Up next, we discuss, and here I quote the press release, the “surprisingly high fraction of dead galaxies found in an ancient galactic city.” The pictures are stunning. I just wish we had better language for some of the things we study.

Looking around our nearby universe, we see massive clusters of galaxies that have gravitationally come together and, through violent interactions, have stripped one another of the material needed to form stars. These systems are ancient, and we understand their appearance as the result of thirteen billion years of evolution. They are old. They are dead. This is how it should be.

The corollary of this was an expectation that when we look at the most distant clusters of galaxies, we’ll see smaller systems still forming and galaxies still rich in star formation.

But, expectation isn’t reality until observed.

And this brings us to one of the more amusing acronyms of recent episodes. The “Massive Ancient Galaxies At Z > 3 NEar-infrared,” or MAGAZ3NE, survey was designed to look at massive galaxies in the early universe using the Keck Observatory in Hawai’i. Working from the ground, this team looked back in time to see just what the early universe was doing. This literal case of looking back in time is possible because light takes time to travel, and like lag in a live broadcast, what we see is delayed by how long it takes the information to reach us. A bad YouTube delay might show me a rocket launch thirty seconds after it happened. With light, we know we see the Sun as it was eight minutes ago, we see Andromeda as it was when humans first started exploring the Earth, and as we look at things twelve billion light-years away, we see light from the first couple billion years of our universe.

According to the lead author of a new study in The Astrophysical Journal, Ian McConachie: In the early universe, all protoclusters discovered until now are full of vigorously star-forming galaxies.

Okay, expectations met, but I sense a “but” coming on.

Coauthor Gillian Wilson adds: We are seeing this protocluster [MAGAZ3NE J0959] as it appeared when the universe was less than 2 billion years old. It is as if you took a cluster like Coma, the nearest rich cluster of galaxies to Earth, and plopped it into the early universe.

Coma is nearby, old, and dead. This implies that this particular system, in the early universe, looks old and dead. That does not meet expectations.

MAGAZ3NE J0959 is a cluster with at least 38 member galaxies and contains an ultramassive galaxy in its core. Coauthor Benjamin Forrest nails the mystery of this system when he points out: Why this ultramassive galaxy and so many of its neighbors formed most of their stars and then became inactive when the universe was still so young, in contrast to other known protoclusters from the same time, is a big mystery. Why its galaxies are so unlike those in all the other known protoclusters, and so similar to those in Coma, is a complete mystery.

Finding these systems is still extremely difficult, and the fact that all other systems seen look young and vibrant tells us we may mostly understand what’s going on, but we need to figure out how this exception happens.

Unless of course, we learn these systems exist in large numbers, and we just haven’t been able to find them effectively because distant red galaxies are generally harder to see than distant star-bursting bluer galaxies.

And this is where we wait eagerly for the next generation of telescopes to tell us just how big a science mystery this system is. Are we seeing a random kind of formed fast, died young from a massive overdensity of material in the universe kind of thing? Or was the early universe weirder than we imagined?

This is your friendly reminder that scientists don’t know everything, but we really do want to, and this is why we science.

More Information

UC Riverside press release

“Spectroscopic Confirmation of a Protocluster at z = 3.37 with a High Fraction of Quiescent Galaxies,” Ian McConachie et al., 2022 February 9, The Astrophysical Journal