Molecular Physics seminar

Propagation of gamma-rays over intergalactic distances: A Probe for cosmology and new physics

by Manuel Meyer (Oscar Klein Center)

FA 32 ()

FA 32

Gamma rays with energies above tens of GeV originating from extragalactic sources undergo pair production with photons of the extragalactic backgroundlight (EBL), leading to an attenuation of the primary gamma-ray flux. The EBL stretches from ultra-violett to far infrared wavelengths and encodes the emitted starlight and starlight absorbed and re-emitted by dust in galaxies integrated over the entire history of the universe. The exact level of the EBL photon density remains unknown as direct observations are impeded due to strong foreground contaminations. Moreover, evidence exists that the gamma-ray opacity may be lower than expected from EBL models. This tension can be mitigated if photons oscillate into hypothetical axion-like particles. The observation of gamma-rays with the larger area telescope on board the Fermi satellite and with imaging air Cherenkov telescopes offers an independent tool study to the EBL and to probe physics beyond the Standard Model. Recent measurements and model constraints derived from gamma-ray data will be reviewed and an outlook for studies the future Cherenkov telescope array is presented.