Mysteriously High Fraction of Dead Galaxies Found in Ancient Galactic City – Unlike All Other Known Protoclusters

Formation of a Galaxy Cluster in the Early Universe

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This artist’s impression depicts the formation of a galaxy cluster within the early Universe. The galaxies are vigorously forming new stars and interacting with one another. Such a scene carefully resembles the Spiderweb Galaxy (formally often called MRC 1138-262) and its environment, which is likely one of the best-studied protoclusters. Credit: ESO/M. Kornmesser

Why cluster’s galaxies are in contrast to these in all the opposite identified protoclusters is a thriller, says UC Riverside-led workforce.

An worldwide workforce of astronomers led by researchers on the University of California, Riverside, has found an uncommon large cluster of younger galaxies forming within the early universe. The newly found rising galactic metropolis, named MAGAZ3NE J095924+022537, is a new child galaxy cluster, or protocluster, consisting of a minimum of 38 member galaxies, and is about 11.eight billion light-years away from Earth.

Galaxy clusters develop over time underneath gravity and, within the present-day universe, can include tons of and even hundreds of galaxies, in addition to sizzling gasoline and darkish matter. As time goes by, their galaxies burn via the gasoline out there and evolve from vigorously star-forming galaxies into pink and useless galaxies.

“In the early universe, all protoclusters discovered until now are full of vigorously star-forming galaxies,” stated Ian McConachie, a graduate pupil within the UC Riverside Department of Physics and Astronomy and the lead writer of the analysis paper revealed in The Astrophysical Journal. “But incredibly, unlike all of the other protoclusters that have been found at this epoch, many galaxies in MAGAZ3NE J0959 appear to have already stopped forming stars.”

Coauthor Gillian Wilson, a professor of physics and astronomy at UCR in whose lab McConachie works, stated J0959 was found from the “Massive Ancient Galaxies At Z > 3 NEar-infrared,” or MAGAZ3NE, survey, designed to find and research ultramassive galaxies and their neighbors.

Protocluster MAGAZ3NE J095924+022537

In the early universe, all beforehand found distant protoclusters like, for instance, “The Spiderweb” (left: artist’s impression) are filled with vigorously star-forming galaxies. In distinction, the newly-discovered protocluster “MAGAZ3NE J095924+022537” accommodates a excessive fraction of pink and useless galaxies just like the close by “Coma” cluster (proper). The discovery of an historic cluster containing galaxies which resemble these present in trendy clusters was an enormous shock. Credit: Spiderweb: M. Kornmesser/ESO; Coma: Russ Carroll, Robert Gendler, & Bob Franke/Dan Zowada Memorial Observatory

“We are seeing this protocluster as it appeared when the universe was less than 2 billion years old,” she stated. “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.”

Coauthor Benjamin Forrest, a former postdoctoral researcher in Wilson’s lab who’s now based mostly at UC Davis, defined that on the coronary heart of MAGAZ3NE J0959 is an ultramassive galaxy that has already shaped a mass of greater than 200 billion suns.

“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,” he stated. “Why its galaxies are so unlike those in all the other known protoclusters, and so similar to those in Coma, is a complete mystery.”

Forrest added that MAGAZ3NE J0959 was found from the bottom, however the creation of highly effective new capabilities, just like the recently-launched James Webb Space Telescope, should soon reveal whether there are other protoclusters like MAGAZ3NE J0959 packed with dead galaxies waiting to be found in the early universe.

“Should such protoclusters be found in large numbers, it would mean that the current paradigm of protocluster formation would require a major revision,” Forrest said. “A new scenario of protoclusters existing in a diversity of states in the early universe would have to be adopted. With many member galaxies quenching in the first two billion years, this would almost certainly pose significant challenges for current models of galaxy simulation.”

The team used spectroscopic observations from the W. M. Keck Observatory’s Multi-Object Spectrograph for Infrared Exploration, or MOSFIRE, to make detailed measurements of MAGAZ3NE J0959 and precisely quantify its distances.

Closely associated to the question of how ultramassive galaxies form is the question of the environment in which they form, for example, are they always found in overdense environments like protoclusters, or can they also form in isolation? Next, the team plans to study the neighborhood of all other ultramassive galaxies in the MAGAZ3NE survey to answer this question.

Reference: “Spectroscopic Confirmation of a Protocluster at z = 3.37 with a High Fraction of Quiescent Galaxies” by Ian McConachie, Gillian Wilson, Ben Forrest, Z. Cemile Marsan, Adam Muzzin, M. C. Cooper, Marianna Annunziatella, Danilo Marchesini, Jeffrey C. C. Chan, Percy Gomez, Mohamed H. Abdullah, Paolo Saracco and Julie Nantais, 9 February 2022, The Astrophysical Journal.
DOI: 10.3847/1538-4357/ac2b9f

Other researchers involved in the study are Cemile Marsan and Adam Muzzin of York University, Canada; Michael Cooper of UC Irvine; Marianna Annunziatella and Danilo Marchesini of Tufts University; Jeffrey Chan and Mohamed Abdullah of UCR; Percy Gomez of Keck Observatory; Paolo Saracco of Astronomical Observatory of Brera, Italy; Julie Nantais of Andrés Bello National University, Santiago, Chile.

The study was supported by grants from the National Science Foundation and NASA.

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