Project F5: "Dark-matter searches with gamma-ray telescopes and wide-field cosmological surveys"

The last decade has seen unprecedented developments on the observational frontier of astroparticle physics. High- and very high-energy (VHE) gamma-ray observatories like H.E.S.S., VERITAS, MAGIC, and the Fermi-LAT have opened the GeV to TeV sky out to redshifts of about unity, corresponding to a very substantial fraction of the age of the Universe. These observations have broadened the scope of high- and very high-energy observations beyond the discovery of individual sources and toward searches for signatures of new physics like decay or annihilation of particle dark matter. While the next generation of instruments in the form of the Cherenkov Telescope Array (CTA) is already in the implementation stage, substantial progress at the crossroads between astroparticle physics and survey science now has to be achieved to fully harvest the discovery potential of these experiments. The identification of dark matter in the Universe remains one of the most pressing and fascinating problems of modern physics. Within the scope of this project we will put the focus on the following key challenges for indirect dark-matter searches:

• Using the power of wide-field cosmological surveys to identify the most promising targets for indirect dark-matter searches, while at the same time improving the understanding of the halo profiles of known and new targets, thereby reducing uncertainties presently existing due to e.g. tidal interactions;
• Carry out a cross-correlation analysis of dark-matter maps based on a weak gravitational lensing mass reconstruction and wide-field Fermi-LAT and CTA data over thousands of square degrees;
• Conduct very deep precision observations of targets newly identified from the cosmological surveys with the MAGIC and CTA VHE gamma-ray telescopes to substantially improve limits on dark-matter annihilation or decay.

In Phase 1 of CIM, MAGIC observations of promising targets identified from the cosmological surveys will be carried out and the diffuse gamma-ray background will be studied via cross-correlation with weak gravitational lensing observations. In Phases 2 and 3, we will use the CTA prototype instruments and the full CTA, respectively, in combination with the stage-IV cosmological surveys Euclid and LSST to achieve the highest sensitivity.