CGCG_RD (G0): Zwicky Catalog of Galaxies (199003)
FILES:
File Dec (2000) range #Galaxies
cgcg_rd1.g0 +20 < Dec <= +90 14911
cgcg_rd2.g0 -04 < Dec <= +20 12895
CONTENTS: Zwicky Catalog of Galaxies, with data reduced to RC2 system
DATASET: These files come in HyperSky dataset G-4, version 199003. Availability on HyperSky CD-ROM: Vol. 1 (1993)
DESCRIPTION: These datafiles contain 27806 galaxies from the Catalog of Galaxies and Clusters of Galaxies (CGCG), by Fritz Zwicky. Diameters and photographic magnitudes in this version of the CGCG have been reduced to the standard systems of the Second Reference Catalog of Bright Galaxies (RC2) by Dr. Harold Corwin of the University of Texas Texas at Austin. Dr. Corwin kindly supplied the CGCG files on which the HyperSky datafiles are based.
The CGCG covers a subset of the fields of the Palomar Sky Survey, extending from the north celestial pole south to the Sky Survey declination zone astride the celestial equator. The CGCG also excludes Survey fields north of the celestial equator which are primarily Milky Way fields.
HyperSky users can identify which CGCG field a CGCG galaxy is in by using these datafiles in conjunction with the HyperSky Palomar Sky Survey field boundaries datafile, which includes CGCG field identifications.
CGCG galaxy identification itself is another matter: there is no standard way of identifying a CGCG galaxy. Zwicky himself identified each galaxy using an arbitrary sequence number within each CGCG field. In order for this to be useful, the associated field number must also be known. Some references thus identify a CGCG galaxy using the form FFF-GGG, where FFF is the field number and GGG is the galaxy number within the field. However, because CGCG fields can overlap, this scheme leads to multiple equivalent identification numbers for each galaxy in any overlapping area.
Other references rely on an approach often used elsewhere, and refer to the galaxy with an identification generated from the galaxy coordinates at a particular equinox. For example, the IRAS (Infrared Astronomical Satellite) Extragalactic Catalog uses the following CGCG identification for galaxy NGC 3326: Z1036.9+0522, where Z stands for Zwicky, and the 1950 position is RA=10h36.9m, Dec=+5 22m. This form is used for all CGCG galaxies referenced in the IRAS catalog. Since coordinates at some equinox are also provided with each reference anyway, such a naming convention is somewhat redundant.
Yet other references do not attempt to construct a CGCG name at all, but instead use identifications from other established catalogs, such as the NGC, UGC, etc, if available. This, plus the position at a given equinox, is considered adequate identification. This last approach was the one taken in the source data used for generation of the CGCG HyperSky datafiles.
DATA: The HyperSky datafile contains the following data from the catalog:
MAG: Apparent photographic magnitude, corrected where possible and reduced to the RC2 standard. Otherwise, the raw photographic magnitude is used. "mpc" or "mpr" will appear on the following comment line to indicate whether the magnitude is corrected or raw.
IDENTIFICATION: The galaxy name from either the RC2 or UGC (Uppsala Galaxy Catalog). The RC2 name is used if a galaxy appears in both catalogs. If a galaxy is not in one of these catalogs it is designated "anon." for anonymous, and its position is considered sufficient for identification (See galaxy identification discussion above).
COMMENTS: The comment line contains the following additional information, provided if available for each galaxy:
(a) "mpc" or "mpr", indicating whether the photographic magnitude provided is corrected or raw.
(b) The galaxy type, which will be one of the following: cE,E,cD,S0-,S0o,S0+,S0/a,Sa,Sab,Sb,Sbc,Sc,Scd,Sd,Sdm,Sm,Im,cIm
(c) One of the following short comments, if applicable:
compact - compact galaxy (! = very compact; !! = extremely compact).
diffuse - diffuse galaxy (! = very diffuse; !! = extremely diffuse).
N gal. - multiple galaxy; N will be a digit from 2 to 9.
star superposed - galaxy with superposed star.
Multiple galaxies or those with superposed stars do not have corrected photographic magnitudes.
(d) Major and minor axis diameters in arc minutes, in form D'=major/minor.
(e) Blue photographic magnitude.