Speaker
Dr
Philipp Mertsch
(Rudolf Peierls Centre for Theoretical Physics, University of Oxford)
Description
Gamma-ray data from Fermi-LAT reveal a bi-lobular structure extending up to 50
degrees above and below the galactic centre, which presumably originated in some form
of energy release there less than a few million years ago. It has been argued that
the gamma-rays arise from hadronic interactions of high energy cosmic rays which are
advected out by a strong wind, or from inverse-Compton scattering of relativistic
electrons accelerated at plasma shocks present in the bubbles. We explore the
alternative possibility that the relativistic electrons are undergoing stochastic
2nd-order Fermi acceleration by plasma wave turbulence through the entire volume of
the bubbles. The observed gamma-ray spectral shape is then explained naturally by the
resulting hard electron spectrum and inverse Compton losses. Rather than a constant
volume emissivity as in other models, we predict a nearly constant surface
brightness, and reproduce the observed sharp edges of the bubbles.
Primary author
Dr
Philipp Mertsch
(Rudolf Peierls Centre for Theoretical Physics, University of Oxford)
Co-author
Prof.
Subir Sarkar
(Rudolf Peierls Centre for Theoretical Physics, University of Oxford)
