A week after talking about a survey of galaxies formed in the early universe that rotates, we are getting a new press release announcing that the Atacama Large Millimeter/submillimeter Array has discovered a particularly massive galaxy in the early universe. DLA0817g is the most distant galaxy found to be rotating. Its light started the journey to our telescopes just 1.5 billion years after the universe formed, and to get a massive galaxy fully formed this early in the universe would require this particular system to grow through the accumulation of massive amounts of cold gas that collapse en masse into this system.
In astronomy, we sometimes talk about how galaxies form either through a bottom-up or a top-down approach, where either a myriad of small galaxies come together through mergers to form giant systems — this is what we talked about last week — or a singular mass of gas collapses into a giant galaxy in one turbulent event. This week’s big, rotating, early-forming galaxy is of the singular collapse variety. Sometimes, there are lots of ways to get to the same outcome, and it’s not “either/or” but instead “and” when it comes to ways to make galaxies grow.
- National Radio Astronomy Observatory press release
- Max Planck Institute press release
- “A Cold, Massive, Rotating Disk 1.5 Billion Years After the Big Bang,” Marcel Neeleman, J. Xavier Prochaska et al., 2020 May 20, Nature (DOI: https://doi.org/10.1038/s41586-020-2276-y)