Dark matter not interacting at all perhaps

https://phys.org/news/2018-04-dark-interactive.html

Looking more elusive as time goes by in new experiments.

Originally posted by @sonhouse
https://phys.org/news/2018-04-dark-interactive.html

Looking more elusive as time goes by in new experiments.

I read the link and basically the astronomers had first collected earlier data that implied that a galaxy had become separated from the dark matter surrounding it, an interesting possibility predicted by some but not all dark-matter models, but then later new data showed it hadn't separated after all.
I really don't see how anything of significance can be concluded from that.
Merely showing that this one particular galaxy hadn't separated from it's dark matter very far by itself rules out the possibility that we will later observe a galaxy which can be observed to have indeed separated from it's dark matter.
And it certainly very far by itself rules out the possibility of the existence of any non-gravitational dark-matter-visible-matter interactions.

Originally posted by @humy
I read the link and basically the astronomers had first collected earlier data that implied that a galaxy had become separated from the dark matter surrounding it, an interesting possibility predicted by some but not all dark-matter models, but then later new data showed it hadn't separated after all.
I really don't see how anything of significance can be co ...[text shortened]... possibility of the existence of any non-gravitational dark-matter-visible-matter interactions.

I wonder if there is somewhere out there the remnants of the dark matter cloud that was previously inside that galaxy, a bare blob of dark matter. Do you know if anything like that has ever been discovered?

I was thinking suppose dark matter had a slightly different reaction to gravity as baryonic stuff we are composed of? Then some disturbance, say a nearby interacting galaxy preferentially grabbed the dark stuff leaving the galaxy without its load of dark. Just a supposition of course.

Originally posted by @sonhouse
I wonder if there is somewhere out there the remnants of the dark matter cloud that was previously inside that galaxy, a bare blob of dark matter. Do you know if anything like that has ever been discovered?

no but I assume if such a thing was discovered it would be big news and we would have heard of it so I doubt such a thing has been (yet) discovered. There would also be the question of how that could be discovered since I assume it could only be observed indirectly from some kind of observable gravitational interaction with a group of galaxies but I would imagine such a kind of observable gravitational interaction would be extremely difficult to interpret and any interpretation would be questionable.

Originally posted by @humy
no but I assume if such a thing was discovered it would be big news and we would have heard of it so I doubt such a thing has been (yet) discovered. There would also be the question of how that could be discovered since I assume it could only be observed indirectly from some kind of observable gravitational interaction with a group of galaxies but I would imag ...[text shortened]... eraction would be extremely difficult to interpret and any interpretation would be questionable.

It seems to me there should be such blobs since we now know of at least one galaxy with no dark stuff inside, either it grew up in a volume of the universe where dark stuff was for some reason a dark matterless region of space and a galaxy was driven inside it but still, another question is how long has it been dark stuff free? Was the galaxy born in such a darkless area or did it shed it later? It might be plan A, darkless when the galaxy was born and stayed in that darkless volume. A darkwhisperer galaxy....
Or back to plan B it somehow shed darkness after it was born, some kind of interaction that separated the two types of matter. News at 11🙂