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98 changes: 98 additions & 0 deletions VEP-25_response-function.txt
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Vocabulary: http://www.ivoa.net/rdf/response-type
Author: Mireille Louys for HEIG IG <mireille.louys@unistra.fr>
Date: 2025-11-13

New Term: response-function
Action: Addition
Label: response-function
Description:
A data product type describing instrumental response functions for calibration and analysis.

Relationships: response-function is a top level term.
Usually related to an event-list data product in high energy astrophysics.

Used-in: Data sets made accessible via the Chandra CS2 catalog

Rationale:
The distribution of event-list data in multi-messenger astronomy.
For example, Chandra primary products distributed via the Chandra
Data Archive include around half a dozen different types of products neces-
sary to analyse Chandra data (for example, L2 event-list, Aspect solution,
bad pixel map, spacecraft ephemeris, V&V Report).
For VHE gamma rays and neutrinos, the DL3 event-lists should manda-
torily be associated to their associated IRFs files. The links between the
event-list and these IRFs should be well defined in the event-bundle.
----------
New Term: Point Spread Function
Action: Addition
Label: psf
Description: A dataset that records the probability density function of
spatial/angular spreading of incident photons from a point source caused
by the instrument (detector and/or mirror and/or analysis)

Relationships: narrower than #response-function

Used-in: CTA example?
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Used-in: CTA example?
Used-in: For HE, VHE and UHE instruments, the PSF permits to analyse the event list to extract spectrum from an ON region (called `1D analysis`) or to adjust a spectral, spatial, temporal model of a source from an extended field of view.



----------
New Term: Effective Area
Action: Addition
Label: aeff
Description: A dataset that records the “effective area” of a telescope
and/or instrument. The effective area is the geometric area
of the telescope and/or instrument reduced by efficiency factors
such as reflectivity and vignetting, among other effects
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such as reflectivity and vignetting, among other effects
such as reflectivity and vignetting, analysis efficiency, among other effects


Relationships: narrower than #response-function
----------
New Term: Ancillary Response File
Action: Addition
Label: arf
Description: A dataset that records the
combined telescope/instru-
ment effective area and
detector quantum efficiency as
a function of energy

Relationships: narrower than #response-function

Used-in: XMM data products ?

----------
New Term: Background Rate
Action: Addition
Label: bkgrate
Description: A dataset that models the rate of residual events that are
not from the expected source type (e.g. for gamma-ray instrument it
measures residual non-gamma-ray events coming.
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measures residual non-gamma-ray events coming.
not from the expected source type. This rate is about mis-reconstructed events that are badly identified as event. It should be distingued from low level instrumental background, such that an electronic noise.


Relationships: narrower than #response-function

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Used-in: For VHE gamma-ray instrument, it measures the residual cosmic-ray event rate.

----------
New Term: Energy Dispersion
Action: Addition
Label: edisp
Description: A dataset that records the
probability density of detecting an event with an energy estimator given the true
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probability density of detecting an event with an energy estimator given the true
probability density function of detecting an event at an energy-proxy estimation given the true

energy of the event.

Relationships: narrower than #response-function

Used-in: HESS data products ?
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Used-in: HESS data products ?
Used-in: For HE, VHE and UHE instruments, `edisp` permits to analyse the event list to extract spectrum from an ON region (called `1D analysis`) or to adjust a spectral, spatial, temporal model of a source from an extended field of view.


----------
New Term: Redistribution Matrix File
Action: Addition
Label: rmf
Description: A dataset that records the probability density function
mapping from energy space into detector pulse height (or position) space

Relationships: narrower than #response-function

Used-in: Chandra response data products ?

Reference:
- IVOA Note: https://github.com/ivoa/HighEnergyObsCoreExt section 5.1.5
- IVOA Note Virtual Observatory and High Energy Astrophysics Version 1.0
https://ivoa.net/documents/Notes/VOHE/20241112/VOHE-Note-draft_1.0.pdf