THE HIGH-REDSHIFT RADIO GALAXY MRC-0406-244

We present HST and ground-based multiwavelength observations of the di stant radio galaxy MRC 0406-244. Ground-based visible and near-IR imag es reveal two distinct components that are aligned with the radio sour ce axis. One of these has the red optical-to-IR and blue UV colors cha racteristic of radio galaxies, while the other is red in all colors. A Ly alpha image reveals a nebula that is 3'' x 5'' in extent and is al igned with the radio source. The HST images reveal a spatially resolve d continuum associated with the southeastern component that is aligned with the radio axis and which has a complex morphology, including a d ouble nucleus and taillike features suggestive of a tidal origin. By c omparing the luminosities of discrete knots in the extended continuum to the luminosity of radio quasars from the MRC/1 Jy survey, we make a quantitative assessment of the optical depth required for scattering models for the alignment effect. The required optical depth is difficu lt to produce from Thomson scattering by electrons associated with the emission-line nebulae, although our inferred tau(T) is within an orde r of magnitude of the required value. A putative intercloud medium wit h densities n(e) < 1 cm(-3) fails to produce the required Thomson dept h by an order of magnitude or more. The required optical depth for dus t necessitates a dust-to-gas ratio comparable to the Galactic value.Th e spectral energy distribution of the extended continuum to the northw est of the nucleus is nearly flat in f(v) units and is only marginally consistent with a Thomson scattering origin. We detect an extension t o the J, H, and K-sh images to the southeast along the radio axis. We believe that this is primarily line emission, the implied Ly alpha/H a lpha ratio being near unity. The spectral energy distribution of the g alaxy near the northwest radio lobe is better fitted by an intermediat e-age population at z = 1.7 than by any plausibly aged model at z = 2. 4. Thus we believe that this galaxy lies in the foreground and that th ere is no evidence for a large-scale infrared alignment effect in this object. The morphology of the extended continuum and the emission-lin e kinematics in MRC 0406-244 are highly suggestive of a merger. The sp ectral energy distributions of the extended continuum and the difficul ty in producing the required Thomson depth lead us to favor scattering by dust in tidal features as the origin of the aligned continuum in t his source.