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The faint glow of cosmic hydrogen



Deep observations with the MUSE spectrograph at the ESO's Very Large Telescope have discovered huge cosmic reservoirs of atomic hydrogen surrounding distant galaxies. The excellent sensitivity of MUSE allowed direct observations of faint hydrogen clouds glowing in the early universe with Lyman alpha emission – showing that almost the entire night sky is invisibly glowing. Credit: ESA / Hubble & NASA, ESO / Lutz Wisotzki et al.

A recent study published in Nature has shown the presence of a hitherto undiscovered component of the universe – large gas masses surrounding distant galaxies. An international team of about ten scientific institutions has shown that almost the entire early universe in the Lyman Alpha line glows weakly. This line is one of the most important "fingerprints" of hydrogen. This evidence shows the existence of extensive gas masses around primitive galaxies. The results of this study are based on observations with the MUSE spectrograph at the Very Large Telescope (VLT) of the European Southern Observatory, Cerro Paranal, Chile.

Lutz Wisotzki, head of research at the Leibniz Institute for Astrophysics in Potsdam, remembers when he presented this picture for the first time at a conference a year ago, a colleague exclaimed: "Twenty years ago There was nowhere Lyman-Alpha, but now it's everywhere! "The high sensitivity of MUSE has shown that Lyman alpha emission spans the entire sky, including seemingly empty spaces between galaxies.

The article published in Nature establishes a link between several astrophysical research lines. Its unprecedented sensitivity provides new knowledge about the gas in galaxy environments, especially during childhood. It also provides a basis for speculation about the sources of energy for all Lyman alpha emissions; The results will be useful for the next generation of theoretical models for galaxy formation.

Astronomical research deals with the fullest possible representation of the universe and its components. The results of this work have provided new information about physical processes in the Universe that were previously invisible. This phenomenon is not linked to a single object of interest, but offers a new view of the entire cosmos through a representative window. It shows that the sky looks very different, depending on what kind of instruments the researchers use to observe it, just as the sky in the radio or X-ray range looks quite different from the visible sky.

"While the Hubble Space Telescope shows us light only where there are galaxies and between which we see nothing, only empty skies, MUSE in Lyman-alpha shows light wherever we look," explains Ana Monreal-Ibero , an IAC researcher and co-author of the publication. With this instrument, researchers could also gather information about some of the weakest known galaxies that are too weak to be observed with the Hubble.

"In the future we want to make even more sensitive measurements," concludes Lutz Wisotzki. "We want to know the details of how these immense cosmic reservoirs of atomic hydrogen are distributed in space."


Further information:
The MUSE spectrograph shows that almost the entire sky in the early universe is lit with Lyman alpha radiation

Further information:
L. Wisotzki et al., Almost the entire sky is covered by Lyman α emission around crimson red galaxies, Nature (2018). DOI: 10.1038 / s41586-018-0564-6

Sources in Journal:
nature

Provided by:
Instituto de Astrofísica de Canarias


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