Sunyaev Zel'dovich effect in galaxy clusters cavities: thermal or
  non-thermal origin?
  Several galaxy clusters host X-ray cavities, often filled with relativistic
electrons emitting in the radio band. In the cluster MS 0735.6+7421 the
cavities have been detected through the Sunyaev Zel'dovich (SZ) effect, but it
has not been possible to determine if this effect is thermal (produced by a
very high temperature gas filling the cavity) or non-thermal (produced by the
relativistic electrons that produce the diffuse radio emission detected in the
cavity). In this paper we discuss the role of the density of the high
temperature gas inside the cavities in determining whether the dominant SZ
effect is the thermal or the non-thermal one, and how it can be possible to
distinguish between the two possibilities, discussing the role of observations
at higher energy bands.
