Dynamical origin of non-thermal states in galactic filaments

Abstract

Observations strongly suggest that filaments in galactic molecular clouds are in a non-thermal state. As a simple model of a filament we study a two-dimensional system of self-gravitating point particles by means of numerical simulations of the dynamics, with various methods: direct $N$-body integration of the equations of motion, particle-in-cell simulations and a recently developed numerical scheme that includes multiparticle collisions in a particle-in-cell approach. Studying the collapse of Gaussian overdensities we find that after the damping of virial oscillations the system settles in a non-thermal steady state whose radial density profile is similar to the observed ones, thus suggesting a dynamical origin of the non-thermal states observed in real filaments. Moreover, for sufficiently cold collapses the density profiles are anticorrelated with the kinetic temperature, i.e., exhibit temperature inversion, again a feature that has been found in some observations of filaments. The same happens in the state reached after a strong perturbation of an initially isothermal cylinder. Finally, we discuss our results in the light of recent findings in other contexts (including non-astrophysical ones) and argue that the same kind of non-thermal states may be observed in any physical system with long-range interactions.

11 pages, 8 figures, MNRAS LaTeX, accepted for publication in MNRAS

References in corpus (10)

• Collisionless relaxation in non-neutral plasmas
• The MASSIVE Survey - VIII. Stellar Velocity Dispersion Profiles and Environmental Dependence of Early-Type Galaxies
• Radial kinematics of brightest cluster galaxies
• Quasi-stationary states and the range of pair interactions
• Polytropic models of filamentary interstellar clouds - I. Structure and stability
• On the equilibrium of rotating filaments
• CO~($J=1-0$) Observations of a Filamentary Molecular Cloud in the Galactic Region Centered at $l = 150\arcdeg, b = 3.5\arcdeg$
• Surprises from quenches in long-range interacting systems: Temperature inversion and cooling
• Newtonian gravity in d dimensions
• Polytropic models of filamentary interstellar clouds -II. Helical magnetic fields

Cited by in corpus (3)

• Violent relaxation in the Hamiltonian Mean Field model: I. Cold collapse and effective dissipation
• The isothermal evolution of a shock-filament interaction
• Non-thermal states in models of filaments: a dynamical study