $\gamma$-ray skymaps. An implementation of the Maximum Entropy Algorithm is provided in the MemSys5 software package by Gull and Skilling (1999). As this algorithm is very sensitive to various input parameters it is essential to understand their influences. We present a study of the influences of these parameters in order to investigate the applicability of the Maximum Entropy Algorithm for the deconvolution of skymaps in $\gamma$-ray astronomy.