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 re- cently 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.

Dynamical origin of non-thermal states in galactic filaments / Di Cintio, Pierfrancesco; Gupta, Shamik; Casetti, Lapo. - In: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY. - ISSN 0035-8711. - STAMPA. - 475:(2018), pp. 1137-1147. [10.1093/mnras/stx3244]

Dynamical origin of non-thermal states in galactic filaments

Casetti, Lapo
2018

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 re- cently 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.
2018
475
1137
1147
Di Cintio, Pierfrancesco; Gupta, Shamik; Casetti, Lapo
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Utilizza questo identificatore per citare o creare un link a questa risorsa: https://hdl.handle.net/2158/1108919
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