Multi-Messenger Astrophysics with the Cherenkov Telescope Array

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Gamma rays are the highest energy form of electromagnetic radiation. Observations of astrophysical gamma rays probe physical conditions and processes in the most extreme environments throughout the Universe, and can be used to test fundamental physics. Gamma-ray detectors may also be capable of observing cosmic rays, which are highly energetic sub-atomic particles that travel near the speed of light. The origins and acceleration mechanisms of cosmic rays are unknown but they likely originate in extreme astrophysical phenomena both within and beyond our galaxy. This award supports scientists at the University of Wisconsin in the development of hardware and analysis techniques for the next-generation gamma-ray telescope, the Cherenkov Telescope Array (CTA), an international gamma-ray observatory currently in the prototyping stage of development. A new design, the Schwarzschild Couder Telescope, is currently under construction in Arizona at the Fred Lawrence Whipple Observatory. This award will support the group's work on the camera for the telescope, including the data processing and analysis procedures for this prototype telescope. They will then test new methods for studying cosmic rays using the unique capabilities of this new instrument. The PI leads the Distributed Electronic Cosmic-ray Observatory (DECO), an education and outreach project that uses cell phones as particle detectors. This award will support the group to work with local teachers to develop lesson plans and projects to use DECO in classrooms. The prototype Schwarzschild Couder Telescope uses silicon photo-detectors with new capabilities, including the ability to operate in moonlight conditions. The University of Wisconsin group will develop the data taking, processing, and analysis procedures for these new detectors. They will then characterize the instrument performance under moonlight conditions and study the cosmic-ray Moon shadow during partial Moon illumination. These studies will lay the groundwork for a measurement using CTA of the positron fraction using the opposite direction of the electron and positron shadows as deflected in the Earth's magnetic field.