# Licensed under a 3-clause BSD style license - see LICENSE.rst
"""Utilities to compute J-factor maps."""
import astropy.units as u
__all__ = ["JFactory"]
[docs]class JFactory:
"""Compute J-Factor maps.
All J-Factors are computed for annihilation. The assumed dark matter
profiles will be centered on the center of the map.
Parameters
----------
geom : `~gammapy.maps.WcsGeom`
Reference geometry
profile : `~gammapy.astro.darkmatter.profiles.DMProfile`
Dark matter profile
distance : `~astropy.units.Quantity`
Distance to convert angular scale of the map
"""
def __init__(self, geom, profile, distance):
self.geom = geom
self.profile = profile
self.distance = distance
[docs] def compute_differential_jfactor(self):
r"""Compute differential J-Factor.
.. math ::
\frac{\mathrm d J}{\mathrm d \Omega} =
\int_{\mathrm{LoS}} \mathrm d r \rho(r)
"""
# TODO: Needs to be implemented more efficiently
separation = self.geom.separation(self.geom.center_skydir)
rmin = separation.rad * self.distance
rmax = self.distance
val = [self.profile.integral(_, rmax) for _ in rmin.flatten()]
jfact = u.Quantity(val).to("GeV2 cm-5").reshape(rmin.shape)
return jfact / u.steradian
[docs] def compute_jfactor(self):
r"""Compute astrophysical J-Factor.
.. math ::
J(\Delta\Omega) =
\int_{\Delta\Omega} \mathrm d \Omega^{\prime}
\frac{\mathrm d J}{\mathrm d \Omega^{\prime}}
"""
diff_jfact = self.compute_differential_jfactor()
return diff_jfact * self.geom.to_image().solid_angle()