THE HEAVY ELEMENT ABUNDANCE IN THE Z=2.076 ABSORPTION SYSTEM TOWARDS THE QSO 2206-199N

The damped Ly α absorption system at z = 2.07625 in the line-of-sight to the zem = 2.55 quasar 2206-199N shows weak heavy-element absorption lines. Highresolution spectra covering lines of H I, C II, C IV, O I, Si II and Si IV reveal that there is a single velocity component with a Doppler parameter b = √2σ∼11 km s-1 for the neutral and singly ionized species, and perhaps a larger value ∼ 19 km s-1 for C IB. The heavy element abundances are very low compared with solar, at [Si/H] ≤ - 2.4, and a best estimate, based on a photo-ionization model, of [Si/H]∼-2.8. The C/Si and O/Si ratios are close to the solar values. In the probable absence of significant dust depletion, the z = 2.07625 system may provide an example of absorption by gas in a chemically young galaxy. © Royal Astronomical Society.