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Specificities of thermal infrared astronomy

Specificities of thermal infrared astronomy

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Specificities of thermal infrared astronomy

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  1. INSTRUMENTAL PROSPECTS IN INFRARED AND SUBMILLIMETER ASTRONOMY Jean-Loup Puget Institut d'Astrophysique Spatiale, Université Paris Sud, Orsay Visions en Astronomie Infrarouge

  2. Specificities of thermal infrared astronomy • the earth atmosphere is opaque from 13 µm to 350 µm (and still mostly opaque up 800 µm) • thermal emission of the atmosphere and of the telescope is a severe limitation to sensitivity increasing very steeply beyond 2 µm • in the range 10 µm to 1mm the diffraction limit is from 20 to 2000 times what it is in the V band: CONFUSION limits the sensitivity • detector array technology progress have been slower than in the optical and near infrared (although major progress were made on individual detectors and related technology like cryogenic systems) Visions en Astronomie Infrarouge

  3. how to overcome these limitations • observing from space allow your telescope: • to be above the atmosphere • to be cooled • uses large telescopes and interferometers • near and thermal IR adaptive optics and interferometry • on the long wavelengths side • in atmospheric windows • in very high altitude sites (JCMT, CSO, IRAM, ALMA) • the far infrared remains the most difficult; space interferomers still require a lot of developments and will not be available before a long time Visions en Astronomie Infrarouge

  4. Cosmic background from radio to gamma rays CMB CIB Visions en Astronomie Infrarouge (D. Scott)

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  6. The HDF seen by ISO (7 and 15 mm) ISOCAM team Orange: 15 mm Green: 7 mm Visions en Astronomie Infrarouge

  7. Fast progress in mid IR detectors and cryogenic telescopes: SPITZER • the Si-As BIB arrays used in MIPS allow to get • deep surveys comparable to optical ones • spectra of galaxies at redshifts beyond 3 with an 85 cm telescope ! • very efficient He cryostat in space have been built through very efficient passive cooling • large telescopes (2 to 3.5 m) for Herschel-Planck can be cooled down below 50 K also with passive cooling Visions en Astronomie Infrarouge

  8. Visions en Astronomie Infrarouge

  9. Typical galaxy spectrum Visions en Astronomie Infrarouge

  10. Source Counts Visions en Astronomie Infrarouge Lagache, Dole, Puget, 2003, MNRAS

  11. z < 0.3 z < 0.8 z < 1 z < 1.3 z < 2 Predictions for Redshifts For S24 < 0.2 mJy: ~30% of z > 2 galaxies • bimodal contribution: • 0.3 < z < 1 (11 to 13 µm features) peaks at 0.5 mJy • 1.6 < z < 2.5 (6 to 9 µm features) peaks at 0.2 mJy • min contribution 1.1 < z < 1.6 Visions en Astronomie Infrarouge Lagache, Dole, Puget et al, 2004, ApJS, 154

  12. 8.6 mm PAH Redshifted at z~2 and Observed at 24 mm ! PAH at z~2 • Normalized Redshift Distribution in GOODS CDFS : • -Ks sample of ~3000 sources (black) • MIPS 24um sample (red), identified at 94% in Ks: ~730 sources: • 36% spectroscopic • 21% COMBO-17 • 43% photo-z • ~30% of Spitzer sources are at z>1.5 Visions en Astronomie Infrarouge K. Caputi et al., 2005b, submitted

  13. 7.7@29 8.6@33 6.2@23 PAHs at z~2.8 M82+linear AGN continuum • 2 Submm Galaxies at z~2.8 observed w/ IRS • ~2hrs of integration • 6.2 & 7.7 (& 8.6) PAHs • Luminosities: 1.3 to 2 1013Lo • SFR>2000Mo/yr Visions en Astronomie Infrarouge Lutz et al, 2005, ApJ

  14. ISO 170 mm surveys The FIRBACK survey Visions en Astronomie Infrarouge

  15. Confusion • two types: if you detect sources S>Smin • keep the probability to have not separable sources directly linked to N(S>Smin) • keep good signal to noise in you beam due to fluctuations of the weaker sources • the far infrared and submillimeter is a special case: the second criteria is often coming from sources much weaker than Smin Visions en Astronomie Infrarouge

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  17. Deep cosmological surveys reveal 8 104 in K band (K<21.5) • MIPS-24µm reveal about 2 104 galaxies per sq deg • 10 per Herschel beam at 550 µm • 250 gal per PLANCK beam ! • Stacking 24 µm sources in long wavelengths maps • possible if you have excellent/stable pointing and effective PSF • limited by number of sources and clustering of sources (cannot do stacking when your angular resolution gets smaller than the correlation scale of the source population you study) Visions en Astronomie Infrarouge

  18. Stacking Analysis 160 Not physically relevant but illustrative: 80<S24<83mJy 330 sources CDFS [z>1.5 ?] Dole, Lagache, Puget, 2005, astro-ph/0503017 Visions en Astronomie Infrarouge

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  23. beat the confusion: future steps in the stacking game • if you can get photometric redshifts for your mid infrared sources such that • galaxies in a redshift and mid IR flux band (typically dz/z~10-20%) have a long wavelength distribution symetrical with respect to the mean you get from stacking • a large enough number of sources per long wavelength beam such that statistical fluctuations are getting small enough • you can then remove these galaxies from the long wavelength maps and be left with a CIB containing only the structures associated with the redshift >2.5 • for example in a Planck map at 550 µm with 250 24 µm galaxies per beam, the error in the removal is the dispersion of the colors divided by about 15 Visions en Astronomie Infrarouge

  24. Instrumentation: other coming steps • at millimeter and submillimeter wavelengths detectors close to quantum limits are being built • for Herschel • Planck • arrays in the far infrared are still being developped • Si detectors are very successful up to 35 µm • Ge photoconductors have met many problems • bolometer arrays will fly on Herschel-PACS • arrays of TES (transition edge supra-conductor detectors) multiplexed, planar antenna detection Visions en Astronomie Infrarouge

  25. Polarization sensitive bolometersAndrew Lange, Jamie Bock,Caltech-JPL Visions en Astronomie Infrarouge

  26. Performances Planck bolometers performances: dark NEP below the photon noise at mm wavelengths Visions en Astronomie Infrarouge

  27. (+0.014) 8 nK Hz-1/2 space qualified dilution cooler (Alain Benoit CRTBT) 30 Stabilisation PID2 N - thermometer PID2 N Visions en Astronomie Infrarouge

  28. integrating sphere CS2 mirror HFI CQM CS1 polariser + crosstalk sources on rocker Visions en Astronomie Infrarouge

  29. CMBspectra: temperature, E and B polarization E < 0 E > 0 B < 0 B > 0 3 observables : T, E, B WMAP B polarization power spectrum is 5 orders of magnitude weaker than T for tensor/scalar =0.1 ! PLANCK dedicated polarization mission Visions en Astronomie Infrarouge

  30. Visions en Astronomie Infrarouge

  31. Observatories • ISOCAM 15 µm 6 arc sec (32*32 array) • ISOPHOT 160 µm 90 arc sec (4 individual pixels) • SPITZER-MIPS • 24 µm 5.6 arcsec (128*128 array) • 160 µm (2*20 array) • JCMT-SCUBA 850 µm • IRAM PdB • HERSCHEL 550 µm • All sky Surveys • IRAS 1.5 arcmin/0.5 Jy at 100 µm, 30 arcsec/0.5Jy at 12 µm • COBE 40 arc minutes • ASTRO-F • PLANCK 550 µm, 5 arc minutes Visions en Astronomie Infrarouge

  32. redshift ranges contributing to the CIB Visions en Astronomie Infrarouge

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  34. CIB SED Visions en Astronomie Infrarouge long wavelengths emissivity 1.5 to 2 Lagache, Dole, Puget, 2003, MNRAS

  35. PAHs at z~1.8 to 2.6 • 8 24 mm galaxies targetted w/ IRS (52 total) • 6 MIR features detections: 1.8 < z < 2.6 • 6.2 & 7.7, 8.6, 11.3 PAHs (+Si abs) • Luminosities: 0.6 to 4 1013Lo Visions en Astronomie Infrarouge Yan et al, 2005, ApJ in press

  36. Cosmic Infrared Background • 24 mm • Down to 60 mJy • 75% resolved • By integration of the source counts, CIB@24 is 2.7 +1.1-0.7 nWm-2sr-1 • 70 mm • Down to 15 mJy • ~23% resolved • 160 mm • Down to 45 mJy • ~7% resolved • References • Papovich et al., 2004 • Dole et al., 2004 Visions en Astronomie Infrarouge

  37. Differential Source Counts 24 mm Papovich, Dole et al, 2004, ApJS Visions en Astronomie Infrarouge Dole et al, 2004a, ApJS

  38. Planck planned capabilities Visions en Astronomie Infrarouge

  39. One year mission CMB performances Visions en Astronomie Infrarouge

  40. Comparison CIB in optical/IR • Energy in the extragalactic background : - l < 6 mm: 2  4.2 10 -8 W m-2 sr-1 - l > 6 mm: 4 - 5.2 10 -8 W m-2 sr-1 => E(Far-IR) / E(opt) ~1 – 1.25 • Local Universe: • E(Far-IR) / E(opt) = 0.4 !!! • Conclusion: • Strong increase of the IR ouput energy with z • Questions: • stars or massive black holes as the main energy source • role of IR galaxies in the building of galaxies as we see them today • does the emerging picture fits or not in the standard model of hierarchical structure formation Visions en Astronomie Infrarouge

  41. Updated 2004 LDP Model 7.5% 3% Visions en Astronomie Infrarouge Lagache, Dole, Puget, et al, 2004, ApJS