The Cherenkov Telescope Array (CTA) observatory will explore the sky with very high energy gamma rays (from 20 GeV to more than 100 TeV) in search of the origin of cosmic rays. It is currently being deployed in the Southern and Northern Hemispheres, near the Cerro Paranal Observatory in the Atacama Desert (Chile) and the Roque de los Muchachos Observatory on the island of La Palma (Canary Islands). Eventually, it will number about 100 telescopes in total.
The CTA will be used to detect the bluish Cherenkov radiation emitted as a result of the interaction of very high energy photons (gamma rays) with the atmosphere. Once the direction and energy of these gamma rays are reconstructed, specialized analysis software is needed to produce images of the sky and to optimize the detection sensitivity of astrophysical objects.
While until now these tools were specific to each collaboration and reserved for its members, the CTA will be an open observatory, with public access to data for scientific users. Along these lines, in June 2021 the collaboration selected the open source software Gammapy as a high-level analysis tool for the data collected by the telescopes and their modeling.
Gammapy uses the Python programming language, which in the last decade has become the new standard in scientific data analysis, and around which an ecosystem of open source libraries in a wide variety of fields has flourished. It will thus benefit from a shared and open development mode, in an environment that is favorable to interdisciplinarity.
It is already being used for the analysis of data from the H.E.S.S. (High Energy Stereoscopic System) collaboration that Irfu participates in, and is poised to become a structuring tool for the gamma-ray astronomy community. Moreover, Gammapy should simplify the fusion of data from several instruments for multi-wavelength and multi-messenger analyses, and help establish a new standard in gamma-ray astronomy for open and reproducible scientific analyses.
As a member of the Gammapy steering committee, the CEA-Irfu has contributed to the analysis methods and the visualization of Gammapy data, within a group of nearly 70 scientists from around the world.