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. Formation theories Ring galaxies are theorized to be formed in various possible ways:
Bar instability: this occurs when 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 forced out into a ring-structure by the pressure, force, and gravitational influence of the baryronic and dark matter furiously orbiting rapidly around 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. Galactic collisions: another process by which ring galaxies are observed to form is by the collision of two or more galaxies. The Cartwheel Galaxy, galaxy pair AM 2026-424, and Arp 147 are all examples of ring galaxies believed to have been formed from this process. In pass-through galactic collisions, an (often smaller) galaxy will pass through the disc of another spiral, causing an outward push of the arms, as if dropping a rock into a pond of still water. In sideswipe and head-on collisions, the emergence of a perfect ring is less likely, with chaotic and warped appearances dominating. 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 thought to be forming, and old galaxies that have migrated into a section of space with a higher gas content than their previous locations.
List NameImageCatalogue numberDistance Notes Cartwheel Galaxy ESO 350-40, PGC 2248 500 Mly lenticular galaxy Hoag's Object PGC 54559, PRC D-51 600 Mly SDSS J151713.93+213516.8 This galaxy can be seen behind Hoag's Object AM 0644-741 AM 0644-741 300 MlyKathryn's WheelESO 179-1330 Mlycollisional ring galaxy, possibly the closest II Hz 4 617.3 ± 43.2 Mly NGC 660 45 Mly polar ring galaxyNGC 922ESO 478-28, ISG 10150 Mlycollisional ring galaxy NGC 985 VV 285, Mrk 1048, MCG -02-07-035, PGC 9817 567 Mly collisional ring galaxyNGC 1015118 MlyNGC 1142NGC 1144, UGC 2389, Arp 118, VV 331a, Mrk 1504, CGCG 389-046, MCG +00-08-048, PGC 11012375 MlySeyfert galaxy NGC 1291 NGC 1291, NGC 1269, PGC 012209 33 Mly NGC 1350 PGC 013059 87.4 Mlyspiral galaxy with ring structure NGC 1386PGC 1333353 Mlyspiral galaxy with ring structureNGC 1387PGC 1334453 Mlylenticular galaxy with nuclear ringNGC 1433PGC 1358649 Mlybarred spiral galaxy with ringNGC 1533 NGC 1533, PGC 14582 62 ± 4 Mly lenticular galaxy with ring structure NGC 1512 PGC 14391 38 Mly Galaxy exhibits a double-ring structure NGC 2859 UGC 5001, PGC 26649 82.8 Mly lenticular galaxy with ring structure NGC 3081IC 2529, ESO 499-G31, AM 0957-223, MCG -04-24-012, PGC 2887683 Mlybarred lenticular galaxyNGC 3821CGCG 127-32, MCG 4-28-30, PGC 36314, UGC 6663271 Mlylow surface brightness galaxyNGC 4138LEDA 38643, UGC 713952 MlyNGC 4245UGC 7328, MCG +05-29-049, PGC 3943737 Mlylenticular galaxy with ring structureNGC 426250 MlyNGC 4513CGCG 315-42, MCG 11-15-59, PGC 41527, UGC 7683110 Mlylenticular galaxy NGC 4622 PGC 42701 200 Mly unbarred spiral galaxy with ring NGC 4650A PGC 42951 126 Mly polar ring galaxy NGC 4774 I Zw 045413 Mly collisional ring galaxy NGC 4777 NGC 4777, PGC 43852 180 MlyNGC 4909PGC 44949, ESO 269-035, MCG -07-27-028162 Mly NGC 6028 NGC 6028, NGC 6046, PGC 56716 203 Mly barred lenticular galaxyNGC 6861124 MlyNGC 7020NGC 7021, ESO 107-13, PGC 66291138 Mlybarred lenticular galaxyNGC 7098ESO 48-5, IRAS 21393-7520, PGC 6726695 Mlydouble barred spiral galaxy NGC 7217 UGC 11914, PGC 68096 50 Mly unbarred spiral galaxy with ring NGC 7552IC 5294, ESO 291- G 012, VV 440, PGC 7088456 Mlybarred spiral galaxyNGC 7742UGC 12760, MCG +02-60-010, UZC J234415.8+104601, 2MASX J23441571+104601572 MlyUnbarred spiral galaxy with ring, Seyfert galaxyESO 509-098 PGC 48609 350 MlyII Zw 28 Zw II 28, 2MASX J05014205+0334278 390 Mly Mayall's Object Arp 148, VV 032, MCG+07-23-019, APG 148 450 Mly collisional ring galaxyVII Zw 466VII Zw 466, UGC 07683637 Mlycollisional ring galaxyArp-Madore 417-391PGC 14881670 Mlycollisional ring galaxyLEDA 3094761938 MlyEmission-line galaxyUGC 459991 MlyUGC 6614PGC 36122322 Mlygiant low surface brightness galaxyUGC 7069PGC 38254, MCG +07-25-017708 MlyLargest ring galaxy Arp 10 Arp 10, UGC 01775, 2MASX J02182639+0539139400 Mly collisional ring galaxyArp 146PGC 5091050 Mlyinteracting pair Arp 147 IC 298 430 Mly interacting pair 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 IC 2628 PGC 34038, CGCG 067-030 601 Mly IC 5285 PGC 70497, UGC 12365 286 Mly LEDA 1405954 2MASX J10064493+1213567 673 ± 47 Mly LEDA 133622 392 Mly Also a Seyfert 2 galaxy UGC 3533 MCG +09-11-030, LEDA 19578, SWIFT J0645.9+5303 492 Mly Also a Seyfert 2 galaxy 2MASX J09015145+5212411 LEDA 2409366 819 Mly lenticular galaxy with ring structure2MASS J09015012+5212226903 MlyPolar ring galaxy, in the lower right side of the imageMCG +07-07-072PGC 12535320 MlyBarred spiral galaxy with a ringWISEA J033303.20-275041.51790 MlyDiscovered in the Hubble Legacy FieldCN AC118 1083757 MlyLT 412MASX J00075757-04332551004 MlyCFRS 14.0685WISEA J141757.82+523050.11153 MlyDiscovered in Extended Groth StripCFRS 14.0117EGSIRAC J141819.73+523424.42613 MlyDiscovered in Extended Groth StripZ 229-15PGC 62756390 MlyAlso a quasar and a Seyfert galaxy.LEDA 1313424567 MlyCollisional ring galaxy, nicknamed the Bullseye.[BZR2017] J051631.16-542938.9CANDELS EGS F160W J141952.0+525115.29813 MlyDiscovered in Extended Groth Strip, its distance calculated with redshift is around 9813 Mly, very faint, very distantDES J024008.08-551047.5DES J02401627 MlyIts rings have a distinct coloration then the main host galaxy2MASX J07273754-02545402MASX J07273754-0254540, PSCz Q07251-0248, IRAS 07251-02481207 Mlyinteracting pair2MASS J01074878+54065411446 MlySpiral ring galaxyWISEA J010752.28+540643.9on the right side of the picture, possibly collisional ring galaxySDSS J091450.23+085326.21825 MlySSTSL2 J182843.93-670006.6Behind IC 4710
See also List of galaxies Polar-ring galaxy
References