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IV. The AllWISE Image Atlas

IV.1. General Information

The AllWISE Image Atlas contains photometrically and astrometrically calibrated images, uncertainty and depth of coverage maps produced by coadding the Single-exposure images in each band from the WISE 4-Band and 3-Band Cryogenic and Post-Cryo survey phases. Because twice as many independent observations were combined in the W1 and W2 bands over most of the sky, the AllWISE Atlas Images reach fainter levels in those bands than their counterparts All-Sky Release and 3-Band Cryo Atlases which were limited to data only from their respective survey the 4-Band and 3-Band Cryogenic survey phases. The additional W1 and W2 observations also fill-in some of the low coverage regions that exist in the All-Sky Release Atlas, virtually removing any coverage holes in those bands. The relative depth of the AllWISE W3 and W4 Atlas Images is comparable to those in the All-Sky Release Atlas, but the AllWISE Images benefit from several improvements to the calibration and position reconstruction of the Single-exposure images that was performed for AllWISE.

A description of the contents and format of the AllWISE Atlas Image sets is given below in IV.1.a. Production of the AllWISE Atlas Images is described in V.3.a. The content of the AllWISE Atlas Image headers is described in IV.1.b. Tips for making and interpreting photometric and positional measurements on the Atlas Images are given in IV.3. The Atlas Image Metadata database that contains many of the elements of the image headers in a queriable form is described in IV.1.c.i, and the database that contains a cross-reference between the Atlas Image sets and the individual Single-exposure images that were combined to construct them are described in IV.1.c.ii. The achieved sky coverage of the AllWISE Atlas is described in IV.2.

Please read the Cautionary Notes to make best use of the AllWISE Atlas Images in your research.

IV.1.a. Description and Format

The AllWISE Atlas is comprised of 18,240 4095x4095 pix @1.375"/pix FITS format image sets that are built on the same fixed 1.56°x1.56° Atlas Tile footprints on the sky as were used for earlier release WISE Atlases. One image set is produced for each Atlas Tile. Each image set consists of:

AllWISE Atlas Images are in the Flexible Image Transport System (FITS) format and follow the World Coordinate System (WCS) standard for astronomical image data.

A montage illustrating the intensity images, and depth-of-coverage and uncertainty maps for AllWISE Tile 0066p636_ac51 is shown in Figure 1.

Atlas Image products have filenames as follows:

where BAND = 1, 2, 3, or 4, and COADDID is a unique identification string pertaining to the sky footprint (see II.2.a). These are variables that match the values of keywords with the same name in FITS headers. The WISE Atlas Image FITS header content is described in IV.1.b.

Several ancillary products provide additional information about the AllWISE Atlas Image sets in a convenient queriable format. The Atlas Metadata Table contains much of the Atlas Image header content, as well as derived statistical and quality assessment information pertaining to both the Atlas Images and extracted source lists for each Atlas Tile. The Atlas Image Frame Cross Reference Table contains a listing of all of the individual Single-exposure image frames that were used in the construction of each Atlas Image in each band. These ancillary tables can be queried using the IRSA Gator catalog search engine.

Figure 1 - 3.4, 4.6, 12, 22 μm intensity images (top row), depth-of-coverage maps (center row), and uncertainty maps (bottom row) for the Atlas Tile 0066p636_ac51 that contains the Tycho A supernova remnant. The color scale on the bottom of the montage refers to the depth-of-coverage maps. Note that the 3.4 and 4.6 μm depth-of-coverage is approximately twice that in 12 and 22 μm because of the addition of the Post-Cryo survey observations.

Last update: 22 November 2013

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