2003ApJ...582L..71R

Perhaps as many as 10% of high-redshift radio galaxy (z>2) candidates that are selected using an ultrasteep radio spectrum criterion fail to show optical emission (continuum, lines) in deep Keck exposures. Their parent objects are only detected in the near-IR and are probably heavily obscured and/or at very high redshift. To search for signatures of dust and help constrain the nature and redshifts of these ``no-z'' radio galaxies, we have conducted a program of submillimeter and millimeter observations. Here we report the first results of a detailed study of one of these objects, WN J0305+3525. It appears associated with a small group of K∼21-22 objects and is strongly detected at both 850 µm and 1.25 mm. On the basis of its faint K-band magnitude, spectral energy distribution, and other evidence, we estimate that the radio galaxy is probably at a redshift z≃3±1. This would make WN J0305+3525 a radio-loud hyperluminous infrared galaxy (L_FIR∼10¹³ L_☉) similar to, but more obscured than, other dusty radio galaxies in this redshift range. This, together with the absence of Lyα emission and compact (θ≲1".9) radio structure, suggests that WN J0305+3525 is embedded in a very dense, dusty medium and is probably at an early stage of its formation.