A multiwavelength comparison of COMPTEL 1.8 MeV Al-26 line data

We search for correlations between 1.809 MeV gamma-ray line emission, attri buted to the radioactive decay of Al-26 and intensity distributions observe d at other wavelengths by confronting CGRO COMPTEL 1.8MeV data with an exte nded database of all-sky maps. The database contains 31 all-sky maps, cover ing the entire explored wavelength range from the radio band up to high-ene rgy gamma-rays. Different data analysis techniques are explored to determin e the similarities between the ail-sky maps and the 1.8091 MeV intensity di stribution, and to estimate the systematic uncertainties of our study. The comparison shows that tracers of the old stellar population or the local in terstellar medium provide only a poor description of COMPTEL 1.8 MeV data. Tracers of the young stellar population considerably improve the fit, confi rming our earlier claims that Al-26 nucleosynthesis is associated to massiv e stars. Residuals are minimal for the 53 GHz free-free emission map that h as been obtained by COBE DMR at microwave wavelengths. Within the statistic s of the present data, this tracer provides an entirely satisfactory fit to COMPTEL 1.8MeV data. Thus, a correlation has been discovered, linking gala ctic Al-26 nucleosynthesis to galactic free-free emission which is a tracer of the ionised interstellar medium.