"""
Compute the dynamical (i.e. free-fall) timescale of the particles set. This is
the time it would take for a pressureless homogeneous sphere of this size and
average density to collapse. If 'mass_fraction' is supplied, only the inner
particles are considered in the computation of the size of the sphere. For
example, 'mass_fraction=0.95' ignores the positions of the outer particles
comprising 5% by mass (useful for density profiles with long tails).
"""
if mass_fraction is None:
total_radius = particles.total_radius()
else:
total_radius = particles.LagrangianRadii(mf=[mass_fraction], cm=particles.center_of_mass())[0][0]
return numpy.pi * (total_radius**3 / (8.0 * G * particles.total_mass())).sqrt()
AbstractParticleSet.add_global_function_attribute("center_of_mass", center_of_mass)
AbstractParticleSet.add_global_function_attribute("center_of_mass_velocity", center_of_mass_velocity)
AbstractParticleSet.add_global_function_attribute("kinetic_energy", kinetic_energy)
AbstractParticleSet.add_global_function_attribute("potential_energy", potential_energy)
AbstractParticleSet.add_global_function_attribute("thermal_energy", thermal_energy)
AbstractParticleSet.add_global_function_attribute("virial_radius", virial_radius)
AbstractParticleSet.add_global_function_attribute("total_mass", total_mass)
AbstractParticleSet.add_global_function_attribute("total_radius", total_radius)
AbstractParticleSet.add_global_function_attribute("total_momentum", total_momentum)
AbstractParticleSet.add_global_function_attribute("total_angular_momentum", total_angular_momentum)
AbstractParticleSet.add_global_function_attribute("moment_of_inertia", moment_of_inertia)
AbstractParticleSet.add_global_function_attribute("dynamical_timescale", dynamical_timescale)
AbstractParticleSet.add_global_function_attribute("potential_energy_in_field", potential_energy_in_field)
AbstractParticleSet.add_global_vector_attribute("position", ["x","y","z"])
the time it would take for a pressureless homogeneous sphere of this size and
average density to collapse. If 'mass_fraction' is supplied, only the inner
particles are considered in the computation of the size of the sphere. For
example, 'mass_fraction=0.95' ignores the positions of the outer particles
comprising 5% by mass (useful for density profiles with long tails).
"""
if mass_fraction is None:
total_radius = particles.total_radius()
else:
total_radius = particles.LagrangianRadii(
mf=[mass_fraction], cm=particles.center_of_mass())[0][0]
return numpy.pi * (total_radius**3 /
(8.0 * G * particles.total_mass())).sqrt()
AbstractParticleSet.add_global_function_attribute("center_of_mass",
center_of_mass)
AbstractParticleSet.add_global_function_attribute("center_of_mass_velocity",
center_of_mass_velocity)
AbstractParticleSet.add_global_function_attribute("kinetic_energy",
kinetic_energy)
AbstractParticleSet.add_global_function_attribute("potential_energy",
potential_energy)
AbstractParticleSet.add_global_function_attribute("thermal_energy",
thermal_energy)
AbstractParticleSet.add_global_function_attribute("virial_radius",
virial_radius)
AbstractParticleSet.add_global_function_attribute("total_mass", total_mass)
AbstractParticleSet.add_global_function_attribute("total_radius", total_radius)
AbstractParticleSet.add_global_function_attribute("total_momentum",
total_momentum)
AbstractParticleSet.add_global_function_attribute("total_angular_momentum",