Inverse Compton Origin of the Hard X-Ray and Soft Gamma-Ray Emission   from the Galactic Ridge
  A recent re-determination of the non-thermal component of the hard X-ray to soft gamma-ray emission from the Galactic ridge, using the SPI instrument on the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) Observatory, is shown to be well reproduced as inverse-Compton emission from the interstellar medium. Both cosmic-ray primary electrons and secondary electrons and positrons contribute to the emission. The prediction uses the GALPROP model and includes a new calculation of the interstellar radiation field. This may solve a long-standing mystery of the origin of this emission, and potentially opens a new window on Galactic cosmic rays. 
Troy A. Porter (SCIPP/UCSC), Igor V. Moskalenko (HEPL/Stanford/KIPAC),   Andrew W. Strong (MPE), Elena Orlando (MPE), Lauren...