Extreme Environment Astrophysics with H.E.S.S. Phase I 2007-2010

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PPARC has supported for the past few years UK participation in the construction, commissioning and operation of a very high energy (VHE) gamma ray telescope in Namibia, South West Africa, called the H.E.S.S. array. The first 4 telescopes of the array began routine operations in January 2004, and are revealing to us a wealth of astronomical objects acting as huge particle accelerators - supermassive black holes in distant galaxies, supernova remnants and pulsars. UK astronomers are particularly interested in variability in such objects, particularly how active galaxies accelerate particles and in mini versions of these objects in our own galaxy known as microquasars, and in the mechanisms of particle acceleration in pulsars. We are also interested in the solution of one of the great puzzles of the last 100 years, which is the origin of the cosmic rays that bombard us all the time. It has long been suspected that they are produced in supernova remnants, and now we are beginning to find evidence that this might well be the case. However, the final pieces of the jigsaw need to come from more extensive VHE gamma ray observations and observations at other wavelengths. As well as analysing the data from the telescopes, UK scientists are responsible for some of the technical tasks that ensure the whole collaboration is able to get the scientific results from the telescopes. The Durham group is responsible for the calibration systems used with the telescopes in order to ensure that the achieve full sensitivity. Uniquely, in the case of VHE gamma ray telescopes, the atmosphere actually forms part of the detector, and so we have to understand the atmosphere and then use that information in computer simulations to calculate the energies of the incoming gamma rays. In addition, data often have to be corrected for atmospheric variations, so that these can be disentangled from variations in the gamma ray emission of the objects that we observe, which obviously has an important bearing on our scientfic interests. Dr. Jim Hinton at Leeds is responsible for parts of the electronic system and software that ensure the telescopes work properly together. This grant requests funding for two postdoctoral scientists to continue working on H.E.S.S. data and perform the important calibration tasks for the collaboration.