Title: A Submillimeter Perspective on the GOODS Fields (SUPER GOODS) - II. The High Radio Power Population in the GOODS-N,
Abstract: We use ultradeep 20 cm data from the Karl G. Jansky Very Large Array and 850
micron data from SCUBA-2 and the Submillimeter Array of an 124 arcmin^2 region
of the Chandra Deep Field-north to analyze the high radio power (P_20cm>10^31
erg s^-1 Hz^-1) population. We find that 20 (42+/-9%) of the spectroscopically
identified z>0.8 sources have consistent star formation rates (SFRs) inferred
from both submillimeter and radio observations, while the remaining sources
have lower (mostly undetected) submillimeter fluxes, suggesting that active
galactic nucleus (AGN) activity dominates the radio power in these sources. We
develop a classification scheme based on the ratio of submillimeter flux to
radio power versus radio power and find that it agrees with AGN and
star-forming galaxy classifications from Very Long Baseline Interferometry. Our
results provide support for an extremely rapid drop in the number of high SFR
galaxies above about a thousand solar masses per year (Kroupa initial mass
function) and for the locally determined relation between X-ray luminosity and
radio power for star-forming galaxies applying at high redshifts and high radio
powers. We measure far-infrared (FIR) luminosities and find that some AGNs lie
on the FIR-radio correlation, while others scatter below. The AGNs that lie on
the correlation appear to do so based on their emission from the AGN torus. We
measure a median radio size of 1.0+/-0.3 arcsecond for the star-forming
galaxies. The radio sizes of the star-forming galaxies are generally larger
than those of the AGNs.