Preprint typeset using L ATEX style emulateapj v. 14/09/00 A VLT/FORS2 MULTI-SLIT SEARCH FOR LY-α EMITTING GALAXIES AT Z ∼ 6.5 1

We present results from a deep spectroscopic search in the 9150Å atmospheric window for z ∼ 6.5 Lyα emitting galaxies using the VLT/FORS2. Our multi-slit+narrow-band filter survey covers a total spatial area of 17.6 arcmin in four different fields and reaches fluxes down to 5×10 erg s cm (7σ detection). Our detection limit is significantly fainter than narrow-band searches at this redshift and fainter also than the unlensed brightness of Hu et al.’s HCM6A at z = 6.56, and thus provides better overlap with surveys at much lower redshifts. Eighty secure emission line galaxies are detected. However, based on their clear continuum emission shortward of the line or the presence of multiple lines, none of these can be Lyα emission at z ∼ 6.5. Our null result of finding no z ∼ 6.5 Lyα emitters suggests that the number density of Lyα emitters with L ≥ 2 × 10 erg s declines by & 2 between z ∼ 3 and z ∼ 6.5. Subject headings: cosmology: observations – early universe – galaxies: evolution – galaxies: formation