IFU projects in Durham

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IFU projects in Durham

• Jeremy Allington-Smith

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Summary

• Fibre-lenslet
• GMOS-IFU ?2 (Gemini) ? recent results Andrew
  Bunker
• IMACS-IFU (Magellan) ? J?rgen Schmoll
• Image-slicing
• GNIRS-IFU (Gemini)
• NIRSPEC-IFU (NGST) ? Olivier Le Fevre
• MIRI (NGST)
• New technology
• MEIFUS concept (8m/30m)
• Multiple IFS (fibre-lenslet or image-slicing)
• GIRMOS (Gemini)
• KMOS (VLT) ? Ray Sharples
• FMOS-IFU (Subaru - design study))

Collaborators in Durham include Graham Murray,
Robert Content, George Dodsworth, Marc Dubbeldam,
Gil Moretto, Colin Dunlop, David Robertson, Ray
Sharples, Simon Morris
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GMOS-IFU

• 1500 lensed fibres
• 7 x 5 arcsec2 3.5 x 5 arcsec2 fields separated
  by 60 arcsec
• 0.2 arcsec/sample (hexagonal)
• 0.4-1?m with R ? 8000
• IFU reformats two fields into two slits
• One slit can be blocked to maximise spectrum but
  halve contiguous field
• Remote insertion of IFU into focal plane of GMOS
  in place of masks

• Commissioned 2001 on Gemini-N
• 60-70 throughput of IFU alone
• Only 3 non-functioning fibres
• Second unit to be installed in GMOS-S.

astro-ph/0202330 PASP (Aug)
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Gemini Multiobject Spectrographs

• GMOS
• 0.07 arcsec/pixel image scale
• 5.5 x 5.5 arcmin field
• 0.4 - 1.1mm wavelength coverage
• R 10,000 with 0.25 slits
• Multiobject mode using slit masks
• Integral field spectroscopy mode
• Active control of flexure

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GMOS-IFU raw data (NGC1068)
Red
Blue
OIII
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GMOS-IFU reduced data
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GNIRS-IFU

• Wavelength range
• Optimal 1.0-2.5 ?m
• Total 1.0-5.0 ?m
• Field 3.2 x 4.4 arcsec2
• Sampling 0.15 arcsec
• Spatial elements 625
• Spectrum length 1024 px
• Optimized for use with tip/tilt corrected images
• Cryogenic environment
• IFU fits in module in GNIRS slit slide
• Completion end 2002

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Advanced ImageSlicer (AIS)

• Developed from MPE's 3D by the University of
  Durham for highly-efficient spectroscopy over a
  two-dimensional field
• Optimum use of detector pixels since complete
  slices of sky are imaged (no dead space between
  spatial samples)
• Correct spectral sampling is obtained without
  degrading spatial resolution in dispersion
  direction
• Diffraction is only a 1-D issue
• ? reduction in optics size/mass
• Optics may be diamond-turned from the same
  material as the mount to reduce thermal mismatch
• ? good for space/cryo applications
• Adopted by GEMINI 8m Telescopes Project
  (GNIRS-IFU) and proposed by ESA for NGST

Focal plane
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A 3D capability for GNIRS

• Cryogenic 1-5?m spectrograph for GEMINI with IFU
  deployable via slit slide

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Optical layout
From GNIRS fore-optics
Monolithic S2
Monolithic S3
F1
Slit
F2
F3
S1
Bi-lithic S1
To GNIRS collimator
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Image quality
Images at end of each slice on detector (ellipse
airy disk)
Slice 1
Slice 11
Slice 21
Image on slicing mirror (box slice width)
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GNIRS IFU Assembly
S2
S1
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MEIFUS

• Aim One million spatial elements
• Requires efficient design without excessive
  complexity hybrid of lenslet (Tiger) and
  image-slicer concepts
• Very modular (massively-parallel) design with
  (nearly) identical spectrographs and efficient
  multiple sub-division of the field
• Can be scaled easily from 8m to 30m telescope
• Concept currently being studied for 30m

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MEIFUS concept
Magnifying optics
Anamorphic magnification
Pickoff mirror
F/28 x F/98
F/15

• Spectra dispersed at an angle to avoid spectral
  overlap
• Spectra 200 x 12 pixels on detector (0.092
  arcsec/pixel)
• Inter-spectrum gaps 22 pixels (spectral) and 3
  pixels (spatial)

Microlens optics
Spectrograph
F/1.8
F/4.4
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Optical Principle
cylindrical foreoptics
spectrograph
IFU

• Fore-optics magnify the focal plane
  anamorphically onto the first (rectangular)
  lenslet array which acts as the image slicer
• Cylindrical microlens arrays to divide the input
  focal plane into micro-slices
• Second lenslet array demagnifies
  (anamorphically) the slices onto the input focal
  plane of the spectrograph and puts the pupil onto
  the grating

horizontal cylindrical microlens arrays
Output focus slit plane
vertical cylindrical microlens arrays
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Massively-parallel spectrographs