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Constraints on variations of fundamental constants from QSO Absorption lines

Constraints on variations of fundamental constants from QSO Absorption lines. Measuring wavelengths of radiative transitions. -> α : fine structure constant : Multi-Multiplet Method Patrick Petitjean and R. Srianand Institut d’Astrophysique de Paris IUCAA (India).

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Constraints on variations of fundamental constants from QSO Absorption lines

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  1. Constraints on variations of fundamental constants from QSO Absorption lines Measuring wavelengths of radiative transitions -> α : fine structure constant : Multi-Multiplet Method Patrick Petitjean and R. Srianand Institut d’Astrophysique de Paris IUCAA (India) Hum Chand (ARIES, India) P. Noterdaeme (IAP) C. Ledoux (ESO) N. Gupta (ATNF, Australia) A. Ivanchik (Ioffe Institute, Russia)

  2. Ly-b Ly-a C IV Metals H2

  3. SiII MgII FeII

  4. Take all the systems; fit them and look for a statistical detection Is this reasonable ?

  5. Reality -> Shift is very small in individual systems -> Fit is not unique: * Saturation of the absorptions * Number of components -> Echelle spectroscopy : * Different arms/CCD * Wavelength calibration -> Different species -> Systematics : * Ambiant temperate * Atmospheric refraction * Isotopes

  6. Need to know the position of each line -> Shifts shown for 10-4 ; current precision : 10-5 -> max: q~1000 (cm-1) 1/λ=1/λ0+2000δα/α~20 mA observed or 1/3 of a pixel for δα/α=10-5 0.5 km/s

  7. Reality -> Shift is very small in individual systems -> Fit is not unique: * Saturation of the absorptions * Number of components – complex profile -> Echelle spectroscopy : * Different arms/CCD * Wavelength calibration -> Different species -> Systematics : * Ambiant temperate * Atmospheric refraction * Isotopes

  8. Fit with several lines of same species Degeneracies even in case of moderate saturation Need very high signal-to-noise ratio: one night of VLT for 1 spectrum

  9. Decomposition from FeII2374; what happens for MgII ?

  10. Reality -> Shift is very small in individual systems -> Fit is not unique: * Saturation of the absorptions * Number of components – complex profile -> Echelle spectroscopy : * Different arms/CCD * Wavelength calibration -> Different species -> Systematics : * Ambiant temperate * Atmospheric refraction * Isotopes

  11. Ly-b Ly-a C IV Metals Blue Arm Red Arm

  12. Wavelength calibration Observational series: Lamp-science-Lamp-science etc… 10 s 1 hour 10 s Lack of calibration lines or blended lines => Only local problems

  13. Comparison VLT-UVES – 3.6m-HARPS Simulation of alpha variation from the Lamp Harps: Stable fiber instrument Controled temperature Acceptable at the moment except for local possible problems -> Harps much better

  14. Reality -> Shift is very small in individual systems -> Fit is not unique: * Saturation of the absorptions * Number of components – complex profile -> Echelle spectroscopy : * Different arms/CCD * Wavelength calibration -> Different species -> Other systematics : * Ambiant temperate * Atmospheric refraction * Isotopes

  15. Species should have the same profile : Depletion onto dust grains ? Ionization effets ? -> could vary component to component

  16. Use same species : HE0515-4414 : Very bright=high SNR and resolution; large number of FeII lines BUT highly blended (-0.01±0.08) x 10-5 (Levshakov et al. 2006, A&A 449, 879)

  17. Reality -> Shift is very small in individual systems -> Fit is not unique: * Saturation of the absorptions * Number of components – complex profile -> Echelle spectroscopy : * Different arms/CCD * Wavelength calibration -> Different species -> Other systematics : * Ambiant temperate * Atmospheric refraction * Isotopes

  18. Ambiant temperature : 10oC => 43 mA between 4000 and 7000A => Control of T Atmospheric refraction + seeing Isotopic composition Slit parallel to the parallactic angle Negligible effect

  19. Summary • Can avoid : Refraction problems • Can control : Wavelength calibration - Temperature • Should avoid : Saturation and strong blending • => Selection of systems • Cannot avoid : Isotopes • -> Most of effects are statistically negligible or controled but could be important locally

  20. Srianand et al.; Chand et al. 2004

  21. SNR=30-70 -> Errors / 2 Avoid weak FeII lines

  22. 40 nights on VLT-UVES : Best data ever obtained on QSOAL

  23. Levshakov et al. 2007: Drift of 180+-85 m/s between FeII lines observed in the two arms of UVES. Molaro et al. (2008, AetA, 481, 559) checked for velocity accuracy from asteroid observations < 50 m/s.

  24. Using only one species : FeII Levshakov et al. (2006, AetA, 449, 879) : same quasar (-0.007±0.084)x10-5

  25. Recent criticisms by Murphy et al.

  26. Errors larger We agree that we disagree at the 3σ level

  27. Conclusion Variation of α : Two measurements discrepent at the 3σ level Independent analysis of high SNR UVES+?? data Variation of μ : Agreementdμ/μ< a few x10-6 Increase number of H2 systems Variation of x : dx/x<3x10-6 Increase number of 21cm systems but also other molecules (OH, NH3 etc…) Stable instrument on big telescopes -> Espresso and Codex projects ANR in France : Not a priority …

  28. What theorists should not forget A robust result may be interesting as soon as it is > 5σ Everything below 5σ is a limit Everything above 5σ must be confirmed Be patient : If anything varies today it will vary tomorrow… We agree that nothing varies at the level of 10-5 We are getting at 10-6

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