Astrophysical Jets

Attilio Ferrari I want to recall here the basic points I raised at the beginning of the Workshop as the main targets of discussion (in the name of the Scientific Committee). I attempted to focus the attention of participants on the fact that, in many instances, we tend to discuss jets in terms of simple physics, more or less as one did at the time extragalactic radio sources were discovered: for instance, we still use equipartition arguments. However, we must realize that processes in jets, leading to their morphologies and energetics clearly depend on complex plasma phenomena. Therefore, the same standard arguments used to derive characteristic parameters should be questioned; some of the speakers were invited to attempt a critical analysis of this point, an~ in fact I believe that this "inquisitive attitude" was actually present all along the Workshop. Observers were asked to choose the parameters to be used in a statistical sample of jets. For this they were urged, first of all, to distinguish between primary and secondary features. For instance, are knots and wiggles common to all jets? Are relativistic flow velocities expected in all active nuclei? Are jets denser or lighter than the external medium? On the theoretical side I asked to discuss whether or not existing models are in accordance with the limited statistical sample that we have today. And which should be the lines of development to be pursued first, and to what extent.

Inhalt

Small Scale Structure of Nonthermal Radio Sources.- Arc Second Structure of Compact Radio Sources.- A Summary of Properties of Radio Jets.- Recent Observations of Superluminal Sources.- The Jet in the Quaaar 3C273.- Three Archetypal Radio Jets.- Physical Properties of the Jet in NGC6251.- Bent Jets and Tailed Radio Galaxies.- Jet-Like Structures in Low Frequency Variable Sources.- Curvature in High Redshift Quasars.- Rapid Variability of 3C273 at 300 GHz.- Are There Jets in Spiral Galaxies?.- Optical Emission from Jets.- Astrophysical Jets: Optical Morphologies of Radio Jets and Their Parent Galaxies.- PKS 0521-36, a BL Lac Object with an Optical and Radio Jet.- CCD - Observations of Optical Jets and Extensions in Galaxies.- The Jet in NGC3310.- The Discovery of Optical Emission Knots in the Inner Jet of Centaurus A.- Extranuclear Activity in Mkn 335.- Jets in SS433.- Rapid Radio-Variability at 408 MHz in SS433.- X-Rays from Jets and Lobes.- X-Ray Jets in BL Lac Objects?.- Extended Soft X-Ray Emission from NGC 4151.- Jets from Supercritical Accretion Disks.- Black Hole-Driven Hydromagnetic Flows. Flywheels vs. Fuel.- Supercritical Jets from a "Cauldron".- Propagation and Morphology of Pressure-Confined Supersonic Jets.- Determination of Jet Physical Parameters from Observations.- Jets, Magnetic Fields and the Central Engine.- Wiggles and Knots in Radio Jets.- Reflection Jets and Collimation of Radio Sources.- Instabilities in Astrophyical Jets.- MHD Kelvin-Helmholtz Instabilities and Large Scale Phenomena in Jets.- Concluding Remarks: A Progress Report on Our Understanding of Jets.- Object Index.