Maybe it’s not the year to talk about the death of a galaxy, but this next story intrigued me. Everything dies apparently, even galaxies. I mean, we talk about the heat death of the universe a lot, but I think this is the first time we’ve taken one step down from that.

In new work presented in Nature Astronomy, researchers used the Atacama Large Millimeter/submillimeter Array (ALMA) to watch a galaxy eject a massive amount of its cold gas content. The galaxy is called ID2299, and it’s about 9 billion light-years away from us, and we’re seeing it when the universe was only 4.5 billion years old. Space-time is mind-boggling at this scale.

Anyway, the gas is being ejected at a rate of 10000 Suns’ worth of mass every year, removing 46% of the total cold gas from the galaxy. And the galaxy is also undergoing extremely fast star formation, and calculations show that it will run out of gas in a few tens of million years. That’s very soon in astronomical terms.

The image we’re sharing is an artist’s impression of the galaxy, and you may notice that one startling feature reaching up away from the galaxy. That’s a tidal tail. They’re usually hard to see; and having tried to tease them out of image data, I can attest to that. I learned to hate a program called IRAF while I was trying. In this instance, though, the tidal tail was a relatively bright feature of the galaxy as it was ejected into space, which made it easy to see and identify.

The other unusual part of this story, in an interesting story all around, is that it seems this galaxy’s death is the result of a galactic merger. Co-author Emanuele Daddi notes: Our study suggests that gas ejections can be produced by mergers and that winds and tidal tails can appear very similar. This might lead us to revise our understanding of how galaxies ‘die’.

More Information

ALMA press release 

“A titanic interstellar medium ejection from a massive starburst galaxy at redshift 1.4,” Annagrazia Puglisi et al., 2021 January 11, Nature Astronomy