A legend of object information


1. Galaxies
a. type
  The morphological classification scheme of galaxies has been used the revised Hubble's original division of galaxies, into ellipticals, spirals, barred spirals, and irregulars, established by a French astronomer of de Vaucouleurs.
  At first all galaxies are classed into 4 major shapes of Ellipticals(E), Lenticular(S0), Spirals(S), and Irregulars(I). The S0 class has been newly defined as an intermediate one between E and S. And this scheme does not considers the barred galaxies as a class, - but adds notation for bars in general (B), for the absence of bars (A), and the mixed state (AB). Furthermore other notations representing characteristic shapes added, - for inner and outer ring structure (r and R), and for a global "S" design (s).
  The spiral galaxies are grouped into 10 stages from "0/a", the most closed arms, to "d" with loosely wound arms, and adding a stage of "m", Magellanic unsettled structures.
  For example a face-on galaxy of M101 in Ursa Major is classified as "SAB(rs)cd", meaning that it has an incipient bar (type SAB), its spiral arms are not quite as straggling as they could be (type cd), and that the galaxy has an overall S-shape and its inner arms close in a ring around the central bulge (rs).
  And the luminosity class of spirals, established by van den Bergh, is indicated by a Roman numerical following the de Voucouleurs's type. The class has been ranged from I-V, class I galaxies have very long organized arms, class Vs have very poorly organized patterns. The M101 has fairly developed arms, classified as "SAB(rs)cd I".

  You can refer theoretical descriptions about morphological classification of galaxies at this site for instance.

   Galaxy Classification System by E.Hubble
  1. Ellipticals: E
    8 stages from round shape (E0) to lens-shaped (E7)

  2. Spirals: S
    3 types from closed arms(Sa), medium(Sb) and opened(Sc)

  3. Barred Spirals: SB
    3 types from closed arms(SBa), medium(SBb) and opened(SBc)

  4. Irregulars: I, Ir

  5. Between E & S types: S0, between E & SB: SB

  6. "p" is added in peculiar shaped Galaxies (ex. Sbp, E6p, etc.).

Revised Morphological Galaxy Classification System by de Vaucouleurs
ClassesFamiliesVarietiesStagesTTypes
Ellipticals Compact -6cE
  Elliptical(0-6)-5E0 to E6
  Intermediate-5E0-1 (ex.)
 Giant Ellipticals -4E+
Lenticulars   S0 
Non-barred   SA0
Barred   SB0
Mixed   SAB0
 Inner ring  S(r)0
 S-shaped  S(s)0
 Mixed  S(rs)0
  Early-3S0-
  Intermediate-2S0
  Late-1S0+
SpiralsNon-barred   SA
Barred   SB
Mixed   SAB
 Inner ring  S(r)
 S-shaped  S(s)
 Mixed  S(rs)
  0/a0S0/a
  a1Sa
  ab2Sab
  b3Sb
  bc4Sbc
  c5Sc
  cd6Scd
  d7Sd
  dm8Sdm
  m9Sm
IrregularsNon-barred   IA
Barred   IB
Mixed   IAB
 S-shaped  I(s)
  Non-Magellanic90I0
  Magellanic10Im
 Compact 11cI
Peculiars   99Pec
 Peculiarity pec 
(All types)  Uncertain :
Doubtful ?
Spindle sp
Outer ring (R)
Pseudo outer ring (R')
Column "T" indicates index of Hubble types.

b. Other IDs
  There are several large scaled galaxy catalogs in addition to Messier, NGC or IC catalogs,
some principal numbers of these catalogs are indicated.

CodesNames of Catalogs# of ObjectsFeatures
PGCPrincipal Galaxy Catalog983,261The largest catalog of galaxies in all sphere brighter than 18th magnitude
UGCUppsala General Catalog of Galaxies12,939Galaxies with >1' in size and/or <14.5th magnitude in northern hemisphere by Palomar Observatory Sky Survey(POSS)
UGCAUGC Galaxies (addendum)@Supplement of UGC catalog
MCGMorphological Galaxy Catalog29,003Galaxies positioned north of Dec.=-18° identified by POSS
CGCGCatalog of Galaxies and Clusters of Galaxies9,134Galaxies with <1' and <14.5th magnitude not included in UGC
ESOUppsala Survey of the ESO(B)Atlas 16,164Galaxies positioned <-18° in Dec. surveyed by European Southern Observatory (ESO)
IRASIRAS Point Source Catalog Version 2.0245,889Sources of infrared observed by IRAS satellite
DDODavid Dunlop Observatory Catalog of Dwarf Galaxies222Catalog of dwarf galaxies
HCGHickson Compact Group463100 Compact galaxy groups in all skies and member galaxies
Arp-338Peculiar galaxies by Halton Arp


c. Radial Velocity
  This column indicates relative velocity measured from red shift (or blue shift) of each galaxy, The "+" means leaving and "-" means closing to us.
This values usually used to estimate the distance to each galaxy farther than about 10 millions light years.


2. Galaxy Clusters

  A catalog of "Abell" covers 5250 galaxy clusters in all sphere with # of member galaxies over 50 and red shift z<0.2.
  The type of galaxy cluster consists of 3 parts of Distance Class, Richness Class and Blautz-Morgan Class.
For example the type of "3 2 I-II" means the distance class of 3, richness class of 2, and a bit larger brightness difference of 2 principal members.

3. Planetary Nebula

  The designation of planetary nebula without IDs of NGC or IC is used the scheme of PK (Perek & Kohoutek). The PK catalog contains 1036 planetary nebulae and is represented as format of PK nnn(+ or -)nn.n. The first two terms represent integers of galactic longitude and latitude respectivery, and the last integer is consecutive # in the respective area of 1deg. x 1deg.
  The type of planetary nebula is used the scheme of Vorontsov-Velyaminov as follows.
I...Stellar image
II...Smooth diska...brighter toward center
b...uniform brightness
c...traces of ring structure
III...Irregular diska...very irregular brightness distribution
b...traces of ring structure
IV...Ring structure
V...Irregular form similar to diffuse nebula
VI...Anomalous form


4. Open Clusters

  2 classification codes indicated as possible of Shapley's 5 classes from "very loose" (c type) to "rich & concentrated" (g type) and Trumpler's classification scheme as folows.
  Trumpler's code consists of three parts of Concentration, Brightness range and richness.



5. Globular Clusters

  Shapley-Sawyer's concentration class indicated. Values range from I to XII. The smaller the number, the more concentrated the cluster.

6. Diffuse, Reflection, and Dark Nebulae

  The Lynd's classification classes are indicated.

Class of Bright Nebula...Consists of 2 parts, meaning brightness and kind of emission.

Class of Dark Nebula...Consists of 2 parts, meaning opacity and shape.

  Some principal catalog numbers of nebulae are indicated in addition to Messier, NGC and IC numbers.
Catalog codePrincipal nameFeatures
Sh2SharplessSynthesis catalog of inner-galactic diffused nebulae
LBNLynd's Catalogue of Bright Nebulae Synthesis catalog of diffused and reflection nebulae
RCWRodgers, Campbell, WhiteoakCatalog of H-alpha regions in southern Milky Way plane vicinity
vdBvan den BerghSynthesis catalog of inner-galactic reflection nebulae
BBarnard182 dark nebulae
LDNLynd's Catalogue of Dark Nebulae Synthesis catalog of inner-galactic dark nebulae