University of California, Riverside | 2018 Aug 14
A team of astronomers led by George Becker at the University of California, Riverside, has made a surprising discovery: 12.5 billion years ago, the most opaque place in the universe contained relatively little matter.Computer simulation of a region of the universe wherein a low-density “void” (dark
blue region at top center) is surrounded by denser structures containing numerous
galaxies (orange/white). The research done by Becker and his team suggests that
early in cosmic history, these void regions would have been the murkiest places in
the universe even though they contained the least amount of dark matter and gas.
(Credit: TNG Collaboration)
It has long been known that the universe is filled with a web-like network of dark matter and gas. This “cosmic web” accounts for most of the matter in the universe, whereas galaxies like our own Milky Way make up only a small fraction. Today, the gas between galaxies is almost totally transparent because it is kept ionized— electrons detached from their atoms—by an energetic bath of ultraviolet radiation.
Over a decade ago, astronomers noticed that in the very distant past — roughly 12.5 billion years ago, or about 1 billion years after the Big Bang — the gas in deep space was not only highly opaque to ultraviolet light, but its transparency varied widely from place to place, obscuring much of the light emitted by distant galaxies.
Then a few years ago, a team led by Becker, then at the University of Cambridge, found that these differences in opacity were so large that either the amount of gas itself, or more likely the radiation in which it is immersed, must vary substantially from place to place. ...
For the cosmic web more opacity normally means more gas, and hence more galaxies. But the team found the opposite: this region contained far fewer galaxies than average. Because the gas in deep space is kept transparent by the ultraviolet light from galaxies, fewer galaxies nearby might make it murkier. ...
In Massive Region of Space, Astronomers Find Fewer Galaxies Than Expected
University of California, Los Angeles | 2018 Aug 14
Evidence for Large-Scale Fluctuations in the Metagalactic Ionizing Background Near Redshift Six ~ George D. Becker et al
- Astrophysical Journal 863(1):92 (10 Aug 2018) DOI: 10.3847/1538-4357/aacc73
arXiv.org > astro-ph > arXiv:1803.08932 > 23 Mar 2018