Cosmological evolution of the submillimetre luminosity of high-redshift radio galaxies

A systematic survey measuring the submillimetre continuum luminosity in radio galaxies between redshifts z ∼ 0:1−5 is currently in progress. The first results from observations with the bolometer array SCUBA on the JCMT suggest a trend of increasing submillimetre luminosity with redshift out to z ' 4. Assuming the continuum emission at 850 μm is dominated by thermal radiation from dust heated by young, massive stars, the straightforward interpretation of these data implies that the host galaxies of powerful radio sources, presumably ellipticals or their progenitors, exhibit increased star formation activity with increasing redshift. However a severe bias may distort the true picture since only a subset of 30 galaxies have been observed, which represent the most luminous radio sources (P151MHz > 1027:5 WHz−1sr−1), whilst the complete sample covers ∼ 4 decades in radio power (1025 − 1029 WHz−1sr−1). This on-going observational programme continues to improve coverage of the P − z plane in an attempt to remove this potential bias towards higher AGN activity and hence understand more fully the relationship between high-z AGN, their level of starformation, and the evolutionary status of their host galaxies.