New research using the MUSE instrument shows that galactic winds, which are critical to galaxy evolution, are a frequent phenomenon in the universe, challenging previous assumptions that galactic winds are rare. In some cases, galaxies release large amounts of material into their surroundings, triggered by the explosions of massive stars. The European Southern Observatory's (ESO) Very Large Telescope's MUSE instrument has now demonstrated for the first time that such "galactic winds" are far from rare, but occur regularly.
The discovery of the bipyramidal structure
An international research team led by France's National Center for Scientific Research (CNRS) discovered the characteristic biconical structure of galactic winds while studying a sample of about 100 galaxies. However, these structures are only visible in specific spectral lines, and only with extremely high measurement sensitivity. Only a handful of such cases were previously known, most of which were also discovered with MUSE instruments.
Professor Lutz Wisotzki, Director of the Galaxy and Quasar Research Department at the Leibniz Institute for Astrophysics Potsdam (AIP) and co-author of the article in the scientific journal Nature, said: "MUSE showed us that this galaxy-wide outflow exists in almost every star-forming galaxy. Furthermore, the new results also allow us to accurately identify the size and shape of these galactic winds. Until now, this had only been possible in very rare extreme cases."
The role of outflowing gas in the evolution of the universe
Outflowing gas is thought to play a crucial role in the cosmic evolution of galaxies by regulating their growth and star formation. Theoretical calculations predict that the outflowing gas takes on a "bipolar" shape, extending up and down the plane of the galaxy and into the circumgalactic medium. Similar shapes have been directly observed in some nearby galaxies, such as the "Cigar Galaxy" M82, and even in our own Milky Way, but we can only see the innermost regions and cannot draw an overall picture.
Galactic winds in the young universe
Cosmological simulations of galaxy formation predict that galactic wind phenomena occur more frequently and strongly in the early stages of the young universe: because young galaxies have higher star formation activity, more supernova explosions, and therefore stronger outflows. These outflows transport gas and energy from the galaxy around the galaxy, depriving the galaxy of the fuel it needs for further star formation, while also enriching the galaxy's "ring galaxy" environment. This so-called feedback process may be a key factor in our understanding of galaxy formation and evolution, but we only have an incomplete understanding of it through observations because of the difficulty in detecting the phenomenon.
New insights from MUSE
New research using the MUSE instrument now directly shows that galactic gas flows around the galaxy at a distance of more than 30,000 light-years. The observable signal depends greatly on the orientation of the galaxy relative to the line of sight: if you view the galaxy from the side, there is strong radiation above and below the plane of the galaxy, while if you view the galaxy from "above" or "below" the signal is weaker and more evenly distributed. These observations impressively confirm previously theoretically predicted forms of bipolar outflows perpendicular to the plane of the galaxy.
Reference: "The bipolar outflow of massive galaxies reaches 10kpc when redshift z≈1", authors: Yucheng Guo, Roland Bacon, Nicolas F. Bouché, Lutz Wisotzki, Joop Schaye, Jérémy Blaizot, Anne Verhamme, Sebastiano Cantalupo, Leindert A. Boogaard, JarleJ .J.J. Boogaard, Jarle Brinchmann, Maxime Cherrey, Haruka Kusakabe, Ivanna Langan, Floriane Leclercq, Jorryt Matthee, Léo Michel-Dansac, Ilane Schroetter and Martin Wendt, December 6, 2023, Nature.
DOI:10.1038/s41586-023-06718-w
Compiled source: ScitechDaily