Terapix Star Formation Region IC 1396, © 2002 CFHT
WIRDS-T0002 explanatory table
by RBI - Updated July 26th, 2010

ProductDescription
Stacked Images All stacks are produced by a weighted median of all input images and combined using SWarp using a lancos 2 interpolation kernel. Equatorial Coordinate is system, J2000 (ICRS) and a TAN projection has been used. All images are 19354x19354 pixels and have a pixel scale 0.186 arcsecond/pixel. The center positions of each stack is identical to the corresponding CFHTLS images. 2MASS is used as the astrometric reference catalogue.

FILENAME for stacks:

WIRDS_[filter]_[RA][DEC]_T0002.fits

where filter can be J, H, or Ks and RA and DEC correspond to the tangent point of the field centre.

Weight map images FITS weight map image. There is one weight map image for each FITS image. Output weight maps are produced during the image stacking using Weightwatcher in SWarp. The pixel weight is defined as the local sky background flux variance.

FILENAME:

WIRDS_[filter]_[RA][DEC]_T0002.weight.fits

Seeing In WIRDS T0002, the seeing is the Gaussian FWHM and is calculated (as in the CFHTLS T0005 and T0006 data releases) using the PSFEx software.

Completeness A completeness estimate is computed by adding point sources to the final stack and measuring what fraction of objects are recovered as a function of magnitude using SExtractor.
Effective area Effective area is derived by subtracting from the fields all the masked POLYGON areas defined using the WIRDS_JHK_[RA][DEC]_T0002.reg mask files.

Individual J, H and Ks catalogues These catalogues were produced using SExtractor. Columns are defined in the '.param' files. They are listed in the CFHTLS catalogue parameter list. This set has been SExtracted individually and therefore object ID numbers are not consistent between the three catalogues (i.e. object 1 is not the same object in each of the catalogues). Note that these catalogues have not been corrected for galactic extinction.

FILENAME:

WIRDS_[filter]_[RA][DEC]_T0002.cat

CFHTLS gri-chi2 selected cataloguesThese catalogues were produced using SExtractor in dual-image mode, using the CFHTLS gri-chi2 image as the detection image. The object ID numbers are consistent through this set of catalogues (i.e. object 1 is the same object in each of the catalogues).

Columns of catalogs with '.cat' extensions are defined in the CFHTLS catalogue parameter list.

FILENAME:

WIRDS_[field]-95_grichi2_[filter]_[RA][DEC]_T0002.cat

A merged catalogue for each field is also provided, with columns as defined in this file . The merged catalogue filenames are as follows:

FILENAME:

WIRDS_[field]-95_grichi2_ugrizJHKs_[RA][DEC]_T0002.cat

Note that these catalogues have not been corrected for galactic extinction, although the merged catalogue contains the E(B-V) values.

Ks-band selected cataloguesThese catalogues were produced using SExtractor in dual-image mode, using the WIRDS Ks-band image as the detection image. The object ID numbers are consistent through this set of catalogues (i.e. object 1 is the same object in each of the catalogues).

Columns of catalogs with '.cat' extensions are defined in the CFHTLS catalogue parameter list. Note that these catalogues have not been corrected for galactic extinction, although the merged catalogue contains the E(B-V) values.

FILENAME:

WIRDS_[field]-95-Ks_[filter]_[RA][DEC]_T0002.cat

A merged catalogue for each field is also provided, with columns as defined in this file. The merged catalogue filenames are as follows:

FILENAME:

WIRDS_[field]-95_Ks_ugrizJHKs_[RA][DEC]_T0002.cat

Note that none of the magnitudes have been corrected for galactic extinction, although the merged catalogue contains the E(B-V) dust extinction.

Three colour images Produced by combining the stacked FITS images in JHK using STIFF. These are 2 x 2 binned colour images. The R, G, B color balance and cuts are primarily optimised for visual inspection as a quality assessment tool. It is primarily used to check filter-to-filter astrometric calibration and whether colour gradients are visible in objects, resulting from poor overlaps between each filter, in particular far from the centre of the field.


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