A multiwavelength comparison of COMPTEL 1.8 MeV {(26) } line data

We search for correlations between 1.809 Me gamma -ray line emission, attributed to the radioactive decay of (26) , and intensity distributions observed at other wavelengths by confronting CGRO COMPTEL 1.8 Me data with an extended database of all-sky maps. The database contains 31 all-sky maps, covering the entire explored wavelength range from the radio band up to high-energy gamma-rays. Different data analysis techniques are explored to determine the similarities between the all-sky maps and the 1.809 Me intensity distribution, and to estimate the systematic uncertainties of our study. The comparison shows that tracers of the old stellar population or the local interstellar medium provide only a poor description of COMPTEL 1.8 Me data. Tracers of the young stellar population considerably improve the fit, confirming our earlier claims that (26) nucleosynthesis is associated to massive stars. Residuals are minimal for the 53 GHz free-free emission map that has been obtained by COBE DMR at microwave wavelengths. Within the statistics of the present data, this tracer provides an entirely satisfactory fit to COMPTEL 1.8 Me data. Thus, a correlation has been discovered, linking galactic (26) nucleosynthesis to galactic free-free emission which is a tracer of the ionised interstellar medium.