  By combining our UVES-VLT spectra of a sample of four damped Ly-alpha systems
(DLAs) toward the quasars Q0100+13, Q1331+17, Q2231-00 and Q2343+12 with the
existing HIRES-Keck spectra, we covered the total spectral range from 3150 to
10000 A for the four quasars. This large wavelength coverage and the high
quality of the spectra allowed us to measure the column densities of up to 21
ions, namely of 15 elements - N, O, Mg, Al, Si, P, S, Cl, Ar, Ti, Cr, Mn, Fe,
Ni, Zn. Such a large amount of information is necessary to constrain the
photoionization and dust depletion effects, two important steps in order to
derive the intrinsic chemical abundance patterns of DLAs. We evaluated the
photoionization effects with the help of the Al+/Al++, Fe+/Fe++, N0/N+ and
Ar/Si,S ratios, and computed dust corrections. Our analysis revealed that the
DLA toward Q2343+12 requires important ionization corrections. The access to
the complete series of relatively robust intrinsic elemental abundances in the
other three DLAs allowed us to constrain their star formation history, their
age and their star formation rate by a detailed comparison with a grid of
chemical evolution models for spiral and dwarf irregular galaxies. Our results
show that the galaxies associated with these three DLAs in the redshift
interval z_abs = 1.7-2.5 are either outer regions of spiral disks (radius >= 8
kpc) or dwarf irregular galaxies (with a bursting or continuous star formation
history) with ages varying from some 50 Myr only to >~ 3.5 Gyr and with
moderate star formation rates per unit area of -2.1 < log \psi < -1.5 M_{sol}
yr^{-1} kpc^{-2}.

Astrophysics