A deep, narrow J-band search for protogalactic Lyα emission at redshifts z ∼ 9

We present a deep, narrow J-band search for protogalactic Lyalpha emission at redshifts z similar to 9. We combine an exceptionally deep image of the Hubble Deep Field South, obtained using a narrow-band filter centred on the wavelength 1.187 mum using the VLT/ISAAC facility, with existing deep, broad-band images covering optical to near-infrared wavelengths. We search for z similar to 9 Lyalpha-emitting galaxies displaying a significant narrow-band excess relative to the J(s) band that are undetected at optical wavelengths. We detect no sources consistent with this criterion to the 90 per cent point-source flux limit of the narrow-band image, F-NB = 3.28 x 10(-18) erg s(-1) cm(-2). The survey selection function indicates that we have sampled a volume of approximately 340 h(-3) Mpc(3) to a Lyalpha emission luminosity of 10(43) h(-2) erg s(-1). We conclude by considering the potential implications for the physics of the high-redshift Universe.