versity of Toronto and the National Research
Council-Herzberg (NRC-Herzberg) Institute
of Astronomy and Astrophysics. This instru-
ment will address a key limitation in existing
adaptive optics (AO) facilities where integral
field spectrographs are only able to observe
single objects with adequate atmospheric
correction, significantly limiting many scien-
tific programs that could be efficiently ob-
served with multiple integral field units.
By taking advantage of the latest devel-
opments in multi-object AO (MOAO) and
integral field spectroscopy, GIRMOS is de-
signed to have the ability to observe mul-
tiple sources simultaneously at high angular
resolution while obtaining spectra at the
same time (Sivanandam et al., 2018). It ac-
complishes this by exploiting the AO cor-
rection from both a telescope-based AO
system (either GeMS or the prospective
Gemini North MCAO system — see page 12)
and its own additional MOAO system that
feeds four 1-2.4 µm integral field spectro-
graphs (R ~ 3,000 and 8,000) that can each
observe an object independently within a 2
arcminute field of view.
While GeMS is a multi-conjugate AO (MCAO)
system, which applies a global AO correc-
tion over the entire field, the GIRMOS MOAO
strives to optimally correct the observable
field of each individual spectrograph. In gen-
eral, MOAO applies a better correction to
multiple specific spots over a field of view,
while MCAO provides somewhat less correc-
tion uniformly over the entire field of view.
For the multiple-IFUs of GIRMOS, an MOAO
system provides optimal performance with
improved imaging performance along each
integral field spectrograph’s line of sight. This
powerful capability will be unique to GIRMOS
as no other 8- to 10-meter-class observatory
has a workhorse MOAO instrument.
The current design parameters of the instru-
ment concept are given in the table below.
The instrument will also offer simultaneous
imaging capability that is at a slightly lower
resolution compared to the Gemini South
Adaptive Optics Imager (GSAOI). The chosen
design significantly increases the speed of
integral field spectrograph surveys for sci-
ence projects that target areas with high
source densities, such as detailed observa-
tions of distant galaxies.
Telescope Feed
Gemini 8.1-meter MCAO f/33 beam Individual IFS field of view
(arcseconds)
1.06 × 1.06
2.1 × 2.1
4.2 × 4.2
8.4 × 8.4 (all IFS combined)
MOAO Performance > 50% encircled energy within 0.1’’ IFS Spatial Pixel Size (milliarcseconds)
(H and K bands)
25 × 25
50 × 50
100 × 100
100 × 100 (all IFS combined)
Field of Regard 2’ diameter patrol field Spectral Resolution (R) 3,000 or 8,000
Wavelength Range 1.1−2.4 μm (J, H, or K bands) Spectrograph Throughput > 40%
Number of IFSs
4 (with a goal of 8)
Detector
4,096 × 4,096 HAWAI‘I-4RG
for 4 spectral channels
Imager Field of View 100 × 100’’ Imager Plate Scale (milliarcseconds) 25
Imager Wavelength 1.1−2.4 μm (J, H, or K bands)
Range Imager Detector
14
GeminiFocus
4,096 × 4,096 HAWAI‘I-4RG
October 2018