Toby Moore Liverpool JMU RAS, London, May 2008
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Transcript of Toby Moore Liverpool JMU RAS, London, May 2008
Toby Moore Liverpool JMURAS, London, May 2008
Infrared wavebands
Region Wavelength Temperature Typical Objects
Near-infrared 1 – 5 μm 580 – 2900 K red giant stars, galaxies, YSOs
Thermal near-IR 2.5 – 5 μm 580 – 1160 K
Mid-infrared 5 – 40 μm 70 - 580 K planets, PP disks, warm dust
Far-infrared 40 – 350 μm 8 – 70 K emission from cold dust
AstroNet Science Case recommendation for mid-IR astronomy:
“Near- and mid-infrared imaging and spectroscopy at high spatial resolution and sensitivity provided by an Extremely Large Telescope with high performance adaptive optics will be essential…” (page 138)
The Mid-Infrared Toolbox
Spectroscopy:• Atomic fine-structure lines• Atomic hydrogen lines• Molecular hydrogen lines• Polycyclic aromatic hydrocarbon (PAH) emission features• Silicate emission/absorption features (crystalline and amorphous)• Ices: H2O, CO, CH4, CH3OH, NH3
• Gaseous molecules: CO, H2O, CH4, C2H2, HCN, OH, SiO2, H3+
• e.g. isotope ratios D/H, gas content of circumstellar discs, etc.
Imaging:• Low susceptibility to dust extinction• Continuum emission from dust (and very small grains)• e.g. young circumstellar discs: reduced contrast of star/disk ratio
Polarimetry:• Asymmetric dust grains short axis and L are aligned with B-field dichroic effect radiation passing through a medium partially polarized• Absorption: position angle ║ B-field; emission: ┴ B-field
METIS Science Case• Proto-Planetary Disks
Physical structure of the gas vs. dust disc: evidence for young planets;
timescale and mechanism for gas dissipation (photo-evaporation, disc
winds, planets, …); chemical content of the inner disc as a function of
radius (water, organic molecules, …)
• Properties of Exoplanets• Solar System
Primordial material in cometary nuclei. 3-5μm spectrocopy
• The Growth of Super-massive Black Holes QSO activity at high z; evolution of nuclear starburst activity
• The Formation of Massive Stars & the stellar IMF• The Galactic Centre• Formation of Massive Ellipticals: Morphologies of the hosts of Sub-
mm Galaxies• GRBs at high redshifts
METIS Instrument Modes (TBC)
Derived from science case and subject of Phase-A study
BASELINE:• L M N band diffraction limited high contrast imager (20"×20")• L M N-band high-resolution (R ~ 100,000) IFU spectrometer (1"×1") • Coronagraph• Low resolution (R ≥ 100) spectroscopy (included in imager)
OPTIONAL (subject to phase A study):• Larger field of view• Medium resolution spectroscopy (IFU or long slit)• Q band (imaging and spectroscopy)• Linear polarimetry (imaging and R ≥ 200 spectroscopy)
Space and Ground are Complementary
Can the E-ELT compete with JWST-MIRI?
• Continuous spectral coverage
• Larger FOV with constant PSF
• Better imaging sensitivity
• Much better LSB sensitivity
• Better spectro-photometric stability
• 100% sky coverage, good weather
• Comparable PS spectral sensitivity
• 5-8 times higher angular resolution
• High spectral resolution (kinematics)
• Shorter response times
• Optional polarimetry
• Follow up as for HST →VLT
Anticipated Timeline (TBC)
Sep 05 – Jul 06 MIDIR Small Study (EU)
Oct 07 start preparations for phase-A
Mar 08 submission of phase-A proposal
May 08 – Oct 09 phase-A study
2010 – 2012 phase-B
2013 – 2017 phase C/D
2017 first light
Phase-A Work Distribution
Adaptive Optics for the mid-IR
• wavefront sensing at 589nm correction at 12μm?• effect of water vapour fluctuations?internal (low order) mid-IR wavefront sensor? interaction with E-ELT AO system?
The need for AO... ...and expected performance
Nodding and Chopping
•The E-ELT will not provide classical chopping
•The nodding performance is still unclear
Chopping Method Field Restrictions
Extended Objects
Efficiency(exposure
time)
Comments
Focal Plane Chopping
few arcsecs bad 0.45-0.9 technical risk
Pupil Plane Chopping ~10 arcsec bad 0.45-0.9 technical risk (AO challenging,)
Dicke Switching none good <0.5 very good flat field calibration device; should be implemented in any case
Nodding/Dithering ? good (TBC)
0.15 (– 0.9?) will depend on detector, site and weather; needs testing of suitable fixed pattern noise filtering
Gratings
Need ~1-m gratings for R ~ 100,000 spectroscopy
Directly ruled for longer wavelengths
Explore alternative grating technologies:
• Immersion gratings (development SRON) in silicon for L+M band?
• Volume Phase Holographic Gratings (development ATHOL and within OPTICON FP-6). Q: Are there now photosensitive materials transmissive beyond 2.5 μm?
Other Technology Developments
Mirrors: 3-mirror astigmats require highly aspheric mirrors that can easily be made using diamond milling, but surface roughness too high for METIS.
IR-Detectors: for mid-IR wavefront sensing (not science)
Fibres: (not part of instrument baseline) Could be included if reliable, cryogenic fibres for λ < 13μm exist.
New materials: (not part of the instrument baseline) light-weight and simplified cryostats?
Coatings: filters and dichroics (UK involvement - U of Reading)
UK contribution
The JWST-MIRI Spectrometer pre-optics (SPO) have been developed, built and tested by the UKATC.
At the heart of the MIRI SPO are four all-reflective diffraction-limited integral field units.
The METIS concept includes a requirement for high and medium spectral resolution IFUs similar to those in the MIRI SPO.
We intend to build on the JWST-MIRI spectrometer pre-optics concept to support this area of the METIS Phase A study.
8 x 8 arcsec FOVrelayed fromOTE by IOC
CollimatorCollimator
CollimatorCollimator
Camera 1 & 2
Camera 3 & 4
D1a,b,c
FPA 1
FPA 2
DGA-B
Grating 1c
Grating 1b
Grating 1a
Grating 2c
Grating 2b
Grating 2a
Grating 4c
Grating 4b
Grating 4a
Grating 3c
Grating 3b
Grating 3a
IFU 1 IFU 2
IFU 4 IFU 3
DGA-A
D2a,b,c D3a,b,c
• All aluminium design for ease of alignment.
• Slicer mirrors diamond finished by Cranfield University.
The JWST-MIRI Integral Field Units
The complete MIRI SPO
10.19 m
8.63 m