Astronomy and Astrophysics – Astrophysics
Scientific paper
2005-12-28
Astrophys.J.635:1126-1135,2005
Astronomy and Astrophysics
Astrophysics
11 pages, 5 figures
Scientific paper
10.1086/497561
Dynamically significant magnetic fields are routinely observed in molecular clouds, with mass-to-flux ratio lambda = (2 pi sqrt{G}) (Sigma/B) ~ 1 (here Sigma is the total column density and B is the field strength). It is widely believed that ``subcritical'' clouds with lambda < 1 cannot collapse, based on virial arguments by Mestel and Spitzer and a linear stability analysis by Nakano and Nakamura. Here we confirm, using high resolution numerical models that begin with a strongly supersonic velocity dispersion, that this criterion is a fully nonlinear stability condition. All the high-resolution models with lambda <= 0.95 form ``Spitzer sheets'' but collapse no further. All models with lambda >= 1.02 collapse to the maximum numerically resolvable density. We also investigate other factors determining the collapse time for supercritical models. We show that there is a strong stochastic element in the collapse time: models that differ only in details of their initial conditions can have collapse times that vary by as much as a factor of 3. The collapse time cannot be determined from just the velocity dispersion; it depends also on its distribution. Finally, we discuss the astrophysical implications of our results.
Gammie Charles F.
Krasnopolsky Ruben
No associations
LandOfFree
Nonlinear Criterion for the Stability of Molecular Clouds does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Nonlinear Criterion for the Stability of Molecular Clouds, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Nonlinear Criterion for the Stability of Molecular Clouds will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-668905