Looking for trees in the forest LION, BM Seminar 5 June 2008 Ruth Buning (LCVU, Amsterdam) Wim Ubachs (LCVU, Amsterdam) Michael Murphy (Swinburne University, Melbourne) Lex Kaper (UvA, Amsterdam) Search for a variation of the proton-electron mass ratio on a cosmological timescale

Constants of nature Why these numerical values? Why these numerical values? Really constant? Really constant? Physical Review 82 (1951) 554

The proton-electron mass ratio (Rigid rotor) (Harmonic oscillator) Molecular spectra, i.e. H 2, NH 3

Compare spectra over Δt Compare spectra over Δt –Astronomical data:Δt~Gyr accuracy ~10 -7 –Lab: Δt~yr accuracy → Empirical search for a change in  QSO 12 Gyr ago Lab today nm ~ nm H2H2

Empirical search for a change in 

 /  and spectrum H 2 Previous result, based on 76 lines in 2 QSO absorbers: Previous result, based on 76 lines in 2 QSO absorbers: Accurately calculated Lab: 5 x QSO: (2-10) x σ4σ Decrease of 0.002% over the past 12 billion years PRL 96, (2006)

The QSO absorption sample >2300 HI absorption systems >2300 HI absorption systems ~600 DLA’s ~600 DLA’s 14 H 2 absorption systems 14 H 2 absorption systems 6 useful 6 useful 4 high-quality spectra 4 high-quality spectra Q0405: 37 lines at z abs =2.59 Q0405: 37 lines at z abs =2.59 Q0347: 39 lines at z abs =3.02 Q0347: 39 lines at z abs =3.02 Q2348: ~20 lines at z abs =2.43 observed aug. 07, VLT Q2348: ~20 lines at z abs =2.43 observed aug. 07, VLT J2123: ~50 lines at z abs =2.06 from Prochaska, Keck J2123: ~50 lines at z abs =2.06 from Prochaska, Keck

VLT

Blue CCD chip Red CCD chip 1Red CCD chip 2 Lyman-  of quasar emission z emis = C IV emission DLA at z abs =2.615 H 2 region z abs =2.426 DLA at z abs =2.93 DLA at z abs =2.426 QSO 1: Q2348 (VLT) Wavelength (A)

H 2 region Resolution 103,000 ; z abs = QSO 2: J2123 (Prochaska, Keck telescope) Normalized flux

H2H2 Ly  QSO 2: J2123

Results QSO H 2 spectra for  /  determination QSO H 2 spectra for  /  determination –Q0405: 39 lines –Q0347: 37 lines –Q2348: ~20 lines –J2123: >50 lines ? ?

Conclusions 2 → 4 objects 2 → 4 objects New result agrees on  New result agrees on  No consensus on systematics No consensus on systematics HD detection HD detection Outlook: Observation J2123 with VLT next semester Outlook: Observation J2123 with VLT next semester –4 +16 hrs –Best object (bright, many H 2 lines, HD) for  analysis –Highest quality spectrum

UVES: Ultraviolet – Visual Echelle Spectrograph

nm nm

slitview

CCD chip

CCD chip: ThAr calibration

Blue CCD chip Red CCD chip 1Red CCD chip 2 Lyman-  of quasar emission z emis = C IV emission DLA at z abs =2.615 H 2 region z abs =2.426 DLA at z abs =2.93 DLA at z abs =2.426 QSO 1: Q2348 (VLT) Wavelength (A)

Spectrum Q2348 DLA at z abs =2.615 DLA at z abs =2.426 H 2 region Ly  at z abs =2.615 Lyman limit  at z abs =2.93 QSO 1: Q2348 (VLT)

L0R0 line of H 2 > 7 velocity components QSO 1: Q2348 Normalized flux

Parameters describing 1 absorption line Voigt profile Voigt profile 3 free (‘cloud’) parameters: 3 free (‘cloud’) parameters: –b,z,N molecular data: molecular data: –lab wavelengths –oscillator strengths –damping coefficients b (km/s) (1+z) rest N (molecules /cm 2 ) LCVU/Orsay, Meudon

Parameters describing multiple absorption lines From the same ground state (J=0, J=1, etc.) From the same ground state (J=0, J=1, etc.) From different ground states From different ground states Extra fit parameter:  Extra fit parameter:  z b b N z b b N1N1 N2N2 z, 

Seeing

H Lyman series

Energy levels in a diatomic molecule Electronic Electronic Vibrationalv Vibrationalv RotationalJ RotationalJ