Origin of the Fermi bubbles from multi-wavelength and multi-messenger observations

• Applicant: Dr. Dmitry Malyshev
• Subject Area: Astrophysics and Astronomy
• Term: from 2019 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 427983510

The Fermi bubbles are large gamma-ray emitting lobes above and below the Galactic center discovered in the Fermi Large Area Telescope (LAT) data. Proposed mechanisms for the formation of the Fermi bubbles are either a past activity of the supermassive black hole at the center of our galaxy or a period of intensive star formation near the Galactic center. Although the Fermi bubbles were discovered more than eight years ago, the question of the origin of the Fermi bubbles is still unresolved.Dmitry Malyshev has been the leading author of a Fermi-LAT collaboration publication on diffuse gamma-ray emission near the Galactic center, which showed, in particular, that the Fermi bubbles in this region have a higher intensity and a harder energy spectrum of gamma-ray emission compared to the emission at high Galactic latitudes. This finding opens up the possibility to detect the Fermi bubbles with imaging atmospheric Cherenkov telescopes and with neutrino telescopes. The detection of the Fermi bubbles with Cherenkov telescopes will result in a determination of the gamma-ray energy spectrum and morphology at very high energies, while the analysis of the neutrino data will yield information on the fraction of gamma rays produced in interactions of hadronic cosmic rays, i.e., it will provide constraints on the parent population of particles responsible for the emission from the Fermi bubbles.We propose to perform a more detailed analysis of the morphology and the spectrum of the Fermi bubbles below 1 TeV with the Fermi-LAT data, to study the spectrum of the Fermi bubbles above 1 TeV with H.E.S.S. telescope data, to perform a study using MC simulations of the expected sensitivity of the Cherenkov Telescope Array (CTA) to the FBs at low latitudes, and to determine an optimal survey strategy for CTA observations near the GC in order to detect the Fermi bubbles. We will also collaborate with the members of ANTARES, IceCube, and KM3NeT collaborations at ECAP to search for the associated neutrino emission. The novelty of our analysis is that, due to the high intensity and the harder spectrum of the bubbles at low latitudes, there is a realistic possibility to detect emission from the Fermi bubbles with the H.E.S.S., ANTARES, and IceCube telescopes. This study will also pave the road for a discovery of the bubbles in the future with more sensitive telescopes, such as CTA and the KM3NeT neutrino telescope.For the analysis of the Fermi-LAT and H.E.S.S. data, we will use state-of-the-art diffuse gamma-ray analysis methods, advancing the methods developed by Dmitry Malyshev and used in the Fermi-LAT collaboration publications about the Fermi bubbles and the diffuse gamma-ray emission near the Galactic center. The study will constrain models of the formation of the Fermi bubbles, improve our understanding of the origin of the cosmic rays up to PeV energies and of the high energy astrophysical neutrino flux.

• DFG Programme: Research Grants