Scientists have finally located the long-sought missing half of the Universe's visible matter, discovering it exists as vast, faint clouds of ionized hydrogen surrounding galaxies. Using a novel technique, an international team of astronomers and astrophysicists was able to detect these previously invisible clouds. Survey programs have confirmed that this material forms an intergalactic mist of hydrogen, expelled further from active galactic cores than previously believed.
The research has been submitted to Physical Review Letters and is available on arXiv.
“We think that, once we go further away from the galaxy, we recover all of the missing gas,” said Boryana Hadzhiyska, a Miller postdoctoral fellow at the University of California, Berkeley, and first author of a paper reporting the findings. “To be more accurate, we have to do a careful analysis with simulations, which we haven't done. We want to do a careful job.”
“The measurements are certainly consistent with finding all of the gas,” said her colleague, Simone Ferraro, a senior scientist at Lawrence Berkeley National Laboratory (Berkeley Lab) and at UC Berkeley who saw hints of this extensive ionized hydrogen halo in analyses published three years ago.
The results of the study, co-authored by 75 scientists from institutions around the world, have been presented at recent scientific meetings, posted as a preprint on arXiv and are undergoing peer review at the journal Physical Review Letters. Hadzhiyska and Ferraro are researchers at the Berkeley Center for Cosmological Physics in UC Berkeley's Department of Physics, as well as at Berkeley Lab.
