Résumé / Abstract Journal-club_Univers

Journal-club Univers / Journal-club Universe

« Cosmological constraints from observations of gamma-ray attenuation caused e- e+ pair production  »

Radoslaw Wojtak
DARK Cosmology Centre, Univ. Copenhagen (Copenhague, Danemark)

Gamma-ray photons emitted from distant sources can collide with photons of extragalactic background light producing electron-positron pairs. This process generates attenuation in the spectra of gamma-rays above a critical energy. The gamma-ray attenuation has been recently measured by Fermi-LAT and Cherenkov telescopes for a number of blazars in a wide range of redshifts. Since the effect scales with distance to the source, the observations can be used to constrain cosmological parameters, in particular the Hubble constant and the matter density parameters. In my talk, I will present the first cosmological constraints based on the current gamma-ray attenuation data. I will discuss the results in the context of recent tensions between determinations of the Hubble constant from type Ia supernovae and the CMB. I will also talk about challenges in understanding systematic errors and the perspectives for future developments of the measurement.
mardi 9 avril 2019 - 11:15
Salle Entresol Daniel Chalonge, Institut d'Astrophysique
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