The Building the Bridge survey for z = 3 Lyα emitting galaxies ^*

I. Method and first results

¹ Department of Physics and Astronomy, University of Århus, Ny Munkegade, 8000 Århus C, Denmark
² Astronomical Observatory, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark
³ European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748, Garching by München, Germany
⁴ European Southern Observatory, Casilla 19001, Santiago 19, Chile
⁵ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD21218, USA

Corresponding author: J. P. U. Fynbo, jfynbo@phys.au.dk

Received: 17 March 2003
Accepted: 22 May 2003

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 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 and 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 . The first spectroscopic follow-up of a sub-sample of the candidates resulted in 41 confirmed candidates and 4 foreground emission line galaxies (three [] emitters and one 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 ([CITE]).