Data Formats

Note

Since November 2015 there is the Data formats for gamma-ray astronomy project. This page contains extra information about which formats we support in Gammapy and which class corresponds to which format.

Where available and useful existing standards are used, e.g. for spectral data the X-ray community has developed the PHA, ARF and RMF file formats and they have developed powerful tools to work with data in that format.

Overview

Here’s an overview of the file formats supported by Gammapy and Gammalib:

Type	Format Name	Gammapy	Gammalib
Events	EVENTS	EventList	GEventList
Effective area	AEFF_2D	EffectiveAreaTable2D	GCTAAeff2D
Effective area	ARF	EffectiveAreaTable	GCTAAeffArf
Energy dispersion	EDISP_2D	EnergyDispersion2D	GCTAEdisp2D
Energy dispersion	RMF	EDispKernel	GCTAEdispRMF
PSF	PSF_2D_GAUSS	EnergyDependentMultiGaussPSF	GCTAPsf2D
PSF	PSF_2D_KING	PSFKing	GCTAPsfKing
PSF	no spec available	TablePSF	GCTAPsfVector
PSF	gtpsf output	EnergyDependentTablePSF	N/A
PSF	psf_table	PSF3D	GCTAPsfTable
PSF	no spec available	N/A	GCTACubePsf
Background	BACKGROUND_3D	Background3D	GCTABackground3D
Background	BACKGROUND_2D	Background2D	N/A
Background	no spec available	N/A	GCTAModelRadialAcceptance
Background	no spec available	N/A	GCTACubeBackground
Exposure	EXPOSURE_3D	Map	GCTACubeExposure
Counts	3D	Map	GCTAEventCube
Counts	Image	Map	GSkyMap
Counts	PHA	RegionNDMap	GPha

Notes

• The Gammalib docs contain a nice overview of IRFs here and detailed explanations of some IRF here.

• We probably should unify / shorten the IRF class names in Gammapy.

• There’s quite a few classes in Gammapy that don’t have a well-defined format. We should add a way to serialise every class and document the format for easier interop.

• Maybe add info which format is used by Fermi, HESS HD/PA, CTA?

• For every format there should be one or several test data files. This could even be in a repo that’s shared by Gammalib / Gammapy.