IAU01015
Presentation type requested: EITHER
GALAXIES AT THE HIGHEST REDSHIFTS AND REIONIZATION
Matthew Lehnert
Max-Planck-Institut fuer extraterrestrische Physik
We have spectropically confirmed a sample of high redshift (z>4.8) galaxies selected from deep R, I and Z-band imaging using the VLT. Deep spectroscopy of twelve of a complete subsample of thirteen of these sources, selected to have I(AB)<26.2 and R(AB)-I(AB)>1.5, lead to redshifts being obtained for six. These ranged from z=4.8-5.8. The line and continuum fluxes suggest very young ages (<10^8 yrs). A further line-emitting object with no detectable continuum was serendipitously detected by spectroscopy. This is either a very low luminosity [OII] emitter at z=1.5 or a Ly-alpha emitter at z=6.6, the latter making this the most distant galaxy known. No broad emission line objects (quasars) were detected. The UV luminosity density from galaxies brighter than our flux limit is considerably less than that necessary to keep the volume probed by our field at <z>~5.3 ionized and less than that observed at z~4. Given that there is little time for the luminosity function to evolve, and the lack of detected quasars, imply that the bulk of the UV flux that reionized the universe came from faint galaxies with M(AB)(1700 angstrom)>-21. The number density of star-forming galaxies has declined significantly from redshifts of z=3 to z~5.3.
Malcolm Bremer
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