IRAS Explanatory Supplement
I. Introduction
B. Summary Description of Catalogs and Atlases

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  1. Point Sources
  2. Small Extended Sources
  3. Sky Brightness Images
  4. Low Resolution Spectra
  5. The Extragalactic Sub-catalog

The IRAS data are presented in different ways depending on the angular sizes of the structures involved:

B.1 Point Sources

Sources that appeared as point-like are presented in three different ways depending on their reliability and on the detail of information given for the sources.
  1. A catalog of some 250,000 well-confirmed point sources is available in both printed and machine readable forms. Positions, flux densities, uncertanties, associations with known astronomical objects and various cautionary flags are given for each object. The information available in this catalog should satisfy almost all users.

  2. A file known as the Working Survey Data Base, available only on magnetic tape, is intended for researchers requiring specialized information about the observational and processing history of a source in the catalog.

  3. A file of rejected sources, available only on magnetic tape, includes any sources that did not meet the reliability criteria of the catalog. Some of these sources will be wholly spurious and due, for example, to detector noise, space debris, radiation hits or processing errors; others will be solar system objects such as asteroids and comets; and some will be true extra-solar system objects that failed to meet the confirmation criteria due to their faintness or variability, or to confusion effects. Sources in that small portion of the sky which received only limited survey coverage will also be found here.

B.2 Small Extended Sources

Sources larger than point-like, but smaller than 8' in angular extent are to be found in the catalog of small extended sources which is available in both printed and machine readable versions.

B.3 Sky Brightness Images

The overall view of the sky, and the repository of IRAS data for structures larger than 8', is found in the images of 212 fields that cover the entire celestial sphere. The fields are 16.5° on a side and have been imaged in each of the four wavelength bands with 2' pixels and 4-6' resolution. As many as four images based on observations separated by a few weeks to a few months are presented. These data give absolute surface brightness and are available in both digital and photographic representations.

B.4 Low-Resolution Spectra

Point sources which are bright in the 8-22 µm range may have been detected by the low resolution spectrometer (Chapter IX). Spectra are available in both printed (Astronomy and Astrophyics Supplement Series 1985) and machine readable forms.

B.5 The Extragalactic Sub-catalog

A catalog of well-confirmed sources that are positionally associated with previously identified extragalactic objects is available in printed and magnetic tape versions. All the sources in this catalog are contained in either the catalogs of point or small extended sources, but additional information about the associated galaxies and quasars, obtained from a variety of astronomical catalogs, is presented here.
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