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The Wide-field Infrared Survey Explorer at IPAC |
You are strongly encouraged to read the Explanatory Supplement to the AllWISE Data Release Products before using WISE Image and Source Catalog and Database information. In particular, please familiarize yourself with the Cautionary Notes sections for the AllWISE Source Catalog, AllWISE Multiepoch Photometry Database and AllWISE Image Atlas to make best use of the WISE data products.
The AllWISE Source Catalog is a better product and supersedes the WISE All-Sky Release Catalog for most uses.
The AllWISE Source Catalog was produced by combining the WISE Single-exposure images from the WISE 4-Band Cryo, 3-Band Cryo and NEOWISE Post-Cryo survey phases. The additional data doubles the depth-of-coverage in W1 and W2 compared to the All-Sky Release Catalog, improving the sensitivity in those bands, and improves the photometric accuracy in all bands because of improved pixel calibrations and updated background estimation algorithms. AllWISE exploits the two independent WISE sky coverages by providing apparent motion measurements and improved flux variability statistics for every object. Finally, the AllWISE Source Catalog has better astrometric accuracy than the All-Sky Release Catalog because correction has been made for the proper motion of the 2MASS astrometric reference stars in the 11 years separating WISE and 2MASS in updated position reconstruction.
The WISE All-Sky Release Catalog may provide better W1 and W2 photometric information for sources brighter than W1<8 mag and W2<7 mag that were observed during the NEOWISE Post-Cryo survey phase.
Access modes for the WISE image and tabular data products are described in section I.5 of the AllWISE Explanatory Supplement.
Yes. Both the AllWISE Source Catalog and Reject Table are available for bulk download via the NASA/IPAC Infrared Science Archive. Downloads are available in bzip2 and gzip-compressed ascii formats. The Catalog and Reject Table are each divided into 48 separate files in the bzip2 and gzip-compressed versions. You will need 340 GB (bzip2) or 414 GB (gzip) of storage space available to download the compressed Catalog files, and approximately 1225 GB to store the full uncompressed, ascii Catalog. The compressed Reject Table files require 188 GB and 231 GB for the bzip2 and gzip versions, respectively, and 684 GB to store the full, uncompressed Reject Table.
The WISE filter bandpasses are described in section IV.4.h.v of the WISE All-Sky Data Release Explanatory Supplement. The filter bandpass relative spectral response (RSR) curves are shown graphically in Figures 4a and 4b in that section, and can be downloaded in ASCII table format from links in the captions to those two figures.
AllWISE Catalog and Multiepoch Photometry Database magnitudes are given in the Vega system and represent total in-band brightness measurements. Conversion of AllWISE in-band magnitudes to monochromatic values such as flux density or AB magnitude, along with some helpful examples, are described in section IV.4.h.i of the WISE All-Sky Data Release Explanatory Supplement. The broad WISE bandpasses may require applying significant color corrections when deriving monochromatic brightnesses depending on the spectral energy distribution of the particular object. The nominal system flux zero points are defined for a fν∝ν-2 spectrum through the WISE bandpasses. Color corrections for other spectral slopes are given in section IV.4.h.vi of the All-Sky Release Supplement.
AllWISE Catalog entries have several different photometry measurements available, as described in AllWISE Supplement section II.1.d. The profile-fit magnitudes (w?mpro) and the curve-of-growth corrected "standard" aperture magnitudes (w?mag) systematically underestimate the brightness of sources that are resolved with respect to the WISE PSF. Sources whose shapes are complex and/or or extended with respect to the PSF are identified in the Catalog by having extended source flag (ext_flg) values greater than zero.
For AllWISE sources that are resolved and are associated with 2MASS Extended Source Catalog (XSC) sources, ext_flg=5, you may wish to use the elliptical aperture photometry measurements, w?gmag, that are made using apertures scaled from the 2MASS XSC shape values. These measurements do a better job of capturing the total source brightness, but may still underestimate it slightly. If a WISE source is associated with a 2MASS XSC object but is not resolved (ext_flg=4), then the elliptical aperture magnitudes will overestimate the true brightness. Use the profile-fit magnitudes instead.
For AllWISE sources that are extended but not associated with a 2MASS XSC objects, you may examine the large aperture magnitudes in the AllWISE Source Catalog. These measurements do not have any aperture corrections applied so do not make any assumption about source compactness.
Yes. Links to gzip'd tar files that contain images of the 9x9 grid of PSFs in each band used for profile-fitting source extraction are in section IV.4.c.iii.1 of the WISE All-Sky Release Explanatory Supplement.
The AllWISE Atlas Image pixel values cannot be converted directly to calibrated absolute surface brightness levels for two reasons. First, the absolute instrumental dark-current level in each WISE exposure could not be accurately estimated and tracked. Second, the Single-exposures contributing to each AllWISE Atlas Image have their background-levels matched to an average local value during the coaddition process to minimizing relative offsets in their overlap regions only. The resulting background levels (in DN/pixel) were not placed on a scale that could be converted to absolute surface-brightness units. Consequently, the Atlas (and Single-exposure) Images are designed for relative photometric measurements where the brightness is measured with respect to the local sky background. Instructions for making photometric measurements with the Atlas Images are given in section II.3.a of the AllWISE Explanatory Supplement.
Measurements of objects in the AllWISE Source Catalog are extracted from multiple, independent observations taken at different times. The earliest, latest and average Modified Julian Dates of the observations used in each band for a Catalog source entry are given in the w?mjdmin, w?mjdmax, and w?mjdmean columns (where ?=1,2,3 or 4 for each WISE band). Note that you will need to select the Catalog "Long Form" when using the IRSA/GATOR Catalog Search service service to see the w?mjdmin, w?mjdmax, and w?mjdmean columns.
The AllWISE Multiepoch Photometry Database contains the fluxes of each AllWISE Catalog and Reject Table entry made on the individual Single-exposure images. Each Catalog and Reject Table has a set of entries in the Multiepoch Photometry Database, each of which is contains the Modified Julian Date of the Single-exposure measurements.
No quality filters were applied to the 2MASS PSC entries before positionally associating them with the AllWISE Source Catalog and Reject Table entries. Associations were made with the full composite 2MASS All-Sky PSC, that includes the high reliability Catalog and the lower signal-to-noise extension (see section I.6.b.i of the 2MASS All-Sky Data Release Explanatory Supplement).
Last update - 2013 December 13 Contact the WISE Help Desk
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