The Radio Background Below 100 MHz
  The recent detection of the "cosmic dawn" redshifted 21 cm signal at 78 MHz
by the EDGES experiment differs significantly from theoretical predictions. In
particular, the absorption trough is roughly a factor of two stronger than the
most optimistic theoretical models. The early interpretations of the origin of
this discrepancy fall into two categories. The first is that there is increased
cooling of the gas due to interactions with dark matter, while the second is
that the background radiation field includes a contribution from a component in
addition to the cosmic microwave background. In this paper we examine the
feasibility of the second idea using new data from the first station of the
Long Wavelength Array. The data span 40 to 80 MHz and provide important
constraints on the present-day background in a frequency range where there are
few surveys with absolute temperature calibration suitable for measuring the
strength of the radio monopole. We find support for a strong, diffuse radio
background that was suggested by the ARCARDE 2 results in the 3 to 10 GHz
range. We find that this background is well modeled by a power law with a
spectral index of $-$2.58$\pm$0.05 and a temperature at the rest frame 21 cm
frequency of 603$^{+102}_{-92}$ mK.
