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Variation of the Lifetime and Fragmentation Scale in Molecular Clouds as an Indication of Ambipolar Diffusion

Presentation #112.06 in the session “Origin of Cores and IMF”.

Published onJan 11, 2021
Variation of the Lifetime and Fragmentation Scale in Molecular Clouds as an Indication of Ambipolar Diffusion

Ambipolar diffusion likely plays a pivotal role in the formation and evolution of dense cores in weakly-ionized molecular clouds. Linear analyses show that the evolutionary times and fragmentation scales are significantly greater than the hydrodynamic (Jeans) values even for clouds with mildly supercritical mass-to-flux ratio. We utilize values of fragmentation scales and growth time corresponding to typical ionization fractions within a molecular cloud and apply them to the observations of the lifetime of prestellar cores and the number of embedded cores forming in a parent clump. We fit the observations of prestellar cores in the Aquila cloud identified with Herschel and obtain a range of estimated lifetimes of cores to be in the range 0.1 to a few Myr.

We also model the number of such embedded cores forming in a parent clump as found in the Perseus star-forming complex identified with the Submillimeter Array (SMA). The model makes different predictions than the standard Jeans analysis, and its concurrence with the observations provides a means to understand the formation and evolution of dense cores in molecular clouds.


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