Radio and Millimeter Observations ofz ~ 2 Luminous QSOs

We present Very Large Array observations at 1.4 and 5 GHz of a sample of 16quasi-stellar objects (QSOs) at z = 1.78 to 2.71. Half of the chosen quasarsare bright at mm wavelengths (250 or 350 GHz) while the other half were notdetected at mm wavelengths; the former QSOs were detected at 1.4 GHz, in mostcases at high significance (S/N > ~7), but only three of the latter sourceswere detected at radio frequencies, and only at lower significance (S/N ~ 3).The data are consistent with a correlation between the mm and radio fluxesindicating a physical connection between the mechanisms responsible for theradio and mm emission. However, this conclusion is based on data which includesmany upper limits, and deeper observations are clearly needed to verify thiscorrelation. All eight mm detected QSOs are detected in the radio continuum, with radioflux densities consistent with the radio-to-FIR correlation for low z starforming galaxies. However, four of these have flatter spectral indices than istypical for star forming galaxies (i.e. greater than -0.5) suggesting thatradiation from the central AGN dominates the observed radio emission. All thesources detected at 1.4 GHz are spatially unresolved, with the size limitstypically < 1'' = 6 kpc. High star formation rate galaxies at low redshift aretypically nuclear starbursts, with sizes < 1 kpc. Hence, the current radio sizelimits are insufficient to constrain the emission model (AGN or starburst).Comment: accepted for publication in A