SimulateGalaxy

Provides a suite of functions for defining density profiles and methods to generated simulations with draws from the profiles via a rejection sampler.

Examples

using SimulateGalaxy

#Define Density Profiles
nfw = NFWParameters(2.0, -5.3, 2.5, 0.16, 1.5, -9.0, 6.9, 0.086, 21.0, 1.5)
sfw = SFWParameters(2.0, -5.3, 2.5, 0.16, 1.5, -9.0, 6.9, 0.086, 4229.2, .69444, 1.2, 3.05, 1.1)

#Simulate Spherical Galaxies with 400 Stars
nfw_sph = simulate_galaxy(nfw, 400)
sfw_sph = simulate_galaxy(sfw, 400)

#Draw a random conversion to Euclidean coordinates based on the spherical coordinates
nfw_eu = sample_euclidean(nfw_sph)
sfw_eu = sample_euclidean(sfw_sph)

#Simulate Spherical Galaxies with 400 Stars and a metallicity component
nfw_sph = simulate_galaxy(nfw, -2.0, .003, 400)
sfw_sph = simulate_galaxy(sfw, -2.0, .003, 400)

Density Profiles

Navarro–Frenk–White (NFW) profile

A type containing the parameters to define a NFW profile is included within the type NFWParameters

Generalized Density profile

Support is also provided for a more general density profile as descrbed in

Geringer-Sameth, Alex, Savvas M. Koushiappas, and Matthew Walker. "Dwarf galaxy annihilation and decay emission profiles for dark matter experiments." The Astrophysical Journal 801.2 (2015): 74. http://stacks.iop.org/0004-637X/801/i=2/a=74

The appropriate type for such a profile is SFWParameters

Profile Fields

The fields defined in each profile are as follows:

• NFWParameters{G <: AbstractFloat}
  • a
  • d
  • e
  • Ec
  • rlim
  • b
  • q
  • Jb
  • vmax
  • rmax
  • rs
  • Φs
  • xlim
  • Φlim
  • adjEc
  • adjJb

Only the parameters through rmax need to be defined, the others over define the density profile but are useful for some computations so are automatically generated. See the Examples section.

• SFWParameters{G <: AbstractFloat}
  • a
  • d
  • e
  • Ec
  • rlim
  • b
  • q
  • Jb
  • ρs
  • rs
  • α
  • β
  • γ
  • Φs
  • xlim
  • Φ0
  • Φlim
  • adjEc
  • adjJb

Only the parameters through γ need to be defined, the others over define the density profile but are useful for some computations so are automatically generated. See the Examples section.

RandomGalaxy

The RandomGalaxy{G <: AbstractFloat, T <: Integer} is abstract type which encompasses the different types of output that can be generated. The subtypes which are generated and the fields they contain are as follows:

• SphericalGalaxy{G <: AbstractFloat, T <: Integer}
  • r
  • vr
  • vt
  • nobs
• MetallicSphericalGalaxy{G <: AbstractFloat, T <: Integer}
  • r
  • vr
  • vt
  • m
  • nobs
• EuclideanGalaxy{G <: AbstractFloat, T <: Integer}
  • x
  • y
  • z
  • vx
  • vy
  • vz
  • nobs
• MetallicEuclideanGalaxy{G <: AbstractFloat, T <: Integer}
  • x
  • y
  • z
  • vx
  • vy
  • vz
  • m
  • nobs
• PartialEuclideanGalaxy{G <: AbstractFloat, T <: Integer}
  • x
  • y
  • vz
  • nobs
• MetallicPartialEuclideanGalaxy{G <: AbstractFloat, T <: Integer}
  • x
  • y
  • vz
  • m
  • nobs

SphericalGalaxy and MetallicSphericalGalaxy denote a spherical coordinate space where only radius, radial velocity, and tangential velocity are specified. EuclideanGalaxy and MetallicEuclideanGalaxy are embeded in Euclidean space for both position and veloicty. Finally PartialEuclideanGalaxy and MetallicPartialEuclideanGalaxy denote imperfectly observed galaxies in Euclidean space containing only two coordinates for position and one of velocity. In all cases the Metallic prefix indicates that a m field denoting metallicity is included.

Rejection Sampler

A rejection sampler is used to draw from the density profile returning a radius, radial velocity, and tangential velocity. If parameters defining the mean and standard deviation of a metallicity are included then a normally distributed metallicity observation is generated as well. Simulation is done via the simulate_galaxy function.