The evolving starburst-AGN connection: Implications for SKA and its pathfinders

TL;DR

This paper explores the connection between starburst activity and active galactic nuclei in the early Universe using deep radio surveys, highlighting challenges and implications for future SKA observations.

Contribution

It discusses the observational signatures of high-redshift galaxies and the difficulties in distinguishing starburst from AGN activity with current radio data.

Findings

Discovery of radio-loud AGNs resembling star-forming spirals in optical/infrared

Identification of radio-bright objects invisible in infrared, possibly high-redshift galaxies

Extension of radio-far-infrared correlation to microJy levels

Abstract

How well is the modern-day starburst-AGN connection mirrored in the early Universe? This is starting to be answered by deep wide radio surveys such as ATLAS, which are giving us a new view of high redshift galaxies. For example, we find powerful radio-loud AGNs which look like star-forming spirals in the optical and infrared, a composite which is almost unknown in the modern Universe. We find radio-bright objects which are unexpectedly invisible in the infrared, and which may be very high redshift radio galaxies and quasars. And although the radio-far-infrared correlation for star-forming galaxies has now been extended down to microJy levels, we still cannot reliably distinguish between starburst and AGN. So what do we need to do to ensure that SKA and its pathfinders will be able to understand galaxy evolution in the early Universe?