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Register a new userThe D/H ratio at z = 3.57 toward Q 1937-1009
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Deuterium abundance re-measurements by Burles and Tytler (1998; hereafter BT) yielded D/H = (3.3 +/- 0.3) 10^{-5} and the robust upper limit D/H < 3.9 10^{-5} from the z_a = 3.572 system toward Q1937-1009. In this new analysis BT adopted multicomponent microturbulent models together with the possibility to vary freely the local continuum level around each HI line to improve the fit. The procedure failed, however, to fit adequately D Ly-beta without recourse to an additional H Ly-alpha contamination at the position of D Ly-beta. We show that this obstacle may be successfully overcome within the framework of the mesoturbulent model accounting (in contrast to the microturbulent approximation) for a correlated structure of the large scale velocity field. Using the same observational data and the original continuum as determined by Tytler et al. (1996), we obtained good fits. The one-component mesoturbulent models provide D/H in the range (3.2 - 4.8) 10^{-5} and the total hydrogen column density N(HI) = (5.6 - 7.0) 10^{17} cm^{-2}. This result is consistent with that found by us from the z_a = 2.504 and z_a = 0.701 systems toward Q1009+2956 and Q1718+4807, respectively. The range for D/H common to all three analyses is D/H = (4.1 - 4.6) 10^{-5}. This value is consistent with standard big bang nucleosynthesis [SBBN] if the baryon-to-photon ratio, eta, is in the range 4.2 10^{-10} <= eta <= 4.6 10^{-10}, implying 0.0155 <= Omega_b h^2_{100} <= 0.0167.
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The apparent discrepancy between low and high D abundances derived from QSO spectra may be caused by spatial correlations in the stochastic velocity field. If one accounts for such correlations, one finds good agreement between different observations and the theoretical predictions for standard big bang nucleosynthesis (SBBN). In particular, we show that the H+D Ly-alpha profile observed at z = 0.7 toward Q1718+4807 is compatible with 4.1*10^{-5} <= D/H <= 4.7*10^{-5}. This result is consistent with our previous D/H determination for the z = 2.504 system toward Q1009+2956 and, thus, supports SBBN.
We have identified a new Lyman limit absorption system towards PKS1937-1009, with log N(HI)=18.25 +/- 0.02 at z=3.256. It is suitable for measuring D/H, and we find a 68.3% confidence range for D/H of 1.6^{+0.25}_{-0.30} times 10^{-5}, and a 95.4% range of 1.6^{+0.5}_{-0.4} times 10^{-5}. The metallicity of the cloud where D/H was measured is low, [Si/H] = -2.0 +/- 0.5. At these metallicities we expect that D/H will be close to the primordial value. Our D/H disagrees at a level of 99.4% with the predicted D/H using the baryon density calculated from the cosmic background radiation measured by WMAP, 2.60^{+0.19}_{-0.17} times 10^{-5}. Our result also exacerbates the scatter in D/H values around the mean primordial D/H.
We report on the detection of a z_gal=0.101 galaxy projected on the sky at 4.2 arcsec (or 5.2 h^{-1} kpc for q_o=0.5) from the quasar Q 0439-433 (z_em=0.594). The HST spectrum of the quasar shows strong MgII, FeII, SiII, AlII and CIV absorption lines at the same redshift as the galaxy. The equivalent width ratios of the low ionization lines indicate that this system is probably damped with a neutral hydrogen column density of N_HI~10^{20}cm^{-2}. The CIV doublet presents a complex structure, and in particular a satellite with a velocity v=1100km/s relative to the galaxy. Additional HST and redshifted 21cm observations of this QSO-galaxy pair would offer an ideal opportunity to study the morphology of a damped absorber and the kinematics of the halo of a low-redshift galaxy.
The ratio of deuterium to hydrogen (D/H ratio) of Solar System bodies is an important clue to their formation histories. Here we fit a Neptunian atmospheric model to Gemini Near Infrared Spectrograph (GNIRS) high spectral resolution observations and determine the D/H ratio in methane absorption in the infrared H-band ($sim$ 1.6 {mu}m). The model was derived using our radiative transfer software VSTAR (Versatile Software for the Transfer of Atmospheric Radiation) and atmospheric fitting software ATMOF (ATMOspheric Fitting). The methane line list used for this work has only become available in the last few years, enabling a refinement of earlier estimates. We identify a bright region on the planetary disc and find it to correspond to an optically thick lower cloud. Our preliminary determination of CH$_{rm 3}$D/CH$_{rm 4}$ is 3.0$times10^{-4}$, which is in line with the recent determination of Irwin et al. (2014) of 3.0$^{+1.0}_{-0.9}simtimes10^{-4}$, made using the same model parameters and line list but different observational data. This supports evidence that the proto-solar ice D/H ratio of Neptune is much less than that of the comets, and suggests Neptune formed inside its present orbit.
We report the first extragalactic detection of chloronium (H2Cl+), in the z=0.89 absorber in front of the lensed blazar PKS1830-211. The ion is detected through its 1_11-0_00 line along two independent lines of sight toward the North-East and South-West images of the blazar. The relative abundance of H2Cl+ is significantly higher (by a factor ~7) in the NE line of sight, which has a lower H2/H fraction, indicating that H2Cl+ preferably traces the diffuse gas component. From the ratio of the H2^35Cl+ and H2^37Cl+ absorptions toward the SW image, we measure a 35Cl/37Cl isotopic ratio of 3.1 (-0.2; +0.3) at z=0.89, similar to that observed in the Galaxy and the solar system.
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