Last updated: July-7-99

Purely Morphological Schemes

Systems of classification that in fact are more descriptive than interpretive can be traced back to the early work of Wolf, M. [208] which captured the development of complexity of forms, and that of Shapley, H. [169, 170]. The most extensive application of this approach to galaxy taxonomy is the work of Vorontsov-Velyaminov and his colleagues as published in the five volumes of the Morphological Catalogue of Galaxies [200].

In the MCG no attempt is made to systematize and/or distill the forms found; rather the essential components are all laid out in as much complexity (or simplicity) as the system demonstrates, ordered simply as a function of radial zones within the galaxy; different zones are divided by a semicolon, those referring to the same zone are separated by a colon. A double colon means that the outer details are completely detached from the inner ones. Symbols are placed inside of parentheses, if they are doubtful. An exclamation mark, or the repetition of the lowercase descriptors are used to accentuate a detail or quantity. The following table lists the essential features of this powerful, albeit infrequently used system.

**Morphological Catalogue Symbols** [200]
Symbol used in MCG	Description
E	elliptical
F	flat galaxies usually highly inclined, with no distinguishable form
G	small galaxies, difficult to describe but not stellar
N	large nucleus
n	small nucleus
Ne and ne	elongated nuclei
(N)	overexposed image with traces of structure which imitate a nucleus
N_n and n_n	nebulous nuclei
H	haze or halo
Hp	very asymmetrical or disturbez Haze
D	disk
D^-	incomplete disk
L	lens
R	ring
RR	several rings
R^-	incomplete ring
D ->R	disk is brighter at its rim (ring effect)
B	short bar with no nucleus
B^-	very short bar
BB	long bar
BBB	very long bar
2B	bar seen on both sides of N or L
N;2B	bar is faint relative to nucleus
N,2B	nucleus and bar are of comparable strength
S and Z	long spiral arms 2S = two arms, 3S = three spiral arms, etc.
s and z	short spiral arms
SS and zz	indefinite numbers of arms
SS' and ss'	arms with indefinite direction of winding
ZS	arms wind in opposite directions
Sss	branching spiral arm
r	ray
	emergent spiral arms form a -shape
-> R	-arm tends to form a ring
2S -> 8	spiral returns to nucleus forming a figure-eight
S -> R	arm merges into a ring
(N);ss or F;ss	ends of a flat system are visible
D, (2S) or L, (2s)	arms are suspected in a D or L system
2l	two wings (flattened component seen edge-on)
P	indefinite patch
A	absorption feature
T	tail
C	connecting filament (in interacting systems)
+^*	star superimposed
m	massive
f	filamentary
w	wide open arms
t	tightly wound arms
o	open arms
z	arms start at right-angles to the bar
->	appears to transform to
-> 8	transforms to a figure-eight or loop
a	very smooth
b	smooth
c	patchy
d	very patchy
i	irregular patchiness
p	deformed detail (not the peculiarity in general) used to accentuate any particular detail
( )	symbols are put in parentheses when a detail is only suspected

Examples (click on the figures to see larger versions) :