a mass limit of ~ 0.01 solar mass — only 10
times the mass of Jupiter! Only the gain in
sensitivity brought by GeMS/GSAOI allows
us to reach such a low mass limit in a cluster
as distant as RCW 41.
Brown Dwarfs
Objects below 0.08 solar mass, i.e. below
the hydrogen-burning limit, are known as
brown dwarfs. We demonstrate here that
GeMS/GSAOI opens the way for studies of
brown dwarfs, and brown dwarf formation
processes in distant clusters.
In particular, there have been several proposed mechanisms to explain the origin of
brown dwarfs — such as through turbulent
fragmentation, disk fragmentation, ejection
of newly formed fragments in multiple systems, and photoevaporation. All of these
scenarios may predict a different brown
dwarf fraction. For instance, isolated brown
dwarfs may be the remains of prestellar
cores, after strong ultraviolet emission from
nearby massive stars photoevaporated their
accretion disks. We therefore expect a higher
brown dwarf ratio for clusters hosting massive stars.
RCW 41 does host many massive stars, allowing us to compare its brown dwarf fraction with other known clusters hosting massive stars, such as the Trapezium region in
the Orion Nebula. From this comparison we
found that the fraction of brown dwarfs in
RCW 41 was actually significantly smaller
than that of the Trapezium. This is also true
for another distant cluster — the one in M16,
the Eagle Nebula. This might indicate that
different processes are at work to shape the
low-mass IMF and the brown dwarf content.
April 2015
Coming Next
Accurately deriving the stellar content of
young clusters is a challenge for which
GeMS/GSAOI is certainly a unique facility.
These capabilities offer us an opportunity
to pin down each of the least massive stars
present in distant clusters and push the
observational limits one step further. The
resolution provided by GeMS/GSAOI is also
an ideal complement to the radio observations delivered by the newly commissioned
Atacama Large Millimeter Array (ALMA).
Combining near-infrared, with radio wavelengths — at a similar spatial resolution
— opens the way for strong synergies and
breakthrough discoveries.
We are also exploring the need for new data
reduction tools specifically designed for this
new generation of AO systems. As shown in
this paper, many uncertainties in the data
still exist, and error bars need to be carefully
treated. Finding ways to reduce these error
bars will allow us to push the limits of technology, better constrain theoretical models,
and improve our understanding of those
rich and complex star-forming regions.
Benoit Neichel is an instrument scientist at Laboratoire d’Astrophysique de Marseille. He can be
reached at: [email protected]
Other members of the team are: Manash R. Samal, A. Zavagno, and A. Bernard from Laboratoire d’Astrophysique de Marseille, France; H.
Plana from Universidade Estadual de Santa Cruz,
Brazil; and T. Fusco from ONERA, France.
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