Lines from Galaxy
objects¶
To generate lines from components of a Galaxy
(i.e. parametric or particle based stars or black holes) synthesizer
provides get_lines
methods on component and galaxy objects. These methods are analogous to those on a grid, and return a LineCollection
containing the requested lines (which can either be singular, doublets, triplets, or more).
[1]:
from unyt import Myr, kelvin, Msun
import synthesizer.line_ratios as line_ratios
from synthesizer.emission_models import BimodalPacmanEmission
from synthesizer.emission_models.attenuation import PowerLaw
from synthesizer.emission_models.dust.emission import Blackbody
from synthesizer.grid import Grid
from synthesizer.parametric import SFH, Stars, ZDist
# Get a grid
grid_dir = "../../../tests/test_grid"
grid_name = "test_grid"
grid = Grid(grid_name, grid_dir=grid_dir)
# Make a parametric galaxy
stellar_mass = 10**12 * Msun
sfh = SFH.Constant(max_age=100 * Myr)
metal_dist = ZDist.Normal(mean=0.01, sigma=0.05)
stars = Stars(
grid.log10age,
grid.metallicity,
sf_hist=sfh,
metal_dist=metal_dist,
initial_mass=stellar_mass,
)
# Set up the emission model
model = BimodalPacmanEmission(
grid=grid,
tau_v_ism=0.5,
tau_v_birth=0.7,
dust_curve_ism=PowerLaw(slope=-1.3),
dust_curve_birth=PowerLaw(slope=-0.7),
dust_emission_ism=Blackbody(temperature=100 * kelvin),
dust_emission_birth=Blackbody(temperature=30 * kelvin),
fesc=0.2,
fesc_ly_alpha=0.9,
)
# To get the dust emission at a line we need to first run the
# spectra generation
stars.get_spectra(model)
# Get the lines
lines = stars.get_lines(
(line_ratios.Hb, line_ratios.O3r, line_ratios.O3b), model
)
print(stars.lines["emergent"])
----------
LINE COLLECTION
number of lines: 3
lines: ['H 1 4861.32A' 'O 3 4958.91A' 'O 3 5006.84A']
available ratios: ['R3']
available diagrams: []
----------
In the case of a particle based galaxy you can either get the integrated line emission or per-particle line emission (by using a per particle model) the with get_lines
method.
[2]:
from synthesizer.emission_models import PacmanEmission
from synthesizer.load_data.load_camels import load_CAMELS_IllustrisTNG
# Get the stars from a particle based galaxy
stars = load_CAMELS_IllustrisTNG(
"../../../tests/data/",
snap_name="camels_snap.hdf5",
group_name="camels_subhalo.hdf5",
physical=True,
)[0].stars
# Set up the emission model
model = PacmanEmission(
grid=grid,
tau_v=0.7,
dust_curve=PowerLaw(slope=-1.3),
dust_emission=Blackbody(temperature=50 * kelvin),
fesc=0.5,
fesc_ly_alpha=1.0,
per_particle=True,
)
# Get the spectra and lines
stars.get_spectra(model)
stars.get_lines((line_ratios.Hb, line_ratios.O3r, line_ratios.O3b), model)
print(stars.lines["emergent"])
print(stars.particle_lines["emergent"])
----------
LINE COLLECTION
number of lines: 3
lines: ['H 1 4861.32A' 'O 3 4958.91A' 'O 3 5006.84A']
available ratios: ['R3']
available diagrams: []
----------
----------
LINE COLLECTION
number of lines: 3
lines: ['H 1 4861.32A' 'O 3 4958.91A' 'O 3 5006.84A']
available ratios: ['R3']
available diagrams: []
----------
The line luminosities themselves are extracted and stored in the "nebular"
key of the lines dictionaries. Below we plot the line luminosities and continuum luminosities to compare the different emissions.
Note that we have skipped any lines with little or no contribution.
[3]:
import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.add_subplot(111)
ax.grid(True)
ax.set_axisbelow(True)
# Get the colours
colors = {}
for ind, key in enumerate(stars.lines):
colors[key] = plt.cm.tab10(ind)
for key in stars.lines:
# Don't plot dust emission since it's effectively 0
# for these lines
if key == "dust_emission":
continue
for line_id in stars.lines[key].line_ids:
ax.semilogy(
stars.lines[key][line_id].wavelength,
stars.lines[key][line_id].continuum,
color=colors[key],
marker="+",
linestyle="None",
)
ax.set_xlabel("Wavelength (Angstrom)")
ax.set_ylabel("Continuum (erg/s/Hz)")
# Create the legend
legend_handles = []
for key in stars.lines:
# Don't plot dust emission since it's effectively 0
# for these lines
if key == "dust_emission":
continue
legend_handles.append(
plt.Line2D(
[0],
[0],
color=colors[key],
label=key,
marker="+",
linestyle="None",
)
)
ax.legend(
handles=legend_handles,
loc="upper center",
bbox_to_anchor=(0.5, -0.15),
ncol=3,
)
plt.show()
fig = plt.figure()
ax = fig.add_subplot(111)
ax.grid(True)
ax.set_axisbelow(True)
# Get the colours
colors = {}
for ind, key in enumerate(stars.lines):
colors[key] = plt.cm.tab10(ind)
for key in stars.lines:
for line_id in stars.lines[key].line_ids:
ax.semilogy(
stars.lines[key][line_id].wavelength,
stars.lines[key][line_id].luminosity,
color=colors[key],
marker="+",
linestyle="None",
)
ax.set_xlabel("Wavelength (Angstrom)")
ax.set_ylabel("Luminosity (erg/s)")
# Create the legend
legend_handles = []
for key in stars.lines:
# Skip all spectra types where lines are 0
skip = False
for line_id in stars.lines[key].line_ids:
if stars.lines[key][line_id].luminosity.sum() == 0:
skip = True
break
if skip:
continue
legend_handles.append(
plt.Line2D(
[0],
[0],
color=colors[key],
label=key,
marker="+",
linestyle="None",
)
)
ax.legend(
handles=legend_handles,
loc="upper center",
bbox_to_anchor=(0.5, -0.15),
ncol=3,
)
plt.show()