J/A+A/566/A8 Aspects code (Fioc, 2014)
Probabilistic positional association of catalogs of astrophysical sources:
the Aspects code.
Fioc M.
<Astron. Astrophys. 566, A8 (2014)>
=2014A&A...566A...8F 2014A&A...566A...8F
ADC_Keywords: Models ; Positional data
Keywords: methods: statistical - catalogs - galaxies: statistics -
stars: statistics - astrometry
Abstract:
We describe a probabilistic method of cross-identifying astrophysical
sources in two catalogs from their positions and positional
uncertainties. The probability that an object is associated with a
source from the other catalog, or that it has no counterpart, is
derived under two exclusive assumptions: first, the classical case of
several-to-one associations, and then the more realistic but more
dicult problem of one-to-one associations. In either case, the
likelihood of observing the objects in the two catalogs at their
effective positions is computed and a maximum likelihood estimator of the
fraction of sources with a counterpart - a quantity needed to
compute the probabilities of association - is built. When the
positional uncertainty in one or both catalogs is unknown, this method
may be used to estimate its typical value and even to study its
dependence on the size of objects. It may also be applied when the
true centers of a source and of its counterpart at another wavelength
do not coincide. To compute the likelihood and association
probabilities under the different assumptions, we developed a Fortran
95 code called Aspects ([aspε],
"Association positionnelle/probabiliste de catalogues de sources" in
French); its source files are made freely available. To test Aspects,
all-sky mock catalogs containing up to 105 objects were created,
forcing either several-to-one or one-to-one associations. The analysis
of these simulations confirms that, in both cases, the assumption with
the highest likelihood is the right one and that estimators of unknown
parameters built for the appropriate association model are reliable.
Description:
All files of the "Aspects code" are available as Aspects_v2.0.tar
files.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
Aspects_v2.0.tar 512 6700 All Aspects code files
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Acknowledgements:
Copied at http://www2.iap.fr/users/fioc/Aspects
(End) Patricia Vannier [CDS] 30-May-2014