The INTEGRAL/SPI 26Al signal from the Scorpius-Centaurus region
26Al is uniquely produced by massive stars. These stars eject 26Al
through their winds and supernova explosions, which have a huge impact on the surrounding
interstellar medium. Due to its short, in astronomical terms, decay time of a million
years, 26Al serves as evidence of very recent massive star activity. The
detection of 26Al towards the Scorpius-Centaurus region (see image, bottom
right), therefore, provides a key piece of evidence in the reconstruction of the history
of this massive star forming region. This is demonstrated in a comprehensive
multi-wavelength and simulation study by Krause et al., as also illustrated in the
sketched evolution of this region in the top part of the image.
Groups of stars first start to form in the densest part of a cloud, which in general may
have a filamentary/elongated structure. The massive star activity forms a bubble of hot
gas, which would be 26Al enriched from massive-star ejecta. Gas may be
compressed locally, leading to more star formation, but may also quickly escape along the
minor axis of the cloud. In the tenuous medium around the cloud, the overpressured bubble
could progress much more quickly than through the dense cloud, and thus reach and compress
far-away regions of the cloud. The details of cloud compression and fragmentation of such
a superbubble have been simulated and are shown in the bottom left part of the image. The
26Al signal detected by INTEGRAL/SPI is independent proof for massive-star
activity within approximately the last million years, and a key part of the study of how
massive-star feedback works.
References:
"Surround & Squash: The Interstellar Medium around Scorpius Centaurus OB2",
M.G.H. Krause, A. Burkert, R. Diehl, K. Fierlinger, B. Gaczkowski, D. Kroell, J. Ngoumou, V. Roccatagliata, T. Siegert & T. Preibisch
2018, A&A, in press (arXiv:1808.04788)
https://arxiv.org/abs/1808.04788
