Discovery of the Largest-class Monster Supercluster of Galaxies in the Universe 5.5 Billion Light-Years Away

Figure 1: This color composite image of a supercluster was captured by the Subaru Telescope's prime focus camera. The white contours in the center show the density distribution of galaxies, and the red regions indicate intense concentrations of dark matter. The numbered squares depict the locations of galaxy clusters associated with the supercluster. The surrounding panels are magnified views of these 19 clusters, showing the clusters of red galaxies that are common in galaxy clusters. The moon in the upper left depicts the apparent size of the full moon to provide a sense of scale. (Credit: NAOJ)

A team led by the National Astronomical Observatory of Japan (NAOJ) and Hiroshima University has discovered a massive supercluster of galaxies about 5.5 billion light-years away, based on the Big Data from the Subaru Telescope. Not only is there a strong concentration of galaxies and dark matter across an area of the sky roughly the size of 15 full moons, but there are at least 19 galaxy clusters associated with it, making it the largest supercluster ever identified in the Universe beyond 5 billion light years away.

Galaxies are comprised of gas and countless stars; and galaxy clusters, which are amalgamations of such galaxies, are known as the largest gravitationally-bound structures in the Universe. However, there is a still larger structure in the Universe called a supercluster, which develops after galaxy clusters further assemble. While superclusters extend over an area of about 100 megaparsecs (about 500 times the size of the Milky Way), the definition of a supercluster itself is still ambiguous; its true nature and what is going on inside it are still shrouded in mystery. In fact, the Milky Way is also inside the Laniakea supercluster, consisting of multiple galaxy clusters and superclusters (Note 1).

Hyper Suprime-Cam (HSC) on the Subaru Telescope has made a deep, wide-field survey, equivalent to 4,400 times the apparent size of the full moon, reaching over 10 billion light-years. The high-quality imaging data obtained from this program is currently the best resource for searching for unknown galaxy superclusters.

The research team examined the total stellar mass and dark matter distribution in the largest density excesses among the nearly 100 supercluster candidates (Note 2), which were discovered by the same team in the past (Note 3). As a result, the team detected a supercluster structure consisting of at least 19 clusters of galaxies centered on three dark matter-dense regions (Figure 1).

Comparison with cosmological simulations suggests that this supercluster has a dark matter mass about 10 times the mass of the Virgo supercluster in the local Universe. On top of that, two giant structures equivalent to superclusters have been identified immediately outside of the cluster, which means that the discovered supercluster may be a precursor to supermassive structures such as the Laniakea supercluster, the largest in the nearby Universe.

The lead author, Dr. Rhythm Shimakawa, Project Assistant Professor at NAOJ, says, "Indeed, the probability of finding such a supercluster about 5.5 billion light-years away, was 50-50 based on the data from the Subaru Telescope's strategic program. We plan to further investigate the three-dimensional structure and the morphology of the galaxies by using such instruments as Subaru Telescope’s PFS (wide field spectrograph) and the Euclid space telescope in the near future."

These results appeared as Shimakawa et al. "King Ghidorah Supercluster: Mapping the light and dark matter in a new supercluster at z = 0.55 using the Subaru Hyper Suprime-Cam" in Monthly Notices of the Royal Astronomical Society Letters on November 26, 2022.

Notes:

(Note 1) It is known that our Milky Way is located inside the Virgo supercluster, the core of which is composed of the Virgo cluster. The definition of a supercluster itself is still ambiguous, and thus in some cases, the term "supercluster" is also used to refer to a giant structure that envelops smaller superclusters.

(Note2) The distribution of dark matter was obtained using the weak gravitational lensing effect. The gravitational lensing effect is a phenomenon in which light emitted from distant galaxies appears distorted or brightened due to the bending of the light path when it passes through a strong gravitational field such as a galaxy cluster in the foreground. Weak gravitational lensing refers to relatively weak cases of this phenomenon. The supercluster in this study is the largest structure over 5 billion light-years away ever identified by weak gravitational lensing analysis.

(Note 3) "Subaru Hyper Suprime-Cam excavates colossal over- and underdense structures over 360 deg2 out to z = 1", Shimakawa et al, 2021, MNRAS

Source: Subaru Telescope

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Approaching the Universe’s origins

PSZ2 G138.61-10.84

Credit:ESA/Hubble & NASA, RELICS

This intriguing image from the NASA/ESA Hubble Space Telescope shows a massive galaxy cluster called PSZ2 G138.61-10.84, about six billion light-years away. Galaxies are not randomly distributed in space, but rather aggregated in groups, clusters and superclusters. The latter span over hundreds of millions of light-years and contain billions of galaxies.

Our own galaxy, for example, is part of the Local Group, which in turn is part of the giant Laniakea Supercluster. It was thanks to Hubble that we were able to study massive galactic superstructures such as the Hercules-Corona Borealis Great Wall; a giant galaxy cluster that contains billions of galaxies and extends 10 billion light-years across — making it the biggest known structure in the Universe.

This image was taken by Hubble’s Advanced Camera for Surveys and Wide-Field Camera 3 as part of an observing programme called RELICS (Reionization Lensing Cluster Survey). RELICS imaged 41 massive galaxy clusters with the aim of finding the brightest distant galaxies for the forthcoming NASA/ESA/CSA James Webb Space Telescope (JWST) to study.

Source: ESA/Hubble/Potw

Newly Identified Galactic Supercluster Is Home to the Milky Way

A slice of the Laniakea Supercluster in the supergalactic equatorial plane -- an imaginary plane containing many of the most massive clusters in this structure. The colors represent density within this slice, with red for high densities and blue for voids -- areas with relatively little matter. Individual galaxies are shown as white dots. Velocity flow streams within the region gravitationally dominated by Laniakea are shown in white, while dark blue flow lines are away from the Laniakea local basin of attraction. The orange contour encloses the outer limits of these streams, a diameter of about 160 Mpc. This region contains the mass of about 100 million billion suns. Credit: SDvision interactive visualization software by DP at CEA/Saclay, France.

Two views of the Laniakea Supercluster. The outer surface shows the region dominated by Laniakea’s gravity. The streamlines shown in black trace the paths along which galaxies flow as they are pulled closer inside the supercluster. Individual galaxies’ colors distinguish major components within the Laniakea Supercluster: the historical Local Supercluster in green, the Great Attractor region in orange, the Pavo-Indus filament in purple, and structures including the Antlia Wall and Fornax-Eridanus cloud in magenta. Credit: SDvision interactive visualization software by DP at CEA/Saclay, France.

This is a short video about Laniakea that gives the viewer a general sense of the structure of our home supercluster and of galaxy motions in the nearby Universe. Credit: This video is a preview of "Laniakea Supercluster", a film produced as part of the following publication: "The Laniakea Supercluster of Galaxies" published in Nature, volume 513, number 7516, p.71 (4 September 2014) by R. Brent Tully, Hélène Courtois, Yehuda Hoffman, and Daniel Pomarède.

Astronomers using the National Science Foundation’s Green Bank Telescope (GBT) -- among other telescopes -- have determined that our own Milky Way galaxy is part of a newly identified ginormous supercluster of galaxies, which they have dubbed “Laniakea,” which means “immense heaven” in Hawaiian.

This discovery clarifies the boundaries of our galactic neighborhood and establishes previously unrecognized linkages among various galaxy clusters in the local Universe.

“We have finally established the contours that define the supercluster of galaxies we can call home,” said lead researcher R. Brent Tully, an astronomer at the University of Hawaii at Manoa. “This is not unlike finding out for the first time that your hometown is actually part of much larger country that borders other nations.”

The paper explaining this work is the cover story of the September 4 issue of the journal Nature.

Superclusters are among the largest structures in the known Universe. They are made up of groups, like our own Local Group, that contain dozens of galaxies, and massive clusters that contain hundreds of galaxies, all interconnected in a web of filaments. Though these structures are interconnected, they have poorly defined boundaries.

To better refine cosmic mapmaking, the researchers are proposing a new way to evaluate these large-scale galaxy structures by examining their impact on the motions of galaxies. A galaxy between structures will be caught in a gravitational tug-of-war in which the balance of the gravitational forces from the surrounding large-scale structures determines the galaxy’s motion.

By using the GBT and other radio telescopes to map the velocities of galaxies throughout our local Universe, the team was able to define the region of space where each supercluster dominates. “Green Bank Telescope observations have played a significant role in the research leading to this new understanding of the limits and relationships among a number of superclusters,” said Tully.

The Milky Way resides in the outskirts of one such supercluster, whose extent has for the first time been carefully mapped using these new techniques. This so-called Laniakea Supercluster is 500 million light-years in diameter and contains the mass of one hundred million billion Suns spread across 100,000 galaxies.

This study also clarifies the role of the Great Attractor, a gravitational focal point in intergalactic space that influences the motion of our Local Group of galaxies and other galaxy clusters.

Within the boundaries of the Laniakea Supercluster, galaxy motions are directed inward, in the same way that water streams follow descending paths toward a valley. The Great Attractor region is a large flat bottom gravitational valley with a sphere of attraction that extends across the Laniakea Supercluster.

The name Laniakea was suggested by Nawa‘a Napoleon, an associate professor of Hawaiian Language and chair of the Department of Languages, Linguistics, and Literature at Kapiolani Community College, a part of the University of Hawaii system. The name honors Polynesian navigators who used knowledge of the heavens to voyage across the immensity of the Pacific Ocean.

The other authors are Hélène Courtois (University Claude Bernard Lyon 1, Lyon, France), Yehuda Hoffman (Racah Institute of Physics, Hebrew University, Jerusalem), and Daniel Pomarède (Institute of Research on Fundamental Laws of the Universe, CEA/Saclay, France).

The GBT is the world's largest fully steerable radio telescope. Its location in the National Radio Quiet Zone and the West Virginia Radio Astronomy Zone protects the incredibly sensitive telescope from unwanted radio interference.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Founded in 1967, the Institute for Astronomy at the University of Hawaii at Manoa conducts research into galaxies, cosmology, stars, planets, and the sun. Its faculty and staff are also involved in astronomy education, deep space missions, and in the development and management of the observatories on Haleakala and Maunakea. The Institute operates facilities on the islands of Oahu, Maui, and Hawaii.

Contacts:

Mr. Charles E. Blue, NRAO Public Information Officer
(434) 296-0314; cblue@nrao.edu

Dr. R. Brent Tully
+1 808-956-8606; tully@ifa.hawaii.edu

Dr. Roy Gal
Cell: +1 301-728-8637, rgal@ifa.hawaii.edu 

Ms. Talia Ogliore, Media Contact
(808) 956-4531; togliore@hawaii.edu

Source: NRAO - National Radio Astronomy Observatory