PSFMap

class gammapy.cube.PSFMap(psf_map)

Bases: object

Class containing the Map of PSFs and allowing to interact with it.

Parameters:

psf_map : Map

the input PSF Map. Should be a Map with 2 non spatial axes. rad and true energy axes should be given in this specific order.

Examples

import numpy as np
from astropy import units as u
from astropy.coordinates import SkyCoord
from gammapy.maps import Map, WcsGeom, MapAxis
from gammapy.irf import EnergyDependentMultiGaussPSF
from gammapy.cube import make_psf_map, PSFMap

# Define energy axis. Note that the name is fixed.
energy_axis = MapAxis.from_edges(np.logspace(-1., 1., 4), unit='TeV', name='energy')
# Define rad axis. Again note the axis name
rads = np.linspace(0., 0.5, 100) * u.deg
rad_axis = MapAxis.from_edges(rads, unit='deg', name='theta')

# Define parameters
pointing = SkyCoord(0., 0., unit='deg')
max_offset = 4 * u.deg

# Create WcsGeom
geom = WcsGeom.create(binsz=0.25*u.deg, width=10*u.deg, skydir=pointing, axes=[rad_axis, energy_axis])

# Extract EnergyDependentTablePSF from CTA 1DC IRF
filename = '$GAMMAPY_DATA/cta-1dc/caldb/data/cta/1dc/bcf/South_z20_50h/irf_file.fits'
psf = EnergyDependentMultiGaussPSF.read(filename, hdu='POINT SPREAD FUNCTION')
psf3d = psf.to_psf3d(rads)

# create the PSFMap for the specified pointing
psf_map = make_psf_map(psf3d, pointing, geom, max_offset)

# Get an EnergyDependentTablePSF at any position in the image
psf_table = psf_map.get_energy_dependent_table_psf(SkyCoord(2., 2.5, unit='deg'))

# Write map to disk
psf_map.write('psf_map.fits')

Attributes Summary

data	the PSFMap data
geom	The PSFMap MapGeom object
psf_map	the PSFMap itself (Map)
quantity	the PSFMap data as a quantity

Methods Summary

containment_radius_map(energy[, fraction])	Containment radius map.
get_energy_dependent_table_psf(position)	Returns EnergyDependentTable PSF at a given position
get_psf_kernel(position, geom[, max_radius, …])	Returns a PSF kernel at the given position.
read(filename, **kwargs)	Read a psf_map from file and create a PSFMap object
write(*args, **kwargs)	Write the Map object containing the PSF Library map.

Attributes Documentation

data

the PSFMap data

geom

The PSFMap MapGeom object

psf_map

the PSFMap itself (Map)

quantity

the PSFMap data as a quantity

Methods Documentation

containment_radius_map(energy, fraction=0.68)

Containment radius map.

Parameters:

energy : Quantity

Scalar energy at which to compute the containment radius

fraction : float

the containment fraction (range: 0 to 1)

Returns:

containment_radius_map : Map

Containment radius map

get_energy_dependent_table_psf(position)

Returns EnergyDependentTable PSF at a given position

Parameters:

position : SkyCoord

the target position. Should be a single coordinates

Returns:

psf_table : EnergyDependentTablePSF

the table PSF

get_psf_kernel(position, geom, max_radius=None, factor=4)

Returns a PSF kernel at the given position.

The PSF is returned in the form a WcsNDMap defined by the input MapGeom.

Parameters:

position : SkyCoord

the target position. Should be a single coordinate

geom : MapGeom

the target geometry to use

max_radius : Angle

maximum angular size of the kernel map

factor : int

oversampling factor to compute the PSF

Returns:

kernel : PSFKernel

the resulting kernel

classmethod read(filename, **kwargs)

Read a psf_map from file and create a PSFMap object

write(*args, **kwargs)

Write the Map object containing the PSF Library map.