A Genetic Algorithm–based Exploration of Three Filament Models: A Case for the Magnetic Support of the G11.11−0.12 Infrared‐dark Cloud

Abstract

The G11.11-0.12 infrared-dark cloud has a filamentary appearance, both in extinction against the diffuse infrared emission of the Galactic plane and in emission at 850µm. We use a novel computational technique based on an advanced genetic algorithm to explore thoroughly 3 different models of self-gravitating, pressure truncated filaments and to constrain their parameters. Specifically, the models tested are the non-magnetic Ostriker (1964) model, a generalized version of the magnetic Stodólkiewicz (1963) model, and the magnetic Fiege & Pudritz (2000a) model. Previous results showed that G11.11-0.12 has a much steeper ∼ r −4 radial density profile than other filaments, where the density varies approximately as r −2 , and that this steep density profile is consistent with the Ostriker (1964) model. We present a more complete analysis that shows that the radial structure of G11.11-0.12 is consistent with regimes of each of these models. All of the magnetic models that agree with the data are threaded by a dominant poloidal magnetic field, and most have dynamically significant fields. Thus, G11.11-0.12 is an excellent candidate for radial support by a magnetic field that is predominantly poloidal. We predict the polarization patterns expected for both magnetic models and show that the two magnetic models produce different polarization patterns that should be distingished by observations.

Supersonic turbulence, filamentary accretion and the rapid assembly of massive stars and discs

“…James Clerk Maxwell Telescope submillimetre studies of Orion B (Mitchell et al 2001) reveal a plethora of filamentary structures and their embedded cores. This pattern is also seen in the observational studies by Fiege et al (2004), wherein a few bright cores are seen to be embedded in a larger, isolated filamentary structure. Similar results are also seen in more embedded regions such as the Lupus 3 cloud, where strong links between filaments and emerging star clusters are observed (Teixeira, Lada & Alves 2005).…”

Star formation in Perseus

“…The criteria for a filament are different for those of a uniform medium (Larson 1985). Theoretical models for filaments range from a simple non-magnetic isothermal filament (Ostriker 1964) to magnetised filaments with helical fields which can be toroidal or poloidal or both (Tilley & Pudritz 2003;Fiege & Pudritz 2000;Fiege et al 2004). A key prediction from these models is the ratio of the mass per unit length m to the cylindrical virial mass per unit length m vir , which is given by…”

Initial conditions for massive star birth–Infrared dark clouds

“…1 and 4). Using a sophisticated computational technique Fiege et al (2004) compared observations to three different models of self-gravitating, pressure-truncated filaments, namely the nonmagnetic Ostriker (1964) model, and two magnetic models from the literature. Analysing the 850µm SCUBA observations of G11.11-0.12, Johnstone et al (2003) concluded that this source has a much steeper r −α , (α > ∼ 3) radial density profile than other (lower moss, lower extinction) filaments, where the density varies approximately as r −2 , This steep density profile is consistent with the Ostriker model.…”