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ESA’s Darwin space interferometer

ESA’s Darwin space interferometer. Huub R ö ttgering Sterrewacht Leiden. The InfraRed Space Interferometer DARWIN. 2014 6 1.5 m telescopes Hexagonal configuration Beam combiner Passive cooling (40 K): 5-20 micron. Overview. Introduction Timeline / status project

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ESA’s Darwin space interferometer

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  1. ESA’s Darwin space interferometer Huub Röttgering Sterrewacht Leiden

  2. The InfraRed Space InterferometerDARWIN • 2014 • 6 1.5 m telescopes • Hexagonal configuration • Beam combiner • Passive cooling (40 K): 5-20 micron

  3. Overview • Introduction • Timeline / status project • Relation with NASA’s Terrestrial Planet Finder • Imaging considerations • Science

  4. Science • Finding and characterising exo-Earth’s • Nulling interferometry

  5. The Problem Detecting light from planets beyond solar system is hard: Planet emits few photons/sec/m2 at 10 mm Parent star emits 106 more Planet within 1 AU of star Dust in target solar system 300 brighter than planet Finding a firefly next to a searchlight on a foggy night

  6. Science • Finding and characterising exo-Earth’s • Nulling interferometry • Atmosphere -> CO2 • Wet and pleasant H20 • Life O3 (? / !) • High resolution and sensitive IR imaging • Cophasing using an off-axis reference star Earth at 10pc

  7. Darwin timeline • 1993: Léger et al • ``Darwin proposal’’ • 2000 Presentation Alcatel system level study • 2004 Results significant technology development program (15 Meuro) • Optical components, coolers, thrusters, metrology, control software, 2 breadboards … • 2007 – SMART2 techno demonstration flight • (mainly LISA technology) • 2010 – SMART3 techno demonstration flight • 2-3 space craft • 2014 – launch

  8. NASA’s TPF • Similar goals and timelines 1999: IR interferometer with cooled 4x3.5 m mirrors and ~75-1000 m baseline

  9. Vegetation edge 2000 Blue sky Earth spectrum from Earth- shine

  10. SVS coronagraphe Variable-Pupil Coronagraph IR Nulling Interferometers M2 M1 M3 Hyper-telescope Large Aperture IR Coronagraph 2001: 4 different studies

  11. 2002: down selection for 2 concepts • Coronagraph – Difficult • 10-15 meter mirror with rms surface ~< 1 Å • Deformable mirrors - control to <1 Å rms over wide range of scales • Wavefront sensing - adequate for <1 Å control • Interferometer - Complex • Cryogenic nulling - 10-5 or 10-6 depth across ~1 octave • Wavefront & amplitude control - spatial filter in mid-IR (+ DM for low spatial freqs) + control of thermal & vibration effects + acc. amplitude measurement • Beam transport issues (rejection of stray light at small angles) Variable-Pupil Coronagraph IR Nulling Interferometers

  12. Joined ESA/NASA mission • MOU: aims for a joining in 2006 • Plan • Both sides continue technical studies • Regular scientific contact • Criteria to guide continuation after 2006 • #1: Sensitivity in finding and characterizing exoplanets • #2: Richness of astrophysical science opportunities • #3: Technology development needed • #4: Life-cycle costs • #5: Risk of cost, technology, schedule, on-orbit failures • #6: Reliability and robustness

  13. Astrophysical imaging with Darwin 1. Imaging considerations 2. Science Röttgering et al. 2003, Heidelberg conference

  14. Imaging performance at 10 micron • Sensitivity (Takajima and Matshura, 2001) • Limited by shot noise from the zodiacal background. • Similar to JWST • Point source sensitivity • 1 hour, s/n=5: 2.5 microJy • Image sensitivity • S_integrate/noise > 50 within FOV • > 2.5 microJy for a 100 hour • Resolution • Baselines up to 500 meter • 200 m baseline: 10 mas • JWST 350 mas

  15. Imaging considerations • PSF of an individual telescope: 1.4 arcsec • = maximum FOV for pupil combination • Mapsize (200 m baseline/telescope diameter) <~ 100 * 100 independent pixels • Complexity • per configuration maximum 6*5/2 = 15 uv points • number of uv-points >>~ number of image parameters • for a complex map of 100 * 100 independent pixels: • >>~ 666 configurations

  16. 16 Baseline dynamics Basic reconfiguration approach a single expansion up to baselines of 500 m and contraction coupled to a 60o rotation bang-bang thrust profile both radially and tangentially <dB/dt> = 1.5 cm/s @ 1 mN d’Arcio et al. 2001 Fastest reconfiguration cycle takes about 16 hours Snapshots will be taken “on the fly”

  17. 17 UV coverage • Hexagonal array -> 9 independent visibilities per snapshot • 600 snapshots, ~ 5400 uv points/reconfiguration cycle • -> Filling the UV plane is ’’easy’’ • Ground based telescopes are ``fixed’’ • (radio) Baseline/apertureis huge d’Arcio et al. 2001

  18. Issue: Cophasing • How to phase-up the array not using the target? • Essential to • integrate longer than the coherence time of the interferometer (~10 sec) • Measure complex visibilities (Amplitude and phase) needed for imaging • Off-axis bright stars (there are enough!) • Similar to PRIMA instrument for the VLTI (Quirrenbach, this meeting) • Multiplexing in wavelengths has the advantage that science and reference beams travel along common path (Alcatel) • Implementation • Modification to the nulling beamcombiner (Alcatel) • Separate imaging beamcombiner

  19. How to get a large Field of View? • Mosaicing • Expensive in time • homothetic mapping • Relative complex • Pupil matching in magnification and orientation before image plane combining • Implementation • Pupil matching/zooming optics at central beamcombiner • Pupil matching/zooming at telescopes (see d’Arcio and le Poole, 2003)

  20. Physical processes observable at 6-20 micron • Molecules: Rotational and vibrational lines • Temperatures, densities, kinematics, Chemistry • Ions: Forbidden fine-structure lines • Temperatures, densities, kinematics, abundance's • Dust: PAH features, continuum shape • Composition, temperature • Late type stars: continuum (high z) • Spatial scales ISO observations Starburst galaxy Circinus

  21. Appropriate sensitivity and angular resolution ? Star and planet formation AGN Distant galaxies

  22. Star and Planet formation • Sketch of scenario maybe in place (Shu et al. 87) • Vast range of conditions and relevant timescales • densities 10^4 - 10^13 /cm^3 • temperatures 10 - 10,000 K • month - 10^6 years • Issues • density, temperature and dynamical structure of disks? • At what stage and when do planets form?

  23. Compendium of Monnier and Millan-Gabet of K-band sizes of YSOs Disk models of D’Alessio, Merin

  24. ISOCAM survey of your starclusters at 6.6 and 14.3 micron (Eiroa et al) An unphysical, unrealistic extrapolation -> fainter YSO are small (10-100 mas ?) 4 2 0 MIDI Log Radius[mas] Darwin -2 -1 0 Log flux @ 14 micron [Jy]

  25. Active galactic Nuclei • Zoo: Seyfert, Starburst quasars ... • unification: orientation, time-evolution, mass, spin • 1000 times more AGN at z=2 than z=0 • Every galaxy has a central massive Blackhole (?) • Issues: • Physics? When and how do BH form? • Relation to Galaxy formation?

  26. Models of Tori of Granato et al. • AGN may contain dusty tori • can obscure the central QSO • feeds the massive Black Hole • Radiative transfer model of a dusty torus • size scales with QSO luminosity • SED from l = 1 - 300 mm • morphologies at l = 10 mm Adapted to NGC 1068, Heijligers etal.

  27. Darwin observations of Tori • D = 300 times the sublimation radius • NGC1068: • Bight, low luminosity nearby AGN • ~10 Jy: prime target for MIDI/VLTI in 2003 • 1.7 1031 erg/s/Hz at l = 10 mm • (prime target for MIDI/VLTI in 2003) • Weak AGN observable up to z = 1 - 2 • Stronger AGN up to z = 10 1’’ Ln (10 m m [1030 erg/s/Hz] 0.1’’ NGC1068 50 m Jy 5 m Jy 0.01’’ 0.01 0.1 1 10 redshift

  28. Distant Galaxies • When and how do galaxies form? • Star formation history, galaxies shapes • Relation to black hole formation • 8-10 meter telescopes: a few thousand with 3<z<6 and still counting • Hardly morphological information • Darwin: morphologies of the older stellar component • observe 2 micron rest == 10 micron for z=4 • Semi-analytical models of galaxy formation as guidance • input: evolution of cold-dark matter halos, prescriptions for cooling, star formation and feedback, dust… • output: large samples of mock galaxies and their properties (SF, mass, type)

  29. FIRES survey • IsaacVLT • : 2.5^2 arcmin • 96 h in J, H, K HDFS • limit in K = 24.4 mag • Image HST I+H+K • Franx, Labbe, Forster,schreiber, Rix, Rudnick, Röttgering, etal.

  30. SED fitting • with galaxy templates • Photometric redshift • Estimate 10 micron flux density • Rudnick, Labbe et al.

  31. JWST resolution At 10 micron (0.35 arcsec)

  32. Fn (10 m m ) m Jy 100 hour, S_int/noise=50 100 hour Pointsource S/N=5 (photometric) redshift

  33. Conclusion • Darwin will be a powerful instrument for • Finding and characterizing exo-Earth • Astrophysical studies • Sensitivity is similar to JWST • Cophasing is an important issue • Size scales, AGN, YSOs, distant galaxies are appropriate • Case for larger fields

  34. 2025 Terrestrial planet imager? 20 8-m telescopes

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