Hydrodynamics of galactic cooling flows
Alexei Kritsuk, Tomasz Plewa & Ewald Mueller
Buoyant structures in various environments
Thermodynamics of hot interstellar gas with radiative cooling and mass dropout
Kritsuk (1996)
One-zone model allows us to find an equlibrium `thermodynamic' state for the hot gas with sources and sinks of mass and energy. We use it as a tool to study the stability of these equilibria and its dependence on the control parameters of the model. The movie below shows two major bifurcations which occur when the deposition control parameter increases from 0 to 1. `Blue sky' catastrophe gives rise to an equilibrium solution at b = 0.0975 and Hopf bifurcation creates a stable steady state at b = 0.183.
A phase trajectory in the temperature-density plane, varying a value of deposition efficiency b (MPEG movie) 2.1M
MPEG movies for convection initiated by a global gas density perturbation
Kritsuk, Plewa & Müller (2000)
This 2-D (axial symmetry) simulation shows the formation and evolution of a convective core in the hot interstellar gas of a gE-galaxy. The convective instability of initially hydrostatic model is stimulated by a small departure from thermodynamic equilibrium due to a global negative gas density perturbation (-10%). We also introduce small random velocity perturbations (~ 0.3 km/s). The deposition control b = 0.48.
Temperature   1.3M 0.7M 0.4M
Entropy: the onset of convection 0.5M      
Entropy   1.1M 0.6M 0.4M
Radial velocity   1.4M 0.9M 0.5M
Tangential velocity: the onset of instability 0.2M      
Mach number   1.3M 0.8M 0.5M
Kinetic energy   1.6M 1M 0.6M
Velocity divergence 6.7M 3.6M 1.9M 1M
Vorticity   1.8M 1.1M 0.5M
NB: The links are arranged from left to right in the order of decreasing time resolution.
Convection driven by an excessive central heating The onset of convection in the core: Entropy
In this simulation we perturb the thermal equilibrium of our hydrostatic model by addition of a heat source in the centre (r < 0.5 kpc), which doubles the local value of energy supply to the hot gas. The MPEG movies below show the formation of a ~3 kpc convective core during the first 100 Myr after switching the extra heat source on.
Temperature 1.1M
Entropy: the onset of convection 0.6M
Entropy 1M
Radial velocity 1.2M
Mach number 1.1M
Kinetic energy 1.5M
Velocity divergence 5.3M
Vorticity 1.2M
Low Type Ia SN heating rate (T_o = 2.5e7 K) and additional heat source at the centre. Restart from a spherically symmetric solution at 960 Myr.
  t < 80 Myr t < 150 Myr t < 220 Myr t < 380 Myr
Temperature 1.2M 2.2M 2.3M 2M
Pseudo entropy 1.3M 2.2M 2.1M 2M
Radial velocity 1.2M 2.1M   2M
Tangential velocity 1.2M      
Kinetic energy 1.7M 3M    
Velocity divergence     6.5M  
Vorticity 1M      
The onset of penetrative convection in an isentropic bubble inside the (Rayleigh-Taylor unstable) condensation front (restart from a spherically symmetric solution at 1.5 Gyr with the same as above central heating efficiency). We imposed small random velocity perturbations at the restart.
M87 Color M87 B&W M87 East-West M87 X-rays M87&Dog2 Virgo from Hevel's Uranographia (1690) r < 2.5 kpc r < 6 kpc r < 10 kpc
Entropy: the onset of penetrative convection 0.8M click me for a surprise    
Entropy   0.8M   1.8M 2.9M  1.5M
Radial velocity   0.7M  
The same initial setup as above with an isentropic bubble inside the condensation front. But for this run we switched on an additional (elliptic in shape) heat source at the centre at t=1.5 Gyr. We also imposed small random velocity perturbations at the restart.
  r < 3 kpc r < 15 kpc
Temperature 1.2M 1.5M
Entropy 1.9M 1.5M
Radial velocity   1.1M
Kinetic energy   1.4M
Velocity divergence   5.3M
Elliptic heat source at the centre at t=0 and small random velocity perturbations. Low Type Ia SN heating rate (T_o = 3e7 K).
Model e385
  r < 3 kpc r < 6 kpc r < 8.5 kpc
Entropy 0.3M 0.2M 0.3M   0.7M
Radial velocity   0.2M 0.3M   0.6M
Model e185
  r < 2 kpc r < 5 kpc r < 7 kpc
Entropy 0.4M 0.2M 0.3M   0.3M
Radial velocity   0.2M 0.3M   0.3M
Model eh85 (elliptic source with T_o=0.5)
      r < ? kpc
Entropy     0.3M
Radial velocity     0.3M
Model eq85 (elliptic source with T_o=0.2)
      r < 3 kpc
Entropy     0.3M
Temperature     0.3M
Radial velocity     0.3M
Last modified:
Comments to: akritsuk@ucsd.edu