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Abstract. We present photometry and spectroscopy of the afterglow of GRB 030323. VLT spectra of the afterglow show damped Lyα (DLA) absorption and low-and high-ionization lines at a redshift z = 3.3718 ± 0.0005. The inferred neutral hydrogen column density, log N(H i) = 21.90 ± 0.07, is larger than any (GRB-or QSO-) DLA H  column density inferred directly from Lyα in absorption. From the afterglow photometry, we derive a conservative upper limit to the host-galaxy extinction: A V < 0.5 mag. The iron abundance is [Fe/H] = −1.47 ± 0.11, while the metallicity of the gas as measured from sulphur is [S/H] = −1.26 ± 0.20. We derive an upper limit on the H 2 molecular fraction of 2N(H 2 )/(2N(H 2 ) + N(H i)) < ∼ 10 −6 . In the Lyα trough, a Lyα emission line is detected, which corresponds to a star-formation rate (not corrected for dust extinction) of roughly 1 M yr −1 . All these results are consistent with the host galaxy of GRB 030323 consisting of a low metallicity gas with a low dust content. We detect fine-structure lines of silicon, Si *, which have never been clearly detected in QSO-DLAs; this suggests that these lines are produced in the vicinity of the GRB explosion site. Under the assumption that these fine-structure levels are populated by particle collisions, we estimate the H  volume density to be n H i = 10 2 −10 4 cm −3 . HST/ACS imaging 4 months after the burst shows an extended AB(F606W) = 28.0 ± 0.3 mag object at a distance of 0. 14 (1 kpc) from the early afterglow location, which presumably is the host galaxy of GRB 030323.

Abstract. We present the first results of an observational programme at the ESO Very Large Telescope aimed at detecting a large sample of high-redshift galaxies fainter than the current spectroscopic limit of R = 25.5 for Lyman-Break galaxies. In this paper, we describe the results of deep narrow and broad-band imaging and subsequent follow-up multi-object spectroscopy of faint high-redshift galaxies in the fields of the QSOs BRI 1346−0322 and Q 2138−4427. These QSOs have intervening high neutral hydrogen column density absorbers, at redshifts z = 2.85 and z = 3.15 respectively, for which redshifted Lyα emission falls within less than a few Å from the central wavelengths of existing VLT (∼60 Å-wide) narrow-band filters. We selected 37 and 27 candidate emission-line galaxies in the two fields respectively. Most (∼85%) of the candidates have R-band magnitudes fainter than R = 25.5. The first spectroscopic follow-up of a sub-sample of the candidates resulted in 41 confirmed candidates and 4 foreground emission line galaxies (three [O ] emitters and one C  emitter). The confirmation rate for Lyα emitters is 82% and 68% in the field of BRI 1346−0322 and Q 2138−4427 respectively. In addition, we serendipitously detect a number of other emission-line sources on some of the slitlets not used for candidates. Of these, 9 are also most likely Lyα emitters with redshifts ranging from 1.98 to 3.47. The redshift distribution of confirmed candidates in the field of BRI 1346−0322 is consistent with being drawn from a uniform distribution weighted by the filter response curve, whereas the galaxies in the field of Q 2138−4427 have redshifts clustering very close to the redshift of the damped Lyα absorber. This latter fact indicates the existence of a large "pancake"-like structure confirming the earlier suggestions of Francis & Hewitt (1993).

We present optical I-band light curves of the gravitationally lensed double QSO B1600]434 from observations obtained at the Nordic Optical Telescope (NOT) between 1998 April and 1999 November. The photometry has been performed by simultaneous deconvolution of all the data frames, involving a numerical lens galaxy model. Four methods have been applied to determine the time delay between the two QSO components, giving a mean estimate of *t \ 51^4 days (95% conÐdence level). This is the fourth optical time delay ever measured. Adopting a ) \ 0.3, " \ 0 universe and using the mass model of Maller et al., this time delay estimate yields a Hubble parameter of km s~1 Mpc~1 (95% H 0 \ 52~8 14 conÐdence level), where the errors include time delay as well as model uncertainties. There are timedependent o †sets between the two (appropriately shifted) light curves that indicate the presence of external variations due to microlensing.