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II. The WISE All-Sky Data Products

2. Source Catalog


  1. Column Descriptions
  2. Source Selection Criteria
  3. General Properties
  4. Photometric Properties
  5. Astrometric Properties

The WISE All-Sky Release Source Catalog contains positions and four-band photometry for 563,921,584 objects detected in 18,240 Atlas Tiles. Each Catalog entry gives positions, magnitudes, astrometric and photometric uncertainties, flags indicating the reliability and quality of the source characterizations, and associations with any nearby 2MASS Point and Extended Source Catalog.

The All-Sky Release Catalog contains many types of sources, and is not restricted to point-like objects such as stars and unresolved galaxies. The Catalog contains both point-like objects and close multiple sources, detections on the disks and spiral arms of resolved galaxies and clumps or filaments in Galactic nebulosity if they meet the Catalog criteria described in sections II.2.b below and V.3.

A summary of the properties of the Source Catalog and a detailed Catalog format description are presented below. More detailed descriptions of photometric and astrometric characteristics of the Catalog are presented in section VI. Descriptions of processing algorithms used to generate the Source Catalog can be found in section IV.

Users are strongly encouraged to read the Cautionary Notes before using the All-Sky Release Catalog.

a. Column Descriptions

b. Source Selection Criteria

Sources in the All-Sky Release Catalog were drawn from a Working Database (WDB) of all detections made on the coadded Atlas Images that was generated during second-pass Multiframe Pipeline processing. The WDB contains 847,809,235 entries, significantly more than the Source Catalog because many of the entries are spurious detections of noise and image artifacts. The reliability of the WISE Source Catalog was achieved by selecting entries in the WDB that satisfy the quality criteria that are described in V.3 and summarized in Table 1. WDB entries that were not selected for inclusion inthe All-Sky Release Source Catalog are contained in the Reject Table.

Table 1 - Source Selection Criteria for the All-Sky Release Source Catalog (V.3)
Detection Reliability:
Extractions must have a "reliable" detection in at least one band. A reliable band-detection must satisfy all these criteria in that band.
Signal-to-Noise Ratio (SNR)Source must be detected with a SNR>5 Rejection of spurious detections of low SNR noise excursions.
Frame coverageThere must be five or more single-exposure images on which the source can be measured and characterized. Rejection of single-exposure transient events that can persist into the coadded images because of low coverage.
ArtifactsExtraction must not be identified as a spurious detection of an image artifact from a bright source, including one of the planets.

Sources believed to be real, but whose measurements are affected by artifacts, are included in the Catalog, and are flagged using the cc_flags parameter.

Rejection of spurious detection of image artifacts.
Tile Boundaries Extraction lies >50" from the edge of the Atlas TileTo avoid truncation of the largest measurement aperture used for the source aperture photometry.
Duplicate Source Entries For multiply-detected sources in Atlas Tile overlap regions, the apparition farthest from its respective Tile edge is selected. Sources in the overlap regions not multiply-detected are always included in the Source Catalog if they satisfy all other selection criteria.To eliminate duplicate extractions of the same source

c. General Properties

d. Photometric Properties

e. Astrometric Properties

The astrometric properties of the WISE All-Sky Release Source Catalog are discussed in detail in VI.4. Catalog source are reconstructed with respect to the 2MASS Point Source Catalog reference frame. The RMS accuracy of the reconstructed positions with respect to the 2MASS PSC for unsaturated sources with SNR>50 in unconfused regions of the sky is approximately 200 mas on each axis, with biases typically less than 50 mas. The accuracy is approximately 400 mas at SNR=20, and decreases towards fainter flux levels. Figures 19 and 20 illustrate the distribution of position differences between the WISE All-Sky Catalog and those in the USNO CCD Astrograph Catalog (UCAC3). WISE Catalog position reconstruction did not use any reference to UCAC3, so that Catalog provides a good independent check on the WISE astrometry.

Because of proper motion of 2MASS reference stars used by WISE in the ten years between the surveys, there can be systematic position biases between the WISE reference frame and the ICRS of up to approximately 150 mas depending on direction on the sky (see VI.4.f).

Figure 19 - Histogram of RA (green) and Dec (blue) position residuals between UCAC3 and WISE All-Sky Catalog for sources with SNR(W1)>20 within 10° of the north Galactic pole. Figure 20 - RMS of the UCAC3-WISE RA (green) and Dec (blue) position residuals as a function of WISE W1 source magnitude for sources within 10° of the north Galactic pole

Last Updated: 2012 July 26

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