1 / 31

Concept study for the CO smical D ynamics EX periment

Concept study for the CO smical D ynamics EX periment. The Team. ESO: G. Avila, B. Delabre, H. Dekker, S. D’Odorico, J. Liske, L. Pasquini, P. Shaver Observatoire Geneve : Dessauges-Zavadsky, M. Fleury, C. Lovis, M. Mayor, F. Pepe, D. Queloz, S. Udry INAF-Trieste:

trygg
Download Presentation

Concept study for the CO smical D ynamics EX periment

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Concept study for the COsmical Dynamics EXperiment

  2. The Team ESO: G. Avila, B. Delabre, H. Dekker, S. D’Odorico, J. Liske, L. Pasquini, P. Shaver Observatoire Geneve : 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 OTHERS: F. Bouchy (Marseille), S. Borgani (Daut-Ts), A. Grazian (Roma), S. Levshakov (St-Petersburg), L. Moscardini (OABo-INAF), S. Zucker(Tel Aviv), T. Wilklind (ESA)

  3. The experiment Directly measure the expansion of the Universe ”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” Sandage 1962 ApJ 136,319

  4. Some history Since the discovery of Hubble in the late 20’ of the expansion of the universe, this became one of the pillars of “Big Bang” cosmology (together with CMB, Primordial Nucleosynthesis) Although not all believe to this ‘Big Bang’ .. a large consensus exists among cosmologists, who have produced a ‘standard model’

  5. Standard Model With the assumptions of homogeneity and isotropy, the concordance model finds a FRW metric with a non zero cosmological constant

  6. Why measure dynamics? All the results so far obtained in the ‘concordance model’ assumes that GR in the FRW formulation is the correct theory. 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 and WMAP measure geometry: dimming of magnitudes and scattering at the recombination surface.

  7. Cosmic Signal te=emission epoch t0=actual epoch

  8. The Signal Is SMALL! The change in sign is the signature of the non zero cosmological constant

  9. 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 like to 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 !

  10. QSO absorption lines Quasar To Earth Lyaem SiII CIV Lyman limit Lya SiII CII SiIV Lyb Lybem NVem Lya forest CIVem SiIVem

  11. A LARGE signal .. But this is for 107 years… Having much less time at our disposal the shift is much smaller.. Why can we conceive to detect It NOW?

  12. What’s new • VLT-UVES & Keck HIRES observed hundreds of QSOs at High Res ( 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!!)

  13. The HARPS Experience Th-Th < 10 cm/sec O-C < 80 cm/sec

  14. BASIC SPECTROGRAPH REQUIREMENTS Once QSOs are established targets, through basic knowledge and simulations it is possible to find 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…

  15. Simulation Results 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 several scaling laws:  = 13600/(S/N) cm/sec (0.015 A/pix, Z=4)  ~ (N(QSO))-0.5  ~ (S/N)-1(1+Z)-1.8

  16. Simulation Results Simulating the dependence on Z Information “saturates”: a) Too many lines b) High Redshift makes them broader.

  17. Simulating the full experiment (M. Haenhelt, IoA,C) DT=10 yrs 1500 Hours Metals V=16.5 Eff. 15%

  18. Another Full simulation (J. Liske, ESO) NQSO = 100 randomly distributed in the range 2 < zQSO < 5 S/N = 1250 per 0.015 Å pixel t = 20 years M = 0.07 reject no-shift model at high significance

  19. Can we do it ? Red line:UVES+VLT Measured efficiency V=16.5 QSO 36 QSO each S/N 2000 (0.015 pixel), obtained in 2000 observing hours

  20. Verification of targets and reference mission QSO have been selected from existing catalogues and compilations (Veron SDSS ) Selection criteria: Magnitudes: redwards of Lya Figure:only the 5 brightest QSOs of each 0.25 Z bin. Hypothesis as in the previous Viewgraph (2000 h obs)

  21. CODEX basic parameters Seeing Limited Instrument Modular Concept (Presently 5 clones) Telescope diameter 60 m (100m); 1 arcsec = 0.58 mm (1.1) F/2 Feed Fibre (single or multiple) Entrance aperture 1 arcsec (0.6 arcsec for a 100 m.) Wavelength range (400) 450 – 650 nm Spectral Resolution 110 ~ 140 000 (depends on feed chosen) Main disperser 5 x R4 echelle 42 l/mm 160 x 20 cm Crossdisperser 10 x VPHG 1000 l/mm 20 x 10 cm Camera 10 x F/1.4-2.8 CCD 10 x ~6K x 6K (15 um pixels) 360 Mpix or 810 cm2

  22. How to improve RV accuracy and stability • Scramblers to reduce effect of guiding errors • Image dissector, multiple instruments • Simultaneous wavelength calibration • Use of wavelength calibration “laser comb” • Fully passive instrument, ultra-high temperature stability • Instrument in vacuum tank • High precision control of detector temperature • Underground facility, zero human access

  23. Delabre+ Dekker, ESO CODEX Unit Spectrograph Crossdisperser section #1 Transfer Collimator Camera VPHG 10 x 10 cm To Crossdisperser section #2 Strip mirror TMA Collimator Light from slicer enters here Main Disperser section Echelle mosaic 22 x 170 cm Only one crossdisperser section is shown. Overall optics volume: ~ 3 m x 1 m x 1.5 m

  24. 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

  25. Example of an instrument tank: HARPS

  26. CODEX @ OWL CODEX Lab

  27. Direct measurement • Bias-free determination of cosmological parameters • Different redshift (CMB, SNIa) • Not dependent from evolutionary effects of sources • Legacy Mission to future astronomers (First epoch measurements)

  28. 3 outstanding projects were selected:-Cosmological variation of the Fine-Structure Constant: CODEX will exceed the accuracy of the OKLO reactor (D/ ~ 10-8) -Terrestrial planets in extra-solar systems: Radial velocity of earth mass planets, spectroscopy of planets in transit .. Immediate science -Primordial nucleosynthesis: probing SBB nucleosynthesis: primordial D/H, Li7 , Li6/Li7 Others: The CMBT, the Thermal history , metals in the IGM, nucleochronology

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

  30. Comb/CODEX simulation R=100k, Dn=15GHz, l=5000Å Total velocity precision better than 1cms-1 in a single shot for SNR ~ 1000 (4500-6500Å)

More Related