Die erste Analyse sehr hoch energetischer Gammastrahlung aus der Großen Magellanschen Wolke mit einer neuartigen Analysetechnik

The Cherenkov Telescope Array (CTA) represents the next generation of instruments for the measurement of gamma radiation from galactic and extragalactic sources in the range between several tens of GeV to few hundred TeV. It will consist of two arrays of different types of Imaging Atmospheric Cherenkov Telescopes (IACT) at two sites and is currently in a pre-construction phase. One important calibration of an IACT is the pointing, which is necessary for a precise angular reconstruction of gamma-ray signals. The first part of this thesis introduces the SingleCCD concept, the favoured pointing solution for the medium size telescopes of CTA. This method makes use of an optical CCD camera that is mounted to a telescope and that records images of the night sky and the Cherenkov light detector. These images can be used for precise measurements of the alignment of the telescope and its internal deformations. The results of extensive tests of this method are presented together with a new software solution that can be used the analysis of the recorded CCD images. With the help of simulations and a test setup at an operating IACT, it could be shown that the introduced software provides an efficient way to reach pointing precisions of < 10''. In the second part of the thesis, the 3D likelihood method is used for the analysis of gamma radiation from the Large Magellanic Cloud (LMC) that was observed with H.E.S.S., a contemporary IACT located in Namibia. The application of the 3D likelihood method in the analysis of IACT data is rather novel but is on the rise with the upcoming CTA and provides a straightforward way of analysing complicated regions with overlapping gamma-ray sources. In the analysis, spatial and spectral descriptions of the known point sources in the LMC were obtained that are, within some limitations, compatible with results of earlier analyses with more established methods. Furthermore, the advantages of the 3D likelihood method were used to search for a diffuse gamma-ray signal within the LMC. Indication for this was found within the 30 Doradus region, spatially coincident with emission at lower gamma-ray energies that was detected by the spaceborne gamma-ray telescope Fermi-LAT.Das Cherenkov Telescope Array (CTA) repräsentiert die nächste Generation von Instrumenten zur Messung von Gammastrahlung von galaktischen und extragalaktischen Quellen im Bereich von einigen zehn GeV bis zu wenigen hundert TeV. Es wird aus zwei Anordnungen von unterschiedlichen Typen von Abbildenden Cherenkov Teleskopen (IACT) an zwei Standorten bestehen und befindet sich aktuell in einer Voraufbau Phase. Ein wichtiger Aspekt der Kalibrierung solcher Teleskope ist das Pointing, welches für die präzise räumliche Rekonstruktion von Gammastrahlungssignalen wichtig ist. Im ersten Teil der vorliegenden Arbeit wird das SingleCCD Konzept vorgestellt, welches die bevorzugte Lösung für das Pointingproblem der mittelgroßen CTA-Teleskope darstellt. In dieser Methode wird eine optische CCD-Kamera genutzt, die so am Teleskop montiert ist, dass sie Bilder vom Nachthimmel und vom Cherenkovlichtdetektor aufnehmen kann. Die so gewonnenen Fotos können für präzise Messungen der Ausrichtung des Teleskops und seiner internen Verformungen genutzt werden. Die Ergebnisse ausführlicher Tests dieser Methode werden gemeinsam mit einer neuen Software vorgestellt, welche für die Auswertung der Fotos genutzt werden kann. Mithilfe von Simulationen und einem Testaufbau an einem momentan operierenden IACT konnte gezeigt werden, dass die vorgestellte Software eine effiziente Möglichkeit darstellt, Präzisionen < 10'' zu erreichen. Im zweiten Teil der Arbeit wird die Anwendung der 3D-Likelihood-Methode bei der Analyse von Gammastrahlung von der Großen Magellanschen Wolke (GMW) präsentiert. Die Daten dafür wurden mit \h genommen, einem aktuellen IACT das sich in Namibia befindet. Die Verwendung der 3D-Likelihood-Methode bei der Analyse von IACT-Daten stellt einen neuartigen Ansatz dar, der allerdings, vor allem für zukünftige CTA-Daten, immer mehr an Bedeutung gewinnt und eine geradlinige Möglichkeit bietet, komplizierte Himmelsregionen mit sich gegenseitig überlappenden Quellen zu analysieren. In der Analyse ergaben sich positionelle und spektrale Beschreibungen der bekannten Punktquellen in der GMW, die bis auf einige Einschränkungen mit den Ergebnissen bisheriger Analysen mit etablierten Methoden vereinbar sind. Ferner wurden die Vorteile der 3D-Likelihood-Methode genutzt, um die GMW nach Signalen diffuser Gammastrahlung zu untersuchen. Hinweise auf ein solches Signal wurden in einem Bereich der 30~Doradus Region gefunden, räumlich koinzident mit einem vom satellitengestützten Gammastrahlenteleskop Fermi-LAT bei niedrigeren Photonenenergien detektierten Signal

Towards a 3D likelihood analysis invery-high-energyγ-ray astronomy:the case of H.E.S.S.

The estimation of the residual background due to cosmic ray-induced air showers represents akey element of every analysis of Imaging Atmospheric Cherenkov Telescope (IACT) data. Inthe past, most techniques have relied on a measurement of the background in supposedly sourcefreeregions within the observed field of view. However, this approach is problematic in regionswith many (potentially overlapping) g-ray sources or large-scale diffuse g-ray emission, like e.g.the Galactic Plane. For these cases, a template-based 3D likelihood analysis might be superior.In this approach, a spectro-morphological model template, consisting of one or multiple sourcecomponents and a background component, is fit to the data, resulting in a complete spectral andspatial description of the field of view. In this contribution, we present our efforts to establish a3D likelihood analysis for data taken with the H.E.S.S. system of IACTs, using the open-sourceanalysis packages ctools and Gammapy. In particular, we focus on the development of a templatemodel for the cosmic ray-induced background – a major challenge in such an approach – fromarchival H.E.S.S. data. We characterise the obtained model and demonstrate its application usingpublicly available H.E.S.S. data. The validation of this analysis approach on experimental dataalso constitutes an important step towards the analysis of data from the upcoming CherenkovTelescope Array (CTA)

A pointing solution for the medium size telescopes for the Cherenkov Telescope Array

The pointing capability of a telescope in the Cherenkov Telescope Array (CTA) is a crucial aspect in the calibration of the instrument. It describes how a position in the sky is transformed to the focal plane of the telescope and allows precise directional reconstructions of atmospheric particle showers. The favoured approach for pointing calibrations of the Medium Size Telescopes (MST) is the utilisation of an CCD-camera installed in the centre of the dish, which images the night sky and the focal plane simultaneously. The technical implementation of this solution and test results taken over a period of one year at the MST prototype in Berlin/Adlershof are presented. Investigations of pointing calibration precision with simulated data and real data taken during test runs of the prototype telescope will also be shown

Analysis of the H.E.S.S. public data release with ctools

34 pages, 47 figuresInternational audienceThe ctools open-source software package was developed for the scientific analysis of astronomical data from Imaging Air Cherenkov Telescopes (IACTs), such as H.E.S.S., VERITAS, MAGIC, and the future Cherenkov Telescope Array (CTA). To date, the software has been mainly tested using simulated CTA data; however, upon the public release of a small set of H.E.S.S. observations of the Crab nebula, MSH 15–52, RX J1713.7–3946, and PKS 2155–304 validation using real data is now possible. We analysed the data of the H.E.S.S. public data release using ctools version 1.6 and compared our results to those published by the H.E.S.S. Collaboration for the respective sources. We developed a parametric background model that satisfactorily describes the expected background rate as a function of reconstructed energy and direction for each observation. We used that model, and tested all analysis methods that are supported by ctools, including novel unbinned and joint or stacked binned analyses of the measured event energies and reconstructed directions, and classical On-Off analysis methods that are comparable to those used by the H.E.S.S. Collaboration. For all analysis methods, we found a good agreement between the ctools results and the H.E.S.S. Collaboration publications considering that they are not always directly comparable due to differences in the datatsets and event processing software. We also performed a joint analysis of H.E.S.S. and Fermi-LAT data of the Crab nebula, illustrating the multi-wavelength capacity of ctools. The joint Crab nebula spectrum is compatible with published literature values within the systematic uncertainties. We conclude that the ctools software is mature for the analysis of data from existing IACTs, as well as from the upcoming CTA

GammapyVersion 0.19

Gammapy is a community-developed, open-source Python package for gamma-ray astronomy built on Numpy, Scipy and Astropy. It is the core library for the CTA science tools and can also be used to analyse data from existing imaging atmospheric Cherenkov telescopes (IACTs), such as H.E.S.S., MAGIC and VERITAS. It also provides some support for Fermi-LAT and HAWC data analysis