def make_test_psf(energy_bins=15, theta_bins=12):
"""Create a test FITS PSF file.
A log-linear dependency in energy is assumed, where the size of
the PSF decreases by a factor of tow over tow decades. The
theta dependency is a parabola where at theta = 2 deg the size
of the PSF has increased by 30%.
Parameters
----------
energy_bins : int
Number of energy bins.
theta_bins : int
Number of theta bins.
Returns
-------
psf : `~gammapy.irf.EnergyDependentMultiGaussPSF`
PSF.
"""
energies_all = np.logspace(-1, 2, energy_bins + 1)
energies_lo = energies_all[:-1]
energies_hi = energies_all[1:]
theta_lo = np.linspace(0, 2.2, theta_bins)
def sigma_energy_theta(energy, theta, sigma):
# log-linear dependency of sigma with energy
# m and b are choosen such, that at 100 TeV
# we have sigma and at 0.1 TeV we have sigma/2
m = -sigma / 6.0
b = sigma + m
return (2 * b + m * np.log10(energy)) * (0.3 / 4 * theta**2 + 1)
# Compute norms and sigmas values are taken from the psf.txt in
# irf/test/data
energies, thetas = np.meshgrid(energies_lo, theta_lo)
sigmas = []
for sigma in [0.0219206, 0.0905762, 0.0426358]:
sigmas.append(sigma_energy_theta(energies, thetas, sigma))
norms = []
for norm in 302.654 * np.array([1, 0.0406003, 0.444632]):
norms.append(norm * np.ones((theta_bins, energy_bins)))
return EnergyDependentMultiGaussPSF(
u.Quantity(energies_lo, "TeV"),
u.Quantity(energies_hi, "TeV"),
u.Quantity(theta_lo, "deg"),
sigmas,
norms,
)
def test_psf_cta_1dc():
filename = (
"$GAMMAPY_DATA/cta-1dc/caldb/data/cta/1dc/bcf/South_z20_50h/irf_file.fits"
)
psf_irf = EnergyDependentMultiGaussPSF.read(filename,
hdu="POINT SPREAD FUNCTION")
# Check that PSF is filled with 0 for energy / offset where no PSF info is given.
# This is needed so that stacked PSF computation doesn't error out,
# trying to interpolate for observations / energies where this occurs.
psf = psf_irf.to_energy_dependent_table_psf("4.5 deg")
psf = psf.table_psf_at_energy("0.05 TeV")
assert_allclose(psf.evaluate(rad="0.03 deg").value, 0)
# Check that evaluation works for an energy / offset where an energy is available
psf = psf_irf.to_energy_dependent_table_psf("2 deg")
psf = psf.table_psf_at_energy("1 TeV")
assert_allclose(psf.containment_radius(0.68).deg, 0.053838, atol=1e-4)
def psf(self):
filename = "$GAMMAPY_DATA/tests/unbundled/irfs/psf.fits"
return EnergyDependentMultiGaussPSF.read(filename,
hdu="POINT SPREAD FUNCTION")