Distribution and kinematics of 26Al in the Galactic disc
  26Al is a short-lived radioactive isotope thought to be injected into the
interstellar medium (ISM) by massive stellar winds and supernovae. However,
all-sky maps of 26Al emission show a distribution with a much larger scale
height and faster rotation speed than either massive stars or the cold ISM. We
investigate the origin of this discrepancy using an N-body+hydrodynamics
simulation of a Milky-Way-like galaxy, self-consistently including
self-gravity, star formation, stellar feedback, and 26Al production. We find no
evidence that the Milky Way's spiral structure explains the 26Al anomaly. Stars
and the 26Al bubbles they produce form along spiral arms, but, because our
simulation produces material arms that arise spontaneously rather than
propagating arms forced by an external potential, star formation occurs at arm
centres rather than leading edges. As a result, we find a scale height and
rotation speed for 26Al similar to that of the cold ISM. However, we also show
that a synthetic 26Al emission map produced for a possible Solar position at
the edge of a large 26Al bubble recovers many of the major qualitative features
of the observed 26Al sky. This suggests that the observed anomalous 26Al
distribution is the product of foreground emission from the 26Al produced by a
nearby, recent supernova.
