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Toby Moore Liverpool JMU RAS, London, May 2008
Infrared wavebands AstroNet Science Case recommendation for mid-IR astronomy: “Near- and mid-infrared imaging and spectroscopyat 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 • 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 • 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. • 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)
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 Space and Ground are Complementary
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
Adaptive Optics for the mid-IR The need for AO... ...and expected performance • 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?
Nodding and Chopping • The E-ELT will not provide classical chopping • The nodding performance is still unclear
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.
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 mm l 8.63 mm