  We obtained a high-resolution VLT-UVES spectrum of the quasar Q2348-011 over
a wavelength range that covers most of the prominent metal and molecular
absorption lines from the log N(HI)=20.50+-0.10 damped Lyman-alpha system at
zabs=2.43. From the column density ratios and the relative populations of H2
rotational and CI fine-structure levels, we derive the physical conditions
(relative abundances, dust-depletion, particle density, kinetic temperature and
ionizing flux) and discuss physical conditions in the neutral phase. Molecular
hydrogen is detected in seven components in the first four rotational levels (J
= 0-3) of the vibrational ground state. Absorption lines of H2 J = 4 (resp. J =
5) are also detected in six (resp. two) of these components. This leads to a
total molecular fraction of log f = -1.69+0.37-0.58. We confirm the earlier
findings that there is a correlation between N(FeII)/N(SII) and N(SiII)/N(SII)
indicative of a dust-depletion pattern. Surprisingly, however, the depletion of
metals onto dust in the H2 components is not large in this system: [Fe/S] =
-0.8 to -0.1. The gas in H2-bearing components is found to be cold but still
hotter than similar gas in our Galaxy (T > 130 K, instead of typically 80 K).
and dense (n=100-200 cm^-3). There is an anti-correlation between the logarithm
of the photo-absorption rate, and log N(H2)/N(CI) derived for each H2
component. We show that this is mostly due to shielding effects and implies
that the photo- absorption rate is a good indicator of the physical conditions
in the gas. We find that the gas is immersed in a intense UV field, about one
order of magnitude higher than in the solar vicinity. The results suggest that
the gas in H2-bearing DLAs is clumpy, and star-formation occurs in the
associated object.
