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TeV Gamma-Rays and Radio Signals: Making the Connection

Final Report Summary - TEVGRRS:MTC (TeV gamma-rays and radio signals: Making the connection)

The ultimate objective of the proposed research project was to understand the dynamics of the centre of our own Galaxy, particularly the high-energy aspects of this as revealed by the latest generation of astro-particle detectors (gamma-ray and neutrino telescopes) and radio interferometers and to make predictions to be confirmed by the forthcoming generation of such instruments. We completely succeeded in this endeavour: our work has culminated in the publication of four journal articles, including letters in Nature and in Physical Review Letters which show how the simultaneous analysis of, in particular, radio and gamma-ray data covering the Galactic centre reveal new and important insights into the conditions prevailing in that region of the Galaxy.

In particular, we have been able to show that:
i) the magnetic field in the Galactic centre is very strong, at least ten times stronger than typically found in the Galactic disk;
ii) there is a powerful wind blowing out of the Galactic centre powered by the star-formation activity that occurs there;
iii) this star-formation activity - sustained over timescales approaching the age of the Galaxy - has produced the spectacular gamma-ray features recently observed by the Fermi gamma-ray telesceope to extend 10 kpc above and below the Galactic centre and labelled the 'Fermi Bubbles'. The latter is a potentially revolutionary finding: it suggests that the Fermi Bubbles act as de facto calorimetric recordings of Galactic centre activity over the life of the Milky Way.

From a technical direction we have also succeeded: our main aim was to show how the combined analysis of data obtained at a number of different (very) different wavelengths and with (very) different instrumental modalities can reveal insights not available if data from instruments are analysed separately. All the papers published in the course of this fellowship have demonstrated the profitable use of the multi-wavelength technique, combining, in particular, analysis of data obtained at radio and gamma-ray wavelengths, but also incorporating, e.g. far infrared data. In terms of predictions for forthcoming generations of instruments, we have shown that the Fermi Bubbles referred to above constitute an extremely promising source of neutrinos for a future, Mediterranean-based km-cubed-scale neutrino telescope (in fact, these objects may be the strongest in the sky). They are also promising sources for future TeV gamma-ray detection by the planned/in construction CTA or HAWC projects.