Surprisingly high fraction of dead galaxies found in ancient galactic
city
Why cluster's galaxies are unlike those in all the other known
protoclusters is a mystery

Date:
February 9, 2022
Source:
University of California - Riverside
Summary:
Astronomers have discovered an unusual massive cluster of young
galaxies forming in the early universe. The newly discovered growing
galactic metropolis, named MAGAZ3NE J095924+022537, is a newborn
galaxy cluster, or protocluster, consisting of at least 38 member
galaxies, and is about 11.8 billion light-years away from Earth.



FULL STORY ==========================================================================
An international team of astronomers led by researchers at the University
of California, Riverside, has discovered an unusual massive cluster of
young galaxies forming in the early universe. The newly discovered growing galactic metropolis, named MAGAZ3NE J095924+022537, is a newborn galaxy cluster, or protocluster, consisting of at least 38 member galaxies,
and is about 11.8 billion light-years away from Earth.


========================================================================== Galaxy clusters grow over time under gravity and, in the present-day
universe, can contain hundreds or even thousands of galaxies, as well
as hot gas and dark matter. As time goes by, their galaxies burn through
the fuel available and evolve from vigorously star-forming galaxies into
red and dead galaxies.

"In the early universe, all protoclusters discovered until now are full
of vigorously star-forming galaxies," said Ian McConachie, a graduate
student in the UC Riverside Department of Physics and Astronomy and
the lead author of the research paper published 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,
said J0959 was discovered from the "Massive Ancient Galaxies At Z >
3 NEar-infrared," or MAGAZ3NE, survey, designed to discover and study ultramassive galaxies and their neighbors.

"We are seeing this protocluster as it appeared when the universe
was less than 2 billion years old," she said. "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 is now based at UC
Davis, explained that at the heart of MAGAZ3NE J0959 is an ultramassive
galaxy that has already formed a mass of more 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 said. "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 discovered
from the ground, but the advent of powerful new capabilities, 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.

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
Andre's Bello National University, Santiago, Chile.

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

========================================================================== Story Source: Materials provided by
University_of_California_-_Riverside. Original written by Iqbal
Pittalwala. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. 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,
Julie Nantais. Spectroscopic Confirmation of a Protocluster at z =
3.37 with a High Fraction of Quiescent Galaxies. The Astrophysical
Journal, 2022; 926 (1): 37 DOI: 10.3847/1538-4357/ac2b9f ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220209154944.htm

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