Measuring filament orientation: a new quantitative, local approach
arXiv:1708.01953 · doi:10.3847/1538-4365/aa8507
Abstract
The relative orientation between filamentary structures in molecular clouds and the ambient magnetic field provides insight into filament formation and stability. To calculate the relative orientation, a measurement of filament orientation is first required. We propose a new method to calculate the orientation of the one pixel wide filament skeleton that is output by filament identification algorithms such as \textsc{filfinder}. We derive the local filament orientation from the direction of the intensity gradient in the skeleton image using the Sobel filter and a few simple post-processing steps. We call this the `Sobel-gradient method'. The resulting filament orientation map can be compared quantitatively on a local scale with the magnetic field orientation map to then find the relative orientation of the filament with respect to the magnetic field at each point along the filament. It can also be used in constructing radial profiles for filament width fitting. The proposed method facilitates automation in analysis of filament skeletons, which is imperative in this era of `big data'.
arXiv comment12 pages, 7 figures. Accepted for publication in ApJS, August 2017
References in corpus (15)
- Astropy: A Community Python Package for Astronomy
- Herschel Space Observatory - An ESA facility for far-infrared and submillimetre astronomy
- 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?
- Large-Scale Structure of the Molecular Gas in Taurus Revealed by High Linear Dynamic Range Spectral Line Mapping
- Planck intermediate results. XXXV. Probing the role of the magnetic field in the formation of structure in molecular clouds
- An Imprint of Molecular Cloud Magnetization in the Morphology of the Dust Polarized Emission
- Magnetically Regulated Star Formation in 3D: The Case of Taurus Molecular Cloud Complex
- The identification of filaments on far infrared and submillimiter images. Morphology, physical conditions and relation with star formation of filamentary structure
- Balloon-Borne Submillimeter Polarimetry of the Vela C Molecular Cloud: Systematic Dependence of Polarization Fraction on Column Density and Local Polarization-Angle Dispersion
- Unveiling a network of parallel filaments in the Infrared Dark Cloud G14.225-0.506
- Filaments in the Taurus Molecular Cloud
- Sub-Alfvenic Non-Ideal MHD Turbulence Simulations with Ambipolar Diffusion: I. Turbulence Statistics
- Removing visual bias in filament identification: a new goodness-of-fit measure