Astron. Astrophys. 344, 68-82 (1999)

A multiwavelength comparison of COMPTEL 1.8 MeV ²⁶Al line data

J. Knödlseder ¹, K. Bennett ⁵, H. Bloemen ³, R. Diehl ², W. Hermsen ³, U. Oberlack ⁶, J. Ryan ⁴, V. Schönfelder ² and P. vonBallmoos <sup>1

1</sup> Centre d'Etude Spatiale des Rayonnements, CNRS/UPS, B.P. 4346, F-31028 Toulouse Cedex 4, France
² Max-Planck-Institut für Extraterrestrische Physik, Postfach 1603, D-85740 Garching, Germany
³ SRON-Utrecht, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
⁴ Space Science Center, University of New Hampshire, Durham, NH 03824, USA
⁵ Astrophysics Division, ESTEC, ESA, 2200 AG Noordwijk, The Netherlands
⁶ Astrophysics Laboratory, Columbia University, New York, NY 10027, USA

Received 7 July 1998 / Accepted 23 December 1998

Abstract

We search for correlations between 1.809 MeV -ray line emission, attributed to the radioactive decay of ²⁶Al , and intensity distributions observed at other wavelengths by confronting CGRO COMPTEL 1.8 MeV 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 MeV 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 MeV data. Tracers of the young stellar population considerably improve the fit, confirming our earlier claims that ²⁶Al 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 MeV data. Thus, a correlation has been discovered, linking galactic ²⁶Al nucleosynthesis to galactic free-free emission which is a tracer of the ionised interstellar medium.

Key words: nuclear reactions, nucleosynthesis, abundances methods: data analysis stars: early-type Galaxy: stellar content gamma rays: observations

Send offprint requests to: Jürgen Knödlseder (knodlseder@cesr.fr)

This article contains no SIMBAD objects.

Contents

• 1. Introduction
• 2. Multiwavelength all-sky map database
  • 2.1. General
  • 2.2. The all-sky maps
• 3. All-sky map comparison
  • 3.1. COMPTEL data representation
  • 3.2. Comparison in the imaging data space
    • 3.2.1. Imaging data space
    • 3.2.2. Maximum likelihood analysis
    • 3.2.3. Residual analysis
  • 3.3. Comparison in the energy data space
    • 3.3.1. Energy data space
    • 3.3.2. Results
• 4. Discussion
  • 4.1. The best 1.809 MeV tracer
  • 4.2. Flux asymmetry
  • 4.3. Inner to outer Galaxy contrast
• 5. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 1999

Online publication: March 10, 1999
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