University of
Notre Dame
College of
Science
Department of
Physics

Astrophysics Seminar

 

The Evaporation and Thermal Balance of Tiny HI Clouds in the Interstellar Medium

 

Dr. Jonathan D. Slavin
Harvard-Smithsonian Center for Astrophysics

 

 

Tuesday, January 23, 2007   12:30 pm   NSH 415

Recent observations of very low column density HI clouds bolster the case that the interstellar medium (ISM) has structure on scales much smaller than accounted for in most global models. Questions arise as to how long such clouds can survive in the ISM without being destroyed by thermal evaporation, photoionization or hydrodynamical instabilities.  I will discuss the evaporation of these thin clouds both when embedded in hot gas and in warm neutral medium gas. I examine the thermal balance in these clouds and how a bi-stable medium may serve to protect them from evaporation.  I find that these clouds could have relatively long evaporation timescales despite their small sizes.  Turbulence in the ambient medium may play a role in either creating or destroying the clouds.  The ultimate importance of thermal conduction and turbulence in determining the life cycle of the tiny HI clouds is still unclear, and the answer may hold important clues to the way mass and energy evolve in the ISM.


 

 


All interested persons are cordially invited to attend.