EXTRACTOR - An Astronomical Source Detection Program
What is EXTRACTOR?
EXTRACTOR is a program for automatically detecting objects on an
astronomical image and building a catalogue of their properties. It is
particularly suited for the reduction of large scale galaxy-survey data,
but also performs well on other astronomical images.
EXTRACTOR is basically Emmanuel Bertin's SExtractor
(Source-Extractor) program re-packaged for use with Starlink Software.
This means that it uses the Starlink parameter system, accepts images in
NDF format and uses the AST library for astrometry.
A largely unmodified version of SExtractor (2.5.0) is also
included in the distribution of EXTRACTOR.
How to use EXTRACTOR
The latest version of EXTRACTOR is available in the EAO Starlink
release.
Once you have this installed you should have a copy of the Starlink User
Note SUN/226 available that describes EXTRACTOR. The command:
% showme sun226
should display this in a web browser. After this you should consult the
"Running EXTRACTOR" section.
To understand how EXTRACTOR works you'll need to consult the
associated documentation (MUD/165 and the research paper). The
Source Extractor for Dummies written by Benne Holwerda of the University of Cape Town
is also available.
The GAIA program has an interactive
environment for running EXTRACTOR and SExtractor. It displays the
detection catalogue overlaid on the image (the figure shown above was
created by GAIA). This is probably the easiest way to get started.
Bugs and fixes
For a list of bug and fixes in the current EXTRACTOR see the
news file in the latest EAO release.
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