Proposal Details - 0720003
Probing relativistic electrons in the Galaxy and its halo (Strong)

Proposal Abstract

Recently significant advances have been made in understanding of the diffuse Galactic continuum emission observed by SPI on INTEGRAL. The hard power-law component has been identified with inverse-Compton emission from relativistic (GeV) electrons on the cosmic microwave background and Galactic infrared radiation field. The observed intensity is in good agreement with detailed predictions from the GALPROP model, which accounts for both primary and secondary electrons and positrons. We propose to exploit this with INTEGRAL to obtain a probe of the distribution of cosmic-ray electrons in the Galaxy, in particular in the Galactic halo seen at high latitudes. To this end we propose a multi-year scan covering a wide latitude range in the inner Galaxy, significantly deepening the exposure over what is currently available. The decreasing background due to the solar cycle will improve the signal-to-noise over that for the INTEGRAL mission so far.The results will have implications for Fermi-LAT which will be in operation during this period - taken togetherthe data from the two missions will constrain the cosmic-ray electron spectrum at GeV energies and help to give an unambiguous decomposition of the diffuse gamma-ray sky.

Observation Strategy (Recommended by TAC)

Total of 2.5 Ms performed as 5 scans of 500 ksec each, made at l=0, 10,20,-10,-20. From b=-20 to =90, and from +20 to +90, on a 2 deg customized grid.

Proposal grade: B

Data Rights (Recommended by TAC)

The TAC has allocated the following specific data rights to this proposal: the study of the Galactic diffuse continuum emission with SPI.

Exposure Map

The exposure maps are in galactic coordinates and units of ksec, and the colour scale is indicated at the bottom. The green lines provide the 100 ksec contour.