1999ApJ...526L..77W

We present the discovery of a radio galaxy at a likely redshift of z=4.424 in one of the flanking fields of the Hubble Deep Field (HDF). Radio observations with the Very Large Array and MERLIN centered on the HDF yielded a complete sample of microjansky radio sources, of which about 20% have no optical counterpart to I≤25 mag. In this Letter, we address the possible nature of one of these sources through deep Hubble Space Telescope near-infrared camera and multiobject spectrometer (NICMOS) images in the F110W (J₁₁₀) and F160W (H₁₆₀) filters. VLA J123642+621331 has a single emission line at 6595 Å, which we identify with Lyα at z=4.424. We argue that this faint (H₁₆₀=23.9 mag), compact (r_e≃0".2), red (I₈₁₄-K=2.0) object is most likely a dusty, star-forming galaxy with an embedded active nucleus.