Research conducted by an international team of astronomers, published in the international scientific journal Nature, revealed an enormous nebula around an extreme form of a merging galaxy.

The galaxy named Makani (Hawaiian for 'wind') is pushing a large fraction of its gas into the space between galaxies called the circumgalactic medium. The team observed a wind in a glowing halo of extended oxygen out to extreme distances (one of the largest such nebulae ever observed) at different speeds and locations, corresponding to the different times at which the galaxy began rapidly forming stars. This enabled them to track the detailed energetics of the event. Seeing this expansive outflow also provides a missing link to explaining how metals can be displaced far out into intergalactic medium (the space between galaxies).

"What is also remarkable is that the aging and dying stars appear to be powerful enough on their own to do all of the work without the need for a supermassive black hole's help, though we expect one to be buried down in the center of the merging galaxies, maybe quite literally under a lot of dust and gas," remarked Dr. Paul Sell, who, as a member of a small collaboration, contributed to this research while a scientist at the Institute of Astrophysics of FORTH; Dr. Sell has since recently joined the faculty at the University of Florida, USA.

Though this galaxy weighs about as much as our Milky Way Galaxy, we don't see anywhere near such an extreme situation in our own Galaxy or even in other one relatively nearby. Seeing such heavy galaxies catastrophically colliding is pretty rare, especially those that have lots of cold gas from which to form new stars. The funneling and collision of the cold gas deep in the gravitational well of the merging galaxies produces a very large number of stars in a short time and in a small space. The heaviest stars formed from this burst of star formation quickly die, sending out strong winds and shockwaves that blow the gas out of the galaxy, shooting it at high speeds out into deep space.

This is only one galaxy in a sample this international team of researchers has been studying. Further observations are being gathered on some of the most sensitive telescopes in the world to ascertain the uniqueness of this situation.

The lead author and primary contact for this publication is Prof. David Rupke at Rhodes College, USA. This study was supported by Rhodes College, the National Science Foundation, NASA, and the Royal Society.

https://www.nature.com/articles/s41586-019-1686-1

https://vimeo.com/369269470

A volume rendering revealing the structure of Makani.

Credit: David Tree & Peter Richardson, Games and Visual Effects Research Lab, University of Hertfordshire