Missing matter

Andrey Kravtsov
Two independent teams have found Gas filaments between pairs of Red Galaxies, so solving a missing Baryon mass problem. From the abstract of the second article: "This result establishes the presence of ionised gas in large-scale filaments, and suggests that the missing baryons problem may be resolved via observations of the cosmic web." The method of detection is the Sunyaev-Zeldovich effect.
For more details, see Scienc Alert or New Scientist. From that later article:
"Two separate teams found the missing matter - made of particles called baryons rather than dark matter - linking galaxies together through filaments of hot, diffuse gas. "The missing baryon problem is solved," says Hideki Tanimura at the Institute of Space Astrophysics in Orsay, France, leader of one of the groups. The other team was led by Anna de Graaff at the University of Edinburgh, UK. Learn more: Missing matter - Where did half the universe go? Because the gas is so tenuous and not quite hot enough for X-ray telescopes to pick up, nobody had been able to see it before. (...) Both teams took advantage of a phenomenon called the Sunyaev-Zel'dovich effect that occurs when light left over from the big bang passes through hot gas. As the light travels, some of it scatters off the electrons in the gas, leaving a dim patch in the cosmic microwave background - our snapshot of the remnants from the birth of the cosmos. (...) Finally finding the extra baryons that have been predicted by decades of simulations validates some of our assumptions about the universe."