Mueller, Cornelia

The unusual jet morphology of the hard gamma-ray source PMN J1603-4904 revealed by TANAMI.

Author list: C. Müller, M. Kadler, R. Ojha, G.B. Taylor, F. Krauß, A. Kreikenbohm, E. Ros, J. Wilms & the TANAMI Team

The TANAMI VLBI monitoring program provides regular, dual-frequency (at 8GHz and 22GHz), milliarcsecond (mas) monitoring of extragalactic jets south of -30 degrees declination using the Australian Long Baseline Array (LBA) and associated telescopes in Antarctica, Chile, New Zealand and South Africa. Supporting programs provide simultaneous multi-wavelength coverage of all sources. Besides a brief description of this program and its current status we will present our latest results on the bright, hard spectrum gamma-ray source PMN J1603-4904. Our VLBI observations reveal an unusual jet structure which has an overall flat to steep spectrum (alpha=-0.4) on mas scales. A classification of PMN J1603-4904 is not straightforward due to its low Galactic latitude, the lack of optical identification, and low multiwavelength variability. We discuss different classification scenarios, which suggest that PMN J1603-4904 is either an atypical blazar or a gamma-ray bright young radio galaxy, and the corresponding implications.