1220035

Our group has recently found a systematic shift of the centroid of the 26Al emission line at 1.8 MeV across the inner part of the Galactic plane inconsistent with Galactic rotation but consistent with a spiral arm population of 26Al sources with an excess velocity of about 200 km s-1 away from spiral arms. We have suggested that this velocity offset may be due to an interaction of the superbubbles generated by the massive star groups that also produce the 26Al with dense gas in the spiral arms of the Milky Way. This interpretation implies that 26Al stays at least for some time entirely within the hot tenuous gas because colder gas (HI H2) is known to possess much smaller velocities. Because it is not possible to resolve the Galactic plane signal into individual components attributable to individual groups of stars we propose to test the scenario further with observations of the nearby star forming region in Scorpius-Centaurus (Sco-Cen). The region has produced an X-ray bright superbubble which indicates recent supernova activity. In our scenario we expect the 26Al to be distributed similarly to the X-ray bright gas which moves at its sound speed of around 500 km/s. Any projection on to the line of sight very likely results in detectable 26Al velocity shifts. An earlier INTEGRAL campaign detected the 1.8 MeV line at above 5 significance but could constrain the line shift only to 13775 km s-1 (towards Earth) i.e. consistent with zero within 2. We propose therefore more observations of Sco-Cen to improve the error on the line shift and map 26Al within the Sco-Cen superbubble. [truncated! Please see actual data for full text]