TY  - JOUR
A1  - Wendt, Martin
T1  - Constraints on variations of m(p)/m(e) based on UVES observations of H-2
JF  - Astronomische Nachrichten = Astronomical notes
N2  - This article summarizes the latest results on the proton-to-electron mass ratio derived from H-2 observations at high redshift in the light of possible variations of fundamental physical constants. The focus lies on UVES observations of the past years as enormous progress was achieved since the first positive results on / were published. With the better understanding of systematics, dedicated observation runs, and numerous approaches to improve wavelength calibration accuracy, all current findings are in reasonable good agreement with no variation and provide an upper limit of / < 1 x 10(-5) for the redshift range of 2 < z < 3. ((
KW  - cosmology: observations
KW  - early Universe
KW  - quasars: absorption lines
Y1  - 2014
U6  - https://doi.org/10.1002/asna.201312008
SN  - 0004-6337
SN  - 1521-3994
VL  - 335
IS  - 1
SP  - 106
EP  - 112
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Wendt, Martin
A1  - Molaro, P.
T1  - QSO 0347-383 and the invariance of m(p)/m(e) in the course of cosmic time
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Context. The variation of the dimensionless fundamental physical constant mu = m(p)/m(e) - the proton to electron mass ratio - can be constrained via observation of Lyman and Werner lines of molecular hydrogen in the spectra of damped Lyman alpha systems (DLAs) in the line of sight to distant QSOs.
 Aims. Our intention is to maximize the possible precision of quasar absorption spectroscopy with regard to the investigation of the variation of the proton-to-electron mass-ratio mu. The demand for precision requires an understanding of the errors involved and effective techniques to handle present systematic errors.
 Methods. An analysis based on UVES high resolution data sets of QSO 0347-383 and its DLA is put forward and new approaches to some of the steps involved in the data analysis are introduced. We apply corrections for the observed offsets between discrete spectra and for the first time we find indications for inter-order distortions.
 Results. Drawing on VLT-UVES observations of QSO 0347-383 in 2009 our analysis yields Delta mu/mu = (4.3 +/- 7.2) x 10(-6) at z(abs) = 3.025.
 Conclusions. Current analyzes tend to underestimate the impact of systematic errors. Based on the scatter of the measured redshifts and the corresponding low significance of the redshift-sensitivity correlation we estimate the limit of accuracy of line position measurements to similar to 220 m s (1), consisting of roughly 150 m s (1) due to the uncertainty of the absorption line fit and about 150 m s (1) allocated to systematics related to instrumentation and calibration.
KW  - cosmology: observations
KW  - quasars: absorption lines
KW  - quasars: individual: QSO 0347-383
KW  - early Universe
Y1  - 2012
U6  - https://doi.org/10.1051/0004-6361/201218862
SN  - 0004-6361
VL  - 541
IS  - 3
PB  - EDP Sciences
CY  - Les Ulis
ER  -