Astrophysical Jets

Abstract

Highly collimated jets are observed in many classes of astrophysical objects, ranging from active galactic nuclei (AGN) to young stellar objects (YSOs). In the present paper, like in a couple of previous reviews [1, 2], I will make the assumption that the jet formation mechanism, namely, the mechanism for acceleration and collimation, is the same in most if not all of the different classes of objects which exhibit jets (see [2] for details and relevant references). Adopting a mostly phenomenological approach, I will then attempt to determine to which constraints such an assumption can lead. However, with the discovery of new classes of objects which produce jets (see Sect. 2 below) and with recent developments in theoretical work, the constraints become more meaningful. It should be noted right away that the emission mechanisms which render jets observable in the different classes of objects, are very different in objects like, for example, YSOs and AGN. Here, I therefore concentrate only on acceleration and collimation.