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A new result on space-time variation of α – part B

A new result on space-time variation of α – part B. Julian King (UNSW) Collaborators : John Webb (UNSW), Victor Flambaum (UNSW) Michael Murphy (Swinburne) Bob Carswell (IOA Cambridge ) …and others. The previous status of α. Δα / α (10 -5 ).

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A new result on space-time variation of α – part B

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  1. A new result on space-time variation of α – part B • Julian King (UNSW) • Collaborators: John Webb (UNSW), Victor Flambaum (UNSW) • Michael Murphy (Swinburne) • Bob Carswell (IOA Cambridge) • …and others

  2. The previous status of α Δα/α (10-5) • Current largest sample of quasar absorber constraints on Δα/α come from Murphy et al (2004) from Keck/HIRES • Found that Δα/α = ( -0.57 ± 0.11 ) x 10-5 • Effect larger at z>1 ?? • Obvious question: what would a different telescope find? 

  3. The VLT sample • The goal: • To use archive spectra from UVES (Ultraviolet and Visual Echelle Spectrograph) on the VLT in Chile to try to confirm (or dispute) the Keck results • The method: • In the same manner as the previous Keck results, we fit Voigt profiles to the quasar profiles and determine Δα/α • We derive a sample of 153 final quasar absorbers = 153 x Δα/α • We have verified that our uncertainties are correct using Markov Chain Monte Carlo methods • Other improvements in technique (Levenberg-Marquardt algorithm, determining number of components using Akaike Information Criterion, robust statistical methods) 

  4. Δα/α vs redshift – VLT sample Error bars increased by  0.9 x 10-5 Weighted mean: Δα/α = (0.23 ± 0.12) x 10-5 (after increasing error bars to account for χ2ν=1.78) compare with Murphy et al (2004): Δα/α = (-0.57 ± 0.11) x 10-5 

  5. Δα/α vs redshift – comparison with Keck VLT + Keck Keck VLT 

  6. VLT – Correlation with declination? 2.1σ correlation Declination is equivalent to latitude 

  7. Correlation with declination after adding in Keck data VLT Keck 

  8. Δα/α data for different sightlines

  9. 4.1σ evidence for a Δα/α dipole from VLT + Keck Δα/α = c + A cos(θ) 

  10. The Keck & VLT dipoles point in the same direction 20 degrees p = 0.05 VLT Keck Combined 

  11. Low and high redshift cuts are consistent in direction... ...but the effect is larger at high redshift... z > 1.6 z < 1.6 Combined 

  12. ...so add in a simple time relationship Δα/α = c + A t cos(θ) 4.1σ evidence 

  13. What next? • Although the results appear consistent, important to look for systematics (next talk!) • And of course... More observations! 

  14. Could increase signal through high-declination observations

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