Spectral and intensity variations of Galactic Al emission
Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany e-mail: firstname.lastname@example.org
2 National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China
3 AstroParticule et Cosmologie (APC), 11 place Marcelin Berthelot, 75231 Paris, France
4 Centre d'Étude Spatiale des Rayonnements, BP 4346, 31028 Toulouse Cedex 4, France
5 ESA-ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
Accepted: 28 January 2009
Aims. Gamma-ray line emission from the radioactive decay of 26Al reflects nucleosynthesis in massive stars and supernovae. We use INTEGRAL 26Al measurements to characterize the distribution and characteristics of 26Al source regions throughout the Galaxy.
Methods. The spectrometer SPI aboard INTEGRAL has accumulated over five years of data on 26Al gamma-ray emission from the Galactic plane. We analyzed these data using suitable instrumental-background models and adopted sky distribution models to produce high-resolution 26Al spectra of Galactic emission, spatially resolved along the Galaxy plane.
Results. We detect the 26Al line from the inner Galaxy at ~ significance. The line appears narrow, and we constrain broadening in the source regions to <1.3 keV (). Different sky distribution models do not significantly affect those large-scale results. The 26Al intensity for the inner Galaxy is derived as , consistent with earlier results from COMPTEL and SPI data. This can be translated to an 26Al mass of 2.7 ± 0.7 in the Galaxy as a whole. The 26Al intensity is also confirmed to be somewhat brighter in the 4th than in the 1st quadrant (ratio ~1.3 ± 0.2). 26Al spectra separately derived for regions along the Galactic plane show clear line centroid shifts, attributed largely to the Galaxy's large-scale rotation. The 26Al line toward the direction of the Aquila region () appears somewhat broadened. Latitudinal variations of 26Al emission towards the inner Galaxy are studied, finding a latitudinal scale height of pc for 26Al in the inner Galaxy and a hint (3σ) of peculiar 26Al emission towards the region , .
Key words: Galaxy: abundances / ISM: abundances / nuclear reactions, nucleosynthesis, abundances / gamma rays: observations
© ESO, 2009