Editing Ring galaxy (section)

===Ring Accretion===

==== 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. [[Polar-ring galaxy|Polar-ring galaxies]] may form through cold accretion, as gas from the [[galaxy filament]] flows into the disk and halo regions of a galaxy early in evolution. Resulting star formation interferes with the formation of spiral structures in the stellar disk, and a stable ring structure is created. Similarly, pre-existing elliptical galaxies may also experience cold accretion and result in polar-ring galaxies.<ref>{{Cite journal |last=Finkelman |first=Ido |last2=Moiseev |first2=Alexei |last3=Brosch |first3=Noah |last4=Katkov |first4=Ivan |date=2011-12-11 |title=Hoag’s Object: evidence for cold accretion on to an elliptical galaxy |url=https://academic.oup.com/mnras/article/418/3/1834/1063423 |journal=Monthly Notices of the Royal Astronomical Society |volume=418 |issue=3 |pages=1834–1849 |doi=10.1111/j.1365-2966.2011.19601.x |issn=0035-8711|arxiv=1108.3079 }}</ref> 

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 have migrated into a section of space with a higher gas content than its previous locations.

==== Tidal Accretion ====
Besides intergalactic medium accretion, tidal interactions between a gas-rich host galaxy and a donor galaxy in a polar orbit may lead to the formation of polar-ring galaxies. Observations indicate that rings formed through accretion have a greater inclination angle, compared to rings formed through merging galaxies, as some angular momentum from the gas of the donor galaxy is lost through dispersion; consequentially, the inclination angle is allowed to deviate from the donor. The accretion model is particularly insightful for galaxies with rings that intersect with the central portion's poles, as opposed to lying along the same orbital plane.<ref>{{Cite journal |last=Bournaud |first=F. |last2=Combes |first2=F. |date=2003-04-01 |title=Formation of polar ring galaxies |url=https://www.aanda.org/articles/aa/abs/2003/15/aa3148/aa3148.html |journal=Astronomy & Astrophysics |language=en |volume=401 |issue=3 |pages=817–833 |doi=10.1051/0004-6361:20030150 |issn=0004-6361 |via=EDP Sciences|arxiv=astro-ph/0301391 }}</ref>