Looking for trees in the forest Diavolezza meeting feb 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 -> H 2

Empirical search for a change in  Compare H 2 spectra of different epochs: Compare H 2 spectra of different epochs: QSO 12 Gyr ago Lab today nm ~ nm

Empirical search for a change in 

 /  and spectrum H 2 Recent finding, based on 76 lines in 2 QSO absorbers: Recent finding, 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

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

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

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

H2H2 Ly  QSO 2: J2123

Parameters describing 1 absorption line 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, 

HD Observation Only J=0 lines Only J=0 linesInterpretation T<50 K (H 2 : ~120 K) Information about physical conditions 2 nd detection at high z (Varshalovich 2001, 4 lines)

HD Observation Only J=0 lines Only J=0 lines N(HD)/N(H 2 )~10 -3 N(HD)/N(H 2 )~10 -3Interpretation T<50 K (H 2 : ~120 K) Enhanced HD formation Connection to primordial D/H? Include in  analysis, together with H 2 lines Information about physical conditions 2 nd detection at high z (Varshalovich 2001, 4 lines) H2H2 HD

Conclusions QSO H 2 spectra for  /  determination QSO H 2 spectra for  /  determination –Q0347: 37 lines –Q0405: 39 lines –Q2348: ~20 lines –J2123: >50 lines HD absorption in J2123 HD absorption in J2123 –Include in  /  analysis –Insight in physical conditions Working on analysis

Outlook Observation J2123 with VLT next semester Observation J2123 with VLT next semester –4 +16 hrs –Best object (bright, many H 2 lines, HD) for  analysis –Highest quality spectrum

Aug. ’07 observations: The Instrument

UVES: Ultraviolet – Visual Echelle Spectrograph

nm nm

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