A Monte Carlo study of the relevance of fluorescence radiation in VHE gamma ray observations with Cherenkov telescopes

TL;DR

This study uses detailed Monte Carlo simulations to evaluate the potential impact of fluorescence radiation on Cherenkov telescope observations of very high energy gamma-ray showers, challenging the common assumption of its insignificance.

Contribution

The paper implements fluorescence radiation tracking in CORSIKA and assesses its relevance in gamma-ray shower detection with Cherenkov telescopes, providing new insights into systematic errors.

Findings

Fluorescence radiation can be significant under certain conditions.

Simulation results agree with numerical calculations.

Results help estimate systematic errors in observations.

Abstract

It is generally assumed that fluorescence radiation does not play a significant role in the performance of Cherenkov telescopes. However, this assumption is required to be verified using detailed Monte Carlo simulations. In order to do this, we have implemented the production and tracking of fluorescence radiation inside the CORSIKA code, and simulated gamma-ray induced showers in the very high energy range. The most accurate fluorescence-yield data available so far was used for this purpose. The distribution of both light components on the ground has been studied as a function of various parameters affecting the detection and reconstruction of gamma-ray showers such as the angular aperture. From these distributions, we determined the conditions under which fluorescence radiation becomes significant. These results will also be useful to estimate the corresponding systematic errors in Cherenkov telescope observations. The full simulation results have been cross-checked, on a small sample of events, against numerical calculations based on a one-dimension shower profile and found to be compatible with each other. Both tools can be used for further investigations, like studying the possibility to modify Cherenkov telescopes for the measurement of fluorescence induced by extensive air showers.