Polytropic models of filamentary interstellar clouds - I. Structure and stability

Abstract

The properties of filamentary interstellar clouds observed at sub-millimetre wavelengths, especially by the Herschel Space Observatory, are analysed with polytropic models in cylindrical symmetry. The observed radial density profiles are well reproduced by negative-index cylindrical polytropes with polytropic exponent $1/3\lesssim {\gamma }_{\mathrm{p}}\lesssim 2/3$ (polytropic index $-3\lesssim n\lesssim -3/2$), indicating either external heating or non-thermal pressure components. However, the former possibility requires unrealistically high gas temperatures at the filament's surface and is therefore very unlikely. Non-thermal support, perhaps resulting from a superposition of small-amplitude Alfvén waves (corresponding to ${\gamma }_{\mathrm{p}}=1/2$), is a more realistic possibility, at least for the most massive filaments. If the velocity dispersion scales as the square root of the density (or column density) on the filament's axis, as suggested by observations, then polytropic models are characterised by a uniform width. The mass per unit length of pressure-bounded cylindrical polytropes depends on the conditions at the boundary and is not limited as in the isothermal case. However, polytropic filaments can remain stable to radial collapse for values of the axis-to-surface density contrast as large as the values observed only if they are supported by a non-isentropic pressure component.

arXiv comment9 pages, 4 figures. Accepted for publication in MNRAS

References in corpus (32)

• From filamentary clouds to prestellar cores to the stellar IMF: Initial highlights from the Herschel Gould Belt survey
• Clouds, filaments and protostars: the Herschel Hi-GAL Milky Way
• Characterizing interstellar filaments with Herschel in IC5146
• Herschel view of the Taurus B211/3 filament and striations: Evidence of filamentary growth?
• Dynamic star formation in the massive DR21 filament
• Helical Fields and Filamentary Molecular Clouds
• Observing the gas temperature drop in the high-density nucleus of L 1544
• The Turbulent Shock Origin of Proto--Stellar Cores
• SDC13 infrared dark clouds: Longitudinally collapsing filaments?
• From Filamentary Networks to Dense Cores in Molecular Clouds: Toward a New Paradigm for Star Formation
• Dense core formation by fragmentation of velocity-coherent filaments in L1517
• Collapse and Fragmentation in Finite Sheets
• Filaments in Simulations of Molecular Cloud Formation
• On the origin of non self-gravitating filaments in the ISM
• Physical properties of interstellar filaments
• Formation and evolution of interstellar filaments; Hints from velocity dispersion measurements
• The structure and stability of molecular cloud cores in external radiation fields
• The Different Structures of the Two Classes of Starless Cores
• A Model for the Internal Structure of Molecular Cloud Cores
• Variation in dust properties in a dense filament of the Taurus molecular complex (L1506)
• Ion-neutral friction and accretion-driven turbulence in self-gravitating filaments
• Multi--Pressure Polytropes as Models for the Structure and Stability of Molecular Clouds. I. Theory
• The G11.11-0.12 Infrared-Dark Cloud: Anomalous Dust and a Non-Magnetic Isothermal Model
• Core and filament formation in magnetized, self-gravitating isothermal layers
• Does Turbulent Pressure Behave as a Logatrope?
• Composite Polytrope Models of Molecular Clouds. I. Theory
• Is the Taurus B213 Region a True Filament?: Observations of Multiple Cyanoacetylene Transitions
• Linear Graviational Instability of Filamentary and Sheet-like Molecular Clouds with Magnetic Fields
• Local stability of a gravitating filament: a dispersion relation
• Estimating distance, pressure, and dust opacity using submillimeter observations of self-gravitating filaments
• Polytropic models of filamentary interstellar clouds -II. Helical magnetic fields
• Non-isothermal filaments in equilibrium

Cited by in corpus (22)

• The density structure and star formation rate of non-isothermal polytropic turbulence
• Magnetic fields in star forming systems (I): Idealized synthetic signatures of dust polarization and Zeeman splitting in filaments
• Temperature inversion in long-range interacting systems
• Magnetic Field Structure in Spheroidal Star-Forming Clouds
• Star-forming filament models
• Polytropic models of filamentary interstellar clouds -II. Helical magnetic fields
• Magnetohydrostatic Equilibrium Structure and Mass of Polytropic Filamentary Cloud Threaded by Lateral Magnetic Field
• Dynamical origin of non-thermal states in galactic filaments
• The origin of a universal filament width in molecular clouds
• Morphology of prestellar cores in pressure confined filaments
• Stability of filaments in star-forming clouds and the formation of prestellar cores in them
• Dynamical Instability of Charged Gaseous Cylinder
• Fragmentation of Filamentary Cloud Permeated by Perpendicular Magnetic Field II. Dependence on the Initial Density Profile
• Gravitational instability of filamentary molecular clouds, including ambipolar diffusion; Non-isothermal filament
• Temperature inversion in a gravitationally bound plasma: Case of the solar corona
• The isothermal evolution of a shock-filament interaction
• Temperature inversion in a confined plasma atmosphere: coarse-grained effect of temperature fluctuations at its base
• Non-ideal magnetohydrodynamics of self-gravitating filaments
• Emergence of high-mass stars in complex fiber networks (EMERGE) IV. Environmental dependence of the fiber widths
• What causes the fragmentation of debris streams in TDEs?
• Analytic growth rate of gravitational instability in self-gravitating planar polytropes
• Unveiling the role of magnetic fields in an accreting filament onto a young protocluster