region = CircleSkyRegion(center=src_pos, radius=0.6 * u.deg)
mask = geom2d.region_mask([region])
# ## Modeling the source
#
# This is the important thing to note in this analysis. Since modeling and fitting in `gammapy.maps` needs to have a combination of spectral models, we have to use a dummy Powerlaw as for the spectral model and fix its index to 2. Since we are interested only in the integral flux, we will use the `PowerLaw2SpectralModel` model which directly fits an integral flux.
# In[ ]:
spatial_model = PointSpatialModel(
lon_0="0.01 deg", lat_0="0.01 deg", frame="galactic"
)
spectral_model = PowerLaw2SpectralModel(
emin=emin, emax=emax, index=2.0, amplitude="3e-12 cm-2 s-1"
)
model = SkyModel(spatial_model=spatial_model, spectral_model=spectral_model)
model.parameters["index"].frozen = True
# ## Modeling the background
#
# Gammapy fitting framework assumes the background to be an integrated model.
# Thus, we will define the background as a model, and freeze its parameters for now.
# In[ ]:
background_model = BackgroundModel(maps2D["background"])
background_model.parameters["norm"].frozen = True
dict(
name="powerlaw",
model=PowerLawSpectralModel(
index=2 * u.Unit(""),
amplitude=4 / u.cm**2 / u.s / u.TeV,
reference=1 * u.TeV,
),
val_at_2TeV=u.Quantity(1.0, "cm-2 s-1 TeV-1"),
integral_1_10TeV=u.Quantity(3.6, "cm-2 s-1"),
eflux_1_10TeV=u.Quantity(9.210340371976184, "TeV cm-2 s-1"),
),
dict(
name="powerlaw2",
model=PowerLaw2SpectralModel(
amplitude=u.Quantity(2.9227116204223784, "cm-2 s-1"),
index=2.3 * u.Unit(""),
emin=1 * u.TeV,
emax=10 * u.TeV,
),
val_at_2TeV=u.Quantity(4 * 2.0**(-2.3), "cm-2 s-1 TeV-1"),
integral_1_10TeV=u.Quantity(2.9227116204223784, "cm-2 s-1"),
eflux_1_10TeV=u.Quantity(6.650836884969039, "TeV cm-2 s-1"),
),
dict(
name="ecpl",
model=ExpCutoffPowerLawSpectralModel(
index=1.6 * u.Unit(""),
amplitude=4 / u.cm**2 / u.s / u.TeV,
reference=1 * u.TeV,
lambda_=0.1 / u.TeV,
),
val_at_2TeV=u.Quantity(1.080321705479446, "cm-2 s-1 TeV-1"),
See also: https://fermi.gsfc.nasa.gov/ssc/data/analysis/scitools/source_models.html
"""
# %%
# Example plot
# ------------
# Here is an example plot of the model:
from astropy import units as u
import matplotlib.pyplot as plt
from gammapy.modeling.models import Models, PowerLaw2SpectralModel, SkyModel
energy_bounds = [0.1, 100] * u.TeV
model = PowerLaw2SpectralModel(
amplitude=u.Quantity(1e-12, "cm-2 s-1"),
index=2.3,
emin=1 * u.TeV,
emax=10 * u.TeV,
)
model.plot(energy_bounds)
plt.grid(which="both")
# %%
# YAML representation
# -------------------
# Here is an example YAML file using the model:
model = SkyModel(spectral_model=model, name="power-law2-model")
models = Models([model])
print(models.to_yaml())