Herschel-ATLAS/GAMA: a difference between star-formation rates in
  strong-line and weak-line radio galaxies
  We have constructed a sample of radio-loud objects with optical spectroscopy
from the Galaxy and Mass Assembly (GAMA) project over the Herschel-ATLAS Phase
1 fields. Classifying the radio sources in terms of their optical spectra, we
find that strong-emission-line sources (`high-excitation radio galaxies') have,
on average, a factor ~4 higher 250-micron Herschel luminosity than weak-line
(`low-excitation') radio galaxies and are also more luminous than
magnitude-matched radio-quiet galaxies at the same redshift. Using all five
H-ATLAS bands, we show that this difference in luminosity between the
emission-line classes arises mostly from a difference in the average dust
temperature; strong-emission-line sources tend to have comparable dust masses
to, but higher dust temperatures than, radio galaxies with weak emission lines.
We interpret this as showing that radio galaxies with strong nuclear emission
lines are much more likely to be associated with star formation in their host
galaxy, although there is certainly not a one-to-one relationship between star
formation and strong-line AGN activity. The strong-line sources are estimated
to have star-formation rates at least a factor 3-4 higher than those in the
weak-line objects. Our conclusion is consistent with earlier work, generally
carried out using much smaller samples, and reinforces the general picture of
high-excitation radio galaxies as being located in lower-mass, less evolved
host galaxies than their low-excitation counterparts.
