Volume 542, June 2012
|Number of page(s)||4|
|Published online||08 June 2012|
Deuterium at high redshift
Primordial abundance in the zabs = 2.621 damped Ly-α system towards CTQ 247⋆
CNRS-UPMC, UMR7095, Institut d’Astrophysique de Paris,
98bis bd Arago,
2 Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile
3 European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago 19, Chile
4 Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, 34131 Trieste, Italy
Received: 21 April 2012
Accepted: 17 May 2012
We report the detection of neutral deuterium in the low-metallicity damped Lyman-α system at zabs = 2.621 towards the quasar CTQ 247. Using a high signal-to-noise and high spectral resolution (R = 60 000) spectrum from the Very Large Telescope Ultraviolet and Visual Echelle Spectrograph, we precisely measure the deuterium-to-oxygen ratio log N(D i)/N(O i) = 0.74 ± 0.04, as well as the overall oxygen abundance, log N(O i)/N(H i) = −5.30 ± 0.10 (or equivalently [O/H] = −1.99 ± 0.10 with respect to the solar value). Assuming uniform metallicity throughout the system, our measurement translates into (D/H) = (2.8+0.8-0.6) × 10-5. This ratio is consistent within errors (<0.4σ) with the primordial ratio, (D/H)p = (2.59 ± 0.15) × 10-5, predicted by standard Big-Bang nucleosynthesis using the WMAP7 value of the cosmological density of baryons (100 Ωbh2 = 2.249 ± 0.056). The D i absorption lines are observed to be broader than the O i absorption lines. From a consistent fit of the profiles we derive the turbulent broadening to be 5.2 km s-1 and the temperature of the gas to be T = 8800 ± 1500 K, corresponding to a warm neutral medium.
Key words: cosmology: observations / primordial nucleosynthesis / quasars: absorption lines / ISM: abundances / quasars: individual: J 040718 / 441014
© ESO, 2012
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