The innermost regions of the jet in NRAO 150 Wobbling or internal rotation?

NRAO 150 is a very bright millimeter to radio quasar at redshift z=1.52 for which ultra-highresolution VLBI monitoring has revealed a counter-clockwise jet-position-angle wobbling at an angular speed ∼11◦/yr in the innermost regions of the jet. In this paper we present new total and linearly polarized VLBA images at 43 GHz extending previous studies to cover the evolution of the jet in NRAO 150 between 2006 and early 2009. We propose a new scenario to explain the counter-clockwise rotation of the jet position angle based on a helical motion of the components in a jet viewed faced-on. This alternative scenario is compatible with the interpretation suggested in previous works once the indetermination of the absolute position of the self-calibrated VLBI images is taken into account. Fitting of the jet components motion to a simple internal rotation kinematical model shows that this scenario is a likely alternative explanation for the behavior of the innermost regions in the jet of NRAO 150.