Distortion of Magnetic Fields in a Starless Core VI: Application of Flux Freezing Model and Core Formation of FeSt 1-457

Abstract

Observational data for the hourglass-like magnetic field toward the starless dense core FeSt 1-457 were compared with a flux freezing magnetic field model (Myers et al. 2018). Fitting of the observed plane-of-sky magnetic field using the flux freezing model gave a residual angle dispersion comparable with the results based on a simple three-dimensional parabolic model. The best-fit parameters for the flux freezing model were a line-of-sight magnetic inclination angle of ${\gamma }_{\mathrm{mag}}=35^{\circ }\pm 15^{\circ }$ and a core center to ambient (background) density contrast of ${\rho }_{\mathrm{c}}/{\rho }_{\mathrm{bkg}}=75$. The initial density for core formation (${\rho }_0$) was estimated to be ${\rho }_{\mathrm{c}}/75=4670$ cm${}^{-3}$, which is about one order of magnitude higher than the expected density ($\sim 300$ cm${}^{-3}$) for the inter-clump medium of the Pipe Nebula. FeSt 1-457 is likely to have been formed from the accumulation of relatively dense gas, and the relatively dense background column density of $A_V\simeq 5$ mag supports this scenario. The initial radius (core formation radius) $R_0$ and the initial magnetic field strength $B_0$ were obtained to be 0.15 pc ($1.64R$) and $10.8-14.6$ $\mu$G, respectively. We found that the initial density ${\rho }_0$ is consistent with the mean density of the nearly critical magnetized filament with magnetic field strength $B_0$ and radius $R_0$. The relatively dense initial condition for core formation can be naturally understood if the origin of the core is the fragmentation of magnetized filaments.

Accepted for publication in ApJ

References in corpus (22)

• Theory of Star Formation
• MAMBO Mapping of Spitzer c2d Small Clouds and Cores
• Radiative torques: Analytical Model and Basic Properties
• 2MASS wide field extinction maps - I. The Pipe nebula
• Interstellar Extinction Law toward the Galactic Center II: V, J, H, and Ks Bands
• Optical polarimetry toward the Pipe nebula: Revealing the importance of the magnetic field
• On the radiation driven alignment of dust grains: Detection of the polarization hole in a starless core
• Grain Alignment in Starless Cores
• The nature of the dense core population in the Pipe Nebula: A survey of NH3, CCS, and HC5N molecular line emission
• The Dynamical State of the Starless Dense Core FeSt 1-457: A Pulsating Globule?
• The Dynamical State fo the Starless Dense Core FeSt 1-457: A Pulsating Globule?
• Nonlinear Evolution of Gravitational Fragmentation Regulated by Magnetic Fields and Ambipolar Diffusion
• Distortion of Magnetic Fields in a Starless Core: Near-Infrared Polarimetry of FeSt 1-457
• Fragmentation of Filamentary Cloud Permeated by Perpendicular Magnetic Field
• Star-forming filament models
• Formation of dense structures induced by filament collisions. Correlation of density, kinematics and magnetic field in the Pipe nebula
• Distortion of Magnetic Fields in a Starless Core II: 3D Magnetic Field Structure of FeSt 1-457
• How the power spectrum of dust continuum images may hide the presence of a characteristic filament width
• Submillimeter Polarimetry with PolKa, a reflection-type modulator for the APEX telescope
• Induced Core Formation Time in Subcritical Magnetic Clouds by Large-Scale Trans-Alfvénic Flows
• A Survey of Magnetic Field Strengths in the Envelopes of Molecular Clouds via the 18 cm OH Zeeman Effect
• A correlation between chemistry, polarization and dust properties in the Pipe Nebula starless core FeSt 1-457

Cited by in corpus (8)

• Magnetic Properties of Star-Forming Dense Cores
• Three-dimensional magnetic fields of molecular clouds
• Magnetic Field Structure in Spheroidal Star-Forming Clouds. II. Estimating Field Structure from Observed Maps
• Distortion of Magnetic Fields in BHR 71
• Fitting an Analytic Magnetic Field to a Prestellar Core
• Distortion of Magnetic Fields in the Dense Core CB81 (L1774, Pipe 42) in the Pipe Nebula
• Distortion of Magnetic Fields in the Dense Core SL42 (CrA-E) in the Corona Australis Molecular Cloud Complex
• Grain alignment and dust evolution physics with polarisation (GRADE-POL). I. Dust polarisation modelling for isolated starless cores