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  - 
TY  - JOUR
A1  - Draganova, Nadya
A1  - Richter, Philipp
A1  - Fechner, Cora
T1  - High-resolution observations of two O VI absorbers at z approximate to 2 toward PKS 1448-232
JF  - Astronomy and astrophysics : an international weekly journal
N2  - To explore the ionization conditions in highly-ionized absorbers at high redshift, we study in detail two intervening O vi absorbers at z approximate to 2 toward the quasar PKS 1448-232, based on high (R approximate to 75 000) and intermediate (R approximate to 45 000) resolution optical VLT/UVES spectra. We find that both absorption systems are composed of several narrow subcomponents with typical Civ/O VI Doppler-parameters of b < 10 km s(-1). This implies that the gas temperatures are T < 10(5) K and that the absorbers are photoionized by the UV background. The system at z = 2.1098 represents a simple, isolated O VI absorber that has only two absorption components and is relatively metal-rich (Z similar to 0.6 solar). Ioinization modeling implies that the system is photoionized with O VI, C IV, and H I coexisting in the same gas phase. The second system at z = 2.1660 represents a complicated, multi-component absorption system with eight O VI components spanning almost 300 km s(-1) in radial velocity. The photoionization modeling implies that the metallicity is non-uniform and relatively low (<= 0.1 solar) and that the O VI absorption must arise in a gas phase that differs from that traced by C IV, C III, and H I. Our detailed study of the two O VI systems towards PKS 1448-232 shows that multi-phase, multi-component high-ion absorbers similar to the one at z = 2.1660 can be described by applying a detailed ionization modeling of the various subcomponents to obtain reliable measurements of the physical conditions and the metal abundances in the gas.
KW  - intergalactic medium
KW  - quasars: absorption lines
KW  - cosmology: observations
Y1  - 2012
U6  - https://doi.org/10.1051/0004-6361/201116730
SN  - 0004-6361
VL  - 538
IS  - 1
PB  - EDP Sciences
CY  - Les Ulis
ER  -