Title: The Cygnus X region: a nucleosynthesis laboratory for INTEGRAL


Proposal ID: 0120157
Subject category: Nucleosynthesis
Principal investigator: knoedlseder
Institute: Centre d'Etude Spatiale des Rayonnements

Abstract

We propose to map the emission lines due to radioactive decay of 26Al (1.809 MeV) and 60Fe (1.173 and 1.332 MeV) and the positron annihilation line at 511 keV and positronium continuum in the Cygnus X region with unprecedented spatial and spectral resolution. Cygnus X is an extremely active nearby region containing several star forming regions, OB associations and open clusters, and, most interestingly, a massive young proto-globular cluster (Cyg OB2) recently identified from 2MASS data (Knoedlseder, 2000). Apart from the inner galactic ridge, Cygnus X shows the most prominent emission in the COMPTEL all-sky 1.809 MeV map. Given the youth (2.5 +/- 1 Myr) of Cyg OB2, the 26Al production from this cluster is expected to be solely due to nucleosynthesis in the hydrostatic burning phases of massive mass-loosing stars. This finding and its unique richness --- the number of massive stars make it the most massive star forming region in our Galaxy rivalling even 30 Doradus ! --- render this region unique to study the nucleosynthetic origin of 26Al and to disentangle hydrostatic and supernovae nucleosynthetic yields. For the first time this will be possible thanks to the spatial resolution of INTEGRAL. The study of the morphology of the 1.809 MeV emission and its line profile will also allow us to investigate the transport mechanism and dynamics of the 26Al ejecta in the region. We will also search for possible emission in the 1.173 and 1.332 MeV lines due to 60Fe, not produced in mass-losing stars, in order to study the contribution of core-collapse nucleosynthesis overall in the Cygnus X region. If detected, the 511 keV line and annihilation continuum will provide interesting constraints on the positron escape fraction and mixing processes in core-collapse supernovae, and thus yield new insight into the origin of galactic positrons.