This is a list of ring galaxies. A ring galaxy, as the name suggests, is a disc or spiral galaxy with its galactic disc structured or distorted into a ring or torus-like appearance. Hoag's Object, discovered by Art Hoag in 1950, is the prototypical example of a ring galaxy.__TOC__
Ring galaxies are theorized to be formed through multiple possible situations:
1. Bar instability – a phenomenon where the rotational velocity of the bar in a barred spiral galaxy increases to the point of spiral spin-out. Under typical conditions, gravitational density waves would favor the creation of spiral arms. When bar instability occurs, these density waves are instead migrated out into a ring-structure by the pressure, force, and gravitational influence of the byronic and dark matter furiously orbiting about the bar. This migration forces the stars, gas and dust found within the former arms into a torus-like region, forming a ring, and often igniting star formation.
2. Galactic collisions- another observed way that ring galaxies can form is through the process of two or more galaxies colliding. The cartwheel galaxy, galaxy pair AM 2026-424, and Arp 147 are all examples of ring galaxies believed to be formed from this process. In pass-through galactic collisions, an often smaller galaxy will pass through the disc of an often larger spiral, causing an outward push of the arms, as if dropping a rock into a pond of still water. In side-swipe and head-on collisions, the appearance of a perfect ring are less likely, with chaotic and warped appearances dominating.
3. Intergalactic medium accretion- this method has been inferred through the existence of Hoag's object, along with UV observations of several other large and ultra-large super spiral galaxies and current formation theories of spiral galaxies. UV-light observations show several cases of faint, ring-like and spiral structures of hot young stars that have formed along the network of cooled inflowing gas, extending far from the visible luminous galactic disc. If conditions are favorable, a ring can form in the place of a spiral structure. Since some spiral galaxies are theorized to have formed from massive clouds of intergalactic gas collapsing and then rotationally forming into a disc structure, one could assume that a ring disc could form in place of a spiral disc if, as mentioned before, conditions are favorable. This holds true for protogalaxies, or galaxies just throughout to be forming, and old galaxies that has migrated into a section of space with a higher gas content than its previous locations.
| Name | Image | Catalogue number | Distance | Notes | |
|---|---|---|---|---|---|
| Cartwheel Galaxy | ESO 350-40, PGC 2248 | 500 Mly | lenticular galaxy | ||
| NGC 6028 | NGC 6028, NGC 6046, PGC 56716 | 203 Mly | barred lenticular galaxy | ||
| NGC 1015 | |||||
| PGC 54559, PRC D-51 | 600 Mly | ||||
| SDSS J151713.93+213516.8 | This galaxy can be seen behind Hoag's Object | ||||
| AM 0644-741 | 300 Mly | ||||
| NGC 4909 | PGC 44949, ESO 269-035, MCG -07-27-028 | ||||
| NGC 1291 | NGC 1291, NGC 1269,[1] PGC 012209 | 33 Mly | |||
| NGC 1512 | PGC 14391 | 38 Mly | Galaxy exhibits a double-ring structure | ||
| NGC 1433 | PGC 13586 | 49 Mly | barred spiral galaxy with ring | ||
| NGC 1533 | NGC 1533, PGC 14582[2] | 62 ± 4 Mly [3] | lenticular galaxy with ring structure | ||
| NGC 2859 | UGC 5001, PGC 26649 | 82.8 Mly | lenticular galaxy with ring structure[4] | ||
| NGC 1350 | PGC 013059 | 87.4 Mly | spiral galaxy with ring structure | ||
| NGC 1386 | PGC 13333 | 53 Mly | spiral galaxy with ring structure | ||
| NGC 1387 | PGC 13344 | 53 Mly | lenticular galaxy with nuclear ring | ||
| NGC 4622 | PGC 42701 | 200 Mly | unbarred spiral galaxy with ring | ||
| NGC 4777, PGC 43852 | 180 Mly | ||||
| NGC 6861 | |||||
| NGC 7217 | UGC 11914, PGC 68096 | 50 Mly | unbarred spiral galaxy with ring | ||
| ESO 509-???098 | PGC 48609 | 350 Mly | |||
| II Zw 28[5] | Zw II 28, 2MASX J05014205+0334278 | 390 Mly | |||
| Arp 148, VV 032, MCG+07-23-019, APG 148 | 450 Mly | collisional ring galaxy | |||
| NGC 4774[6] | I Zw 045 | 413 Mly | collisional ring galaxy | ||
| VII Zw 466 | VII Zw 466, UGC 07683 | 637 Mly | collisional ring galaxy | ||
| Arp-Madore 417-391[7] | PGC 14881 | 670 Mly | collisional ring galaxy | ||
| UGC 4599 | 91 Mly | ||||
| Arp 10 | Arp 10, UGC 01775, 2MASX J02182639+0539139[8] | 400 Mly | collisional ring galaxy | ||
| Arp 146 | PGC 509 | 1050 Mly | interacting pair | ||
| Arp 147 | IC 298 | 430 Mly | interacting pair | ||
| NGC 4650A | PGC 42951 | 126 Mly | polar ring galaxy | ||
| NGC 660 | polar ring galaxy | ||||
| NGC 922 | ESO 478-28, ISG 10 | 150 Mly | collisional ring galaxy | ||
| ESO 198-13 | PGC 9463 | 237 Mly | three ring structures | ||
| LEDA 1000714 | PGC 1000714, 6dFGS gJ112316.4-084007, 2MASX J11231643-0840067 | 360 Mly | two nearly round rings, but with different characteristics | ||
| NGC 985 | VV 285, Mrk 1048, MCG -02-07-035, PGC 9817 | 567 Mly | collisional ring galaxy | ||
| NGC 1142 | NGC 1144, UGC 2389, Arp 118, VV 331a, Mrk 1504, CGCG 389-046, MCG +00-08-048, PGC 11012 | 375 Mly | Seyfert galaxy | ||
| NGC 3081 | IC 2529, ESO 499-G31, AM 0957-223, MCG -04-24-012, PGC 28876 | 83 Mly | barred lenticular galaxy | ||
| NGC 3821 | CGCG 127-32, MCG 4-28-30, PGC 36314, UGC 6663 | 271 Mly | low surface brightness galaxy | ||
| NGC 4513 | CGCG 315-42, MCG 11-15-59, PGC 41527, UGC 7683 | 110 Mly | lenticular galaxy | ||
| NGC 7020 | NGC 7021, ESO 107-13, PGC 66291 | 138 Mly | barred lenticular galaxy | ||
| NGC 7098 | ESO 48-5, IRAS 21393-7520, PGC 67266 | 95 Mly | double barred spiral galaxy | ||
| NGC 7552 | IC 5294, ESO 291- G 012, VV 440, PGC 70884 | 56 Mly | barred spiral galaxy | ||
| NGC 7742 | UGC 12760,[2] MCG +02-60-010,[2] UZC J234415.8+104601,[2] 2MASX J23441571+1046015 | 72 Mly | Unbarred spiral galaxy with ring, Seyfert galaxy | ||
| IC 2628 | PGC 34038, CGCG 067-030 | 601 Mly | |||
| IC 5285 | PGC 70497, UGC 12365 | 286 Mly | |||
| MCG +07-07-072 | PGC 12535 | 320 Mly | Barred spiral galaxy with a ring[9] | ||
| WISEA J033303.20-275041.5 | 1790 Mly | Discovered in the Hubble Legacy Field | |||
| CN AC118 108 | 3757 Mly | ||||
| LT 41 | 2MASX J00075757-0433255 | 1004 Mly | |||
| CFRS 14.0685 | WISEA J141757.82+523050.1 | 1153 Mly | Discovered in Extended Groth Strip | ||
| CFRS 14.0117 | EGSIRAC J141819.73+523424.4 | 2613 Mly | Discovered in Extended Groth Strip | ||
| Z 229-15 | PGC 62756 | 390 Mly | Also a quasar and a Seyfert galaxy. | ||
| [BZR2017] J051631.16-542938.9 | |||||
| CANDELS EGS F160W J141952.0+525115.2 | 9813 Mly | Discovered in Extended Groth Strip, its distance calculated with redshift is around 9813 Mly, very faint, very distant | |||
| DES J024008.08-551047.5 | DES J0240 | Its rings have a distinct coloration then the main host galaxy[10] | |||
| 2MASX J07273754-0254540 | 2MASX J07273754-0254540, PSCz Q07251-0248, IRAS 07251-0248 | 1207 Mly | interacting pair |