The Westerbork Northern Sky Survey ( WENSS ) and the NRAO/VLA Sky Survey ( NVSS ) were used to determine an upper limit to the diffuse radio flux from the nearby cluster Abell 2199 .
For the entire cluster , this limit is < 3.25 Jy at 327 MHz from WENSS ; for the inner 15′ radius , the limit is < 168 mJy at 1.4 GHz .
These limits are used to constrain the cluster magnetic field by requiring that the radio flux be consistent with the hard X-ray ( HXR ) flux observed by BeppoSAX , assuming that the observed HXR excess is due to inverse Compton ( IC ) scattering of cosmic microwave background photons by relativistic electrons in the intracluster gas .
We find that the magnetic field must be very weak ( < 0.073 \mu G ) in order to avoid producing an observable radio halo .
We also consider the possibility that the HXR excess is due to nonthermal bremsstrahlung ( NTB ) by a population of suprathermal electrons which are being accelerated to higher energies .
We find that a NTB model based on a power-law electron momentum distribution with an exponent of \mu \approx 3.3 and containing about 5 % of the number of electrons in the thermal ICM can reproduce the observed HXR flux .