AGN, star formation, and the NanoJy sky

Abstract

I present simple but robust estimates of the types of sources making up the faint, sub-μJy radio sky. These include star-forming galaxies and radio-quiet active galactic nuclei but also two "new" populations, that is low radio power ellipticals and dwarf galaxies, the latter likely constituting the most numerous component of the radio sky. I then estimate for the first time the X-ray, optical, and mid-infrared fluxes these objects are likely to have, which are very important for source identification and the synergy between the upcoming SKA and its various pathfinders with future missions in other bands. On large areas of the sky the SKA, and any other radio telescope producing surveys down to at least the μJy level, will go deeper than all currently planned (and past) sky surveys, with the possible exception of the optical ones from PAN-STARRS and the LSST. On the other hand, most sources from currently planned all-sky surveys, with the likely exception of the optical ones, will have a radio counterpart within the reach of the SKA. JWST and the ELTs might turn out to be the main, or perhaps even the only, facilities capable of securing optical counterparts and especially redshifts of μJy radio sources. © Springer-Verlag Berlin Heidelberg 2012.