IRAS_PS (E0): IRAS Infrared Point Source Catalog (19930606)
FILES:
File Dec (2000) Ran #Sources
iras_ps1.e0 northern sky: +50<= Dec <+90 27995
iras_ps2.e0 northern sky: +20<= Dec <+50 40814
iras_ps3.e0 northern sky: 0 <= Dec <+20 33169
iras_ps4.e0 southern sky: -20< Dec < 0 37168
iras_ps5.e0 southern sky: -50< Dec <=-20 60517
iras_ps6.e0 southern sky: -90< Dec <=-50 46226
CONTENTS: IRAS Infrared Point Source Catalog
DATASET: These files come in HyperSky dataset E-4, version 19930606 Availability on HyperSky CD-ROM: Vol. 1 (1993)
DESCRIPTION: This dataset contains a total of 245,889 infrared sources from the IRAS (Infrared Astronomical Satellite) Point Source Catalog. The data in the HyperSky files is based on the machine-readable version of the IRAS Point Source Catalog, as provided on the NASA/GSFC Astronomical Data Center (ADC) cd-rom "Selected Astronomical Catalogs", Volume 1.
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. Flux measurements were obtained for infrared sources at four wavelengths, extending from 12 and 25 microns (um) in the near infrared to 60 and 100 um in the far infrared.
USAGE NOTES: Because magnitudes used here are HyperSky-derived values and not primary IRAS data (see below), the IRAS files are organized only by Declination zones, not magnitude. As a result, wide-field views of IRAS sources may be drawn slowly since all sources of all magnitudes must be examined in each file. In general, for wide-field IRAS views (> 10 deg) it is best to set the limiting magnitude for type "e0" files (emission sources) to 8th magnitude or brighter. This can be done from main menu option 'M'.
HyperSky shows that extremely bright IRAS sources (< ~8th magnitude) define very precisely the plane of the Milky Way galaxy in the region about the galactic center. As fainter infrared sources are brought into the field, they tend to extend farther and farther from this tight plane.
DATA: The HyperSky datafile contains the following data from the catalog:
POSITION: HyperSky positions are the IRAS equinox 1950 positions, precessed to equinox 2000.
MAG: the infrared "magnitude" of the source, 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.
Note that this magnitude is NOT taken from the IRAS catalog, but has been derived from IRAS catalog flux values.
Strictly speaking, this magnitude definition is valid only for extragalactic objects such as galaxies and quasars, which emit very little if anything in the near infrared at 12 and 25 um. Galactic sources, however, may have significant 12 and 25 um emission, and thus are not well characterized by the above magnitude. Nevertheless, this magnitude definition is used by HyperSky to give at least a rough indication of (far-infrared) brightness for all IRAS sources in the HyperSky catalog.
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 for each IRAS source contains the following information:
* A number of the form NN", giving in arc seconds the size of the major axis of the infrared source position uncertainty ellipse. This value is also used to define the size of the symbol representing the source in small-scale HyperSky fields.
* The above number may be followed by one of two characters, indicating the general type of the infrared source according to the IRAS catalog:
x : Indicates the infrared source is associated with an EXTRAGALACTIC object by the IRAS catalog. The HyperSky-derived magnitudes for these sources may be considered reliable (see above discussion).
* : Indicates the infrared source is associated with a STAR by the IRAS catalog.
Absence of either character implies that the infrared source is not associated with any cataloged object, or is associated with multiple cataloged objects.