IRAS (G0): IRAS Extragalactic Catalog Ver.2 (19900416)
FILE: iras.g0 (11444 galaxies and quasars)
CONTENTS: Infrared Astronomical Satellite (IRAS) Extragalactic Catalog, Version 2
DATASET: This file is part of HyperSky dataset G-6 (G-6.1), version (19900416) Availability on HyperSky CD-ROM: Vol. 1 (1993)
DESCRIPTION: The IRAS Extragalactic Catalog contains 11,444 infrared point sources from the IRAS Point Source Catalog, Version 2.0, that have been positionally associated with previously known galaxies and quasars. The IRAS Point Source Catalog contains about 245,000 objects. There are also a few associations with extended sources from the IRAS Small-Scale Structure Catalog.
The IRAS mission lasted from January to November 1983, during which 96% of the sky surveyed was covered with at least 2 hours of confirming sets of scans, and 72% was covered with 3 or more hours of confirming scans. Only two areas were missed completely. These were 120-degree-long cusps 5 degrees wide at their maximum, and were on opposite sides of the sky, centered at ecliptic longitudes 160 and 340 degrees, and were 60 degrees above and below the ecliptic plane.
Since all objects in the IRAS Extragalactic Catalog can be identified with galaxies or quasars, all objects in the HyperSky datafile iras.g0 are assigned the HyperSky object type Gx, for galaxy. (The IRAS object data provides no way to distinguish between a galaxy and quasar). These same sources would be assigned HyperSky object type Ei, for infrared source, in any future conversion of the entire IRAS Point Source Catalog for HyperSky.
Because generous search windows were allowed in making the association between the IRAS point sources and associated galaxies or quasars, IRAS Extragalactic Catalog users were cautioned against assuming that all IRAS source associations with galaxies or quasars were correct. For that reason, no associated galaxy or quasar names are included in the HyperSky IRAS file. HyperSky users who are interested in making such associations should instead use the IRAS file in conjuction with other HyperSky galaxy or quasar datafiles.
DATA: The HyperSky datafile contains the following data from the catalog:
MAG: the infrared "magnitude" of the galaxy or quasar, defined as:
m(FIR) = -20 - 2.5 log(FIR),
where FIR is the IRAS "far infrared flux parameter", defined as: FIR = 1.26 [2.58 flux(60um) + flux(100um)] X 10^-14 watts/sq meter.
Only the IRAS 60um and 100um fluxes are used, since galaxies emit very little if anything in the IRAS 12um and 25um bands. m(FIR) lies in the general range of 9-15, and can be treated as the infrared equivalent of a visual magnitude for most purposes.
IDENTIFICATION: The IRAS identification number. This number has the general form HHMMM+DDMM, corresponding to the equinox 1950 RA and Dec of the IRAS source.
COMMENTS: The comment line, if present, will contain one of the following two comments on the quality of the IRAS far infrared flux parameter used in calculating the above magnitude:
Q(FIR) = moderate
Q(FIR) = upper limit
If neither comment appears, the infrared flux parameter quality is high.