2012A&A...542L..33N

We report the detection of neutral deuterium in the low-metallicity damped Lyman-α system at z_abs=2.621 towards the quasar CTQ247. Using a high signal-to-noise and high spectral resolution (R = 60000) spectrum from the Very Large Telescope Ultraviolet and Visual Echelle Spectrograph, we precisely measure the deuterium-to-oxygen ratio logN(DI)/N(OI)=0.74±0.04, as well as the overall oxygen abundance, logN(OI)/N(HI)=-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)x10^–5. This ratio is consistent within errors (<0.4σ) with the primordial ratio, (D/H)_p=(2.59±0.15)x10^–5, predicted by standard Big-Bang nucleosynthesis using the WMAP7 value of the cosmological density of baryons (100Ω_bh²=2.249±0.056). The DI absorption lines are observed to be broader than the OI absorption lines. From a consistent fit of the profiles we derive the turbulent broadening to be 5.2km/s and the temperature of the gas to be T=8800±1500K, corresponding to a warm neutral medium.