Imaging simulated relativistic radio jets.

Abstract

Flux maps of simulated relativistic jets are presented. Both 2-D axially symmetric (Duncan & Hughes, 1994: ApJ, 436, L119) and 3-D (Hardee, et al., 2001: ApJ, 555, 744 and Hughes, et al., 2002, ApJ, 572, in press) jets are examined. Three models of emissivity are studied, assuming different relationships between the hydrodynamic variables and the magnetic field and radiating particles. The 2-D jets are examined at three angles of view, both with and without accounting for time-delay effects, and one model is examined with differing opacities. We calculate peak and mean flux light curves and display evolutionary sequences, finding that (a) mildly relativistic jets (gamma = 2.5) show complex radio structure, reflective of their internal hydrodynamics even at small angles of view, and evolve more complex forms over time, (b) highly relativistic jets (gamma = 10.0) show little structure from any angle of view and do not evolve into substantially more complex forms. We find that modeling emissivity as a function of sound speed leads to the most complex maps for slower jets, whereas assuming that pressure alone determines emissivity produces the most complex maps for faster jets. We find that for mildly relativistic jets the radio core arises from Kelvin-Helmholtz instabilities occurring near the axis of flow, while the extended emission is a manifestation of the bow shock. We also find that time-delay effects have a major impact on the jet's radio morphology. We discuss how these simulations could apply to CSOs. Three 3-D jets are examined; a perturbed gamma = 2.5 jet, a precessing gamma = 5.0 jet, and a deflected gamma = 2.5 jet. Only single epoch maps were made of the 3-D jets. We find that for the perturbed and precessing jet the underlying hydrodynamics can be discerned at high angles of view to the axis of flow in alternating 'hot spots' on opposite side of the axis of flow, but the jets are much less intense than their 2-D counterparts at all angles, due to the lack of K-H instabilities in the high boost center of the jet. These maps resemble in form VLBI maps of parsec scale AGN jets. Features in the maps of the deflected jet, however, do not bear a simple relation to features seen in the hydrodynamics.