Lyαemission galaxies at a redshift ofz ≈ 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 l uminosity 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 fil ters, we identified candidates for high-redshift Lyα galaxies. We then used FORS2 in spectroscopic mode to verify the identific ations 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 p resence of Lyα emission at z = 5.7 was confirmed spectroscopically. The line fluxes of the 15 candidates range between 3× 10 −21 Wm −2 and 16× 10 −21 Wm −2 , which corresponds to star-formation rates not corrected f or dust between 1 and 5 M⊙yr −1 . The luminosity function derived for our photometrically identified objects extends the published luminosity functio ns of intrinsically brighter Lyα galaxies. Conclusions. With this technique the study of high-redshift Lyα emission galaxies can be extended to low intrinsic luminosities.