Optical polarimetry of nebulae in regions of star formation

Optical polarization data are presented for nebulosities associated with dark clouds and regions of star formation.Illuminating sources are identified, and it is found that these usually show evidence of polarization induced by aligned grains, which we believe indicates the presence of magnetic fields in the gas–dust tori that surround the central objects.

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Magnetic-field strengths from optical polarization data

Symposium - International Astronomical Union ◽

10.1017/s0074180900101263 ◽

1967 ◽

Vol 31 ◽

pp. 381-383

Author(s):

J. M. Greenberg

Keyword(s):

Magnetic Field ◽

Optical Polarization ◽

Polarization Data ◽

Term Model ◽

Source Of Information ◽

Field Strengths

Van de Hulst (Paper 64, Table 1) has marked optical polarization as a questionable or marginal source of information concerning magnetic field strengths. Rather than arguing about this–I should rate this method asq+-, or quarrelling about the term ‘model-sensitive results’, I wish to stress the historical point that as recently as two years ago there were still some who questioned that optical polarization was definitely due to magnetically-oriented interstellar particles.

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SiO as a chemical signature of outflows from bright, compact sources in MSX IR-dark clouds

Canadian Journal of Chemistry ◽

10.1139/v04-078 ◽

2004 ◽

Vol 82 (6) ◽

pp. 740-743 ◽

Cited By ~ 1

Author(s):

P A Feldman ◽

R O Redman ◽

L W Avery ◽

J Di Francesco ◽

J D Fiege ◽

...

Keyword(s):

Star Formation ◽

Young Stellar Objects ◽

Line Profiles ◽

Bipolar Outflows ◽

Dark Cloud ◽

Stellar Objects ◽

Dark Clouds ◽

Dense Cores ◽

Infrared Dark Clouds ◽

Compact Sources

The line profiles of dense cores in infrared-dark clouds indicate the presence of young stellar objects (YSOs), but the youth of the YSOs and the large distances to the clouds make it difficult to distinguish the outflows that normally accompany star formation from turbulence within the cloud. We report here the first unambiguous identification of a bipolar outflow from a young stellar object (YSO) in an infrared-dark cloud, using observations of SiO to distinguish the relatively small amounts of gas in the outflow from the rest of the ambient cloud. Key words: infrared-dark clouds, star formation, bipolar outflows, SiO, G81.56+0.10.

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The Formation of Massive Stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311000184 ◽

2010 ◽

Vol 6 (S270) ◽

pp. 57-64

Author(s):

Ian A. Bonnell ◽

Rowan J Smith

Keyword(s):

Star Formation ◽

Magnetic Fields ◽

Massive Star ◽

Massive Stars ◽

Cluster Formation ◽

High Mass ◽

Prestellar Cores ◽

Stellar Mergers ◽

Massive Clusters ◽

Viable Mechanism

AbstractThere has been considerable progress in our understanding of how massive stars form but still much confusion as to why they form. Recent work from several sources has shown that the formation of massive stars through disc accretion, possibly aided by gravitational and Rayleigh-Taylor instabilities is a viable mechanism. Stellar mergers, on the other hand, are unlikely to occur in any but the most massive clusters and hence should not be a primary avenue for massive star formation. In contrast to this success, we are still uncertain as to how the mass that forms a massive star is accumulated. there are two possible mechanisms including the collapse of massive prestellar cores and competitive accretion in clusters. At present, there are theoretical and observational question marks as to the existence of high-mass prestellar cores. theoretically, such objects should fragment before they can attain a relaxed, centrally condensed and high-mass state necessary to form massive stars. Numerical simulations including cluster formation, feedback and magnetic fields have not found such objects but instead point to the continued accretion in a cluster potential as the primary mechanism to form high-mass stars. Feedback and magnetic fields act to slow the star formation process and will reduce the efficiencies from a purely dynamical collapse but otherwise appear to not significantly alter the process.

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Fire from Ice - Massive Star Birth from Infrared Dark Clouds

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317009784 ◽

2017 ◽

Vol 13 (S332) ◽

pp. 139-152

Author(s):

Jonathan C. Tan

Keyword(s):

Star Formation ◽

Massive Star ◽

Initial Conditions ◽

Massive Star Formation ◽

Dark Clouds ◽

Complex Process ◽

Infrared Dark Clouds

AbstractI review massive star formation in our Galaxy, focussing on initial conditions in Infrared Dark Clouds (IRDCs), including the search for massive pre-stellar cores (PSCs), and modeling of later stages of massive protostars, i.e., hot molecular cores (HMCs). I highlight how developments in astrochemistry, coupled with rapidly improving theoretical/computational and observational capabilities are helping to improve our understanding of the complex process of massive star formation.

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Understanding the Links among the Magnetic Fields, Filament, Bipolar Bubble, and Star Formation in RCW 57A Using NIR Polarimetry

The Astrophysical Journal ◽

10.3847/1538-4357/aa917e ◽

2017 ◽

Vol 850 (2) ◽

pp. 195 ◽

Cited By ~ 3

Author(s):

Chakali Eswaraiah ◽

Shih-Ping Lai ◽

Wen-Ping Chen ◽

A. K. Pandey ◽

M. Tamura ◽

...

Keyword(s):

Star Formation ◽

Magnetic Fields

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Submillimeter Array Observations of Magnetic Fields in Star Forming Regions

Proceedings of the International Astronomical Union ◽

10.1017/s174392131100024x ◽

2010 ◽

Vol 6 (S270) ◽

pp. 103-106

Author(s):

R. Rao ◽

J.-M. Girart ◽

D. P. Marrone

Keyword(s):

Magnetic Field ◽

Star Formation ◽

Magnetic Fields ◽

Computational Models ◽

Dominant Role ◽

Theoretical Models ◽

Mass Star ◽

Star Forming ◽

Star Forming Regions ◽

Low Mass

AbstractThere have been a number of theoretical and computational models which state that magnetic fields play an important role in the process of star formation. Competing theories instead postulate that it is turbulence which is dominant and magnetic fields are weak. The recent installation of a polarimetry system at the Submillimeter Array (SMA) has enabled us to conduct observations that could potentially distinguish between the two theories. Some of the nearby low mass star forming regions show hour-glass shaped magnetic field structures that are consistent with theoretical models in which the magnetic field plays a dominant role. However, there are other similar regions where no significant polarization is detected. Future polarimetry observations made by the Submillimeter Array should be able to increase the sample of observed regions. These measurements will allow us to address observationally the important question of the role of magnetic fields and/or turbulence in the process of star formation.

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