Deep, ultra-high-resolution radio imaging of submillimetre galaxies using Very Long Baseline Interferometry

摘要

We present continent-scale VLBI - obtained with the European VLBI Network(EVN) at a wavelength of 18cm - of six distant, luminous submm-selectedgalaxies (SMGs). Our images have a synthesized beam width of ~30 milliarcsecFWHM - three orders of magnitude smaller in area than the highest resolutionVLA imaging at this wavelength - and are capable of separating radio emissionfrom ultra-compact radio cores (associated with active super-massive blackholes - SMBHs) from that due to starburst activity. Despite targeting compactsources - as judged by earlier observations with the VLA and MERLIN - weidentify ultra-compact cores in only two of our targets. This suggests that theradio emission from SMGs is produced primarily on larger scales than thoseprobed by the EVN, and therefore is generated by star formation rather than anAGN - a result consistent with other methods used to identify the presence ofSMBHs in these systems.