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
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 (X(II), b(II)) are given to a precision
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
Number of Sightings: NH
The number of hours-confirmed sightings.
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
|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%.
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
Low-Resolution Spectra: LRS
The presence of a low-resolution spectrum is indicated by
this two-digit classification of the spectrum
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
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:
Catalogs in Order of Printing Priority
|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)
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