IRAS Asteroid and Comet Survey Data

The Galaxies and Quasars catalog consists of two files in FITS table format, one with IRAS point source information ordered by right ascension and the other with identified associations with other catalogs, keyed to the IRAS data records. FITS extension headers in each file describe each column in the data tables. The information in the extension headers is given in a more easily-readable format below in Tables 1 and 5, which contain brief descriptions of each variable in the files, including their logical types and lengths in bytes.

        Table 1.  Format of IRAS Data for Extragalactic Catalog File
Start
Byte   Name            Description                    Units             Format
  1    NAME        IRAS source name                   ---                 A11
 12    RAHR        Right Ascension 1950               Hours               I2
 15    RAMIN       Right Ascension 1950               Minutes             I2
 18    RASEC       Right Ascension 1950               Seconds             F4.1
 23    DECSGN      Declination Sign                   +,-                 A1
 24    DECDEG      Declination 1950                   Arc degrees         I2
 27    DECMIN      Declination 1950                   Arc minutes         I2
 30    DECSEC      Declination 1950                   Arc seconds         I2
 33    GLAT        Galactic latitude 1950             Arc degrees         I3
 37    UNCMAJ      Uncertainty ellipse                Arc seconds         I3
                   semi-major axis
 40    UNCMIN      Uncertainty ellipse                Arc seconds         I3
                   semi-minor axis
 44    POSANG      Uncertainty ellipse                Degrees             I3
                   position angle                     (East of North)
 47    NHCON       Number of times observed           ---                 I2
 49    FNU_12      12 um flux density                 Janskys             F6.2
                   averaged, non color corrected      (10E-26 W/m**2/Hz)
 55    FQUAL_12    12 um flux quality where           ---                 A1
                   (blank) = high quality
                         : = moderate quality
                         L = upper limit
 56    FNU_25      25 um flux density                 Janskys             F6.2
                   averaged, non color corrected      (10E-26 W/m**2/Hz)
 62    FQUAL_25    25 um flux quality where           ---                 A1
                   (blank) = high quality
                         : = moderate quality
                         L = upper limit
 63    FNU_60      60 um flux density                 Janskys             F7.2
                   averaged, non color corrected      (10E-26 W/m**2/Hz)
 70    FQUAL_60    60 um flux quality where           ---                 A1
                   (blank) = high quality
                         : = moderate quality
                         L = upper limit
 71    FNU_100     100 um flux density                Janskys             F7.2
                   averaged, non color corrected      (10E-26 W/m**2/Hz)
 78    FQUAL_100   100 um flux quality where          ---                 A1
                   (blank) = high quality
                         : = moderate quality
                         L = upper limit
 79    FIR         Log (FIR) far infrared flux        W/m**2              F6.2
                   combined 60 & 100 um flux
 85    FQFIR       FIR flux quality where             ---                 A1
                   (blank) = high quality
                         : = moderate quality
                         L = upper limit
 86    RELUNC [1]  Percent relative flux density      ---                 4A1
                   uncertainties, one value per band,
                   A -  0% < UNCS <  4%
                   B -  4  < UNCS <  8
                   C -  8  < UNCS < 12
                   D - 12  < UNCS < 16
                   E - 16  < UNCS < 20
                   F -       UNCS > 20
 91    CC [1]      Point source correlation           ---                 4A1
                   coefficient, one value per band
                   A = 100%
                   B =  99
                   C =  98
                   .
                   .
                   M =  87
 96    CIRR1       Cirrus indicator, number of        ---                 I1
                   100 um only sources in window
 97    CIRR2       Cirrus indicator, ratio of         ---                 I1
                   cirrus flux to source flux
 99    CONFUSE     Confusion flag, hex encoded        ---                 I1
                   see Table 3 and PSC Format
               
100    PNEARH      Number hours-confirmed point       ---                 I1
                   sources in window
                   PNEARH > 9 = 9
101    PNEARW      Number of weeks-confirmed          ---                 I1
                   point sources in window
                   PNEARW > 9 = 9
102    HSDFLG      High source density flag, hex      ---                 I1
                   encoded, see Table 3 and
                   PSC Format
104    SES1 [1]    Number of seconds-confirmed small  ---                 4I1
                   extended sources in window,
                   one value per band
108    SES2        Number of weeks-confirmed small    ---                 I1
                   extended sources in window,
                   hex encoded, see Table 3 and
                   PSC Format
109    NSSS        Number of associations from        ---                 I2
                   Small-Scale Structure Catalog
112    SSSNAM      Name of closest SSS association    ---                 A10
122    DISSSS      Separation from the SSS source     Arc minutes         I3
125    NONGAL      Number of associations from        ---                 I2
                   non-galaxy catalogs listed in
                   Table 5 of PSC format
128    IDNGAL      Code indicating non-galaxy         ---                 A1
                   catalog with closest association,
                   see Table 4.
130    DSNGAL      Separation of the non-galaxy       Arc minutes         I3
                   source
133    NRECS       Number of lines in association     ---                 I2
                   file which are keyed on this
                   IRAS name
135    BLANKS      Blank space for possible added     ---                 A26
                   data

[1] In the FITS header, these quantities are suffixed by the wavelength.
    Example: CC(4) is given as CC_12, CC_25, CC_60, and CC_100.

Name: NAME

The IRAS source name is derived from its position by combining the hours, minutes, and tenths of minutes of right ascension, and the sign, degrees, and minutes of the declination. The right ascension and declination have been truncated. A letter 'A', 'B', 'C', etc. is appended to names of sources so close together that they would otherwise have had identical names.

Position: RAHR, RAMIN, RASEC, DECSGN, DECMIN, DECSEC

IRAS positions are given for the equinox 1950.0.

Galactic Latitude: GLAT

Galactic latitude bII rounded to the nearest degree.

Positional Uncertainties: UNCMAJ, UNCMIN, POSANG

The uncertainty is expressed as a 95% confidence uncertainty ellipse. The semi-major (UNCMAJ) and semi-minor (UNCMIN) axes (arcsec) of the confidence ellipse are given. The orientation of the ellipse on the sky, (POSANG), is expressed in terms of the angle between the major axis of the ellipse and the local equatorial meridian, expressed in degrees east of north. The uncertainty is overestimated for large uncertainties; further information is available in Explanatory Supplement V.D.9 and VII.C.

Number of Sightings: NHCON

The number of hours-confirmed sightings of a source (see Explanatory Supplement V.D).

Flux Densities and Their Qualities: FNU, FQUAL

Flux densities in Janskys (10^-26 W m^-2 Hz^-1) are given in the four bands, each followed by a flag indicating the quality of the measurement. The flux densities assume an underlying energy distribution f(nu) proportional to nu^-1, i.e., they have not been color-corrected. The quoted flux densities are averages of all the hours-confirmed sightings as obtained by the prescription in Explanatory Supplement V.H.5. If no flux quality flag is given, the flux density is a high quality one. A colon (:) denotes a moderate quality flux density, and an 'L' denotes an upper limit. An 'S' indicates a saturated flux density. An upper limit is usually a 3-sigma value but may be much more than this if the flux was deleted by the high-source-density processor (Explanatory Supplement V.H.6 and High Source Density Bins). The assignment of flux qualities is described in Explanatory Supplement V.H.5.

Combined 60 and 100 um Flux and Quality: FIR, FQFIR

This quantity is a convenient representation of the far-infrared flux of a galaxy, as measured by IRAS, at least for thermal infrared sources; it is effectively the total flux between 42.5 and 122.5 um. It is in units of W m^-2. A full description of this parameter is given in Appendix B of the Cataloged Galaxies and Quasars reference; numerically the quantity tabulated is given by:

           Log(FIR) = Log(1.26 x [F(60) + F(100)]),

where F(60) and F(100) are the fluxes measured for the source, in W m^-2, in the 60 and 100 um bands respectively. These fluxes can be recovered from the nominal flux densities listed in the IRAS catalogs using the formulae:

           F(60)  = 2.58 x 10^-14 x f(nu;60)
            F(100) = 1.00 x 10^-14 x f(nu;100)

where f(nu;60) and f(nu;100) are the flux densities at the two wavelengths, measured in Janskys.

The flux quality assigned to FIR is carried over from the flux qualities of the 60 and 100 um flux densities. FIR is of course subject to the same uncertainties in the calibration as the individual flux densities.

Flux Uncertainties: RELUNC(4)

Each high or moderate-quality flux density measurement has an associated uncertainty expressed as a 1-sigma value in units of delta[f(nu)]/f(nu). Uncertainties are discussed in Explanatory Supplement V.H.5. These flux qualities have been encoded according to the scheme in Table 2 (where the uncertainty was first rounded to two significant figures).

                 Table 2.  Meaning of RELUNC Flag
            _______________________________________________________
           |       Symbol           Uncertainty Range              |
           |_______________________________________________________|
           |          A       0.00 <= delta[f(nu)]/f(nu) < 0.04    |
           |          B       0.04 <= delta[f(nu)]/f(nu) < 0.08    |
           |          C       0.08 <= delta[f(nu)]/f(nu) < 0.12    |
           |          D       0.12 <= delta[f(nu)]/f(nu) < 0.16    |
           |          E       0.16 <= delta[f(nu)]/f(nu) < 0.20    |
           |          F               delta[f(nu)]/f(nu) >=0.20    |
           |_______________________________________________________|

Correlation Coefficient: CC(4)

The correlation coefficient, one per band, ranges from 87 to 100%. It is derived from a least squares fit of the data for a source to the point source template. The coefficient is described fully in Explanatory Supplement V.C.4. In the Extragalactic Catalog the coefficient is encoded as alphabetic characters with A=100%, B=99%, etc., to M=87%, one for each band. The value quoted is the highest correlation coefficient found for that source on any sighting.

Cirrus Indicators: CIRR1, CIRR2

Over a large range of Galactic latitudes the infrared sky at 100 um is characterized by emission from interstellar dust on a wide range of angular scales. As described in Cataloged Galaxies and Quasars II.F, this so-called "infrared cirrus" can seriously hamper efforts to extract point source detections from the data. To aid the user in interpreting the quoted 100 um measurements, three cirrus-related quantities have been established (Explanatory Supplement V.H.4 and VII.H). Two of these are given in the Extragalactic Catalog.

CIRR1 gives the number of 100 um-only hours-confirmed sources located within a ±0.5° box in ecliptic coordinates centered on the source. The sources included in this count are the weeks-confirmed sources prior to high-source-density processing, if applicable (see Cataloged Galaxies and Quasars II.E), plus those sources hours-confirmed but not weeks-confirmed. Values of greater than 3 may indicate contamination by cirrus with structure on the point-source size scale.

CIRR2 gives a cirrus indication on a larger scale than CIRR1 and compares a "cirrus flux" with the source flux at 100 um (see Explanatory Supplement V.H.4 for derivation of CIRR2). Values of CIRR2 larger than 4 or 5 indicate the presence of considerable structure in the 100 um emission on a 0.5° scale. A value of 0 indicates that no 100 um extended emission data were available for the source in question.

Confusion Status Flags: CONFUSE, PNEARH, PNEARW, HSDFLAG

A great deal of care went into trying to untangle instances of confusion between neighboring sources (Explanatory Supplement V.D.2, D.3; see also Cataloged Galaxies and Quasars II.E). In parts of the sky where the source density is low, confusion processing was often able to separate sources that are quite close together. The CONFUSE flag is set if two or more sightings of the source in a given band had confusion status bits set, indicating confusion in the seconds-confirmation or band-merging processes. This flag is hex encoded by band (see Table 3).

Other indicators of possible confusion are given by PNEARH and PNEARW which are, respectively, the number of hours and weeks-confirmed point sources located within a 4.5 arcmin cross-scan and 6 arcmin in-scan window centered on the source. Values larger than 9 are given as 9 (Explanatory Supplement VII.H.1.a, X.B).

Regions of high source density received special processing to improve the reliability of the quoted sources (see Cataloged Galaxies and Quasars II.E and Explanatory Supplement V.H.6). The regions are band dependent. If a particular band of a given source went through high source density processing, then the appropriate bit in HSDFLAG. HSDFLAG is hex encoded by band (see Table 3).

                Table 3.  Meaning of Hex Encoded Flags
      Flag Set in A Particular Band (microns)    Resultant Value
   100        60        25         12            of Encoded Flag
 (Bit 3)    (Bit 2)   (Bit 1)    (Bit 0)         xxxx = HEX = Decimal
    0          0         0          0              0000 = 0 =  0
    0          0         0          1              0001 = 1 =  1
    0          0         1          0              0010 = 2 =  2
    0          0         1          1              0011 = 3 =  3
    0          1         0          0              0100 = 4 =  4
    0          1         0          1              0101 = 5 =  5
    0          1         1          0              0110 = 6 =  6
    0          1         1          1              0111 = 7 =  7
    1          0         0          0              1000 = 8 =  8
    1          0         0          1              1001 = 9 =  9
    1          0         1          0              1010 = A = 10
    1          0         1          1              1011 = B = 11
    1          1         0          0              1100 = C = 12
    1          1         0          1              1101 = D = 13
    1          1         1          0              1110 = E = 14
    1          1         1          1              1111 = F = 15

Small Extended Source Flags: SES1(4), SES2(1)

SES1 is the number of seconds-confirmed small-scale structure detections in a given band found within a window centered on the source. The size of the window is 6 arcsec in-scan x 4.5 arcsec cross-scan. As described in Explanatory Supplement VII.H.1, values of SES1 greater than 1 indicate that significant extended structure may exist in the region and that the source in question may be a point-source-like piece of a complex field.

SES2 is the number of weeks-confirmed small-scale structure sources in a given band located within a 6 arcsec in-scan x 4.5 arcsec cross-scan window centered on the source. Values greater than zero mean that the point source flux measurement should be treated with caution as the source in question may, in fact, be extended, and the flux density quoted in the Small-Scale Structure Catalog may provide a better representation of the source. SES2 is hex encoded by band (see Table 3).

Small-Scale Structure Associations: NSSS, SSSNAM, DISSSS

The Small-Scale Structure associations were established by searching the Small-Scale Structure Catalog near the positions of IRAS point sources rather than near galaxies. The associations were made in much the same way as was used for associations in other astronomical catalogs with entries in the Point Source Catalog. NSSS is the number of small-scale structure sources that associate with the point source. In the Extragalactic Catalog N is never larger than one. SSSNAM is the name of the associated source as in the Small-Scale Structure Catalog, and DISSSS is the separation in arcseconds between the point source and the small-scale structure source.

For many galaxies, the SES2 flag is set but no extended-source associations are given. This situation arises primarily because the SES2 flag is based on weeks-confirmed small-scale structure sources (which numbered about 40,000), whereas associations were established with the Small-Scale Structure Catalog which contains only 16,740 entries. The presence of a SES2 flag is sufficient cause for suspecting that the galaxy may have been resolved by IRAS, though the extended detection did not make it through the stringent final catalog selection process. (See the Explanatory Supplement for more details.)

Another reason that may have led to the situation described above is that SES2 flags were based on a slightly larger search window than associations with the Small Scale Structure Catalog.

Other Associations: NONGAL, IDNGAL, DSNGAL

If an IRAS point source associates with an object from any of the various non-galaxy catalogs listed in Table 5 of the Format of the Point Source Catalog, that fact is indicated here. NONGAL is the number of associations made for the source among these non-galaxy catalogs and IDNGAL is a code which indicates which catalog the nearest of these associations is from (see Table 4). DSNGAL is the separation of this object from the point source (arcsec). There is a priority scheme in selecting the nearest association: if an association exists from one of the first nine catalogs in Table 4 it takes priority over the remainder. Similarly, associations from catalogs A-E take precedence over F-J, and catalogs F-I are preferred over J. Although this field is included primarily to warn of possible confusion of the galaxy with a star or nebula, the catalog of extragalactic radio sources, J, is included on the lowest priority, since it provides a useful piece of additional information.

      Table 4.  Key to Identifications from Non-Galaxy Catalogs [1]
   __________________________________________________________________________
  | Code   Catalog                                                           |
  |__________________________________________________________________________|
  |   1    Smithsonian Astrophysical Observatory Star Catalog, 1966          |
  |   2    Bright Star Catalogue - 4th Edition, Hoffleit and Jascheck 1982   |
  |   3    Dearborn Observatory Catalogue of faint Red Stars, Lee et al.     |
  |           1943, 1944, 1947                                               |
  |   4    General Catalogue of Variable Stars, Kukarkin et al. 1970, 1971   |
  |   5    Early Type Stars with Emission Lines, Wackerling 1970             |
  |   6    New Catalog of Suspected Variable Stars, Kukarkin et al. 1981     |
  |   7    General Catalogue of Cool Carbon Stars                            |
  |   8    Catalog of Nearby Stars, Gliese 1969                              |
  |   9    General Catalog of S Stars, Stephenson 1973, 1976                 |
  |   A    Strasbourg Planetary Nebulae                                      |
  |   B    Parkes HII Region Survey, Haynes et al. 1979                      |
  |   C    Bonn HII Region Survey, Altenhoff et al. 1979                     |
  |   D    Catalog of CO Radial Velocities Toward Galactic HII Regions,      |
  |           Blitz et al. 1982                                              |
  |   E    Catalogue of Dark Nebulae, Lynds 1962                             |
  |        Comparison Catalog of HII Regions, Marsalkova 1974                |
  |        Catalog of Star Clusters and Associations, Alter et al. 1970      |
  |        Catalog of Bright Diffuse Nebulae, Cederblad 1946                 |
  |        Untersuchungen Uber Reflexionsnebel am Palomar Sky Survey,        |
  |           Dorschner and Gurtler 1964                                     |
  |        A Study of Reflection Nebulae, van den Bergh 1966b                |
  |        Catalog of Southern Stars Embedded in Nebulosity,                 |
  |           van den Bergh and Herbst 1975                                  |
  |   F    Revised Air Force Geophysical Laboratory Four-Color Survey,       |
  |           Price and Murdock 1983                                         |
  |   G    Two Micron Sky Survey, Neugebauer and Leighton 1969               |
  |   H    Equatorial Infrared Catalogue, Sweeney et al. 1978                |
  |   I    Two Micron Sky Survey with Improved Positions,                    |
  |           Kleinmann and Joyce 1984                                       |
  |   J    Catalog of Extragalactic Radio Sources Having Flux Densities      |
  |           Greater than 1 Jy at 5 Ghz, Kuhr et al. 1981                   |
  |__________________________________________________________________________|

  [1] One extragalactic catalog, J, is included.

    Table 5.  Format of Association Data for Extragalactic Catalog File
Start
Byte   Name        Description                        Units             Format
  1    NAME        Repeat of IRAS source name         ---                 A11
 12    PGCNAM      Galaxy name from Primary Galaxy    ---                 A12
                   Catalog (UGC, UGCA, ESO, OR CGCG)
 25    NPGC        Number of appearances              ---                 I1
 27    DIAMP       Major axis diameter                Arc seconds         I4
 33    DISPGC      Distance from IRAS source          Arc seconds         I3
 37    PAPGC       Position angle of separation       Degrees East        I3
                   vector                             of North
 41    POSFLG      Position flag, see Sec.IX          ---                 A1
                   of Cat. Galaxies and Quasars ref.
 42    MAGFLG      Magnitude flag, see Sec.IX         ---                 A1
 44    MAGPGC      Magnitude from Primary Galaxy      Magnitude           F4.1
                   Catalog
 49    CLASSN      Classification field               ---                 A7
 57    MCGNAM      Galaxy name from MCG               ---                 A11
 69    NMCG        Number of appearances              ---                 I1
 71    DIAMM       Major axis diameter                Arc seconds         I4
 76    DISMCG      Distance from IRAS source          Arc seconds         I3
 80    PAMCG       Position angle of separation       Degrees East        I3
                   vector                             of North
 84    NGCIC       NGC or IC identification of        ---                 A7
                   Primary Catalog or MCG galaxy
 91    AMDNAM      ARP, MKN, DDO associations         ---                 A7
 99    NAMD        Number of appearances              ---                 I1
101    DISAMD      Distance from IRAS source          Arc seconds         I3
105    PAAMD       Position angle of separation       Degrees East        I3
                   vector                             of North
109    VVZNAM      VCV, VV, Zwicky list associations  ---                 A11
121    NVVZ        Number of appearances              ---                 I1
123    DISVVZ      Distance from IRAS source          Arc seconds         I3
127    PAVVZ       Position angle of separation       Degrees East        I3
                   vector                             of North
131    VCVFLG      VCV identifier or VV flag,         ---                 A2
                   see Sec. IX
133    RECNO       Main Data Table record number      ---                 I5
                   for IRAS source
138    BLANKS      Blank space for possible           ---                 A23
                   added data

Name: NAME

Repeat of the IRAS name.

Primary Galaxy Catalog Names: PGCNAM

This column lists the name of the galaxy from four of the five main galaxy catalogs; the UGC (U), the UGC Appendix (UA), the CGCG (Z), and the ESO (E), with which the IRAS source is associated. A UGC galaxy with the suffix 'A' is from the addendum to the UGC. MCG associations appear elsewhere. As described in Cataloged Galaxies and Quasars III.A, these four catalogs were fully combined prior to making the associations (see III.C and D), so there is at most one entry for each IRAS source in this column unless the IRAS source is associated with more than one galaxy. Details of the catalogs and nomenclature used in various regions of the sky are given in Cataloged Galaxies and Quasars III.C and in Table III.C.1. Positions for the galaxies have been taken from the same catalog as the name, except in the case of the Dressel and Condon (1976) positions for UGC galaxies, and except for a few errors discovered in the UGC coordinates (see Sec. III.F).

If more than one Primary Catalog Galaxy associates with a particular IRAS source, the one matching the IRAS source more closely in position is listed first. The next galaxy appears on the following line.

Number of Appearances of the Galaxy: NPGC

An entry in this column indicates that the galaxy named in the preceding column appears more than once in the Extragalactic Catalog. The value of NPGC is the number of times that the galaxy name appears, i.e., the number of IRAS sources with which the galaxy was associated. Galaxies appearing more than twice in the Extragalactic Catalog are listed in Table III.A.2 in the Cataloged Galaxies and Quasars reference.

Major Axis Diameter: DIAMP

The major axis diameter of the galaxy listed in the Primary Galaxy Catalog column (arcsec). For catalogs that list both blue and red sizes, the blue one has been adopted. The size quoted here is that used to decide whether the galaxy should be treated as a large or small galaxy for the association procedure (see Cataloged Galaxies and Quasars III.B). For a large galaxy (> 90 arcsec in semi-major axis), the association search radius used was one-half of the major axis given here. If no size was available in the catalog the number zero appears in this column.

Separation: DISPGC

Distance of the galaxy from the IRAS Source (arcsec).

Position Angle: PAPGC

Position angle of the separation vector from the IRAS source to the optical galaxy, in degrees east of north.

Position and Magnitude Flags: POSFLG, MAGFLG

POSFLG is a flag indicating any special circumstances concerning the optical position used for the galaxy. MAGFLG is a flag that refers to the magnitude quoted. Explanations of both flags are given in Cataloged Galaxies and Quasars IX. These flags only indicate discrepancies that came to light during the merger process; they are not intended to indicate all discrepancies that may be present in the galaxy catalogs.

Magnitude: MAGPGC

The magnitude is carried over from the galaxy catalog in question. Most often it is a photographic blue magnitude derived ultimately from the CGCG.

Classification Field: CLASSN

In this column the first seven characters of the classification field of the catalog in question have been reproduced. There is no guarantee that these types are in any way homogeneous, and they are often truncated.

MCG Galaxies: MCGNAM

This column contains MCG identifications for the Primary Catalog Galaxy, and also MCG galaxies that have not been identified with the Primary Catalog galaxy for which an independent association has been made with the IRAS source (see Cataloged Galaxies and Quasars III.D). MCG identifications for Primary Catalog galaxies may be identified by the absence of any diameter or separation information for the MCG galaxy.

If a single UGC, UGCA or ESO galaxy is identified with two or more MCG galaxies, this is usually indicated with a '+' symbol. The second and subsequent MCG galaxies will not appear by name in the Extragalactic Catalog. If there is both an identification with a Primary Catalog galaxy and an independent association with another MCG galaxy for a particular source, the identification will appear first, and the independent association will be on the following line. Additional MCG independent associations will appear on subsequent lines, in order of proximity to the IRAS source.

Number of Appearances of the MCG name: NMCG

This column lists the number of times that a given MCG name appears in the Extragalactic Catalog. Unlike the situation for the Primary Galaxy Catalog entries, NMCG does not necessarily indicate the number of IRAS sources that the MCG galaxy is associated with, because there exist cases in which two or more components of a galaxy or galaxy pair have the same MCG name.

Major Axis Diameter: DIAMM

Outer major axis diameter of the MCG galaxy, if the MCG name is not just an identification for a Primary Catalog galaxy (arcsec). If no size was available for the galaxy, the number zero is entered in this column. For large galaxies (> 180 arcsec in semi-major axis) the association search radius used was one-half of the major axis given here.

Separation: DISMCG

Separation of the MCG galaxy from the IRAS source (arcsec), if that MGC galaxy has been associated independently with the IRAS source.

Position Angle: PAMGC

Position angle of the radius vector from the IRAS source to the MCG galaxy, in degrees east from north, if that MCG galaxy has been associated independently with the IRAS source.

NGC/IC Name: NGCIC

NGC or IC identification for the Primary Catalog galaxy, if available, or for the MCG galaxy. If size and separation information exists for the MCG galaxy, then the NGC/IC identification belongs to it; otherwise, the NGC/IC identification belongs to the Primary Catalog galaxy. No identifications are available for CGCG galaxies. Only six characters of the identification field have been copied into the Extragalactic Catalog. The symbols '+', '/' or '=' indicate additional NGC/IC names, which will not appear by name in the Extragalactic Catalog. A '?' or ':' denotes an uncertain identification. These symbols have the same meaning as they do in the optical catalog in question. Note that NGC or IC galaxies that are IRAS sources but that do not appear in the optical catalogs (Table II.A.1 of Cataloged Galaxies and Quasars), if any exist, will not appear here.

Secondary Catalogs: AMDNAM

This column contains the names of galaxies from the Markarian lists (MKN), the Atlas of Peculiar Galaxies (ARP) and the Catalogue of Dwarf Galaxies (DDO). No attempt has been made to identify objects appearing in this column with each other or with Primary Catalog and MCG galaxies.

Number of Appearances of the Name: NAMD

NAMD indicates the number of appearances of the ARP, MKN or DDO name in the Extragalactic Catalog.

Separation: DISAMD

Separation of the ARP, MKN or DDO galaxy from the IRAS source (arcsec).

Position Angle: PAAMD

The position angle of the radius vector from the IRAS source to the galaxy, in degrees east from north.

Secondary Catalogs: VVZNAM

This column contains the names of galaxies and quasars from the compilation of Veron-Cetty and Veron (nomenclature from the original listings combined by Veron-Cetty and Veron), the Atlas of Interacting Galaxies (V) and the eight lists of F. Zwicky (1ZW through 8ZW). As for the previous secondary column, no attempt has been made to internally identify objects in this column amongst themselves, or with objects in any of the other galaxy-name columns.

Number of Appearances of the Name: NVVZ

NVVZ indicates the number of times that the galaxy name appears in the Extragalactic Catalog.

Separation: DISVVZ

Separation of the galaxy from the IRAS source (arcsec).

Position Angle: PAVVZ

Position angle of the radius vector of the IRAS source from the galaxy, in degrees east of north.

VCV Type or VV Flag: VCVFLG

This column is used to identify VCV entries because many entries from this catalog are duplicated in one of the other secondary catalogs - most notably the Markarian lists. The type of the galaxy from VCV has been used as this identification flag. For VCV galaxies with no type, the letters "AN", for "Active Nucleus", have been inserted to mark the entry.

This column also contains a number of flags for VV galaxies; the meaning of these flags is explained in Cataloged Galaxies and Quasars IX.

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