Generating a Milky Way galaxy based on the MW2014 Bovy model¶
The script ic_makeMW2014 allows to create the Bovy MW model model at equilibrium, combining
a stellar disk (Miyamoto disk) a bulge (trucated power law model) and a dark halo (NFW).
The equilibrium is obtained by solving the Jean equation in both spherical and cylindrical coordinates.
By default the script creates the exact MW2014 model. The command:
ic_makeMW2014 -o MW_galaxy.hdf5
will create the MW_galaxy.hdf5 file containing all the particles.
The script can however take the parameters from a yaml file:
ic_makeGalaxy -p params.yml
where the params.hdf5 file contains for example the following parameters:
# using default parameters in tmp_parameter_file.yml
OutputUnits:
UnitLength_in_cm: 3.085e21 # 1 kpc in centimeters
UnitMass_in_g: 1.98848e43 # 10^10 M_sun in grams
UnitVelocity_in_cm_per_s: 1e5 # 1 km/s in centimeters per second
Galaxy:
m_ref: 200000 # reference mass of particles [solar mass]
nf: 1 # particle count multiplicative factor (used to reduce noise)
ftype: "swift" # output format (swift, gh5, gadget)
outputfilename: "galaxy.hdf5" # output file name
irand: 0 # random seed
boxsize: 1500 # boxsize [kpc]
# Parameters for disk component
Disk:
fm: 1 # particle mass to ref. mass ratio (set to 0 disable the component)
mass: 6.8e10 # component mass [solar mass]
Hr: 3.0 # radial scale [kpc]
Hz: 0.280 # vertical scale [kpc]
rmax_to_Hr_ratio: 10 # rmax to Hr ratio
zmax_to_Hz_ratio: 10 # zmax to Hz ratio
toomre: 2 # Toomre stability criterion
# Parameters for bulge component
Bulge:
fm: 1 # particle mass to ref. mass ratio (set to 0 disable the component)
alpha: 1.8 # power law slope
r_c: 1.9 # cutting radius [kpc]
r_1: 1.0 # radius [kpc]
amplitude: 2.22646e8 # density factor [Msol/kpc3]
fr: 10 # rmax to r_c ratio
dR: 0.01 # grid resolution [kpc]
# Parameters for dark halo component
Halo:
fm: 5 # particle mass to ref. mass ratio (set to 0 disable the component)
r_s: 16 # scale radius [kpc]
M_200: 0.6438e12 # virial mass [msol]
r_200: 157.174455004 # virial radius [kpc]
fr: 1.0 # rmax to r200 ratio
dR: 0.25 # grid resolution [kpc]
Plotting the corresponding rotation curve¶
To check the rotation curve corresponding to the model generated, pNbody offers the following command:
plotCylindricalProfile -y vcirc --xmax 50 --rmax 50 --nr 64 --nr 64 --eps 0.1 --forceComovingIntegrationOff MW_galaxy.hdf5
Scripts¶
ic_makeMW2014¶
usage: ic_makeMW2014 [-h] [-p PARAMETER_FILE] [-o OUTPUTFILENAME] [--debug]
[--print-parameters] [--HubbleParameter HUBBLEPARAMETER]
Generates a mulit-component galaxy model
options:
-h, --help show this help message and exit
-p PARAMETER_FILE, --parameter-file PARAMETER_FILE
Name of the parameter file
-o OUTPUTFILENAME Name of the output file
--debug debug mode: save intermediate files
--print-parameters print parameters and quit
--HubbleParameter HUBBLEPARAMETER
Hubble parameter
The model is made out of four components:
a stellar disk (Exponential disk)
a bulge (Power law model)
a dark halo (generic two slope model)
All components can be fine tuned using parameters provided by a parameter file (see below).
Examples:
--------
ic_makeMW2014
ic_makeMW2014 -p params.yml
ic_makeMW2014 -p params.yml -o galaxy.hdf5
ic_makeMW2014 --print-parameters
where the file params.yml contains the following parameters:
'''
OutputUnits:
UnitLength_in_cm: 3.085e21 # 1 kpc in centimeters
UnitMass_in_g: 1.98848e43 # 10^10 M_sun in grams
UnitVelocity_in_cm_per_s: 1e5 # 1 km/s in centimeters per second
Galaxy:
m_ref: 200000 # reference mass of particles [solar mass]
nf: 1 # particle count multiplicative factor (used to reduce noise)
ftype: "swift" # output format (swift, gh5, gadget)
outputfilename: "galaxy.hdf5" # output file name
irand: 0 # random seed
boxsize: 1500 # boxsize [kpc]
# Parameters for disk component
Disk:
fm: 1 # particle mass to ref. mass ratio (set to 0 disable the component)
mass: 6.8e10 # component mass [solar mass]
Hr: 3.0 # radial scale [kpc]
Hz: 0.280 # vertical scale [kpc]
rmax_to_Hr_ratio: 10 # rmax to Hr ratio
zmax_to_Hz_ratio: 10 # zmax to Hz ratio
toomre: 2 # Toomre stability criterion
# Parameters for bulge component
Bulge:
fm: 1 # particle mass to ref. mass ratio (set to 0 disable the component)
alpha: 1.8 # power law slope
r_c: 1.9 # cutting radius [kpc]
r_1: 1.0 # radius [kpc]
amplitude: 2.22646e8 # density factor [Msol/kpc3]
fr: 10 # rmax to r_c ratio
dR: 0.01 # grid resolution [kpc]
# Parameters for dark halo component
Halo:
fm: 5 # particle mass to ref. mass ratio (set to 0 disable the component)
r_s: 16 # scale radius [kpc]
M_200: 0.6438e12 # virial mass [msol]
r_200: 157.174455004 # virial radius [kpc]
fr: 1.0 # rmax to r200 ratio
dR: 0.25 # grid resolution [kpc]
'''
