Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 3-D Simulations of Protostellar Jets in Stratified Ambient Media   We present fully three-dimensional hydrodynamical simulations of radiative
cooling jets propagating into stratified isothermal ambient media with
power-law density and pressure distributions. The parameters used are mainly
suitable for protostellar jets but results applicable to extragalactic jets are
also presented. Comparisons are made with previous simulations of jets through
homogeneous media. We find that for radiative cooling jets propagating into
regions where the ambient medium has an increasing density (and pressure)
gradient, the ambient gas tends to compress the cold, low-pressure cocoon of
shocked material that surrounds the beam and destroy the bow shock-like
structure at the head. The compressing medium collimates the jet and promotes
the development of Kelvin-Helmholtz instabilities which cause beam focusing,
wiggling and the formation of internal traveling shocks, $close$ $to$ $the$
$head$, via pinching along the beam. This remarkably resembles the structure of
some observed systems (e.g. Haro 6-5B northern and HH 24G jets). These effects
are larger for jets with smaller density ratio between jet and environment
$\eta $ (tested for $\eta $=1, 3, and 10) and larger Mach number $M_a=v_j/c_a$
(tested for $M_a=$12 and 24, where $v_j$ is the jet velocity and $c_a$ the
ambient sound speed). In an ambient medium of decreasing density (and
pressure), the beam is poorly collimated and relaxes, becoming faint. This
could explain ''invisible'' jet sections, like the gap between the parent
source and collimated beam (e.g., in HH30 jet). Although, on average, jets
propagating into an increasing (decreasing) density environment are decelerated
(accelerated) by the increasing (decreasing) ram pressure of the ambient
medium, we find that their propagation velocities have an oscillating pattern.

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The categories of this paper are: gr-qc
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The categories of this paper are: hep-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: chao-dyn
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The categories of this paper are: eess
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The categories of this paper are: hep-lat
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The categories of this paper are: quant-ph
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The categories of this paper are: econ
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The categories of this paper are: funct-an
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The categories of this paper are: q-bio
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The categories of this paper are: q-fin
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The categories of this paper are: mtrl-th
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The categories of this paper are: cs
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The categories of this paper are: atom-ph
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The categories of this paper are: stat
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The categories of this paper are: nucl-th