Modeling Galaxy Interactions

 
Physics involved: 
  • Gravity:N-body treecodes
  • Gas dynamics: Smooth Particle Hydrodynamics
  • Star formation: density/temperature dependent Schmidt law or Jeans criterion
  • Feedback: thermal/kinetic effects on gas
Dynamical Phases:
  • Collisional perturbation
  • Self gravitating response
  • Gas inflow + activity
  • Merger

So what determines how, when, and if starburst/AGN activity is triggered during an interaction?
    Encounter parameters? Gas fraction? Galaxy type? Environment?
 

Gaseous inflow and central activity are driven by gravitational torques:
(Noguchi 1987; Barnes & Hernquist 1991; Mihos & Hernquist 1996)
 
Gas Angular Momentum
Physical Torques
Gravitational Torques
(from Mihos & Hernquist 1996)

 
Inflow can be suppressed if instabilities are suppressed:
  • Including a central bulge (Mihos & Hernquist 1994, 1996)

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  • Reducing the disk surface density (eg, LSBs; Mihos, McGaugh, & de Blok 1997; Mihos 1999)

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  • Suppressing orbital resonances (Barnes & Hernquist 1996)

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...but other influences (gas fraction, environment, etc) must surely also play a role...

 

Response is closely coupled to the dynamical and structural properties of the colliding galaxies. This has important ramifications for: