ORION'S VEIL: MAGNETIC FIELD STRENGTHS and OTHER PROPERTIES of A PDR in front of the TRAPEZIUM CLUSTER

T. H. Troland, W. M. Goss, C. L. Brogan, R. M. Crutcher, D. A. Roberts

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

We present an analysis of physical conditions in the Orion Veil, an atomic photon-dominated region (PDR) that lies just in front (≈2 pc) of the Trapezium stars of Orion. This region offers an unusual opportunity to study the properties of PDRs, including the magnetic field. We have obtained 21 cm H i and 18 cm (1665 and 1667 MHz) OH Zeeman effect data that yield images of the line-of-sight magnetic field strength B los in atomic and molecular regions of the Veil. We find B los ≈ -50 to -75 μG in the atomic gas across much of the Veil (25″ resolution) and B los ≈ -350 μG at one position in the molecular gas (40″ resolution). The Veil has two principal H i velocity components. Magnetic and kinematical data suggest a close connection between these components. They may represent gas on either side of a shock wave preceding a weak-D ionization front. Magnetic fields in the Veil H i components are 3-5 times stronger than they are elsewhere in the interstellar medium where N(H) and n(H) are comparable. The H i components are magnetically subcritical (magnetically dominated), like the cold neutral medium, although they are about 1 dex denser. Comparatively strong fields in the Veil H i components may have resulted from low-turbulence conditions in the diffuse gas that gave rise to OMC-1. Strong fields may also be related to magnetostatic equilibrium that has developed in the Veil since star formation. We also consider the location of the Orion-S molecular core, proposing a location behind the main Orion H+ region.

Original languageEnglish
Article number2
JournalAstrophysical Journal
Volume825
Issue number1
DOIs
StatePublished - Jul 1 2016

Bibliographical note

Funding Information:
This work has been supported in part by NSF grant AST 0908841 to T.H.T.

Publisher Copyright:
© 2016. The American Astronomical Society. All rights reserved.

Keywords

  • H II regions
  • ISM: individual objects (Orion Nebula)
  • ISM: magnetic fields
  • photon-dominated region (PDR)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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