Supersonic extragalactic jets with turbulent boundary layers: Preliminary consideration

Abstract

Numerical calculations are used to study the properties of stationary pressure-matched supersonic jets with boundary layers, propagating through interstellar and intergalactic mediums. It is shown that for low initial Mach numbers, M = 1 − 2, the jets become slow, fully turbulent, wide, and subsonic on a scale typical of FRI radio sources. These slow, distant parts of the jets could be identified with the edge-darkened lobes of FRIs. For slightly higher M the jets remain quite narrow and supersonic up to a distance of 150 kpc and more but still become fully turbulent. It is possible that the jets produce radio sources having a transitional morphology between classical FRIs and FRIIs. Edge-brightened lobes with extended ‘warm spots’ and jets that are more prominent and wider than those in FRIIs should be distinguishable features of these sources. A rise of brightness near the jet boundary seems to be possible only in the case of low initial contributions of relativistic electrons to the full jet pressure and effective particle acceleration in the turbulent layer.