Far out cosmology: finding missing mattter (Introduction)

by David Turell , Saturday, August 05, 2023, 16:43 (474 days ago) @ David Turell

Latest studies:

https://bigthink.com/starts-with-a-bang/missing-baryons-too-hot/?utm_campaign=swab&...

"The cosmic web that we see, the largest-scale structure in the entire Universe, is dominated by dark matter. On smaller scales, however, baryons can interact with one another and with photons, leading to stellar structure but also leading to the emission of energy that can be absorbed by other objects. Neither dark matter nor dark energy can accomplish that task; our Universe must possess a mix of dark matter, dark energy, and normal matter.

"Unlike what we see, our Universe is mostly non-luminous.

***

"...it’s only the luminous matter (i.e., stars) that is typically seen by our telescopes; most of the matter, including most of the normal matter and all of the dark matter, is non-luminous.

"To form galaxies, galaxy clusters, and the large-scale cosmic web, both normal and dark matter are required.

"Today, our Universe’s composition is:

"5% normal matter,
27% dark matter,
and 68% dark energy.

"But much of the normal matter remains elusive. Galaxies contain stars, planets, gas, dust, and black holes, but not enough. The intergalactic medium, rich in ionized plasma, helps, but insufficiently so. Where’s the rest of the Universe’s normal matter? X-ray astronomy suggests a solution to this “missing baryons” problem: the circumgalactic medium.

"The “missing baryons” problem may be solved by the presence of a very hot, very sparse circumgalactic medium. This sparse, diffuse material surrounds every massive galaxy: ranging far beyond their stellar extents.

"With such low densities, very high temperatures are achieved. Its constituent atoms, as a result, lose most of their electrons. Several recent X-ray studies have detected this hot, ionized, galaxy-surrounding material. Light from distant sources must travel through the circumgalactic medium to reach us. Ionized atoms can absorb light at very specific frequencies. We see this for our Milky Way, including omnidirectionally, for many different extragalactic sources, and even around faraway galaxies. The hot, diffuse circumgalactic medium may finally solve our Universe’s “missing baryons” problem.

"Light from a distant galaxy shows key absorption lines from six-times ionized oxygen from its own circumstellar medium, providing strong evidence that the “missing baryons” around galaxies may actually be found in their circumgalactic mediums."

Comment: rich with informative illustrations. For full comprehension, see the website article.