Luminous Lyα-emitting galaxy at redshift z=6.535:: Discovery and spectroscopic confirmation

We present a redshift z=6.535 galaxy discovered by its Lyalpha emission in a 9180 8Angstrom narrowband image from the Large Area Lyman Alpha survey. The Lyalpha line luminosity (1.1x10(43) ergs s(-1)) is among the largest known for star-forming galaxies at zapproximate to6.5. The line shows the distinct asymmetry that is characteristic of high-redshift Lyalpha. The 2 sigma lower bound on the observer-frame equivalent width is greater than 530 Angstrom. This is hard to reconcile with a neutral intergalactic medium (IGM) unless the Lyalpha line is intrinsically strong and is emitted from its host galaxy with an intrinsic Doppler shift of several hundred km s(-1). If the IGM is ionized, it corresponds to a rest-frame equivalent width greater than 40 Angstrom after correcting for Lyalpha forest absorption. We also present a complete spectroscopic follow-up of the remaining candidates with line flux greater than 2x10(-17) ergs cm(-2) s(-1) in our 1200 arcmin(2) narrowband image. These include another galaxy with a strong emission line at 9136 Angstrom and no detected continuum flux, which, however, is most likely an [O III] lambda5007 source at z=0.824, on the basis of a weak detection of the [O III] lambda4959 line.