Template spectral model

This model is defined by custom tabular values.

The units returned will be the units of the values array provided at initialization. The model will return values interpolated in log-space, returning 0 for energies outside of the limits of the provided energy array.

The class implementation follows closely what has been done in naima.models.TemplateSpectralModel

Example plot

Here is an example plot of the model:

import numpy as np
from astropy import units as u
import matplotlib.pyplot as plt
from gammapy.modeling.models import (
    Models,
    PowerLawNormSpectralModel,
    SkyModel,
    TemplateSpectralModel,
)

energy_bounds = [0.1, 1] * u.TeV
energy = np.array([1e6, 3e6, 1e7, 3e7]) * u.MeV
values = np.array([4.4e-38, 2.0e-38, 8.8e-39, 3.9e-39]) * u.Unit("MeV-1 s-1 cm-2")
template = TemplateSpectralModel(energy=energy, values=values)
template.plot(energy_bounds)
plt.grid(which="both")

Spectral correction Corrections to templates can be applied by multiplication with a normalized spectral model, for example gammapy.modeling.models.PowerLawNormSpectralModel. This operation create a new gammapy.modeling.models.CompoundSpectralModel

new_model = template * PowerLawNormSpectralModel(norm=2, tilt=0)

print(new_model)

CompoundSpectralModel
    Component 1 : TemplateSpectralModel

    Component 2 : PowerLawNormSpectralModel

type    name     value    unit   error   min max frozen is_norm link prior
---- --------- ---------- ---- --------- --- --- ------ ------- ---- -----
          norm 2.0000e+00      0.000e+00 nan nan  False    True
          tilt 0.0000e+00      0.000e+00 nan nan   True   False
     reference 1.0000e+00  TeV 0.000e+00 nan nan   True   False
    Operator : mul

YAML representation

Here is an example YAML file using the model:

model = SkyModel(spectral_model=template, name="template-model")
models = Models([model])

print(models.to_yaml())

components:
-   name: template-model
    type: SkyModel
    spectral:
        type: TemplateSpectralModel
        parameters: []
        energy:
            data:
            - 1000000.0
            - 3000000.0
            - 10000000.0
            - 30000000.0
            unit: MeV
        values:
            data:
            - 4.4e-38
            - 2.0e-38
            - 8.8e-39
            - 3.9e-39
            unit: 1 / (cm2 MeV s)
metadata:
    creator: Gammapy 1.2
    date: '2024-02-29T10:21:58.614452'
    origin: null