detect
Section: User Manuals (1)
Updated: 22 JUL 2011
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NAME
detect - Source extraction tool for CRUSH maps and more.
SYNOPSIS
detect
criterion
[options]
<file>
Parameters:
- criterion
-
A criterion for setting a false-detection rate goal.
- [options]
-
Various options, including pre-processing options of
imagetool(1).
- <file>
-
A
crush(1)
or BoA
FITS
image.
DESCRIPTION
detect
extracts point sources from a
FITS
image produced
crush(1)
or
BoA.
In addition to the source-detection options, the tool accepts all options of
imagetool(1)
for processing images before the extraction begins.
The extraction algorithm implements a false-detection rate approach, that is it continues until a set false detection (or detection confidence) goal is reached. Each source extracted from the map has an assigned confidence level, based on the likelihood of a false detection at the same significance level in the given extraction area, as well as a cumulative number of false detections that are expected at levels above each source.
When applied to
crush(1)
maps, the algorithm properly accounts for the effect of any map filtering/processing steps (including a filtered beam profile!), as long as these steps were also performed by other
CRUSH
tools (e.g.
crush(1), imagetool(1))
to yield unbiased flux estimates.
The output is an ASCII source catalog to the console, with some essential supplementaty information, which you can redirect to a file using the
'>'
operator on the command line, e.g.:
detect false=3.0 my-image.fits > my-sources.cat
which will write a source catalog from
my-image.fits
to
my-source.cat
containing no more that 3 false detections.
The program also creates a FITS image (named
<source-name>.residual.fits)
written to the same directory as the input image, containing the residuals after the source-extraction. The beams around the extracted sources are flagged, since these no longer contain useful information after the extraction took place.
CRITERIA
The following criteria can be used to specify how the false-detection rate goal is to be achieved. The
criterion
is a mandatory argument of
detect.
- confidence=
-
Set a minimum confidence level for each detection (e.g. 0.95).
- s2n=
-
Set a minimum S/N level for all detections (e.g. 3.5).
- nofalse=
-
The confidence level that there is not a single false detection in the catalog (e.g. 0.95).
- false=
-
The expected number of false detections (e.g. 3.0).
- help
-
Provides a help screen similar to this one.
OPTIONS
All options of
imagetool(1)
are also used by
detect.
Additionally
detect
defines the following option(s):
- -area=
-
Specify the extraction area (in sq-armin) if it is different from the unflagged area of the supplied map.
- -dynamic
-
Re-estimate the noise with every extraction round.
- -gaussian
-
Use strictly Gaussian statistics for calculating cumulative
false detections and confidence levels.
- -symmetric
-
Always use symmetric noise estimates. (The default is to use the negative-side distribution only for estimating the prevailing noise levels -- which is great if the positive fluxes are teeming with sources.)
FILES
- ~/.crush2/startup/detect/
-
Location of user-specific
java(1)
runtime configurations.
BUGS
If you find them, please report them to the author (see below).
AUTHOR
Attila Kovács <attila[AT]sigmyne.com>
SEE ALSO
crush(1),
imagetool(1),
coadd(1),
show(1)
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Time: 23:56:58 GMT, January 03, 2020