A deep , narrow J – band search for proto – galactic Ly α emission

We present a deep, narrow J–band search for proto–galactic Lyα emission at redshifts z ∼ 9. We combine an exceptionally deep image of the Hubble Deep Field South, obtained using a narrow band filter centred on the wavelength 1.187μm using the VLT/ISAAC facility, with existing deep, broad band images covering optical to near infrared wavelengths. We search for z ∼ 9 Lyα–emitting galaxies displaying a significant narrow band excess relative to the Js–band that are undetected at optical wavelengths. We detect no sources consistent with this criterion to the 90% point source flux limit of the NB image, FNB = 3.28×10 −18 ergs s cm. The survey selection function indicates that we have sampled a volume of approximately 340 h Mpc to a Lyα emission luminosity of 10h ergs s. We conclude by considering the potential implications for the physics of the high–redshift universe.