Hubble Space Telescope NICMOS Polarization Measurements of OMC-1

Abstract

We present 2micron polarization measurements of positions in the BN region of the Orion Molecular Cloud (OMC-1) made with NICMOS Camera 2 (0.2'' resolution) on HST. Our results are as follows: BN is sim 29% polarized by dichroic absorption and appears to be the illuminating source for most of the nebulosity to its north and up to sim 5'' to its south. Although the stars are probably all polarized by dichroic absorption, there are a number of compact, but non-point-source, objects that could be polarized by a combination of both dichroic absorption and local scattering of star light. We identify several candidate YSOs, including an approximately edge-on bipolar YSO 8.7'' east of BN, and a deeply-embedded variable star. Additional strongly polarized sources are IRc2-B, IRc2-D, and IRc7, all of which are obviously self-luminous at mid-infrared wavelengths and may be YSOs. None of these is a reflection nebula illuminated by a star located near radio source I, as was previously suggested. Other IRc sources are clearly reflection nebulae: IRc3 appears to be illuminated by IRc2-B or a combination of the IRc2 sources, and IRc4 and IRc5 appear to be illuminated by an unseen star in the vicinity of radio source I, or by Star n or IRc2-A. Trends in the magnetic field direction are inferred from the polarization of the 26 stars that are bright enough to be seen as NICMOS point sources. The most polarized star has a polarization position angle different from its neighbors by sim 40^o, but in agreement with the grain alignment inferred from millimeter polarization measurements of the cold dust cloud in the southern part of OMC-1.

arXiv comment41 pages, 8 figures, 4 tables, to appear in The Astrophysical Journal

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Cited by in corpus (19)

• Explosive Outflows Powered by the Decay of Non-Hierarchical Multiple Systems of Massive Stars: Orion BN/KL
• A census of molecular hydrogen outflows and their sources along the Orion A molecular ridge: characteristics and overall distribution
• Extended High Circular Polarization in the Orion Massive Star Forming Region: Implications for the Origin of Homochirality in the Solar System
• Complex Organic Molecules at High Spatial Resolution Toward Orion-KL II: Kinematics
• Complex Organic Molecules at High Spatial Resolution Toward Orion-KL I: Spatial Scales
• ALMA Imaging of Millimeter/Submillimeter Continuum Emission in Orion KL
• Near Infrared Polarization Images of the Orion Nebula
• First Science Observations with SOFIA/FORCAST: 6 TO 37 micron Imaging of Orion BN/KL
• Near-Infrared Imaging Polarimetry of M42: Aperture Polarimetry of Point-like Sources
• OMC-1 dust polarisation in ALMA Band 7: Diagnosing grain alignment mechanisms in the vicinity of Orion Source I
• Short- and long-term variability of young stars in the Orion Nebula Cluster and Molecular Cloud
• A High Spatial Resolution Study of the λ=3 mm Continuum of Orion-KL
• Hubble Space Telescope NICMOS Polarization Observations of Three Edge-on Massive YSOs
• The mid-infrared molecular inventory towards Orion IRc2
• Proper Motions of the Radio Source Orion MR, Formerly Known as Orion n, and New Sources with Large Proper Motions in Orion BN/KL
• Multi-Scale Analysis of Magnetic Fields in Filamentary Molecular Clouds in Orion A
• Keck Adaptive Optics Observations of the Protostellar Disk around Radio Source I in the Orion Kleinmann-Low Nebula
• Aligned grains and inferred toroidal magnetic fields in the envelopes of massive young stellar objects
• Near-infrared polarization images of the Orion proplyds