From an ESO press release, October 26, 2016:
An international team of astronomers has discovered glowing gas clouds surrounding distant quasars, active galaxies less than two billion years after the Big Bang. This new survey by ESO’s Very Large Telescope indicates that halos around quasars are far more common than expected. The properties of the halos in this surprising find are also in striking disagreement with currently accepted theories of galaxy formation in the early Universe.
The study involved 19 quasars, selected from among the brightest that are observable with the telescope’s MUSE instrument. Previous studies have shown that around 10% of all quasars examined were surrounded by halos, made from gas known as the intergalactic medium. These halos extend up to 300,000 light-years away from the centers of the quasars. This new study, however, has thrown up a surprise, with the detection of large halos around all 19 quasars observed – far more than the two halos that were expected statistically.
The newly detected halos also revealed another surprise: they consist of relatively cold intergalactic gas – approximately 10,000 degrees Celsius. This revelation is in strong disagreement with currently accepted models of the structure and formation of galaxies, which suggest that gas in such close proximity to galaxies should have temperatures upwards of a million degrees.
Links: full ESO press release, including video animations.