No, while the observations were of oxygen, this doesn't imply that the gas is primarily made of oxygen. The issue with the warm-hot IGM is that it is a strange temperature where virtually nothing emits much light. Highly ionized oxygen (in this case, only one electron out of the original eight remain bound) is one of the few things that does. Here, based on X-ray observations they have estimated the density of this oxygen, and then estimated the overall density of the IGM based on the ratio of oxygen to hydrogen.
Thanks for that explanation. With it, the abstract makes sense regarding the fully ionized hydrogen. The phys.org article ("That lost matter exists as filaments of oxygen gas") does not.
So, since baryons are protons and neutrons, if I understand this, then 40% of the ordinary matter in the universe can be found outside of galaxies?
Why can't that missing ordinary matter serve the same role as recent beloved explanation "dark matter" does? Or is it just too diffuse to affect things like the galaxy rotation curve?
I guess (IANAP) that's because hydrogen is easier to observe as part of interstellar gas within a galaxy as opposed to the thinner intergalactic filaments which is also further away and doesn't get illuminated by stars or stellar remnants.
So the baryonic matter in galaxies is already accounted for to a larger extent than the filaments.
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[ 3.1 ms ] story [ 33.3 ms ] threadI thought the elemental distribution of the universe is around 90% hydrogen, 8% helium, and 2% all the other elements (going off memory here).
Why can't that missing ordinary matter serve the same role as recent beloved explanation "dark matter" does? Or is it just too diffuse to affect things like the galaxy rotation curve?
So the baryonic matter in galaxies is already accounted for to a larger extent than the filaments.