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

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

from gammapy.modeling.models import (
    Models,
    PowerLawNormSpectralModel,
    SkyModel,
    TemplateSpectralModel,
)

energy_range = [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_range)
plt.grid(which="both")


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

print(new_model)

Out:

CompoundSpectralModel
    Component 1 : TemplateSpectralModel

    Component 2 : PowerLawNormSpectralModel

   name     value    unit min max frozen   error
--------- ---------- ---- --- --- ------ ---------
     norm 2.0000e+00      nan nan  False 0.000e+00
     tilt 0.0000e+00      nan nan   True 0.000e+00
reference 1.0000e+00  TeV nan nan   True 0.000e+00
    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())

Out:

components:
-   name: template-model
    type: SkyModel
    spectral:
        type: TemplateSpectralModel
        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)