Diffuse Galactic emission spectrum between 0.5 and 8.0 MeV

Understand

The last measurement of the diffuse emission spectrum of the Milky Way in the megaelectronvolt (MeV) photon energy range was performed by CGRO/COMPTEL more than 20 years ago.

• We report a new analysis with the spectrometer SPI aboard INTEGRAL in the band 0.5-8.0 MeV, finally superseding the signal-to-noise ratio of the historic observations.
• This is possible thanks to an elaborate instrumental background model and careful considerations of the selected data, which are strongly affected by solar activity.
• We base our analysis on energy-dependent spatial template fitting in a region of $\Delta l \times \Delta b = 95^\circ \times 95^\circ$ around the Galactic centre.