A very large telescope FORS2 multislit search for Lyα-emitting galaxies at z∼6.5

We present results from a deep spectroscopic search in the 9150 Angstrom atmospheric window for Lyalpha-emitting galaxies using the VLT/FORS2. Our multislit + narrowband filter survey covers a total spatial area of 17.6 arcmin(2) in four different fields and reaches fluxes down to 5 x 10(-18) ergs s(-1) cm(-2) (7 sigma detection). Our detection limit is significantly fainter than narrowband searches at this redshift and fainter also than the unlensed brightness of Hu et al.' s HCM 6A at z = 6.56, and thus it 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 Lyalpha emission at z similar to 6.5. Our null result of finding no z similar to 6.5 Lyalpha emitters suggests that the number density of Lyalpha emitters with Lgreater than or equal to2 x 10(42) ergs s(-1) declines by greater than or similar to2 between z similar to 3 and z similar to 6.5.