\citet{Banfield_2014} examine the polarization properties of 1.4 GHz sources out to \(z\leq3\). Presumably the polarization of these galaxies is being caused by intrinsic magnetic fields. They look at two populations:
passive quiescent galaxies
luminous, quasar-like galaxies
There are significant differences between the populations: passive galaxies have higher % polarization, smaller radio sizes, and lower radio luminosities that the quasar-like galaxies. Presumed cause is due to environment.
They also look at the colors of the host galaxies based on WISE data. THe majority of objects have \([4.6]-[12]\) and \([3.4]-[4.6]\) colors consistent with either QSOs or stars/ellipticals. There are very few galaxies with the intermediate \([4.6]-[12]\) colors associated with spirals \citep{Jarrett_2011}.
Note that WISE is not sensitive to elliptical galaxies at high (how much?) redshifts since they have little dust or gas. High-\(z\) galaxies will be either luminous AGN or starbursts.
\citet{Brown_2014} examine galaxy SEDs from ultraviolet to mid-infrared, including WISE. He thinks the radio sources in red elliptical galaxies is due to star formation. Therefore, the critical question is whether our “dusty ellipticals” are double or more (agn) radio sources, or star formation limited to the size of the galaxies.
\citet{Brown_2011} also look at the continuum emission from early-type galaxies. The median radio power is proportional to K-band luminosity to the power \(\alpha=2.78\pm0.16\). It is thus highly likely that the most massive galaxies always host an active galactic nucleus or have recently undergone star formation.
Brown’s galaxies are optically selected and low redshift. So the “dusty elliptical” regime are probably a different population than ours. He says that examination of morphology (I don’t know whether this is reflected in paper) suggests that these are disk galaxies with what he calls “pseudo-bulges”. It could be that this is all a continuum of properties. Perhaps merging system systems where there is various levels of dominance of the disk and bulge components?
Brown has quite a bit of expertise that might be useful for us. As we proceed with the color paper, we might want to think of bringing him in – just something to keep in mind as a possibility.
\citet{Kalfountzou_2014} look at infrared colors of radio hosts, including Herschel. These results suggest that powerful radio jets are associated with star formation, especially at lower accretion rates.