The spatial distribution of the OH masers in Orion-KL

Johnston, K. J.; Migenes, V.; Norris, R. P.

doi:10.1086/167543

Cited by 23 publications

(28 citation statements)

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“…Hansen & Johnston (1983) found a magnetic field strength ∼ 3 mG from 0.2-arcsec VLA observations. Norris (1984), observing with MERLIN at 0.3-arcsec resolution, also found a magnetic field strength ∼ 3 mG, while Johnston et al (1989) estimated a magnetic field strength of 1 − 3 mG based on 0.3-arcsec resolution VLA observations. Tang et al (2010) determine a magnetic field strength ≥ 3 mG in Orion BN/KL.…”

Section: Comparison With Existing Measurementsmentioning

confidence: 98%

The JCMT BISTRO Survey: The Magnetic Field Strength in the Orion A Filament

Pattle

Ward-Thompson

Berry

et al. 2017

ApJ

143

204

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We determine the magnetic field strength in the OMC 1 region of the Orion A filament via a new implementation of the Chandrasekhar-Fermi method using observations performed as part of the James Clerk Maxwell Telescope (JCMT) B-Fields In Star-Forming Region Observations (BISTRO) survey with the POL-2 instrument. We combine BISTRO data with archival SCUBA-2 and HARP observations to find a plane-of-sky magnetic field strength in OMC 1 of B pos = 6.6 ± 4.7 mG, where δB pos = 4.7 mG represents a predominantly systematic uncertainty. We develop a new method for measuring angular dispersion, analogous to unsharp masking. We find a magnetic energy density of ∼ 1.7 × 10 −7 J m −3 in OMC 1, comparable both to the gravitational potential energy density of OMC 1 (∼ 10 −7 J m −3 ), and to the energy density in the Orion BN/KL outflow (∼ 10 −7 J m −3 ). We find that neither the Alfvén velocity in OMC 1 nor the velocity of the super-Alfvénic outflow ejecta is sufficiently large for the BN/KL outflow to have caused large-scale distortion of the local magnetic field in the ∼500-year lifetime of the outflow. Hence, we propose that the hour-glass field morphology in OMC 1 is caused by the distortion of a primordial cylindrically-symmetric magnetic field by the gravitational fragmentation of the filament and/or the gravitational interaction of the BN/KL and S clumps. We find that OMC 1 is currently in or near magnetically-supported equilibrium, and that the current large-scale morphology of the BN/KL outflow is regulated by the geometry of the magnetic field in OMC 1, and not vice versa.

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Section: Comparison With Existing Measurementsmentioning

confidence: 98%

The JCMT BISTRO Survey: The Magnetic Field Strength in the Orion A Filament

Pattle

Ward-Thompson

Berry

et al. 2017

ApJ

143

204

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“…We have updated the B-n relation by Troland & Heiles (1986) with more recent measurements : the H I Zeeman observations by Verschuur (1995) ; the OH and CN Zeeman-splitting measurements by Crutcher et al (1993Crutcher et al ( , 1996Crutcher et al ( , 1999 ; the OH maser measurements by Johnston, Migenes, & Norris (1989) ; and the maser measure-H 2 O ments by Fiebig & (1989). Gu sten In Figure 7 observational detections of the Ðeld strength and upper limits are plotted versus the estimated value of the gas density.…”

Section: T He B-n Relationmentioning

confidence: 99%

A Super‐Alfvenic Model of Dark Clouds

Padoan

Nordlund²

1999

ApJ

348

376

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Supersonic random motions are observed in dark clouds and are traditionally interpreted as Alfve n waves, but the possibility that these motions are has not been ruled out. In this work we super-Alfve nic report the results of numerical experiments in two opposite regimes : and whereMach numberÈthe ratio of the rms velocity to the speed. Our results show Alfve nicAlfve n that models with are consistent with the observed properties of molecular clouds that we have M A ? 1 tested (statistics of extinction measurements, distribution of integrated antenna temperature, Zeemansplitting measurements of magnetic Ðeld strength, line width versus integrated antenna temperature of molecular emission-line spectra, statistical B-n relation, and scatter in that relation), while models with have properties that are in conÑict with the observations. We Ðnd that both the density and the M A D 1 magnetic Ðeld in molecular clouds may be very intermittent. The statistical distributions of the magnetic Ðeld and gas density are related by a power law, with an index that decreases with time in experiments with decaying turbulence. After about one dynamical time it stabilizes at B P n0.4. Magnetically dominated cores form early in the evolution, while later on the intermittency in the density Ðeld wins out, and also cores with a weak Ðeld can be generated by mass accretion along magnetic Ðeld lines.

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“…However, the recent SiO observations of Plambeck et al (2009) carried out with CARMA seem to indicate an age 3000 years. Nonetheless, our understanding of this region has been transformed by high spatial resolution A&A 540, A119 (2012) imaging in molecular hydrogen for which resolution can be better than 100 mas (Lacombe et al 2004) in the K-band around 2 μm, in the MIR continuum (Shuping et al 2004) and through radio-interferometry of a range of species, most recently methyl formate, acetone, acetic acid and dimethyl ether (Favre et al 2011a,b;Friedel et al 2005;Friedel & Snyder 2008;Guélin et al 2008), methyl cyanide (Wang et al 2010) and ammonia (Goddi et al 2011a), including numerous maser observations in SiO, OH and H 2 O (Doeleman et al 2002;Goddi et al 2009a,b;Kim et al 2008;,Matthews et al 2010;Wright et al 1995;Johnston et al 1989;Cohen et al 2006;Genzel & Downes 1977;Genzel et al 1981;Matveenko et al 2000;Matveyenko et al 2007). Nevertheless the driving sources of the outflows still remain uncertain although it is at least apparent that the high and low velocity outflows are largely independent of each other and arise through different phenomena.…”

Section: Introductionmentioning

confidence: 99%

A 3D view of the outflow in the Orion Molecular Cloud 1 (OMC-1)

Nissen¹,

Cunningham²,

Gustafsson³

et al. 2012

A&A

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Context. Stars whose mass is an order of magnitude greater than the Sun play a prominent role in the evolution of galaxies, exploding as supernovae, triggering bursts of star formation and spreading heavy elements about their host galaxies. A fundamental aspect of star formation is the creation of an outflow. The fast outflow emerging from a region associated with massive star formation in the Orion Molecular Cloud 1 (OMC-1), located behind the Orion Nebula, appears to have been set in motion by an explosive event. Aims. We study the structure and dynamics of outflows in OMC-1. We combine radial velocity and proper motion data for near-IR emission of molecular hydrogen to obtain the first 3-dimensional (3D) structure of the OMC-1 outflow. Our work illustrates a new diagnostic tool for studies of star formation that will be exploited in the near future with the advent of high spatial resolution spectro-imaging in particular with data from the Atacama Large Millimeter Array (ALMA). Methods. We used published radial and proper motion velocities obtained from the shock-excited vibrational emission in the H 2 v = 1−0 S(1) line at 2.122 μm obtained with the GriF instrument on the Canada-France-Hawaii Telescope, the Apache Point Observatory, the Anglo-Australian Observatory, and the Subaru Telescope. Results. These data give the 3D velocity of ejecta yielding a 3D reconstruction of the outflows. This allows one to view the material from different vantage points in space giving considerable insight into the geometry. Our analysis indicates that the ejection occurred < ∼ 720 years ago from a distorted ring-like structure of ∼15 (6000 AU) in diameter centered on the proposed point of close encounter of the stars BN, source I and maybe also source n. We propose a simple model involving curvature of shock trajectories in magnetic fields through which the origin of the explosion and the center defined by extrapolated proper motions of BN, I and n may be brought into spatial coincidence.

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The spatial distribution of the OH masers in Orion-KL

Cited by 23 publications

References 0 publications

The JCMT BISTRO Survey: The Magnetic Field Strength in the Orion A Filament

The JCMT BISTRO Survey: The Magnetic Field Strength in the Orion A Filament

A Super‐Alfvenic Model of Dark Clouds

A 3D view of the outflow in the Orion Molecular Cloud 1 (OMC-1)

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