A group of astronomers led by ETH Zurich scientist Elena Borisova has spotted giant clouds of glowing intergalactic gas around distant quasars.
This image shows a bright gaseous halo around the quasar Q0042-2627. Image credit: Elena Borisova et al.
Dr. Borisova and co-authors have used the observing power of the Multi Unit Spectroscopic Explorer (MUSE) on ESO’s Very Large Telescope to study gas around distant active galaxies, called quasars, less than two billion years after the Big Bang.
According to astronomers, quasars contain supermassive black holes in their centers, which consume material at an extremely high rate. This, in turn, causes the galaxy center to emit huge amounts of radiation, making quasars the most luminous and active objects in the Universe.
The study involved 19 quasars (CTS G18.01, Q0041-2638, Q0042-2627, Q0055-269, UM669, J0124+0044, UM678 etc), selected from among the brightest that are observable with the MUSE spectrograph.
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.
The current 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 authors suspects this is due to the vast increase in the observing power of MUSE over previous similar instruments, but further observations are needed to determine whether this is the case.
“It is still too early to say if this is due to our new observational technique or if there is something peculiar about the quasars in our sample,” Dr. Borisova said.
“So there is still a lot to learn; we are just at the beginning of a new era of discoveries.”
This mosaic shows 18 of the 19 quasars observed by the team. Each observed quasar is surrounded by a bright gaseous halo. Image credit: Elena Borisova et al / ESO.
The original goal of the study was to analyze the gaseous components of the Universe on the largest scales; a structure sometimes referred to as the cosmic web, in which quasars form bright nodes.
The gaseous components of this web are normally extremely difficult to detect, so the illuminated halos of gas surrounding the quasars deliver an almost unique opportunity to study the gas within this large-scale cosmic structure.
The 19 newly-detected halos also revealed another surprise: they consist of relatively ‘cold’ intergalactic gas — approximately 18,000 degrees Fahrenheit (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.
The team’s findings have been accepted for publication in an upcoming edition of the Astrophysical Journal. The article is also publicly available at arXiv.org.
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Elena Borisova et al. 2016. Ubiquitous giant Ly α nebulae around the brightest quasars at z – 3.5 revealed with MUSE. ApJ, accepted for publication; arXiv: 1605.01422
