Double loop galaxy

How are these “double loop” galaxies formed? They seem to be intermediate between a spiral and a ring galaxy, with two offset loops either side of the galactic centre.

An interesting find! To me, this looks like a galaxy with a very strong bar as featured by the elongated central brightness in the image. These bars tend to form via instabilities in the stellar disk (either spontaneously or due to a nearby interaction) which place stars on very eccentric orbits. This then has the effect of sweeping out regions of stars on either side of the bar, presumably causing that inner ring to form. If the gravitational instability is violent enough, it can set up multiple gravitational density waves, which may explain the second outer ring?

So the upshot is that this is likely a bar-induced multiple-ringed galaxy.

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I’ve found another one for you to scratch your head over…