extragalactic studies, only a few natural guide
stars are available to provide AO corrections,
which limits the areas of the sky available to
study. With its five laser guide stars, GeMS increases the portion of the sky that can benefit from AO correction, and surpasses the
previous generation of laser guide star AO
systems. Put another way, only GeMS can provide this kind of uniform, sharp image quality in regions with few natural guide stars.
In this field, the team led by Rodrigo Carrasco
from Gemini wants to explore not only the
structure of potential massive compact galaxies in galaxy clusters but also the detailed
properties of the massive galaxies with average sizes. Looking for “signatures” that could
be related to ongoing merger activity (such
as tidal tails, clumps of star formation, etc.),
they would be able to decide between different competing evolutionary scenarios.
2013 and Beyond
The team continued their SV runs on 8 nights
in January and 11 nights in February 2013. A
total of 12 targets out of the 13 selected were
observed, under different conditions, providing very useful information to the team
on how to run and optimize this complex
system. Also included in the SV observations,
the researchers targeted planetary nebula
NGC 2346, several star clusters (e.g. RCW 41
and R 136), NGC 4038 in the Antennae Galaxies (see Figure 5), a candidate supernova in a
nearby Luminous Infra-Red Galaxy, a pulsar,
a quasar, and gravitational lenses induced by
a galaxy cluster. See many of these images in
an image release issued concurrent with this
issue of GeminiFocus. All these data are also
now publicly available on the Gemini archive
website at: http://www.cadc-ccda.hia-iha.
nrc-cnrc.gc.ca/gsa/sv/dataSVGSAOI_v1.html
The team also used the 2013 SV period to
stabilize and characterize the performance
delivered by the system. They determined
July2013
that 50 percent of the time, GeMS delivers an image quality of 95 milliarcseconds
(mas) or better in K band and 75 mas or
better in the H band. This is not yet at the
original specification level but two primary, well-understood reasons explain this.
Figure 4.
Galaxy cluster Abell
780 in a single-band
image obtained with
GeMS/GSAOI during
System Verification.
First, one of the three deformable mirrors in
GeMS failed. These mirrors are optically conjugated at 0, 4.5, and 9 kilometers. However,
since the system is currently running with
only two deformable mirrors, at 0 and 9 km,
corrections are not optimal. Second, while
the laser itself is performing very reliably, the
overall transmission of its projection system
is under specification. Consequently, the AO
corrections are applied at a lower-than-normal rate, so the performance suffers