2023.08.31 - Mordecai-Mark Mac Low
Channel: Coloquio IRyA
Date: 01/09/2023

Speaker info: Dr. Mordecai-Mark Mac Low Curator, Division of Physical Sciences, American Museum of Natural History

Title: Dynamical Collapse of Molecular Clouds
Abstract:
The association of molecular emission with dark clouds and star 
formation now dates back over fifty years. For nearly that long it has 
been debated whether these clouds are long-lived, quasi-static objects, 
or short-lived, rapidly evolving ones.  Recently, it has become clear 
that, though they are rapidly evolving, with dynamics controlled by 
internal gravitational collapse, they are not as short-lived as one 
might expect because they are continually accreting new mass from their 
environment. I present evidence for their rapid evolution drawn from 
clouds self-consistently formed within kiloparsec scale numerical models
 of magnetized turbulence in a stratified medium driven by supernovae, 
as well as from full galaxy models using gas dynamics. The evidence 
includes comparisons to observations of the angle between field 
direction and density gradients. I support the argument with an analytic
 calculation showing that clouds likely accumulate due to gravitational 
instability rather than shock wave sweeping.  Finally, I show 
preliminary results from models of cloud destruction by feedback from 
newly forming star clusters, emphasizing the difficulty of disrupting 
the most massive clouds.