2004ApJ...612L..89T

We present results from a deep spectroscopic search in the 9150 Å atmospheric window for z∼6.5 Lyα-emitting galaxies using the VLT/FORS2. Our multislit+narrowband filter survey covers a total spatial area of 17.6 arcmin² in four different fields and reaches fluxes down to 5x10^–18 ergs/s/cm2 (7 σ 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 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≥2x10⁴² ergs/s declines by ≳2 between z∼3 and z∼6.5.