Gravitational Infall onto Molecular Filaments II. Externally Pressurized Cylinders

TL;DR

This paper investigates the evolution of externally pressurized molecular filaments, examining accretion effects, magnetic fields, and embedding environments, and compares models with observations to understand filament structure and dynamics.

Contribution

It extends previous models by analyzing accretion, magnetic influence, and embedding effects on filament properties, providing insights into their observed profiles and stability.

Findings

Accretion models are inconsistent with observations unless for low-mass, isothermal, or magnetized filaments.

Magnetic fields with $B\,\propto\,n^{1/2}$ can reproduce observed filament parameters.

Filament profiles are intrinsically flatter than isothermal models suggest.

Abstract

In an extension of Fischera & Martin (2012a) and Heitsch (2013), two aspects of the evolution of externally pressurized, hydrostatic filaments are discussed. (a) The free-fall accretion of gas onto such a filament will lead to filament parameters (specifically, FWHM--column density relations) inconsistent with the observations of Arzoumanian et al. (2011), except for two cases: For low-mass, isothermal filaments, agreement is found as in the analysis by Fischera & Martin (2012b). Magnetized cases, for which the field scales weakly with the density as $B\propto n^{1/2}$, also reproduce observed parameters. (b) Realistically, the filaments will be embedded not only in gas of non-zero pressure, but also of non-zero density. Thus, the appearance of sheet-embedded filaments is explored. Generating a grid of filament models and comparing the resulting column density ratios and profile shapes with observations suggests that the three-dimensional filament profiles are intrinsically flatter than isothermal, beyond projection and evolution effects.