thick” for both UV photon and cosmic ray electrons [see e.g. @2010ApJ...717....1L]. Therefore, a more detailed tuning of the model is needed. @1993ApJ...415...93H make an assumption that the magnetic field and gas are well coupled locally, leading to similar optical depths for UV photons and cosmic rays. Their argument depends on a simplified condition, a roughly constant effective escape length (the distance travelled within galaxy before escape) for cosmic rays. But it is unlikely to be universal, especially for dwarf galaxies due to its small size. @2010ApJ...717....1L propose a more detailed model, suggesting that some “conspiracy” is necessary to solve the problem for low gas surface density case. In galaxies with low gas surface density, which is the case for many dwarf galaxies, the lower radio emission due to cosmic ray escaping is somehow compensated by lower FIR emission due to low dust content. They also predict in their “standard” model that the FRC will eventually break at very low gas mass surface density .

Dwarf galaxies, with their typical lower stellar mass surface density, are important for testing the theoretical models. However, due to observational difficulties, only a few studies were done in this low luminosity regime. @2001ApJ...554..803Y investigated 