One of the key questions in this field of research is what is the causal link between
the first generation massive stars (the ones
associated with the large HII regions) and
the young (possibly second-generation)
stars observed at the edges of HII regions?
Dissecting the young clusters that formed
at the edges of HII regions is therefore an
important step to refine our knowledge on
star-formation mechanisms.
The Sharp Gemini Eye
Studies of young star clusters are still limited. Young, recently formed stars in clusters
are shy, and usually hide inside a heavily obscured and dense environment. High spatial
resolution in the near infrared (NIR) is needed to resolve individual members and detect
the fainter ones.
The Gemini South telescope offers one of the
most advanced adaptive optics (AO) suites
currently available on a large telescope.
Among these capabilities, the Gemini Multiconjugate adaptive optics System (GeMS)
delivers a uniform, almost diffraction-limited image quality at nearinfrared wavelengths over an
extended field-of-view of 2
arcminutes across.
GeMS utilizes five artificial laser guide stars, up to three natural guide stars, and multiple
deformable mirrors (DMs) that
are optically conjugated with
the main atmospheric turbulence layers. This results in an
AO corrected field that is 10 to
20 times larger than previous
generations of AO systems.
GeMS works in conjunction
with the Gemini South Adaptive Optics Imager (GSAOI),
which covers an 85” × 85” fieldof-view with a plate scale of
January 2016
Figure 2.
JHK color-composite
image of RCW 41
observed with GeMS
at Gemini South.
about 20 milliarcseconds. This combination of
new instruments is perfectly suited for young
cluster studies, as it provides a uniform and
unprecedented spatial resolution spanning
a large portion of the young cluster’s angular
extent.
Back in 2013, during the GeMS science verification period, we pointed this high-resolution machine toward RCW 41, a Galactic
ionized region located in the Vela molecular
ridge. We used three filters (J, H, and Ks), combined to produce the image shown in Figure
2. In this image, the resolution is ~ 0.1 arcsecond, and quite uniform over
the field. At the cluster’s distance, ~ 4,200 light years (1.3
kiloparsecs), the field covered
by the image represents ~ 1.5
light years (0.5 pc), with a resolution corresponding to 130
astronomical units. This is 5
to 10 times better than previously available images, which
were obtained in seeing-limited circumstances.
To highlight the gain in resolution brought by GeMS/
GSAOI, Figure 3 compares
the seeing-limited images
obtained with the European Southern Observatory’s
large-field infrared spectrograph and imaging camera
2015 Year in Review
GeminiFocus
Figure 3.
GeMS/GSAOI (top) and
SofI (bottom) images of
the central part of the
RCW 41 cluster observed
in H-band.
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