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CODEX …Opening a new parameter Space…

CODEX …Opening a new parameter Space…. Why a new window now. High wavelength calibration accuracy… Very accurate Doppler shift measurements… Measurement of isotopic ratios… High Precision Spectroscopy requires very high S/N ratios  photon starved

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CODEX …Opening a new parameter Space…

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  1. CODEX …Opening a new parameter Space… High Precision Spectroscopy 2006 - LP

  2. Why a new window now High wavelength calibration accuracy… Very accurate Doppler shift measurements… Measurement of isotopic ratios… High Precision Spectroscopy requires very high S/N ratios  photon starved Very and Extremely Large Telescopes High Precision Spectroscopy 2006 - LP

  3. ESO is operating the VLT… Four 8 Meter telescopes 11 Instruments at Cass or Nasmyth Foci + Combined coherent focus+VLTI+ Combined Incoherent Focus (16m equivalent) High Precision Spectroscopy 2006 - LP

  4. And ESO is planning the E-ELT! 42 Meter ‘adaptive’ Telescope First light 2015 High Precision Spectroscopy 2006 - LP

  5. CODEX @ ELT ESO: G. Avila, B. Delabre, H. Dekker, S. D’Odorico, J. Liske, L. Pasquini, P. Shaver Observatoire Geneve : M. Dessauges-Zavadsky, M. Fleury, C. Lovis, M. Mayor, F. Pepe, D. Queloz, S. Udry INAF-Trieste: P. Bonifacio, S. Cristiani, V. D’Odorico, P. Molaro, M. Nonino, E. Vanzella Institute of Astronomy Cambridge: M. Haehnelt, M. Murphy, M. Viel Instituto de Astrofisica Canarias: R. Garcia-Lopez, R. Rebolo, M. Zapatero Others: Bouchy (Marseille), S. Borgani (Daut-Ts), A. Grazian (Roma), S. Levshakov (St-Petersburg), L. Moscardini (OABo-INAF), S. Zucker (Tel Aviv), T. Wilklind (ESA) High Precision Spectroscopy 2006 - LP

  6. - Direct measurement of the dynamics of the Universe - Cosmological variation of the Fine-Structure Constant: CODEX will aim at an accuracy of ∆/ ~5x 10-9 - Terrestrial planets in extra-solar systems: RV of earth mass planets, spectroscopy of transits Four Outstanding Cases - Primordial nucleosynthesis: probing SBB nucleosynthesis: primordial Li7, Li6/Li7 Many additional applications (as from this conference....): Asteroseismology,Abundances in Stars, Variability of µ, Temperature evolution of CMB, Chemical evolution of IGM.. High Precision Spectroscopy 2006 - LP

  7. Dynamics of the Universe Directly measure the expansion of the Universe by observing the change of redshift with a time interval of a few (10-20) years ”It should be possible to choose between various models of the expanding universe if the deceleration of a given galaxy could be measured. Precise predictions of the expected change in z=dl/l0 for reasonable observing times (say 100 years) is exceedingly small. Nevertheless, the predictions are interesting, since they form part ofthe available theory for the evolution of the universe” Sandage 1962 ApJ 136,319 High Precision Spectroscopy 2006 - LP

  8. Cosmic Signal t0=actual epoch In a homogeneous, isotropic Universe a FRW metric te=emission epoch High Precision Spectroscopy 2006 - LP

  9. Direct measurement ! • Bias-free determination of cosmological parameters • Different redshift (CMB, SNIa); measure dynamics and not geometry • Not dependent from evolutionary effects of sources • Legacy Mission to future astronomers (First epoch measurements) High Precision Spectroscopy 2006 - LP

  10. High Redshift Supernovae.. SNae: observe magnitudes at different Redshifts Assume SNae are standard candles at all z Require non-trivial K corrections Require determination of Reddening… High Precision Spectroscopy 2006 - LP

  11. The measurement concept ….. But this is for 107 years… Having much less time at our disposal the shift is much smaller…. High Precision Spectroscopy 2006 - LP

  12. The expected acceleration Is SMALL! Note: the standard model was not always standard.. The change in sign is the signature of the non zero cosmological constant High Precision Spectroscopy 2006 - LP

  13. Results of Simulation (..) Simulating the dependence on Z Information “saturates”: a) Too many lines b) High Redshift makes them broader. High Precision Spectroscopy 2006 - LP

  14. Results of simulations (…) Many simulations have been carried out independently by 3 groups; using observed and fully simulated spectra. A very good agreement is found, and we can produce a simple scaling law: v = 1.4*(2350/(S/N))(30/NQSO)0.5 (5/(1+Z))1.8 cm/sec Where v is the total uncertainty (difference between 2 epochs) while the other parameters refers to the characteristics of one epoch observation; Pixel size considered: 0.0125. About half of the signal is coming from the metal lines associated to the Ly High Precision Spectroscopy 2006 - LP

  15. Result of simulations (……) The full experiment NQSO = 30 randomly distributed in the range 2 < zQSO <4.5 S/N = 3000 per 0.0125 Å pixel/epoch (no metal lines used) t = 20 years Green points: 0.1 z bins Blue: 0.5 z bins Red line: Model with H0=70 Km/s/Mpc Ωm=0.3 Ω=0.7 The cosmic signal is Detected at >99% significance(!) High Precision Spectroscopy 2006 - LP

  16. Scaling with telescope diameter With a telescope in the range of the 30-40m the experiment will be possible: 20 yrs baseline With a timeline of 20 yrs the accuracy scales to 2 cm/sec Use the full spectral range, including the Ly region VLT and Keck have devoted already > 1000 h each to QSOs.. High Precision Spectroscopy 2006 - LP

  17. CODEX design parameters Location Underground in nested stabilized environment Telescope diameter 42 m Feed Coude’ + Fibre or Fibre only Overall DQE 20% Coude’ + Fibre , 13% Fibre only Entrance aperture 1 arcsec Wavelength range 380 – 680 nm Spectral Resolution 150 000 Number of Spectrographs 3 (for 1 arcsec aperture at 42 m) Main disperser 3 x R4 echelle 42 l/mm 160 x 20 cm Crossdisperser 6 x VPHG 1500 l/mm 20 x 10 cm Camera 6 x F/1.4-2.8 CCD 6 x 8K x 8K (15 um pixels) High Precision Spectroscopy 2006 - LP

  18. How to improve accuracy and stability • Scramblers to reduce effect of guiding errors • Image dissector, multiple instruments • Simultaneous wavelength calibration • Use of wavelength calibration based on “laser comb” • Fully passive instrument, ultra-high temperature stability • Instrument in vacuum tank • High precision control of detector temperature • Underground facility, zero human access • Blaze Correction and Flat Fielding • System PRECURSOR @ VLT High Precision Spectroscopy 2006 - LP

  19. CODEX laboratory floor plan Underground hall 20 x 30 m; height 8 m 1 K Instrument room 10 x 20 m; height 5 m 0.1 K Instrument tanks, dia. ~ 2.5 x 4 m, 0.01 K Optical bench and detector 0.001 K Control room and aux. equipment (laser) 1 K High Precision Spectroscopy 2006 - LP

  20. Telescope Link: Transmission The case was studied for the combined focus of the 4 VLT telescopes: Coude’ train is the most efficient solution and the only one which preserves the BLUE High Precision Spectroscopy 2006 - LP

  21. CODEX Unit Spectrograph B. Delabre ESO Light from fibres enters here High Precision Spectroscopy 2006 - LP

  22. I(1) n 2n Calibration System: Laser Frequency Comb • Metrology labs recently revolutionized by introduction of femtosecond-pulsed, self-referenced lasers driven by atomic clock standards Cesium atomic clock n 2n • (or even GPS signal!) • Result is a reproducible, stable “comb” of evenly spaced lines who’s frequencies are known a priori to better than 1 in 1015 High Precision Spectroscopy 2006 - LP

  23. Comb: spectra simulations R=100k, Dn=15GHz, l=5000Å Total velocity precision better than 1cms-1 in a single shot for SNR ~ 1000 (4500-6500Å) Running study with MPQ (Nobel Prize 2005) High Precision Spectroscopy 2006 - LP

  24. Precision Spectroscopy @ ELT Extremely Large Telescopes will provide for the first time enough photons to guarantee a quantum jump in high resolution spectroscopy To open these new windows, High Resolution must be coupled to extremely high accuracy and stability We have developed a design for such an instrument, and we will propose ESPRESSO, the CODEX precursor @ the VLT High Precision Spectroscopy 2006 - LP

  25. Laser Comb: Advantages and Challenges Advantages: • Absolute calibration • Long term frequency stability • Evenly spaced and highly precise frequencies allow mapping of distortions, drifts and intra-pixel sensitivity variations of CCD • Naturally fibre feed system. HARPS prototype possible. Challenges: • Line-spacing currently limited to ~1GHz. We need ~10–15 GHz... • Large spectral range required (380-680 nm): Existing technology can possibly be extended. High Precision Spectroscopy 2006 - LP

  26. Peculiar motions at the Earth The solar acceleration in the Galaxy will be measured with an accuracy of ~ 0.5 mm/sec/yr by GAIA High Precision Spectroscopy 2006 - LP

  27. Why measure dynamics? All the results so far obtained in the ‘concordance model’ assumes that GR in the FRW formulation is the correct theory. ~0.7 : but we do not know what  is and how it evolves. If GR holds, geometry and dynamics are related, matter and energy content of the Universe determine both. Dynamics has, however, never been measured. All other experiments, extremely successful such as High Z SNae search and WMAP measure geometry: dimming of magnitudes and scattering at the recombination surface. High Precision Spectroscopy 2006 - LP

  28. Challenges & Feedback • Calibration source, stable, reproducible, equally spaced.. LASER COMB • CCD control (thermal… ) • High throughput of the spectrograph and injection system: EFFICIENT COUDE’ FOCUS • Light scrambling capabilities (1 cm/sec  0.0000003 arcsec centering accuracy on a slit…) TELESCOPE POINTING AND CENTERING ~0.02 arcsec • System aspects (from pointing to calibration to data reduction) ALL aspects strongly suggest extensive prototyping High Precision Spectroscopy 2006 - LP

  29. BASIC SPECTROGRAPH REQUIREMENTS Once QSOs are established targets, through basic knowledge and simulations we determine the spectrograph parameters. Spectral range: QSO in the range Z~1.5 - 5. At higher Z too many absorbers wipe out information, Ly is visible from earth at Z>1.8 For lower Z, metal lines only can be used. But to span a large Z range is important also to link it to lower Z experiments: ideal range 300-680 nm. UV: trade-off (less sensitivity, few Ly absorbers..) Resolving Power: Ly line have a typical width of 20-30 Km/sec and R=50000 would suffice. Higher spectral resolution is required by metallic lines (b<~3 Km/sec) and by calibration accuracy requirement; R~150000 Such a resolution is challenging for any seeing limited ELT: the final number will be a trade off between size, sky aperture, detector noise… High Precision Spectroscopy 2006 - LP

  30. CODEX Image and Pupil Evolution Several new features : Anamorphic collimator Pupil Slicer Anamorphic Crossidsperser (Slanted VPH) High Precision Spectroscopy 2006 - LP

  31. Standard Cosmological Model With the assumptions of homogeneity and isotropy, the concordance model finds a FRW metric with a non zero cosmological constant High Precision Spectroscopy 2006 - LP

  32. How to Measure this signal? Masers : in principle very good candidates: lines are very narrow and measurements accurate: however they sit at the center of huge potential wells: large peculiar motions, larger than the Cosmic Signal are expected Radio Galaxies with ALMA : The CODEX aim has been independently studied for ALMA: as for Masers, local motions of the emitters are real killers. Few radio galaxies so far observed show variability at a level much higher than the signal we should detect Ly forest: Absorption from the many intervening lines in front of high Z QSOs are the most promising candidates. Simulations, observations and analysis all concur in indicating that Ly forest and associated metal lines are produced by systems sitting in a warm IGM following beautifully the Hubble flow ! High Precision Spectroscopy 2006 - LP

  33. Results of simulations (1) Simulating the dependence on resolution ( Ly forest only) Above a R~50000 there is no more gain for the Ly Forest. Higher Resolution is required by metal lines and Calibration accuracy. High Precision Spectroscopy 2006 - LP

  34. Results of simulation (2): real spectrum Dependence on cumulative S/N/pixel (0.015 A) High Precision Spectroscopy 2006 - LP

  35. Can we do it ? Telescope + Instrument Efficiency required to complete the experiment under the following assumptions: •V=16.5 QSO • 36 QSO each S/N 2000 (0.015 pixel), for a total of • 2000 obs. hs/epoch ( 1cm/sec/yr) Red line: VLT+UVES peak efficiency In 1st approx. precision scales as D for a given efficiency. High Precision Spectroscopy 2006 - LP

  36. PECULIAR MOTIONS Ly = vacc~100 Km/sec Tacc~109 yr.. negligible Metal systems associated to damped Ly:vacc~3-400 Km/sec Tacc~108BUT hundreds systems-statistically level out Different from the maser and radio-galaxy case… Calls for many line of sight High Precision Spectroscopy 2006 - LP

  37. PECULIAR MOTIONS: Simulations Detailed, state of the art hydrodynamical simulations confirm that the effects are negligible High Precision Spectroscopy 2006 - LP

  38. What’s new • VLT-UVES & Keck HIRES observed hundreds of QSOs at High Res (R>40000), z between 2 and 5, V=16-18. Ly clouds have been extensively simulated: their hot gas belongs to the IGM and they trace the Hubble flow • Exoplanets (HARPS) long term accuracy 1m/s, short term (hours) 0.1m/s (and largely understood) • ELT !! LOT OF PHOTONS (we need them!!) High Precision Spectroscopy 2006 - LP

  39. Verification of targets and reference mission QSO have been selected from existing catalogues and compilations (Veron, SDSS ) Selection criteria: magnitude and z Magnitudes: redwards of Ly, selected band depends on z In this Figure only the 5 brightest QSOs of each 0.25 z bin are shown. Hypothesis: e.g. 2000 h observations with an 80 m telescope and 14% efficiency; all QSO brighter or around the iso-accuracy lines are suitable. High Precision Spectroscopy 2006 - LP

  40. Fiber feed + Pre-slit Entrance aperture 1” on 60 m or 0.65” on 100 m 37 Fibres array, 8 fibres/spectrograph OWL Lightpipe: forming an homogeneously illuminated Slit & scrambling High Precision Spectroscopy 2006 - LP

  41. CODEX @ ELT More info & discussion at the Aveiro Conference on Precision Spectroscopy in Astrophysics 11-15 September 2006, Aveiro, Portugal http://www.oal.ul.pt/psa2006 High Precision Spectroscopy 2006 - LP

  42. Results of simulations (….) The full experiment DT=10 yrs 1500 Hours Metals V=16.5 Eff. 15% High Precision Spectroscopy 2006 - LP

  43. QSO absorption lines Quasar To Earth Lyaem SiII CIV Lyman limit Lya SiII CII SiIV Lyb Lybem NVem Lya forest CIVem SiIVem High Precision Spectroscopy 2006 - LP

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