MCG (G0): Morphological Catalog of Galaxies (19930523)
FILES:
File Dec (2000) range #Galaxies
mcg1.g0 +20 <= Dec < +90 14965
mcg2.g0 -34 <= Dec < +20 14038
mcg3.g0 -46 <= Dec < -32 1639 (Whiteoak extension)
mcg_n.ls Position-list for finding MCG galaxies by name, zone +00 to +15
mcg_s.ls Position-list for finding MCG galaxies by name, zone -01 to -07
CONTENTS: Morphological Catalog of Galaxies
DATASET: These files come in HyperSky dataset G-5, version 19930523 Availability on HyperSky CD-ROM: Vol. 1 (1993)
DESCRIPTION: These datafiles contain a total of 30642 galaxies from the Russian MORPHOLOGICAL CATALOG OF GALAXIES (Morfologiceskij Katalog Galaktik) or MCG, by Vorontsov-Veljaminov et al. The MCG is based on examination of copy prints of the Palomar Sky Survey plates, and is approximately complete to a photographic magnitude of 15. It was not possible to ensure completeness to 15 by including all galaxies down to 16 since, according to the authors, below 15 the increase in the number of galaxies is "catastrophic".
HyperSky datafiles mcg1.g0 and mcg2.g0 contain the first four volumes of the MCG. Source data for these files was obtained through Dr. Harold Corwin of the Astronomy Dept of the University of Texas at Austin. Together these two files (and the first four MCG volumes) cover all of the original Palomar survey, down to the -30 declination zone.
HyperSky datafile mcg3.g0 contains the 5th volume of the MCG, which is based on the Palomar Survey Whiteoak extension and covers southern declination zones -36 and -42. Source data for MCG volume 5 was not available in machine readable form, and so was manually transcribed into source files used to build HyperSky datafile mcg3.g0. The MCG volume 5 data in mcg3.g0 has been kept separate from the combined data from volumes 1-4 both to isolate any possible transcription errors, and because the Whiteoak survey data is considered less reliable than data from the original survey.
Each MCG galaxy is identified by a 3-part number of form AA-BB-CCC. The first part, AA, identifies the Palomar Survey declination zone. AA may be signed positive or negative, indicating a zone north or south of the celestial equator. AA runs from +15 at the north pole through 0 at the equator to -7 for the southernmost (-42 degree) zone of the Whiteoak extension. Since the Palomar Survey zones are about 6 degrees wide, AA may be used to determine a galaxy's approximate declination. For example, 6 * -7 yields zone -42. The second number, BB, is the field number within the Declination zone. BB ranges from 1 to 60 for the equatorial zone, but this range decreases with increasing distance from the equator. The final number, CCC, is an arbitrary identification number for the galaxy within the field defined by AA-BB.
MCG field identifications are also included in the HyperSky Palomar Sky Survey field boundaries datafile. Using that file, one can easily determine the MCG field for galaxies or other objects without MCG identifications.
Position-lists MCG_N.LS and MCG_S.LS, included as an installation option, let you set your field position on an MGC galaxy by selecting it from the appropriate list. See manual page MGC.MLS for more details.
DATA: The HyperSky datafile contains the following data from the catalog:
MAG: photographic magnitude, about accurate to the nearest whole number.
IDENTIFICATION: The MCG identification number, as discussed above.
COMMENTS: The comment line contains the following additional information, provided if available for each galaxy:
(a) NCG or IC catalog number, if available. For datafile mcg3.g0, some additional NGC and IC identifications have been provided by Dr. Harold Corwin of the University of Texas at Austin.
(b) i : approximate inclination, coded by the following letters:
E - edge-on.
e - approaching edge-on
m - midway between edge-on and face-on.
f - approaching face-on
F - face-on.
(c) I=inner/outer : surface brightness of the galaxy's inner and outer regions, coded by the following letters:
B! - extremely bright (overexposed image; similar to star image; brighter than magnitude 21.5 per square arc second)
B - very bright (very dense image; some structure visible within; about magnitude 22.3 per square arc second)
b - slightly bright (dark gray image; distinct structure throughout; about magnitude 22.8 per square arc second)
d - slightly dim (light gray image entirely; about magnitude 23.5 per square arc second)
D - very dim (weak but clearly visible picture; about magnitude 24.5 per square arc second)
D! - extremely dim (almost indistinguishable from background; weaker than magnitude 25.5 per square arc second)
As an example, a galaxy described by "i=F, I=B/d" would be a face-on object with a very bright inner core and slightly dim surrounding outer area.
POSITION-LISTS: of all MCG galaxies, and are intended to allow you to quickly set your field center position at the location of any MGC galaxy simply by selecting its number from the appropriate position-list. List mcg_n.ls contains galaxies in the MCG northern (+) zones, and list mcg_s.ls contains galaxies in the MCG southern (-) zones.
Because of the number of galaxies in the MGC (about 30000), each list has three levels: a zonal menu, a field menu, and finally individual lists of galaxies in each zone field. For example, to set your HyperSky field center at the position of MGC galaxy +01-23-04, you would use position-list MCS_N.LS and select zone "+01" from the toplevel zone menu, then select field "+01-23" from the second-level field menu, and finally select galaxy +01-23-04 from the resulting MGC galaxy list.
The field menu headings also show the approximate count of galaxies in each MCG field. The intent of these galaxy counts is only to give you an indication of the length of each field list. In most cases the galaxy counts are correct, but they ignore field galaxies with letter subscripts on their names (eg, MCG +03-29-12b), so are imprecise for the relatively few MCG fields containing such galaxies. This is irrelevant for their intended purpose, however.
Remember that these lists are only position-lists; they do not display or identify the MGC galaxy at the position you select. An MGC galaxy will be displayed at the chosen HyperSky field position only if you have also loaded HyperSky MGC galaxy catalog files MGC1.G0, MGC2.G0 and MGC3.G0.