Generate composite galaxy

Finall, in this example we’re going to demonstrate how to make a composite galaxy, including with imaging. For more information on defining parametric morphology see the Imaging examples.

import numpy as np
from unyt import Msun, Myr, angstrom, kpc

from synthesizer.emission_models import IncidentEmission
from synthesizer.filters import UVJ
from synthesizer.grid import Grid
from synthesizer.parametric import SFH, Stars, ZDist
from synthesizer.parametric.galaxy import Galaxy
from synthesizer.parametric.morphology import Sersic2D

/tmp/ipykernel_6948/2794591620.py:5: FutureWarning: The filters module has been moved to the instruments module. Please update your imports synthesizer.filters -> synthesizer.instruments
  from synthesizer.filters import UVJ

Let’s begin by defining the geometry of the images:

# Define geometry of the images
resolution = 0.1 * kpc  # resolution in kpc
npix = 50
fov = resolution * npix

And initialising the Grid object:

grid_dir = "../../../tests/test_grid"
grid_name = "test_grid"
grid = Grid(
    grid_name, grid_dir=grid_dir, new_lam=np.logspace(3, 4.2, 1000) * angstrom
)

And initialising a FilterCollection, in this case the rest-frame UVJ filters.

filters = UVJ(new_lam=grid.lam)

Disk

Let’s now build the disk component of our composite galaxy.

Starting by defining the morphology:

morph = Sersic2D(
    r_eff=2.0 * kpc, sersic_index=1.0, ellipticity=0.5, theta=35.0
)

Define the parameters of the star formation and metal enrichment histories

sfh_p = {"max_age": 10 * Myr}
Z_p = {
    "log10metallicity": -2.0
}  # can also use linear metallicity e.g. {'Z': 0.01}
stellar_mass = 10**9.5 * Msun

Define the functional form of the star formation and metal enrichment histories

sfh = SFH.Constant(**sfh_p)  # constant star formation
metal_dist = ZDist.DeltaConstant(**Z_p)  # constant metallicity

Get the 2D star formation and metal enrichment history for the given SPS grid. This is (age, Z).

stars = Stars(
    grid.log10age,
    grid.metallicity,
    sf_hist=sfh,
    metal_dist=metal_dist,
    initial_mass=stellar_mass,
    morphology=morph,
)

/opt/hostedtoolcache/Python/3.10.16/x64/lib/python3.10/site-packages/unyt/array.py:1832: RuntimeWarning: divide by zero encountered in log10
  out_arr = func(np.asarray(inp), out=out_func, **kwargs)

Initialise the Galaxy object, make an image and plot it. In this case, we can make a colour image using our UVJ filters:

# Initialise Galaxy object
disk = Galaxy(stars=stars)

# Generate stellar spectra
incident = IncidentEmission(grid)
disk.stars.get_spectra(incident)

# Get photometry
disk.get_photo_lnu(filters)

# Make images
disk_img = disk.get_images_luminosity(
    resolution=resolution,
    fov=fov,
    emission_model=incident,
)

print(disk)

# Make and plot an rgb image
disk_img.make_rgb_image(rgb_filters={"R": "J", "G": "V", "B": "U"})
fig, ax, _ = disk_img.plot_rgb_image(show=True)

+-------------------------------------------------------------------------------+
|                                    GALAXY                                     |
+---------------+---------------------------------------------------------------+
| Attribute     | Value                                                         |
+---------------+---------------------------------------------------------------+
| galaxy_type   | 'Parametric'                                                  |
+---------------+---------------------------------------------------------------+
| stars         | <synthesizer.parametric.stars.Stars object at 0x7fa80d9c1300> |
+---------------+---------------------------------------------------------------+
| name          | 'parametric galaxy'                                           |
+---------------+---------------------------------------------------------------+
| sfzh (51, 13) | 0.00e+00 -> 5.84e+08 (Mean: 4.77e+06)                         |
+---------------+---------------------------------------------------------------+

/home/runner/work/synthesizer/synthesizer/src/synthesizer/utils/ascii_table.py:67: FutureWarning: The `photo_fluxes` attribute is deprecated. Use `photo_fnu` instead. Will be removed in v1.0.0
  self.attributes[name] = getattr(obj, name)
/home/runner/work/synthesizer/synthesizer/src/synthesizer/utils/ascii_table.py:67: FutureWarning: The `photo_luminosities` attribute is deprecated. Use `photo_lnu` instead. Will be removed in v1.0.0
  self.attributes[name] = getattr(obj, name)

Bulge

Lets do the same but make a Bulge this time to combine.

# Define bulge morphology
morph = Sersic2D(r_eff=0.5 * kpc, sersic_index=4.0)

# Define the parameters of the star formation and metal enrichment histories
stellar_mass = 10**9.2 * Msun
stars = Stars(
    grid.log10age,
    grid.metallicity,
    sf_hist=10.0 * Myr,
    metal_dist=0.01,
    morphology=morph,
    initial_mass=stellar_mass,
)

# Get galaxy object
bulge = Galaxy(stars=stars)

# Get spectra
bulge.stars.get_spectra(incident)

# Get photometry
bulge.get_photo_lnu(filters)

# make images
bulge_img = bulge.get_images_luminosity(
    resolution=resolution,
    fov=fov,
    emission_model=incident,
)

# Make and plot an rgb image
bulge_img.make_rgb_image(rgb_filters={"R": "J", "G": "V", "B": "U"})
fig, ax, _ = bulge_img.plot_rgb_image(show=True)

Total

Finally we can combine the disk and bulge together to make a composite galaxy.

# Combine galaxy objects
combined = disk + bulge

print(combined)

# Combine images
total = disk_img + bulge_img

# Make and plot an rgb image
total.make_rgb_image(rgb_filters={"R": "J", "G": "V", "B": "U"})
fig, ax, _ = total.plot_rgb_image(show=True)

+-------------------------------------------------------------------------------+
|                                    GALAXY                                     |
+---------------+---------------------------------------------------------------+
| Attribute     | Value                                                         |
+---------------+---------------------------------------------------------------+
| galaxy_type   | 'Parametric'                                                  |
+---------------+---------------------------------------------------------------+
| stars         | <synthesizer.parametric.stars.Stars object at 0x7fa80bb5ace0> |
+---------------+---------------------------------------------------------------+
| name          | 'parametric galaxy'                                           |
+---------------+---------------------------------------------------------------+
| sfzh (51, 13) | 0.00e+00 -> 1.91e+09 (Mean: 7.16e+06)                         |
+---------------+---------------------------------------------------------------+

And plot the spectra for good measure…

from synthesizer.emissions import plot_spectra

plot_spectra(
    spectra={
        "Combined": combined.stars.spectra["incident"],
        "Disk": disk.stars.spectra["incident"],
        "Bulge": bulge.stars.spectra["incident"],
    },
    show=True,
    ylimits=(10**29.0, 10**31.0),
    xlimits=(900, 10**4.3),
    figsize=(6, 5),
)

(<Figure size 600x500 with 1 Axes>,
 <Axes: xlabel='$\\lambda/[\\mathrm{\\AA}]$', ylabel='$L_{\\nu}/[\\mathrm{\\rm{erg} \\ / \\ \\rm{Hz \\cdot \\rm{s}}}]$'>)