Command line arguments

Command line arguments#

Program Arguments#

  1. python ../nway.py --help … display help page

usage: nway.py [-h] --radius RADIUS [--mag-radius MAG_RADIUS]
               [--mag-auto-minprob MAG_AUTO_MINPROB]
               [--mag-exclude-radius MAG_EXCLUDE_RADIUS]
               [--prior-completeness COMPLETENESS]
               [--ignore-unrelated-associations]
               [--mag MAGCOLUMN+MAGFILE MAGCOLUMN+MAGFILE]
               [--acceptable-prob PROB] [--min-prob MIN_PROB] --out OUTFILE
               [--prefilter-pair CATNAME1 CATNAME2 radius CATNAME1 CATNAME2 radius CATNAME1 CATNAME2 radius]
               catalogues [catalogues ...]

Multiway association between astrometric catalogue. Use --help for usage.
Example: nway.py --radius 10 --prior-completeness 0.95 --mag GOODS:mag_H auto
--mag IRAC:mag_irac1 auto cdfs4Ms_srclist_v3.fits :Pos_error
CANDELS_irac1.fits 0.5 gs_short.fits 0.1 --out=out.fits

positional arguments:
  catalogues            input catalogue fits files and position errors.
                        Example: cdfs4Ms_srclist_v3.fits :Pos_error
                        CANDELS_irac1.fits 0.5 gs_short.fits 0.1

options:
  -h, --help            show this help message and exit
  --radius RADIUS       exclusive search radius in arcsec for initial matching
                        (default: None)
  --mag-radius MAG_RADIUS
                        search radius for building the magnitude histogram of
                        target sources. If not set, the Bayesian posterior is
                        used. (default: None)
  --mag-auto-minprob MAG_AUTO_MINPROB
                        minimum posterior probability (default: 0.9) for the
                        magnitude histogram of secure target sources. Used in
                        the Bayesian procedure. (default: 0.9)
  --mag-exclude-radius MAG_EXCLUDE_RADIUS
                        exclusion radius for building the magnitude histogram
                        of field sources. If not set, --mag-radius is used.
                        (default: None)
  --prior-completeness COMPLETENESS
                        expected matching completeness of sources (prior)
                        (default: 1)
  --ignore-unrelated-associations
                        Ignore in the calculation source pairings unrelated to
                        the primary source (not recommended) (default: True)
  --mag MAGCOLUMN+MAGFILE MAGCOLUMN+MAGFILE
                        name of <table>:<column> for magnitude biasing, and
                        filename for magnitude histogram (use auto for auto-
                        computation within mag-radius). Example: --mag
                        GOODS:mag_H auto --mag IRAC:mag_irac1
                        irac_histogram.txt (default: [])
  --acceptable-prob PROB
                        ratio limit up to which secondary solutions are
                        flagged (default: 0.5)
  --min-prob MIN_PROB   lowest probability allowed in final catalogue. If 0,
                        no trimming is performed (default). (default: 0)
  --out OUTFILE         output file name (default: None)
  --prefilter-pair CATNAME1 CATNAME2 radius CATNAME1 CATNAME2 radius CATNAME1 CATNAME2 radius
                        name of two <table>s where combinations more distant
                        than radius (in arcsec) should not considered. This
                        reduces the memory needs when several large catalogs
                        with high accuracy are matched against some with low
                        accuracy (high --radius). Example: --prefilter-pair
                        GOODS IRAC 0.1 (default: [])

Johannes Buchner (C) 2013-2025 <johannes.buchner.acad@gmx.com>

  1. python ../nway.py catalogue1 catalogues ... … input catalogues as FITS files.

  2. python ../nway.py --out … Output file name (also a FITS file).

  3. python ../nway.py --radius This radius (in degrees) is used to discard distant pairs. Always choose a value that is much larger than the largest positional uncertainty, then this value will not change the results. Smaller values make the code run faster and use less memory by reducing the number of combinations to explore.

  4. python ../nway.py --prior-completeness 1 … set expected matching completeness (default: 1)

  5. python ../nway.py --mag MAGCOLUMN MAGFILE … name of <table>:<column> for magnitude biasing, and file name for magnitude histogram (use auto for auto-computation within mag-radius). Example: --mag OPT:MAG auto --mag IRAC:mag_irac1 irac_histogram.txt

  6. python ../nway.py --mag-radius … If set, and a auto prior is defined, then the selected sources are taken from within this radius of the primary sources (in arc seconds). If not set (recommended), the Bayesian posterior from distance matching is used, which incorporates positional errors.

  7. python ../nway.py --min-prob … only retain associations in the output catalogue exceeding this p_i value. Recommended: 0.1.

  8. python ../nway.py --acceptable-prob … affects the flagging of secondary solutions (match_flag column). If the secondary is within this difference (default: 0.005), it is marked as a secondary solution.

Input file specifications and units#

  1. Each catalogue needs to be a FITS file. The second extension should be the table (first extension is a header).

  2. The data table needs to have a extension name.

  3. The header of the data table needs the keyword SKYAREA, which specifies the area covered by the catalogue in square degrees.

  4. Each catalogue needs to have a column RA and DEC in degrees. To make your life easier, Nway  tries to be a bit fuzzy and detect the columns named RA_something etc.

  5. The primary catalogue needs to have a ID column. To make your life easier, Nway  tries to be a bit fuzzy and detect the columns named ID_something etc.

  6. Positional error columns, if used, need to be in arcseconds.

Example catalogues are provided in the doc/ directory: COSMOS_IRAC.fits, COSMOS_OPTICAL.fits and COSMOS_XMM.fits.

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