arXiv subjects

A. Ivanchik

Publications and source records attributed to A. Ivanchik.

5 recordsLinked to original sources

arXiv2008

HD molecules at high redshift: A low astration factor of deuterium in a solar-metallicity DLA system at z=2.418

We present the detection of deuterated molecular hydrogen (HD) in the remote Universe in a damped Lyman-alpha cloud at zabs=2.418 toward the quasar SDSS J143912.04+111740.5. This is a unique system in which H2 and CO molecules are also detected. The chemical enrichment of this gas derived from ZnII and SII is as high as in the Sun. We measure N(HD)/2 N(H2)=1.5+0.6-0.4 x 10^-5, which is significantly higher than the same ratio measured in the Galaxy and close to the primordial D/H ratio estimated from the WMAP constraint on the baryonic matter density Omega_b. This indicates a low astration factor of deuterium that contrasts with the unusually high chemical enrichment of the gas. This can be interpreted as the consequence of an intense infall of primordial gas onto the associated galaxy. Detection of HD molecules at high-z also opens the possibility to obtain an independent constraint on the cosmological-time variability of mu, the proton-to-electron mass ratio.

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arXiv2005

A new constraint on the time dependence of the proton-to-electron mass ratio. Analysis of the Q 0347-383 and Q 0405-443 spectra

A new limit on the possible cosmological variation of the proton-to-electron mass ratio μ=m_p/m_e is estimated by measuring wavelengths of H_2 lines of Lyman and Werner bands from two absorption systems at z_abs = 2.5947 and 3.0249 in the spectra of quasars Q 0405-443 and Q 0347-383, respectively. Data are of the highest spectral resolution (R = 53000) and S/N ratio (30\div70) for this kind of study. We search for any correlation between z_i, the redshift of observed lines, determined using laboratory wavelengths as references, and K_i, the sensitivity coefficient of the lines to a change of μ, that could be interpreted as a variation of μover the corresponding cosmological time. We use two sets of laboratory wavelengths, the first one, Set (A) (Abgrall et al.), based on experimental determination of energy levels and the second one, Set (P) (Philip et al.), based on new laboratory measurements of some individual rest-wavelengths. We find Δμ/μ= (3.05+-0.75)10^-5 for Set (A), and Δμ/μ= (1.65+-0.74)10^-5 for Set (P). The second determination is the most stringent limit on the variation of μover the last 12 Gyrs ever obtained. The correlation found using Set (A) seems to show that some amount of systematic error is hidden in the determination of energy levels of the H$_2$ molecule.

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arXiv2002

Does the proton-to-electron mass ratio vary in the course of cosmological evolution?

The possible cosmological variation of the proton-to-electron mass ratio was estimated by measuring the H_2 wavelengths in the high-resolution spectrum of the quasar Q~0347-382. Our analysis yielded an estimate for the possible deviation of μvalue in the past, 10 Gyr ago: for the unweighted value $Δμ/ μ= (3.0\pm2.4)\times10^{-5}$; for the weighted value \[ Δμ/ μ= (5.02\pm1.82)\times10^{-5}\] Since the significance of the both results does not exceed 3$σ$, further observations are needed to increase the statistical significance. In any case, this result may be considered as the most stringent estimate on an upper limit of a possible variation of μ(95% C.L.): \[ |Δμ/ μ| < 8\times 10^{-5} \] This value serves as an effective tool for selection of models determining a relation between possible cosmological deviations of the fine-structure constant αand the elementary particle masses (m$_p$, m$_e$, etc.).

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arXiv2002

Do the Fundamental Constants Vary in the Course of the Cosmological Evolution?

We estimate the cosmological variation of the proton-to-electron mass ratio μ=m_p/m_e by measuring the wavelengths of molecular hydrogen transitions in the early universe. The analysis is performed using high spectral resolution observations (FWHM ~ 7 km/s) of two damped Lyman-αsystems at z_{abs}=2.3377 and 3.0249 observed along the lines of sight to the quasars Q 1232+082 and Q 0347-382 respectively. The most conservative result of the analysis is a possible variation of μover the last ~ 10 Gyrs, with an amplitude Δμ/μ= (5.7+-3.8)x10^{-5}. The result is significant at the 1.5σlevel only and should be confirmed by further observations. This is the most stringent estimate of a possible cosmological variation of μobtained up to now.

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arXiv2001

HD Molecular Lines in an Absorption System at Redshift z = 2.3377

We have analyzed the spectrum of the quasar PKS 1232+082 obtained by Petitjean et al. (2000). HD molecular lines are identified in an absorption system at the redshift z=2.3377. The column density of HD molecules in the system is estimated, N(HD)=(1-4)x10^{14} cm^{-2}. The temperature of excitation of the first rotational level J=1 relative to the ground state J=0 is T_ex=70+-7 K. This is, to our knowledge, the first detection of HD molecules at high redshift.

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