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2001 Observational Techniques Workshop
Gemini
• Overview of the telescopes
• Gemini’s core science goals
• Gemini instrumentation
• Applying for Gemini time
Warrick Couch, UNSW
Gemini
North
Overview of the telescopes
(total capital cost = US$187M)
Gemini
South
Primary mirror:
• 8.1m diameter
• 20cm thick
• mass = 22.2 tonnes
• coated for UV/IR
performance
Gem-N
Gem-S
Primary mirror supported by
air pressure + 180 actuators
which maintain shape to
better than a micron.
Secondary mirror (f/16):
• 1.0m diameter
• Mass 45kg
• Fast tip-tilt at up to 200Hz
Cassegrain Focus: Instrument Support Structure + A&G
Core Science Goals
• Circumstellar disks and planetary systems
• Formation of the elements
• Formation and evolution of galaxies
• Star formation
• Stellar interiors structure
Circumstellar disks and possible planetary
systems
The nature of the particle disks
discovered around stars like Pic  detailed mapping to
understand the process of planet
formation.
• Map at 10m and beyond, where Gemini should deliver a
resolution of better than 0.3 arcsec, corresponding to
1-2AU for the nearest examples.
• Gemini’s competitive edge: diffraction-limited imaging
and low thermal emissivity.
Formation of the elements
Determination of the chemical
enrichment history of the
Galaxy and the Universe via
high resolution spectroscopy of
the oldest stars in the Milky
Way and gas clouds illuminated
by distant quasars.
• High-resolution (R=50-150,000) spectroscopy of
faint objects at uv-optical wavelengths
This science program severely compromised with the
cancellation of HROS, and its replacement with
HRBS which, being fibre-fed, will be unable to
observe at   3800Å.
Formation and evolution of galaxies
Determine the morphology,
content, and composition of
nascent and adolescent galaxies
in the early universe. Do this at
optical wavelengths, to reveal
the properties of the youngest
stars in such systems, through to
the thermal infrared where dust
re-radiates the emission at
shorter wavelengths.
• Imaging and multi-object spectroscopy at optical and
infrared wavelengths, with high spatial resolution.
Star formation
Address the age-old question
of how stars form and what
conditions lead to protostellar collapse. In particular,
study the role of outflows in
the star formation process
• Near infrared imaging and spectroscopy at the
highest possible spatial resolution
• Gemini advantage: diffraction-limited performance
(or near to) in the near-infrared.
Stellar structure
Determination of the internal
structure of stars through the study of
the small and complex oscillations
that take place at their visible surface.
• Very high resolution optical spectroscopy and continual
monitoring for many hours.
Performance: it’s not just
(aperture) size that counts!
If sky- or detector-noise limited, then speed of
observation (1/t) is proportional to:
(D/)2
where D = aperture size and  = image size.
 is usually dominated by seeing, with seeing-0.2  20%
reduction V  K.
If can achieve diffraction-limited performance*, then
dl1/D (Rayleigh) and speed proportional to:
D4 [factor of 16 in going from 4m to
8m telescope!!]
* For 8m, dl~0.02” in V, 0.07” in K, requiring wavefront
correction using Adaptive Optics (only practical in IR)
Seeing Constraints
2001B Instrument Availability
Mauna Kea
NIRI
GMOS
Hokupa’a/QUIRC
Cerro Pachon
FLAMINGOS-1
OSCIR
Acquisition
Camera
2002A Instrument Availability
Mauna Kea
NIRI
GMOS
MICHELLE
Hokupa’a
CIRPASS
Cerro Pachon
T-ReCS
PHOENIX
2002B Instrument Availability
Mauna Kea
NIRI
GMOS
MICHELLE
ALTAIR (NGS)
CIRPASS
Cerro Pachon
T-ReCS
GMOS
FLAMINGOS-1
PHOENIX
2004B Instrument Availability
Mauna Kea
NIRI (NIR)
GMOS (Opt)
NIFS (NIR)
OSCIR (MIR)
ALTAIR+(LGS/AO)
Cerro Pachon
T-ReCS (MIR)
GMOS (Opt)
GNIRS (NIR)
NICI (NIR)
HRBS (Opt)
FLAMINGOS-2
(NIR)
MCAO (LGS/AO)
Hokupa’a/QUIRC
Hokupa’a  36 element curvature wavefront
sensor and bimorph mirror which uses
natural guide stars.
QUIRC  1 – 2.5 m near-IR camera which is
fed by Hokupa’a. 1024x1024 HgCdTe array;
pixel size = 20 mas  20.2 arcsec FoV!
Performance: near diffraction-limited (d-l)
resolution in H & K; FWHM = 2x d-l in J.
The rub: must have a bright point-source
within 30arcsec of target!
Very high
Filters:
extinction
clouds
•H
•K’
•CO
•CO cont.
IRS8 (bow shock)
40”
4’
5”
Bow shock
>10 stars
per arcsec2
at K~18
>220 stars in 5”x5”
UH-88”, Courtesy W.Brandner, 0.65” seeing
IRS7
SgrA*
Public SV Data: M32
 Used core of
this nearby
elliptical
galaxy as WFS
reference
 K’
 480s
 0.13” FWHM
0.5 arcsec
Public SV Data: M15
20 arcsec
 Measured PSF
variation over
field and H/Q
stability and
repeatibility on
this globular
cluster
 2 datasets
released
 K’
 18 x 30s
 0.12” FWHM
Example QS Data
(GN-2000QS-Q-9)
FWHM 65 milli-arcsec
Elliptical galaxy at 150Mpc
IR surface brightness fluctuations
Example QS Data: Galaxies
in Abell 665
 Colour composite of
Abell 665 (z=0.18)




K’ (28min)
J (20 min)
HST-I (80 min)
0.2 arcsec FWHM
(GN-2000QS-Q-29)
NIRI – Near Infrared Imager
Detector: 1024x1024 Aladdin InSb array
Imaging:
 ‘wide-field’ (2’x2’) f/6 mode ( J – L bands)
 ‘low-bg’ (0.9’x0.9’) f/14 mode ( J, H, K )
 ‘high-bg’ (0.9’x0.9’) f/14 mode ( L & M )
 Spectroscopy:
 Long-slit + grism ( 1 – 5.5 microns)
[ R of up to ~1700 (in H) with 0.23” slit ]
 Wavefront correction:
 Active optics (aO) only, with IR on-instrument
wavefront sensor available except in f/6 mode
 f/32 camera will be fed by ALTAIR (laser g/s)
NIRI Filters available for 2001B
J
H
K, Kshort, K´
L´
M´
Order sorting
filters:
[Fe II]
H-continuum
H2 1-0 S(1)
Br Gamma
K-continuum (2)
PK50 long-wave
blocker
J, H, K, L, M
 Integration Time Calculator (ITC) available 
GMOS – Gemini Multi-Object
Spectrograph
Optical spectrograph/imager with a 5.5’ field
of view [duplicated for both telescopes]
Spectroscopic modes:
 standard ‘long-slit’
 ‘multi-object’ using aperture mask with multiple
slits [ up to several hundred in 5.5’ FoV]
 Integral Field Unit (IFU) covering 50 arcsec2 with
0.2” sampling
Spectral resolution: R = 670 – 4400 (0.5” slit)
ITC available
FLAMINGOS-1
 World’s first fully cryogenic multi-object
near-IR ( J, H, K ) spectrograph/imager.
 Field of view = 2.7 arcmin (f/16 + 2048x2048
Rockwell HgCdTe array).
 ‘Long-slit’ and ‘multi-slit’ modes
 Spectral resolution: R = 300 (low!) [grisms
giving R~2400 planned].
OSCIR
Mid-infrared (8-25m) imager
and low/medium resolution
(R=100-1000) spectrograph.
Uses a 128x128 SiAs detector.
Field of view = 11 arcsec!
Range of broad/narrow filters
available centred on: 7.9, 8.8,
9.8, 10.3, 11.7, 12.5, 18, 20.8 m +
N-band (10.8 m)
Uses chopping secondary capability of Gemini telescopes.
Acquisition Camera
Optical CCD camera, which can provide
U,B,V,R,I imaging over a 2’x2’ field.
Offered in 2001B to develop `quick response’
mode of operation (e.g. for SN and gamma-ray
burst follow-up).
ITC available
Applying for time on Gemini –
it’s the PITs!
• Proposals to use Australia’s share of time on
Gemini are considered by ATAC; semester
deadlines are:
 March 31st (for ‘B’ semester, Aug-Jan)
 Sep 30th (for ‘A’ semester, Feb-July)
• If you collaborate with people from other
partner countries, then time can be sought
from their TACs as well.
Applying for time on Gemini –
it’s the PITs!
• Gemini proposals are assembled and submitted using
the Phase-I Tool (PIT), a supposedly user-friendly
‘GUI’-styled program* which solicits:
 all the usual info: title, abstract, instrument/mode
required, nights (D,G,B), list of targets, guide stars, etc
 PLUS attached 3-page postscript file containing
scientific justification (and figures) for ATAC
• Once complete, hit the “SUBMIT” button in PIT; it then
verifies your proposal and (if OK) sends it to the AAO for
official submission.
*that should be generally available at your institute; ask your
system manager!
Applying for time on Gemini –
extra requirements
• Guide stars:
 these need to be selected and listed along with each
target object: at a minimum, 1 is required for the
peripheral wave front sensor (PWFS), with additional
guide stars required if instrument has an On-Instrument
Wave Front Sensor (OIWFS), and/or observations
involve AO.
 The PIT makes the selection process simple through
internet links to a guide-star catalog (USNO) and digital
sky survey.
Applying for time on Gemini –
extra requirements
• “Classical” or “Queue” time (where there’s a
choice)?
 Classical time is the traditional type of allocation where
your nights are scheduled and you travel to the telescope
(minimum allocation = 0.5 nights).
 Queue scheduled time is where your observations are
executed by Gemini Observatory staff at a time when
the conditions best suit your program. In this case you
have to be much more specific about the observing
conditions: seeing, cloud cover, water vapour content, sky
and telescope background, air mass.
Key web addresses
www.gemini.anu.edu.au (Australian mirror
of the main Gemini web site – with all the
information on the telescopes/instruments)
www.ausgo.unsw.edu.au (Australian
Gemini Office web site – with all the
information relevant to Australian users)
www.aao.gov.au/local/www/sll/applicati
ons/ATAC-applications.html (information
on applying for time through ATAC)