Title:

The Massive Red Supergiant Clusters at the Base of the Scutum-Crux
Spiral Arm



Ben Davies
Rochester Institute of Technology



Abstract:

I present the recent discoveries of two Galactic massive young
clusters, which together contain 40 Red Supergiants -- 20\% of all
those known in the Galaxy, and as many in the entire Large Magellanic
Cloud. From observations and evolutionary synthesis models, we argue
that the cluster masses are comparable to the other Galactic 'Super
Star Clusters' such as Westerlund 1 and the Arches Cluster.

These clusters are evidence of on-going, region-wide star forming
activity in the Scutum-Crux arm, and this is supported by the zoo of
interesting objects found in this part of the Galaxy -- seen in detail
for the first time by the recent imaging surveys of GLIMPSE, MIPSGAL
and MAGPIS.

The distinctly different ages of the clusters, uniform metallicity,
and large number of RSGs, mean that these objects now offer an
unprecedented opportunity to study the pre-supernova evolution of
massive stars.  Further, their location at the point where the
Scutum-Crux spiral arm meets the bulge allows us to study the
metallicity gradient at this location in the Galaxy, key to the
constraining of Galaxy evolution models.