GMC formation

 

Some of the main questions relating to Giant Molecular Clouds (GMCs) are:

  • How do GMCs form?
  • What are the properties of GMCs?
  • How do GMCs evolve?
  • What do the formation and properties of GMCs imply for star formation?
  • I perform high resolution numerical simulations, like that shown above to try and answer these questions. The image above is from a simulation which includes the thermodynamics of the ISM, a 2 armed spiral potential, self gravity and stellar feedback. The black / white colour scale shows the total gas column density, and the blue / yellow scale shows the molecular gas. The formation of GMCs appears to be a complex process. Simulations of GMC formation in a spiral galaxy appear to show that smaller clouds (present in the gas due to thermal instability) coalesce into more massive GMCs as they pass through spiral shocks in a galaxy. Self gravity aids GMC formation and produces more dense, massive GMCs. Stellar feedback then disrupts the clouds within a timescale of 10 Myrs or so. What these simulations do not show however is the detailed evolution of GMCs, and how star formation proceeds within these GMCs. For this we need higher resolution simulations (see here).