# Instrument response function (IRF) functionality (gammapy.irf)¶

## Introduction¶

gammapy.irf handles instrument response functions (IRFs):

• Effective area (AEFF)
• Energy dispersion (EDISP)

Most of the formats defined at IACT IRF are supported. Otherwise, at the moment, there is very 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.

## Getting Started¶

see data_iact.ipynb 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:

## Reference/API¶

### gammapy.irf Package¶

Instrument response functions (IRFs).

#### Functions¶

 multi_gauss_psf_kernel(psf_parameters[, ...]) Create multi-Gauss PSF kernel.

#### Classes¶

 EffectiveAreaTable(energy_lo, energy_hi, data) Effective area table. EffectiveAreaTable2D(energy_lo, energy_hi, ...) 2D effective area table. EnergyDependentMultiGaussPSF(energy_lo, ...) Triple Gauss analytical PSF depending on energy and theta. EnergyDependentTablePSF(energy, rad[, ...]) Energy-dependent radially-symmetric table PSF (gtpsf format). EnergyDispersion(e_true_lo, e_true_hi, ...) Energy dispersion matrix. EnergyDispersion2D(e_true_lo, e_true_hi, ...) Offset-dependent energy dispersion matrix. GaussPSF([sigma]) Extension of Gauss2D PDF by PSF-specific functionality. HESSMultiGaussPSF(source) Multi-Gauss PSF as represented in the HESS software. IRFStacker(list_aeff, list_livetime[, ...]) Stack instrument response functions. PSF3D(energy_lo, energy_hi, offset, rad_lo, ...) PSF with axes: energy, offset, rad. PSF3DChecker(psf[, d_norm, ...]) Automated quality checks for gammapy.irf.PSF3D. PSFKing(energy_lo, energy_hi, offset, gamma, ...) King profile analytical PSF depending on energy and offset. PositionDependentMultiGaussPSF(hdu_list) Position-dependent multi-Gauss PSF. SherpaMultiGaussPSF(source) Multi-Gauss PSF as represented in the Sherpa software. TablePSF(rad, dp_domega[, spline_kwargs]) Radially-symmetric table PSF.