A weird thing n the Virgo cluster

This is a very interesting little object in the Virgo cluster. It consists of two connected clumps of hydrogen gas with a smattering of stars in or near to each clump. What's strange is that all these stars appear to be very young, < 50 Myr old, but it's far away from any other galaxies. It's almost like seeing a galaxy that's lighting up for the first time. Although its velocity dispersion (how fast the gas is moving around internally) is not especially large, it's high enough that it indicates it needs a dark matter component to hold it together.

The other interpretation, favoured by the authors, is that this is some form of debris either from galaxy-galaxy interactions or more likely ram pressure stripping. No dark matter, just random motions of gas that's dispersing. This might work in this case. The velocity dispersion of the object is low, easily low enough to be explicable by interactions. But it's also very isolated : at least 350 kpc (about 1 million light years) from the nearest galaxy. If the stars had stared forming as soon as the gas left its parent galaxy, it would have needed a velocity of almost 7,000 km/s to become so isolated within the maximum age of 50 Myr. That's about ten times faster than the typical velocities of galaxies in the cluster, which isn't really credible.

On the other hand perhaps the gas was removed much longer ago and has only now just started forming stars. That's much more plausible, though it implies there's a great deal of unseen gas streams lying around that have not yet collapsed to the point where star formation can occur. Which is fine by itself, since simulations show such gas streams could remain confined over the necessary timescales. My concern is : why are we only seeing this one very small patch of star formation ? Why aren't we seeing huge rivers of star formation throughout the whole stripped gas stream ? The team look for other objects and find two, which are also isolated patches of apparently young stars.

Now I might believe that we happen to be seeing one stream at almost the precise moment star formation was triggered - 50 Myr is a very short time. But in general, if we're really seeing star formation in the long tails of gas stripped by ram pressure, I'd expect to see star formation over much larger areas. To find three streams just at the moment star formation starts in very localised areas seems unlikely. And the velocity dispersion of the gas is so low that it would take about a billion years for the patch of newly-formed stars to double in size. This means that each star-forming region in the stream should remain small and easy to detect (lots of stars in a small area) for a long time. So why don't we see more of them ?
https://arxiv.org/abs/1702.07719