Lyα emission galaxies at a redshift of z ≈ 5.7 in the FORS deep field

Abstract

Context. We present the results of a search for Lyα emission galaxies at z ≈ 5.7 in the FORS Deep Field. Aims. The objective of this study is to improve the faint end of the luminosity function of high-redshift Lyα emitting galaxies and to derive properties of intrinsically faint Lyα emission galaxies in the young universe. Methods. Using FORS2 at the ESO VLT and a set of special interference filters, we identified candidates for high-redshift Lyα galaxies. We then used FORS2 in spectroscopic mode to verify the identifications and to study their spectral properties. Results. The narrow-band photometry resulted in the detection of 15 likely Lyα emission galaxies. Spectra with an adequate exposure time could be obtained for eight galaxies. In all these cases the presence of Lyα emission at z ≈ 5.7 was confirmed spectroscopically. The line fluxes of the 15 candidates range between 3 × 10-21 W m-2 and 16 × 10 -21 W m-2, which corresponds to star-formation rates unconnected for dust absorption between 1 and 5 M⊙ yr -1. The luminosity function derived for our photometrically identified objects extends the published luminosity functions of intrinsically brighter Lyα galaxies. Conclusions. With this technique the study of high-redshift Lyα emission galaxies can be extended to low intrinsic luminosities. © ESO 2006.