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