irf - Instrument response functions

Introduction

For a definition of the response function you are invited to read IRF Theory.

gammapy.irf handles the following instrument response functions (IRFs):

• Effective area (AEFF)

• Energy Dispersion (EDISP)

• Point Spread Function (PSF)

• Background (BKG)

Most of the formats defined at IACT IRFs are supported. At the moment, there is little support for Fermi-LAT or other instruments.

Most users will not use gammapy.irf directly, but will instead use IRFs as part of their spectrum, image or cube analysis to compute exposure and effective EDISP and PSF for a given dataset.

Most (at some point maybe all) classes in gammapy.irf have an gammapy.utils.nddata.NDDataArray as data attribute to support interpolation.

IRF Axis naming

In the IRF classes we use the following axis naming convention:

Variable	Definition
energy	Reconstructed energy axis (\(E\) in IRF Theory)
energy_true	True energy axis (\(E_{\rm true}\) in IRF Theory)
offset	Field of view offset from center (\(p_{\rm true}\) in IRF Theory)
fov_lon	Field of view longitude
fov_lat	Field of view latitude
migra	Energy migration (\(\mu\) in IRF Theory)
rad	Offset angle from source position (\(\delta p\) in IRF Theory)

Getting Started

See cta.html for an example how to access IACT IRFs.

Using gammapy.irf

If you’d like to learn more about using gammapy.irf, read the following sub-pages:

• IRF Theory
• Effective area
• Energy Dispersion
• Point Spread Function
• Background

Reference/API

gammapy.irf Package

Instrument response functions (IRFs).

Functions

load_cta_irfs(filename)

load CTA instrument response function and return a dictionary container.

Classes

Background2D(energy_axis, offset_axis, data)	Background 2D.
Background3D(energy_axis, fov_lon_axis, …)	Background 3D.
EDispKernel(energy_axis_true, energy_axis, data)	Energy dispersion matrix.
EDispKernelMap(edisp_kernel_map, exposure_map)	Energy dispersion kernel map.
EDispMap(edisp_map[, exposure_map])	Energy dispersion map.
EffectiveAreaTable(energy_axis_true, data[, …])	Effective area table.
EffectiveAreaTable2D(energy_axis_true, …)	2D effective area table.
EnergyDependentMultiGaussPSF(…[, …])	Triple Gauss analytical PSF depending on energy and theta.
EnergyDependentTablePSF(energy_axis_true, …)	Energy-dependent radially-symmetric table PSF (gtpsf format).
EnergyDispersion2D(energy_axis_true, …[, …])	Offset-dependent energy dispersion matrix.
PSF3D(energy_axis_true, offset_axis, …[, …])	PSF with axes: energy, offset, rad.
PSFKernel(psf_kernel_map[, normalize])	PSF kernel for Map.
PSFKing(energy_axis_true, offset_axis, …)	King profile analytical PSF depending on energy and offset.
PSFMap(psf_map[, exposure_map])	Class containing the Map of PSFs and allowing to interact with it.
Registry	Registry class.
TablePSF(rad_axis, psf_value[, interp_kwargs])	Radially-symmetric table PSF.

Variables

IRF_REGISTRY

Registry class.