  We present a detailed study of the emission from a z = 2.35 galaxy that
causes damped Lyman-alpha absorption in the spectrum of the background QSO,
SDSS J 2222-0946. We present the results of extensive analyses of the stellar
continuum covering the rest frame optical-UV regime based on broad-band HST
imaging, and of spectroscopy from VLT/X-Shooter of the strong emission lines:
Ly-alpha, [OII], [OIII], [NII], H-alpha and H-beta. We compare the metallicity
from the absorption lines in the QSO spectrum with the oxygen abundance
inferred from the strong-line methods (R23 and N2). The two emission-line
methods yield consistent results: [O/H] = -0.30+/-0.13. Based on the absorption
lines in the QSO spectrum a metallicity of -0.49+/-0.05 is inferred at an
impact parameter of 6.3 kpc from the centre of the galaxy with a column density
of hydrogen of log(N_HI)=20.65+/-0.05. The star formation rates of the galaxy
from the UV continuum and H-alpha line can be reconciled assuming an amount of
reddening of E(B-V) = 0.06+/-0.01, giving an inferred SFR of 13+/-1 M_sun / yr
(assuming a Chabrier IMF). From the HST imaging, the galaxy associated with the
absorption is found to be a compact (re=1.12 kpc) object with a disc-like,
elongated (axis ratio 0.17) structure indicating that the galaxy is seen close
to edge on. Moreover, the absorbing gas is located almost perpendicularly above
the disc of the galaxy suggesting that the gas causing the absorption is not
co-rotating with the disc. We investigate the stellar and dynamical masses from
SED-fitting and emission-line widths, respectively, and find consistent results
of 2x10^9 M_sun. We suggest that the galaxy is a young proto-disc with evidence
for a galactic outflow of enriched gas. This galaxy hints at how star-forming
galaxies may be linked to the elusive population of damped Lyman-alpha
absorbers.
