Testing molecular-cloud fragm0065ntation theories: Self-consistent analysis of OH Zeeman observations

Telemachos Ch Mouschovias, Konstantinos Tassis

Research output: Contribution to journalLetter

Abstract

The ambipolar-diffusion theory of star formation predicts the formation of fragments in molecular clouds with mass-to-flux ratios greater than that of the parent-cloud envelope. By contrast, scenarios of turbulence-induced fragmentation do not yield such a robust prediction. Based on this property, Crutcher et al. recently proposed an observational test that could potentially discriminate between fragmentation theories. However, the analysis applied to the data severely restricts the discriminative power of the test: the authors conclude that they can only constrain what they refer to as the 'idealized' ambipolar-diffusion theory that assumes initially straight- parallel magnetic field lines in the parent cloud. We present an original, self-consistent analysis of the same data taking into account the non-uniformity of the magnetic field in the cloud envelopes, which is suggested by the data themselves, and we discuss important geometrical effects that must be accounted for in using this test. We show quantitatively that the quality of current data does not allow for a strong conclusion about any fragmentation theory. Given the discriminative potential of the test, we urge for more and better-quality data.

Original languageEnglish (US)
JournalMonthly Notices of the Royal Astronomical Society: Letters
Volume400
Issue number1
DOIs
StatePublished - Nov 1 2009

Fingerprint

molecular clouds
ambipolar diffusion
fragmentation
diffusion theory
data quality
envelopes
magnetic field
magnetic fields
nonuniformity
star formation
turbulence
fragments
analysis
test
prediction
predictions

Keywords

  • Diffusion
  • ISM: clouds
  • ISM: magnetic fields
  • MHD
  • Stars: formation
  • Turbulence

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

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title = "Testing molecular-cloud fragm0065ntation theories: Self-consistent analysis of OH Zeeman observations",
abstract = "The ambipolar-diffusion theory of star formation predicts the formation of fragments in molecular clouds with mass-to-flux ratios greater than that of the parent-cloud envelope. By contrast, scenarios of turbulence-induced fragmentation do not yield such a robust prediction. Based on this property, Crutcher et al. recently proposed an observational test that could potentially discriminate between fragmentation theories. However, the analysis applied to the data severely restricts the discriminative power of the test: the authors conclude that they can only constrain what they refer to as the 'idealized' ambipolar-diffusion theory that assumes initially straight- parallel magnetic field lines in the parent cloud. We present an original, self-consistent analysis of the same data taking into account the non-uniformity of the magnetic field in the cloud envelopes, which is suggested by the data themselves, and we discuss important geometrical effects that must be accounted for in using this test. We show quantitatively that the quality of current data does not allow for a strong conclusion about any fragmentation theory. Given the discriminative potential of the test, we urge for more and better-quality data.",
keywords = "Diffusion, ISM: clouds, ISM: magnetic fields, MHD, Stars: formation, Turbulence",
author = "Mouschovias, {Telemachos Ch} and Konstantinos Tassis",
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T2 - Self-consistent analysis of OH Zeeman observations

AU - Mouschovias, Telemachos Ch

AU - Tassis, Konstantinos

PY - 2009/11/1

Y1 - 2009/11/1

N2 - The ambipolar-diffusion theory of star formation predicts the formation of fragments in molecular clouds with mass-to-flux ratios greater than that of the parent-cloud envelope. By contrast, scenarios of turbulence-induced fragmentation do not yield such a robust prediction. Based on this property, Crutcher et al. recently proposed an observational test that could potentially discriminate between fragmentation theories. However, the analysis applied to the data severely restricts the discriminative power of the test: the authors conclude that they can only constrain what they refer to as the 'idealized' ambipolar-diffusion theory that assumes initially straight- parallel magnetic field lines in the parent cloud. We present an original, self-consistent analysis of the same data taking into account the non-uniformity of the magnetic field in the cloud envelopes, which is suggested by the data themselves, and we discuss important geometrical effects that must be accounted for in using this test. We show quantitatively that the quality of current data does not allow for a strong conclusion about any fragmentation theory. Given the discriminative potential of the test, we urge for more and better-quality data.

AB - The ambipolar-diffusion theory of star formation predicts the formation of fragments in molecular clouds with mass-to-flux ratios greater than that of the parent-cloud envelope. By contrast, scenarios of turbulence-induced fragmentation do not yield such a robust prediction. Based on this property, Crutcher et al. recently proposed an observational test that could potentially discriminate between fragmentation theories. However, the analysis applied to the data severely restricts the discriminative power of the test: the authors conclude that they can only constrain what they refer to as the 'idealized' ambipolar-diffusion theory that assumes initially straight- parallel magnetic field lines in the parent cloud. We present an original, self-consistent analysis of the same data taking into account the non-uniformity of the magnetic field in the cloud envelopes, which is suggested by the data themselves, and we discuss important geometrical effects that must be accounted for in using this test. We show quantitatively that the quality of current data does not allow for a strong conclusion about any fragmentation theory. Given the discriminative potential of the test, we urge for more and better-quality data.

KW - Diffusion

KW - ISM: clouds

KW - ISM: magnetic fields

KW - MHD

KW - Stars: formation

KW - Turbulence

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