GNU Astronomy Utilities


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7.3.5.4 MakeCatalog output columns

The final group of options particular to MakeCatalog are those that specify which columns should be written into the final output table. For each column there is an option, if it has been called on the command line or in any of the configuration files, it will included as a column in the output catalog in the same order (see Configuration file precedence). Some of the columns apply to both objects and clumps and some are particular to only one of them. The latter cases are explicitly marked with [Objects] or [Clumps] to specify the catalog they will be placed in.

--i
--ids

This is a unique option it can add multiple columns to the final catalog(s). Calling this option will put the object IDs (--objid) in the objects catalog and host-object-ID (--hostobjid) and ID-in-host-object (--idinhostobj) into the clumps catalog. Hence if only object catalogs are required, it has the same effect as --objid.

--objid

[Objects] ID of this object.

-j
--hostobjid

[Clumps] The ID of the object which hosts this clump.

--idinhostobj

[Clumps] The ID of this clump in its host object.

-C
--numclumps

[Objects] The number of clumps in this object.

-a
--area

The raw area (number of pixels) in any clump or object independent of what pixel it lies over (if it is NaN/blank or unused for example).

--clumpsarea

[Objects] The total area of all the clumps in this object.

--weightarea

The area (number of pixels) used in the flux weighted position calculations.

-x
--x

The flux weighted center of all objects and clumps along the first FITS axis (horizontal when viewed in SAO ds9), see \(\overline{x}\) in Measuring elliptical parameters. The weight has to have a positive value (pixel value larger than the Sky value) to be meaningful! Specially when doing matched photometry, this might not happen: no pixel value might be above the Sky value. For such detections, the geometric center will be reported in this column (see --geox). You can use --weightarea to see which was used.

-y
--y

The flux weighted center of all objects and clumps along the second FITS axis (vertical when viewed in SAO ds9). See --x.

--geox

The geometric center of all objects and clumps along the first FITS axis axis. The geometric center is the average pixel positions irrespective of their pixel values.

--geoy

The geometric center of all objects and clumps along the second FITS axis axis, see --geox.

--clumpsx

[Objects] The flux weighted center of all the clumps in this object along the first FITS axis. See --x.

--clumpsy

[Objects] The flux weighted center of all the clumps in this object along the second FITS axis. See --x.

--clumpsgeox

[Objects] The geometric center of all the clumps in this object along the first FITS axis. See --geox.

--clumpsgeoy

[Objects] The geometric center of all the clumps in this object along the second FITS axis. See --geox.

-r
--ra

Flux weighted right ascension of all objects or clumps, see --x.

-d
--dec

Flux weighted declination of all objects or clumps, see --x.

--geora

Geometric center right ascension of all objects or clumps, see --geox.

--geodec

Geometric center declination of all objects or clumps, see --geox.

--clumpsra

[Objects] Flux weighted right ascension of all clumps in this object, see --x.

--clumpsdec

[Objects] Flux weighted declination of all clumps in this object, see --x.

--clumpsgeora

[Objects] Geometric center right ascension of all clumps in this object, see --geox.

--clumpsgeodec

[Objects] Geometric center declination of all clumps in this object, see --geox.

-b
--brightness

The brightness (sum of all pixel values), see Flux Brightness and magnitude. For clumps, the ambient brightness (flux of river pixels around the clump multiplied by the area of the clump) is removed, see --riverflux. So the sum of clump brightnesses in the clump catalog will be smaller than the total clump brightness in the --clumpbrightness column of the objects catalog.

If no usable pixels (blank or below the threshold) are present over the clump or object, the stored value will be NaN (note that zero is meaningful).

--clumpbrightness

[Objects] The total brightness of the clumps within an object. This is simply the sum of the pixels associated with clumps in the object. If no usable pixels (blank or below the threshold) are present over the clump or object, the stored value will be NaN, because zero (note that zero is meaningful).

--noriverbrightness

[Clumps] The Sky (not river) subtracted clump brightness. By definition, for the clumps, the average brightness of the rivers surrounding it are subtracted from it for a first order accounting for contamination by neighbors. In cases where you will be calculating the flux brightness difference later (one example below) the contamination will be (mostly) removed at that stage, which is why this column was added.

One example might be this: you want to know the change in the clump flux as a function of threshold (see --threshold). So you will make two catalogs (each having this column but with different thresholds) and then subtract the lower threshold catalog (higher brightness) from the higher threshold catalog (lower brightness). The effect is most visible when the rivers have a high average signal-to-noise ratio. The removed contribution from the pixels below the threshold will be less than the river pixels. Therefore the river-subtracted brightness (--brightness) for the thresholded catalog for such clumps will be larger than the brightness with no threshold!

If no usable pixels (blank or below the possibly given threshold) are present over the clump or object, the stored value will be NaN (note that zero is meaningful).

-m
--magnitude

The magnitude of clumps or objects, see --brightness.

-e
--magnitudeerr

The magnitude error of clumps or objects. The magnitude error is calculated from the signal-to-noise ratio (see --sn and Quantifying measurement limits). Note that until now this error assumes un-correlated pixel values and also does not include the error in estimating the aperture (or error in generating the labeled image).

For now these factors have to be found by other means. Task 14124 has been defined for work on adding these sources of error too.

--clumpsmagnitude

[Objects] The magnitude of all clumps in this object, see --clumpbrightness.

--upperlimit

The upper limit value (in units of the input image) for this object or clump. See Quantifying measurement limits and Upper-limit magnitude settings for a complete explanation. This is very important for the fainter and smaller objects in the image where the measured magnitudes are not reliable.

--upperlimitmag

The upper limit magnitude for this object or clump. See Quantifying measurement limits and Upper-limit magnitude settings for a complete explanation. This is very important for the fainter and smaller objects in the image where the measured magnitudes are not reliable.

--riverave

[Clumps] The average brightness of the river pixels around this clump. River pixels were defined in Akhlaghi and Ichikawa 2015. In short they are the pixels immediately outside of the clumps. This value is used internally to find the brightness (or magnitude) and signal to noise ratio of the clumps. It can generally also be used as a scale to gauge the base (ambient) flux surrounding the clump. In case there was no river pixels, then this column will have the value of the Sky under the clump. So note that this value is not sky subtracted.

--rivernum

[Clumps] The number of river pixels around this clump, see --riverflux.

-n
--sn

The Signal to noise ratio (S/N) of all clumps or objects. See Akhlaghi and Ichikawa (2015) for the exact equations used.

--sky

The sky flux (per pixel) value under this object or clump. This is actually the mean value of all the pixels in the sky image that lie on the same position as the object or clump.

--std

The sky value standard deviation (per pixel) for this clump or object. Like --sky, this is the average of the values in the input sky standard deviation image pixels that lie over this object.

-A
--semimajor

The pixel-value weighted semi-major axis of the profile (assuming it is an ellipse) in units of pixels. See Measuring elliptical parameters.

-B
--semiminor

The pixel-value weighted semi-minor axis of the profile (assuming it is an ellipse) in units of pixels. See Measuring elliptical parameters.

-p
--positionangle

The pixel-value weighted angle of the semi-major axis with the first FITS axis in degrees. See Measuring elliptical parameters.

--geosemimajor

The geometric (ignoring pixel values) semi-major axis of the profile, assuming it is an ellipse.

--geosemiminor

The geometric (ignoring pixel values) semi-minor axis of the profile, assuming it is an ellipse.

--geopositionangle

The geometric (ignoring pixel values) angle of the semi-major axis with the first FITS axis in degrees.


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