This poster captures 20 of my favorite star-forming ring galaxies. These star-forming rings are typically wide bluish rings that lie midway between the galaxy core and the outer rim of the galaxy disk. These rings each lie in the plane of their galaxy, and as such our apparent view of them can be a circle, a wide oval, or a narrow oval.
The galaxy are ordered on the poster, from top left to bottom right, accordingly to their star-forming ring brightness and color. This generally corresponds to distance. For example, the top left object (M94) is 14 million light years away, while the bottom right object (IC 528) is 250 million light years away. As the distance from us increases, we see less of the detail and blue color in the ring.
Most galaxies do not have a ring. When they do have a ring, it can be one of several different types. Examples include
collisional rings,
polar rings, and
nuclear rings.
How do rings occur in galaxies? You will see some sources that say that rings are caused by collisions with another galaxy. For rings such as collisional rings and tidal rings, there is enough consistent evidence to confirm that they are caused by a galaxy collision. But I am not convinced that galaxy collisions are responsible for all galaxy rings.
Nuclear rings and their larger cousin shown here, star-forming rings, both contain tremendous amounts of gas and usually are seen without any nearby companions. In fact, such rings seem to thrive on the absence of disturbance from another galaxy and the resulting long-term stability.
I do not know what causes these star-forming rings and I have yet to read an explanation which makes sense to me when looking at all of these examples. I believe the star-forming ring potential may be related to the available gas in the disk and the type of bar across the core. Most of these galaxies have cores that are fairly bright. Also, most have short faint bars that resemble barlenses. Barlenses have incredible star motion patterns throughout the inner region of the disk.
Each of the object images on this poster has been posted to my Astrobin account. The links to each individual image are below:
M94NGC2775NGC2681NGC7742NGC7769NGC4725M96M95NGC 1350NGC 4274NGC 3081NGC 7489UGC 4414NGC 6370NGC 1357NGC 5750NGC 1024NGC 7013UGC 3789IC 528All of the above objects are contained in my
Astrobin Star-forming Ring Galaxy Collection.
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