NICMOS imaging of the dusty microjansky radio source VLA J1236421621331 at Z = 4.4241

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 Ao, which we identify with Lya at z =. We argue that this faint ( mag), compact ( 0.2), red (I4.424 H = 23.9 red I₈₁₄2K = 2.0) object is most likely a 160 e dusty, star-forming galaxy with an embedded active nucleus.