Dark Matter signals from Draco and Willman 1: Prospects for MAGIC II and CTA

TL;DR

This study evaluates the potential of upcoming Cherenkov telescopes MAGIC II and CTA to detect dark matter annihilation signals from dwarf galaxies Draco and Willman 1, emphasizing the impact of internal bremsstrahlung on gamma-ray flux detection prospects.

Contribution

It introduces the first comprehensive analysis considering internal bremsstrahlung effects on dark matter signals for IACTs, enhancing the understanding of detection prospects.

Findings

Internal bremsstrahlung significantly increases gamma-ray flux at high energies.

Detection is challenging unless optimistic dark matter distribution assumptions are made.

Spectral features from internal bremsstrahlung could serve as a smoking gun for dark matter.

Abstract

The next generation of ground-based Imaging Air Cherenkov Telescopes (IACTs) will play an important role in indirect dark matter searches. In this article, we consider two particularly promising candidate sources for dark matter annihilation signals, the nearby dwarf galaxies Draco and Willman 1, and study the prospects of detecting such a signal for the soon-operating MAGIC II telescope system as well as for the planned installation of CTA, taking special care of describing the experimental features that affect the detectional prospects. For the first time in such a study, we fully take into account the effect of internal bremsstrahlung, which has recently been shown to considerably enhance, in some cases, the gamma-ray flux at the high energies where Atmospheric Cherenkov Telescopes operate, thus leading to significantly harder annihilation spectra than traditionally considered. While the detection of the spectral features introduced by internal bremsstrahlung would constitute a smoking gun signature for dark matter annihilation, we find that for most models the overall flux still remains at a level that will be challenging to detect unless one adopts rather (though by no means overly) optimistic astrophysical assumptions about the distribution of dark matter in the dwarfs.