def select_particles():
# reads the coordinates from the file to w0
w0 = int_sgr.read_file('centroid_part_1000', columns=[3, 4, 5, 6, 7, 8], skip_lines=[0])
# gets the default potential object and integrates the orbits using the initial conditions in w0
curr_pot = int_sgr.get_potential()
orbit, pot = int_sgr.integrate(w0, pot=curr_pot)
# plots the orbit at the present timestep
fig = orbit[0].plot()
fig.get_axes()[1].set_title('Full Sgr Stream')
fig.show()
# selects the particles within 0.5 * r_tidal and saves them to w_half_tidal
w_half_tidal = int_sgr.select_tidal_annulus(\
w0, ann_low = 0.0, ann_high = 0.5,\
sat_mass=1e8, mw_mass=130.0075e10, mw_c=32.089)
# integrates the orbits of the particles within 0.5 r_tidal
tidal_orbit, pot = int_sgr.integrate(w_half_tidal, pot=curr_pot)
# plots the orbit at the present timestep
fig = tidal_orbit[0].plot()
fig.get_axes()[1].set_title('Sgr Stream r < 0.5 r_tidal')
fig.show()
def animate_orbit():
# reads the coordinates from the file to w0
w0 = int_sgr.read_file('heavy_sag_7_10', columns=[3, 4, 5, 6, 7, 8], skip_lines=[0])
# gets the default potential object and integrates the orbits using the initial conditions in w0
curr_pot = int_sgr.get_potential()
orbit, pot = int_sgr.integrate(w0, pot=curr_pot)
# plots and saves the particle positions at each timestep to a new folder: 'heavy sag animation'
# NOTE: the folder must not already exist, otherwise an error will be raised
int_sgr.orbit_video(orbit, 'heavy sag animation')
def test_export(file_name):
sat_mass = 1e8 * u.Msun
# reads the coordinates from the file to w0
w0 = int_sgr.read_file('centroid_part_1000', columns=[3, 4, 5, 6, 7, 8], skip_lines=[0])
# selects the particles within 0.5 * r_tidal and saves them to w_half_tidal
w_half_tidal = int_sgr.select_tidal_annulus(\
w0, ann_low = 0.0, ann_high = 0.5,\
sat_mass=1e8, mw_mass=130.0075e10, mw_c=32.089)
# writes the particle data for the particles within 0.5 * r_tidal to the file specified by 'file_name'
int_sgr.export(w_half_tidal.pos, w_half_tidal.vel, sat_mass, file_name)
print('%s has been written' % file_name)
def vary_potential():
# the normal parameters for the potential and the Sgr dSph
sag_mass = 1e8
normal_mw_mass = 130.0075e10*u.Msun
normal_mw_conc = 9.39
normal_mw_rs = 18.927757889861788 * u.kpc
# reads the coordinates from the file to w0
w0 = int_sgr.read_file('centroid_part_1000', columns=[3, 4, 5, 6, 7, 8], skip_lines=[0])
gvs = []
m_ratios = [0.8, 0.9, 1.0, 1.1, 1.2]
c_ratios = [0.8, 0.9, 1.0, 1.1, 1.2]
rs_ratios = [0.8, 0.9, 1.0, 1.1, 1.2]
# makes a potential using 80%, 90%, 100%, 110% and 120% of each of the normal potential parameters
for m_ratio in m_ratios:
for c_ratio in c_ratios:
for rs_ratio in rs_ratios:
# gets the current potential parameters
curr_mass = normal_mw_mass * m_ratio
curr_c = normal_mw_conc * c_ratio
curr_rs = normal_mw_rs * rs_ratio
print('Theta:',\
'mass =', curr_mass,\
'c =', curr_c,\
'rs =', curr_rs,\
)
# creates the current potential object and uses it to integrate the particle orbits
curr_pot = int_sgr.get_potential(total_mass=curr_mass, r_scale=curr_rs, mw_conc=curr_c)
orbit, pot = int_sgr.integrate(w0, pot=curr_pot)
# finds the center of mass of the particle distribution and integrates its orbit
com_p, com_v, com_index = int_sgr.calc_com(w0)
com_orbit,pot = int_sgr.integrate(gd.PhaseSpacePosition(pos=com_p, vel=com_v))
# calculates the generalized variance of the particle distribution
gv = int_sgr.calc_dps(sag_mass, orbit, curr_pot, com_orbit)
print('Generalized Variance:', gv)
gvs.append(gv)
# prints the generalized variances calculated from the potential parameters
np.set_printoptions(precision=3)
print(np.reshape(gvs, [len(m_ratios), len(c_ratios), len(rs_ratios)]))
def integrate_normal_orbit():
# reads the coordinates from the file to w0
w0 = int_sgr.read_file('centroid_part_1000', columns=[3, 4, 5, 6, 7, 8], skip_lines=[0])
# integrates the orbits with initial conditions w0 and with verbose mode on
orbit, pot = int_sgr.integrate(w0, verbose=True)
# plots the orbit at the first timestep (2.65 Gyr ago)
fig = orbit[-1].plot()
# adds a title to the default plotting function from gala
fig.get_axes()[1].set_title('Sgr Stream (2.65 Gyr ago)')
fig.show()
# plots the orbit at the present timestep
fig = orbit[0].plot()
fig.get_axes()[1].set_title('Sgr Stream (Present)')
fig.show()
def plot_dps():
# the parameters for the Sgr dSph
sag_mass = 1e8
# reads the coordinates from the file to w0
w0 = int_sgr.read_file('centroid_part_1000', columns=[3, 4, 5, 6, 7, 8], skip_lines=[0])
# integrates the orbits with initial conditions w0
orbit, pot = int_sgr.integrate(w0)
# finds the center of mass of the particle distribution and integrates its orbit
com_p, com_v, com_index = int_sgr.calc_com(w0)
com_orbit,pot = int_sgr.integrate(gd.PhaseSpacePosition(pos=com_p, vel=com_v))
# calculates the generalized variance of the particle distribution in verbose mode, and displays the dps plot
gv = int_sgr.calc_dps(sag_mass, orbit, pot, com_orbit, \
ylims = [0.2, 400], plot_title = 'Example Dps Plot', show_plot=True, verbose=True)
print('Generalized Variance:', gv)
def integrate_dyn_fric():
sat_mass = 1e10 # Msun
# reads the coordinates from the file to w0
w0 = int_sgr.read_file('heavy_sag_7_10', columns=[3, 4, 5, 6, 7, 8], skip_lines=[0])
# integrates the orbits with initial conditions w0, dynamical friction and with verbose mode on
orbit, pot = int_sgr.integrate_dyn_fric(w0, sat_mass = sat_mass, verbose=True)
# plots the orbit at the first timestep (2.65 Gyr ago)
fig = orbit[-1].plot()
fig.get_axes()[1].set_title('Sgr Stream (2.65 Gyr ago)')
fig.show()
# plots the orbit at the present timestep
fig = orbit[0].plot()
fig.get_axes()[1].set_title('Sgr Stream (Present)')
fig.show()