Coordinated photometric and spectroscopic observations of strong extragalactic 90 GHz sources

Abstract

Nearly simultaneous radio and infrared-optical observations were obtained for several extragalactic radio sources which are strong at 90 GHz. The spectral-flux distributions are generally peaked or flat over the radio portion of the spectrum with a steeper, power-law behavior at infrared-optical frequencies. For all sources, the radio and infrared-optical portions of the spectral-flux distributions can be smoothly joined by physically sensible interpolations over the spectral gap, although spectral breaks are required. For many of the sources, this is consistent with a common (synchrotron) origin of the radio, millimeter, and infrared-optical radiation. However, proof, in terms of correlated temporal variations and polarization properties, is still generally lacking.