All spun up: Image shows a simulated polar ring galaxy (left) next to a real one (NGC 4650A) for comparison. The central spinning galactic discs are surrounded by much larger spinning rings of material, perpendicular to the galactic plane.
Credit: University of Washington/Astrophysical Journal
In support of the researchers 'slow-growth' theory is the fact that both of the other theories presume polar ring galaxies should be found in environments where galactic collisions are common, such as galaxy groups in space. But observations show this isn't the case, the authors said.
Australian astrophysicist Geraint Lewis, from the University of Sydney, says the work is "very interesting and a move in the right direction" in terms of understanding how these rare galaxies form. But he added that in the real universe, different systems – the merger and the authors' 'slow-growth' theory – may noth operate.
"There are several pictures on the table; is this ring formed by one object disrupted into the ring or by a constant rain of material? These guys are saying in some of these cases, gas is coming in in a roughly polar orbit, and if you have enough of this stuff raining in you will form a polar ring," said Lewis. "I wouldn't be surprised if the answer is somewhere between the two."
