Exactly what is the non-thermal Sunyaev-Zel'dovich effect? From what I understand from reading several papers by Mark Birkinshaw and Sergio Colafrancesco, I get the rough idea that the non-thermal SZ effect has something to do with it being in the relativistic realm.
Papers by Sergio Colafrancesco:
- Polarization of the Sunyaev-Zel'dovich effect: relativistic imprint of thermal and non-thermal plasma
- The non-thermal Sunyaev-Zel'dovich effect in clusters of galaxies
- Non-thermal phenomena in galaxy clusters: cosmological relevance
Review by Mark Birkinshaw:
To clarify, I'm not referring to the kinematic SZ effect.
There appears to be a distinction by the authors between the SZ effect due to hot thermal electrons and relativistic electrons. I find the nomenclature ambiguous, as temperature is essentially kinetic energy on a smaller scale, so why would relativistic electrons that have more kinetic energy be 'non-thermal'?
Lastly, is the key distinction between them using a relativistic vs. a non-relativistic formulation?