This image of Haffner 16 illustrates that the GeMS AO system can
successfully sharpen data even under relatively poor imaging conditions.
With the correction, the point sources appeared spread by less than
0.16 arcseconds (full width at half-maximum, in the Ks band). This
represents a significant improvement over the natural quality of the
sky, which, on the night these data were obtained, was roughly 0.8
arcseconds – a value worse than average at Gemini South on Cerro Pachón. Credit: Gemini Observatory/AURA
The first refereed science paper based on data from the Gemini
Multi-conjugate adaptive optics System (GeMS) demonstrates the effective
use of young, lower mass stars to determine the age of a star cluster.
The work, led by Canada’s Tim Davidge, also brings into focus how young
cluster stars “leave the nest” and enter the general population of stars
in our galaxy.
Recent observations using the powerful new GeMS adaptive optics system
at Gemini South catch stars before they settle into their “regular
lives” and reveal clues into the past and future of a low-mass star
cluster – in this case, Haffner 16 - in our Milky Way Galaxy. The
combination of Gemini’s large 8-meter aperture, its infrared
sensitivity, and the latest in adaptive optics (which corrects for the
blurring effects of the Earth’s atmosphere), provide the key elements
for the success of this work. The so-called “pre-main sequence” stars
tend to be fainter, in part because they are less massive than their
counterparts that advance onto the main sequence (where most stars spend
the majority of their lives) more rapidly. Within a low-mass cluster
like Haffner 16 very massive stars may not exist at all, preventing the
use of standard age-dating techniques that rely on studying higher-mass
stars.
According to lead author Tim Davidge (Dominion Astrophysical
Observatory, Canada), “Studies of low mass clusters like Haffner 16
provide insights into how typical stars transition from star-forming
factories to the street.” We have caught this star cluster in the act
of dissolving says Davidge. These direct observations are an important
clue in understanding the local neighborhood of the Sun, where isolated
pre-main sequence stars are observed, without any obvious sign of the
typical clusters, where it is believed most stars are born. Such
isolated pre-main sequence stars could have come from clusters like
Haffner 16 but have since disintegrated.
Davidge has already obtained additional observations using GeMS.
Utilizing the same techniques, he is able to identify the
pre-main-sequence stars in three other, more distant clusters, which he
classifies as older.
The GeMS system uses multiple laser guide stars (5) and several
deformable mirrors to make exceptionally uniform corrections over an
extremely large adaptive optics field-of-view which counteracts for
distortions due to Earth’s turbulent atmosphere. The work engaged an
international team, including several team-members involved in the
development and operation of GeMS. The paper will appear soon in Publications of the Astronomical Society of the Pacific.
Source: Gemini Observatory
