IRAS Explanatory Supplement
X. The Formats of the IRAS Catalogs and Atlases
B. Point Sources
B.2 The Printed Version of the Point Source Catalog
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The printed version of the catalog is a strict subset of the information described in the preceding section. A number of fields have been abbreviated or deleted to make possible a single line entry for each source. The entries in the book are discussed below and shown as a figure in Fig.X.B.1
Name: NAME
The full IRAS name is derived from the hours(HH), minutes(MM) and tenths of minutes (T) of right ascension and from the sign, degrees (DD) and minutes (MM) of declination. The right ascension and declination have been truncated.
Position: RA(s), DEC(")
To conserve space, only the seconds of time for the right ascension and the arcseconds of declination are given. To reconstruct the source position one must also take the hours and minutes of the right ascension and the degrees and minutes of declination from the source name. Because the source name was obtained by truncating rather than rounding the positions, values of RA(s) and DEC(") as large as 60 are possible.
Galactic Coordinates
Galactic coordinates (X(II), b(II)) are given to a precision of 1°.
Positional Uncertainties (SMAJ,SMIN,PA)
Semi-major, semi-minor axes (") and the position angle (degrees) of the uncertainty ellipse are given as described in the previous section.
Number of Sightings: NH
The number of hours-confirmed sightings.
Flux Densities
Non-color-corrected flux densities are given in Janskys in the four bands. A single character following the measurement denotes the flux quality of the observation (Section V.H.5). A blank denotes a high quality measurement, a ':' denotes a moderate quality measurement and an 'L' denotes an upper limit. An 'S' indicates that all measurements in that band were saturated and that the value listed is the largest of all the saturated values.
Flux Density Uncertainties: FLUX/UNCS
The relative uncertainties are given in each band for each high or moderate quality measurement according to the following convention (where the uncertainty was first rounded to two significant figures):| Symbol | Uncertainty Range |
|---|---|
| A 0.00 (X) | (X)fv/fv < 0.04 |
| B 0.04 (X) | (X)fv/fv < 0.08 |
| C 0.08 (X) | (X)fv/fv < 0.12 |
| D 0.12 (X) | (X)fv/fv < 0.16 |
| E 0.16 (X) | (X)fv/fv < 0.20 |
Correlation Coefficient: CORR/COEF
As described in the previous section, the correlation coefficient of the source with the point source template is given in each band according to the convention A=100%, B=99%,...N=87%.
Variability: VAR
The probability (0-99%) that a source detected at 12 and 25 µm is variable is truncated to a single digit 0-9. A blank indicates that the source did not qualify for variability testing.
The Confusion Block
Ten flags or values each consisting of a single digit are combined into a block to denote the presence of nearby sources of possible confusion. The flags are discussed in detail in the preceding section and in Section V.H and include:
| C1 = CIRR1 | the number of 100 µm only point sources. |
| C2 = CIRR2 | the ratio of ½° extended emission to the source flux. |
| CF = CONFUSE | hex-encoded flag indicating bands in which confirmation processor found confusion. |
| PH= PNEARH | number of nearby hours-confirmed sources. |
| PW = PNEARW | number of nearby weeks-confirmed sources. |
| S1-S4 = SES1 | number of nearby hours-confirmed small extended sources per band. |
| HD | hex-encoded flag indicating which bands, if any, were processed according to high source density rules (Section V.H.6). |
Low-Resolution Spectra: LRS
The presence of a low-resolution spectrum is indicated by this two-digit classification of the spectrum (Section IX.D).
Small Extended Source: S2
The presence of one or more weeks-confirmed small extended sources is denoted by a hex-encoded flag denoting the bands in which a small extended source was found.
The Associations Block: NID, CAT, NAME, TYPE, RAD, MAG
When an IRAS source is found to have at least one positional association with objects in other astronomical catalogs, one such association is printed. Six pieces of information are given as described in the previous section and in Section V.H.9. NID gives the total number of associations found in searching all catalogs. CAT is the number of the catalog (Tables V.H.1, X.B.4). The NAME and the TYPE (usually spectral or Hubble type) of the object are given. RAD is the distance from the IRAS source to the position of the associated object in arcsec. FIELD1, which is usually a magnitude, is given in the MAG field, when available, for all catalogs except 2 and 19, for which FIELD2 is given.The association printed is chosen first by catalog within a catalog type (IDTYPE) as follows:
| Printing Sequence | ||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| IDTYPE | Type | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | l0 | ll | l2 | l3 | l4 | l5-3l |
| 1 | Extragalactic | 9 | 6 | 12 | 10 | 29 | 25 | 26 | 27 | 28 | 30 | 31 | - | - | - | - |
| 2 | stellar | 13 | 4 | 15 | 2 | 1 | 7 | 16 | 17 | 18 | 19 | 24 | - | - | - | - |
| 3 | other | 14 | 22 | 21 | 20 | 23 | 3 | 5 | 8 | 11 | - | - | - | - | - | - |
| 4 | multiple | 13 | 9 | 14 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 10 | 11 | 12 | 15-31 |
If more than one association was found in the catalog chosen by the priority scheme, the closest associated source (smallest RAD) is printed.
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