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Figure 1. Part of MACS J0416-2403 seen by GSAOI. The average angular
resolution is about 80 milliarcseconds, the full field-of-view of the
data released is nearly twice as large as shown here.
Figure 2. Comparison of the Ks-band (2.2 micron) image taken with GSAOI
(left) and the H-band (1.6 micron) image as observed with HST/WFC3.
While not as deep as HST data, the new GeMS/GSAOI dataset offers twice
the resolution on the distant universe.
The first data from the Gemini Frontier Fields are now available for
astronomers. This dataset features wide-field adaptive optics images of a
strong lensing galaxy cluster obtained with the GeMS adaptive optics
system and GSAOI on the Gemini South telescope.
Massive clusters of galaxies provide astronomers with a unique view of
the very distant Universe behind them as well as revealing their
galaxies themselves. The deep gravitational potential of clusters
distorts and amplifies the background galaxies - an effect known as
strong gravitational lensing. In this way, galaxies that are otherwise
unobservable with existing telescopes, are acquirable. This circumstance
allows astronomers to study these distant galaxies in great detail,
shedding light on how the very young universe looked, and pushing the
frontiers of our knowledge.
In the course of the Frontier Fields campaign,
Space Telescope (HST) observed six galaxy clusters, selected for their
strong lensing effects. Deep optical and near-infrared images are
already included in the HST dataset, augmented by additional X-ray and
far-infrared observations with the Chandra and Spitzer
space telescopes, respectively. However, one limitation of the HST data
is its sensitivity cut-off at wavelengths longer than 1.7 microns.
A Director's Discretionary Time program at Gemini has helped to fill the
gap at 2.2 microns (Ks-band), utilizing Gemini's advanced
multi-conjugated adaptive optics system, GeMS with the Gemini South
Adaptive Optics Imager (GSAOI). Staff astronomer Rodrigo Carrasco led
the observations, and the first of three targets visible from Gemini
South in Chile is MACS J0416.1-2403, which is available now.
Observations of the galaxy cluster Abell 2744 have started recently, and
Abell 370 is slated for observation at Gemini South over the next year.
GeMS/GSAOI delivers near diffraction-limited images in the near infrared
(0.9-2.5 microns), over a field nearly as large as HST's Wide Field
Camera 3 (WFC3). Using five artificial laser guide stars, and up to
three natural guide stars, GeMS/GSAOI can correct for atmospheric
turbulence at an unprecedented level, making it the most powerful
wide-field adaptive optics system currently available to astronomers.
This system is also the only multi-conjugated adaptive optics system
currently operational at an 8-meter-class telescope. "We have achieved
an angular resolution of 70-100 milliarcseconds with these data, which
is a factor of two better than HST/WFC3, even though we did not go as
deep as HST. These are truly spectacular data!" says Mischa Schirmer, a
staff astronomer at Gemini who led the data processing effort.
The fully calibrated and co-added images of MACS J0416.1-2403 are now available to the scientific community in order to maximize scientific return.