Work

The Millennium Arecibo 21 Centimeter Absorption‐Line Survey. IV. Statistics of Magnetic Field, Column Density, and Turbulence

Year: 2005

Type: article

Abstract: We discuss observations of the magnetic field, column density, and turbulence in the cold neutral medium (CNM). The observed quantities are only indirectly related to the intrinsic astronomical ones. We relate the observed and intrinsic quantities by relating their univariate and bivariate probability distribution functions (pdf's). We find that observations of the line-of-sight component of a magnetic field do not constrain the pdf of the total field B tot very well but do constrain the median value of B tot . In the CNM, we find a well-defined median magnetic field 6.0 ± 1.8 μG. The CNM magnetic field dominates thermal motions. Turbulence and magnetism are in approximate equipartition. We find that the probability distribution of column density N ⊥ (H ) in the sheets closely follows N ⊥ (H ) -1 over a range of 2 orders of magnitude, 0.026 ≲ N ⊥ (H ) ≲ 2.6 × 10 20 cm -2 . The bivariate distributions are not well enough determined to constrain structural models of CNM sheets.

Source: The Astrophysical Journal

DOI: 10.1086/428896

Authors: Carl Heiles, T. H. Troland

Institutions: University of California, Berkeley, University of Kentucky

Language: English

Topic: Astrophysics and Star Formation Studies

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: bronze

Funder: National Science Foundation

Awards: Interstellar Matter and Magnetic Fields, An Observational Study of Magnetic Fields in the Galaxy and Beyond, The Diffuse Interstellar Medium: Magnetic Fields, Physical Parameters and Morphology, The Diffuse Interstellar Medium: Temperatures, Magnetic Fields, Superbubbles