pared to other AO systems: in one shot, the
area of sky covered is 10- to 20-times larger
than any previous AO system. This makes
Gemini’s 8-meter telescope 10- to 20-times
more efficient, giving astronomers the option to expose deeper, or explore more effectively with a wider range of filters.
Globular Cluster NGC 1851:
Going Fainter
Another critical SV target was NGC 1851, a
globular cluster located about 40,000 lightyears from our Sun (see Figure 3). Such a
tightly packed city of starlight is a workhorse
science case for MCAO; the AO corrections
“deblend” multiple systems in crowded fields,
allowing astronomers to access the cluster’s
fainter stars, which are crucial in studies of star
formation in these different environments.
Figure 3.
The globular star
cluster NGC 1851 as
imaged with GeMS/
GSAOI during System
Verification
heating the molecular hydrogen gas in the
Orion Nebula.
By comparing high-angular-resolution images of this region over several years (including observations at Gemini North with
the Altair AO system obtained in 2006), the
team, headed by John Bally and Adam Ginsburg (both of the University of Colorado),
can actually measure a bullet’s motion. By
mapping the proper motions of each, they
can build a complete 3D dynamical model
of the region. A single-pointing version of
this new image also made headlines at the
January 2013 meeting of the American Astronomical Society (held in Long Beach, California) and was featured in a press conference
at the meeting.
This remarkable image also illustrates the
revolution brought by MCAO. The final mosaic, made by three GeMS/GSAOI pointings,
covers a field-of-view measuring almost 4 x 3
arcminutes, resulting in one of the biggest
AO-corrected images ever obtained. This is
the main advantage of MCAO when com-
40
Moreover, by delivering a uniform performance over fields that encompass most
globular star cluster sizes, MCAO greatly improves the photometric precision on these
crowded fields. By studying the MCAO observations of NGC 1851, Alan McConnachie
from the National Research Council’s Herzberg Institute of Astrophysics and colleagues
intend to precisely derive the different star
populations that make up this cluster. By observing NGC 1851 over time, the team also
expects to retrieve the cluster’s orbit within
our Galaxy. In that case, GeMS/GSAOI is also
a perfect complement to the Hubble Space
Telescope (HST): the image quality provided
by the GeMS system in the NIR is very similar to that delivered by HST in visible light,
which opens the possibility of combining
these complementary data sets.
Galaxy Cluster Abell 780:
Better Sky Coverage to Go Deep
The third SV target was Abell 780, a cluster of
galaxies located at z = ~ 0.05 (see Figure 4). In
GeminiFocus 2013 Year in Review
January2014