6. SUMMARY OF NOTATION FOR RING AND LENS PHENOMENA
Tables 1 and 2 summarize the notation and classifications that we will use for resonance ring galaxies in the remainder of this review (see Buta 1995). The classifications in Table 2 are based on multicolor CCD images to be certain of the presence or absence of a nuclear ring. The list of galaxies includes virtually every conceivable combination of structures. It is noteworthy that even prototypical ``grand-design'' barred spirals like NGC 1300 can be included in such a list: it has a small nuclear ring inside the bar region. The list demonstrates that we can identify galaxies with up to four ring or pseudoring structures in co-existence. Doubled outer-ring galaxies appear to come in two types, the R1R2' type discussed in section 4.1, and the type illustrated by NGC 2273 (van Driel & Buta 1991; Figure 22) where the two features are clearly separated. No theory has yet explained this latter morphology, which is so far unique. Two outer-ringed ellipticals are also listed in Table 2. Corwin et al. (1985) classified IC 2006 as (R)SA0-, but the object is now recognized as an elliptical galaxy with an accretion ring of neutral gas that also displays some spiral character in deep B-band images (Schweizer et al. 1987a). It could be classified as an (R')E type, but the ring is not a resonance feature (it is counter-rotating relative to the main stellar body). The other ringed elliptical in Table 2, Hoag's object, is discussed further in section 16.
Feature | symbol |
nr | nuclear ring |
nr' | nuclear pseudoring |
r | inner ring |
rs | inner pseudoring |
R | outer ring |
R' | outer pseudoring |
R1 | Type 1 OLR subclass outer ring |
R1' | Type 1 OLR subclass outer pseudoring |
R2' | Type 2 OLR subclass outer pseudoring |
nl | nuclear lens |
l | inner lens |
rl | inner ring/lens |
L | outer lens |
RL | outer ring/lens |
TABLE II. Examples of Types with Ring Classifications
Object | Revised Hubble Type |
NGC 210 | (R2')SAB(s)b |
NGC 1300 | (R')SB(s,nr)b |
NGC 1317 | (R')SAB(r'l,nr,nl)a |
NGC 1326 | (R1)SAB(r,nr)0/a |
NGC 1433 | (R1')SB(rs,nr)ab |
NGC 1543 | (R)SB(l)0° |
NGC 1553 | SA(rl)0o |
NGC 2273 | (RR)SB(rs)a |
NGC 2983 | (L)SB(rs)0+ |
NGC 3081 | (R1R2')SAB(r,nr)0/a |
NGC 4314 | (R')SB(l,nrr')a |
NGC 4321 | SAB(s,nr')bc |
NGC 4622 | SA(r)ab |
NGC 6753 | (R')SA(nr)b |
NGC 6782 | (R1')SB(r,nr)0/a |
NGC 7187 | (R)SA(r)0+ |
NGC 7217 | (R')SA(rs,nr)ab |
IC 1438 | (R1R2')SAB(r,nr)a |
IC 1993 | (R')SA(s)bc |
IC 2006 | (R')E1 |
IC 4290 | (R')SB(r)a |
IC 5240 | SB(r)ab |
ESO 287-56 | (R1')SB(s)a |
ESO 575-47 | (R1')SB(rs)ab |
ESO 577-3 | (R2')SB(r)ab |
Hoag's Object | (R)E0 |
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