The detection of neutral deuterium in the low-metallicity damped Lyman- \alpha system at z _ { abs } = 2.621 towards the quasar CTQ 247 is reported .
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 \textsc { i } } ) / N ( { O \textsc { i } } ) = 0.74 \pm 0.04 , as well as the overall oxygen abundance , \log N ( { O \textsc { i } } ) / N ( { H \textsc { i } } ) = -5.29 \pm 0.10 ( or equivalently [ O/H ] = -1.99 \pm 0.10 with respect to the solar value ) .
Assuming uniform metallicity throughout the system , our measurement translates to ( D/H ) = ( 2.8 ^ { +0.8 } _ { -0.6 } ) \times 10 ^ { -5 } .
This ratio is consistent within errors ( < 0.4 \sigma ) with the primordial ratio , ( D/H ) _ { p } = ( 2.59 \pm 0.15 ) \times 10 ^ { -5 } , predicted by standard Big-Bang Nucleosynthesis using the WMAP7 value of the cosmological density of baryons ( 100 \Omega _ { b } h ^ { 2 } = 2.249 \pm 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 \pm 1500 K , corresponding to a warm neutral medium .