Proposal Details - 0820002
Probing relativistic electrons in the Galaxy and its halo (Strong)

Proposal Summary (based on proposal abstract)

This is a confirmatory resubmission of the successful AO7 proposal 0720003, currently being carried out, requesting a completion of the programme as described in the original proposal. 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. It is proposed 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 a multi-year scan covering a wide latitude range in the inner Galaxy is proposed, 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 is now in operation - taken together the 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 1.5 Ms performed as scans at l=0, 10, 20, -10, and -20; each scan is from b=+20 to +90, using a 2 degree step size. There are 4 individual scans (for a total of 300 ksec) for each l.

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

Exposure maps are in units of s and shown using Galactic coordinates. The intensity scale is given by the colourbar, and there are contour levels at 100, 300 and 500 ks.