HD molecular lines in an absorption system at redshift z=2.3377

Having analyzed the spectrum of the quasar PKS 1232+0.82 taken by Petitjean et al. (2000), we identified HD molecular lines in an absorption system at redshift z=2.3377. We estimated the column density of HD molecules in this system, N(HD) = (1−4) × 1014cm−2. The excitation temperature of the first rotational level J=1 relative to the ground state J=0 is Tex=70 ± 7 K. As far as we know, this is the first detection of HD molecules at high redshift.