EDispMap¶

class gammapy.irf.EDispMap(edisp_map, exposure_map=None)[source]¶

Bases: gammapy.irf.irf_map.IRFMap

Energy dispersion map.

Parameters

edisp_mapMap: the input Energy Dispersion Map. Should be a Map with 2 non spatial axes. migra and true energy axes should be given in this specific order.
exposure_mapMap, optional: Associated exposure map. Needs to have a consistent map geometry.

Examples

import numpy as np
from astropy import units as u
from astropy.coordinates import SkyCoord
from gammapy.maps import WcsGeom, MapAxis
from gammapy.irf import EnergyDispersion2D, EffectiveAreaTable2D
from gammapy.makers.utils import make_edisp_map, make_map_exposure_true_energy

# Define energy dispersion map geometry
energy_axis = MapAxis.from_edges(np.logspace(-1, 1, 4), unit="TeV", name="energy")
migra_axis = MapAxis.from_edges(np.linspace(0, 3, 100), name="migra")
pointing = SkyCoord(0, 0, unit="deg")
max_offset = 4 * u.deg
geom = WcsGeom.create(
    binsz=0.25 * u.deg,
    width=10 * u.deg,
    skydir=pointing,
    axes=[migra_axis, energy_axis],
)

# Extract EnergyDispersion2D from CTA 1DC IRF
filename = "$GAMMAPY_DATA/cta-1dc/caldb/data/cta/1dc/bcf/South_z20_50h/irf_file.fits"
edisp2D = EnergyDispersion2D.read(filename, hdu="ENERGY DISPERSION")
aeff2d = EffectiveAreaTable2D.read(filename, hdu="EFFECTIVE AREA")

# Create the exposure map
exposure_geom = geom.to_image().to_cube([energy_axis])
exposure_map = make_map_exposure_true_energy(pointing, "1 h", aeff2d, exposure_geom)

# create the EDispMap for the specified pointing
edisp_map = make_edisp_map(edisp2D, pointing, geom, max_offset, exposure_map)

# Get an Energy Dispersion (1D) at any position in the image
pos = SkyCoord(2.0, 2.5, unit="deg")
energy = np.logspace(-1.0, 1.0, 10) * u.TeV
edisp = edisp_map.get_edisp_kernel(pos=pos, energy=energy)

# Write map to disk
edisp_map.write("edisp_map.fits")

Attributes Summary

edisp_map

Methods Summary

`copy`()	Copy IRF map
`cutout`(position, width[, mode])	Cutout IRF map.
`downsample`(factor[, axis, weights])	Downsample the spatial dimension by a given factor.
`from_diagonal_response`(energy_axis_true[, …])	Create an allsky EDisp map with diagonal response.
`from_geom`(geom)	Create edisp map from geom.
`from_hdulist`(hdulist[, hdu, hdu_bands, …])	Create from `HDUList`.
`get_edisp_kernel`(position, energy_axis)	Get energy dispersion at a given position.
`read`(filename[, hdu])	Read an IRF_map from file and create corresponding object
`sample_coord`(map_coord[, random_state])	Apply the energy dispersion corrections on the coordinates of a set of simulated events.
`slice_by_idx`(slices)	Slice sub dataset.
`stack`(other[, weights])	Stack IRF map with another one in place.
`to_edisp_kernel_map`(energy_axis)	Convert to map with edisp kernels
`to_hdulist`()	Convert to `HDUList`.
`write`(filename[, overwrite])	Write IRF map to fits

Attributes Documentation

edisp_map¶

Methods Documentation

copy()¶: Copy IRF map

cutout(position, width, mode='trim')¶

Cutout IRF map.

Parameters

positionSkyCoord: Center position of the cutout region.
widthtuple of Angle: Angular sizes of the region in (lon, lat) in that specific order. If only one value is passed, a square region is extracted.
mode{‘trim’, ‘partial’, ‘strict’}: Mode option for Cutout2D, for details see Cutout2D.

Returns

cutoutIRFMap: Cutout IRF map.

downsample(factor, axis=None, weights=None)¶

Downsample the spatial dimension by a given factor.

Parameters

factorint: Downsampling factor.
axisstr: Which axis to downsample. By default spatial axes are downsampled.
weightsMap: Map with weights downsampling.

Returns

mapIRFMap: Downsampled irf map.

classmethod from_diagonal_response(energy_axis_true, migra_axis=None)[source]¶

Create an allsky EDisp map with diagonal response.

Parameters

energy_axis_trueMapAxis: True energy axis
migra_axisMapAxis: Migra axis

Returns

edisp_mapEDispMap: Energy dispersion map.

classmethod from_geom(geom)[source]¶

Create edisp map from geom.

By default a diagonal edisp matrix is created.

Parameters

geomGeom: Edisp map geometry.

Returns

edisp_mapEDispMap: Energy dispersion map.

classmethod from_hdulist(hdulist, hdu=None, hdu_bands=None, exposure_hdu=None, exposure_hdu_bands=None)¶

Create from HDUList.

Parameters

hdulistHDUList: HDU list.
hdustr: Name or index of the HDU with the IRF map.
hdu_bandsstr: Name or index of the HDU with the IRF map BANDS table.
exposure_hdustr: Name or index of the HDU with the exposure map data.
exposure_hdu_bandsstr: Name or index of the HDU with the exposure map BANDS table.

Returns

irf_mapIRFMap: IRF map.

get_edisp_kernel(position, energy_axis)[source]¶

Get energy dispersion at a given position.

Parameters

positionSkyCoord: the target position. Should be a single coordinates
energy_axisMapAxis: Reconstructed energy axis

Returns

edispEnergyDispersion: the energy dispersion (i.e. rmf object)

classmethod read(filename, hdu=None)¶: Read an IRF_map from file and create corresponding object

sample_coord(map_coord, random_state=0)[source]¶

Apply the energy dispersion corrections on the coordinates of a set of simulated events.

Parameters

map_coordMapCoord object.: Sequence of coordinates and energies of sampled events.
random_state{int, ‘random-seed’, ‘global-rng’, RandomState}: Defines random number generator initialisation. Passed to get_random_state.

Returns

MapCoord.: Sequence of Edisp-corrected coordinates of the input map_coord map.

slice_by_idx(slices)¶

Slice sub dataset.

The slicing only applies to the maps that define the corresponding axes.

Parameters

slicesdict: Dict of axes names and integers or slice object pairs. Contains one element for each non-spatial dimension. For integer indexing the corresponding axes is dropped from the map. Axes not specified in the dict are kept unchanged.

Returns

map_outIRFMap: Sliced irf map object.

stack(other, weights=None)¶

Stack IRF map with another one in place.

Parameters

otherIRFMap: IRF map to be stacked with this one.
weightsMap: Map with stacking weights.

to_edisp_kernel_map(energy_axis)[source]¶

Convert to map with edisp kernels

Parameters

energyMapAxis: Reconstructed enrgy axis.

Returns

edispEDispKernelMap: Energy dispersion kernel map.

to_hdulist()¶

Convert to HDUList.

Returns

hdu_listHDUList: HDU list.

write(filename, overwrite=False, **kwargs)¶: Write IRF map to fits