third had a mean age of about 5 Myr. This
might be the sign of an evolutionary star
formation sequence (progression) at work in
this region.
Evolving Stars?
Figure 5.
Mass distribution of the
young cluster forming
at the edge of the RCW
41 HII region. Thanks to
the gain in resolution
and sensitivity brought
by GeMS/GSAOI, masses
down to 0.01 solar mass
are probed in this cluster.
To test whether different evolutionary stages are present in the cluster, we looked at
the spatial distribution of these two possible populations. From this it appears that
the “red”, highly embedded, and probably
younger, YSOs are mainly distributed around
the northwest region (top right), while the
“blue”, and probably older, population is
preferentially located toward the southeast
(bottom left) region. This distribution seems
to indicate the presence of an age gradient
diagonally across the image, and where the
denser cluster region would be younger
than the blue sub-cluster region.
We also found that one of the bluest massive
stars, located in the southeast sub-cluster, is
likely the ionizing source of the region. This
star probably is the one that originally lit up
RCW 41, and has already cleaned up its environment. On the other hand, moving toward
the dense cluster region, the presence of a
dense clump of molecular gas has been detected, a signpost of active ongoing highmass star formation. This suggests that star
formation progresses toward the clump and
could have been triggered by the interaction of the ionized region with the clump.
Cluster Mass Distribution
To go one step further, we derived the mass
and mass distribution of the
dense cluster, formed at the
edge of the RCW 41 HII region.
The stars in this region have
roughly the same age and metallicity. In addition, since the
effects of stellar and dynamical
evolution are minimal in young
clusters, the observed present
day mass function should be a
fair representation of the underlying Initial Mass Function (IMF).
The IMF is a fundamental parameter to characterize cluster properties, and various theories of
star formation predict different
outcomes for its overall shape.
However, as for the age, deriving
a mass for each star is an indirect
process, and many uncertainties
may add up along the way.
We derived the IMF of the young
cluster, which is presented in
Figure 5. Among the first interesting features is that we can