Three-dimensional structure in field 349 of the southern sky survey. I - Redshifts for a magnitude-limited sample of galaxies from slit spectra

Abstract

Redshifts are presented for a magnitude-limited sample (b<SUB>j</SUB> < 16.5) of 107 galaxies detected from scans with the COSMOS machine in the central 29 square degrees of the ESO/SERC southern sky survey field 349 (centred at 00<SUP>h</SUP>00<SUP>m</SUP>, -35°00', 1950 coordinates). Spectra at a dispersion of &tilde;210 Å mm<SUP>-1</SUP> were obtained with the 1.9-m telescope of the South African Astronomical Observatory (SAAO), using the Image-tube Spectrograph and Reticon Photon Counting System (RPCS). Both cross-correlation techniques against filtered templates and direct measures of emission lines (if present) were used to obtain radial velocities to an accuracy of &tilde;75 km s<SUP>-1</SUP>. The observed sample represents a completeness of &tilde;80 per cent for all the galaxies detected by COSMOS down to b<SUB>j</SUB>=16.5 and provides a significant data base for analysis of the brighter end of the galaxy distribution in this field. The remaining unobserved galaxies were generally fainter than b<SUB>j</SUB>=16.0 although three were of low surface brightness. This survey, going &tilde;2.0 mag fainter than the CfA survey, is compatible with the Durham/AAT redshift survey (Shanks et al.) and should provide further insight into the nature of galaxy clustering.