Models for COMPTEL [sup 26]al Data

The all-sky data from CGRO Phases 1-5 provide the most detailed constraints to date on the Al-26 distribution in the Galaxy. With improved modelling of the instrumental background, different source distribution models can be distinguished. We derive large-scale parameters from first-order models, i.e., a characteristic scale height of 130 pc, and a Galactocentric scale radius of 5 kpc. Spiral structure of the Al-26 source distribution improves the fits, as molecular gas provides a better description than geometrical models in the inner Galaxy, We note that infrared emission from dust also matches the Al-26 emission quite well. Hints for contributions from more local and localized Al-26 components such as Loop I and the Gould Belt are compatible with a massive star origin of Al-26.