Astronomy

How are Galaxy Super Clusters Generated

How are Galaxy Super Clusters Generated


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I have seen pictures of clusters of galaxies, usually used in regards to theories of dark matter and galaxy formations. One of the most famous ones has the perceived shape of a stick-figure. If I am not mistaken some of these clusters seem to be bigger than our observable Universe horizon of $14$ billion light-years, which is as far as we can see because of the age of the Universe.

My assumption is that these are just coordinates plotted into a computer simulation. However, are these clusters the size of our observable Universe horizon or are these more theoretical abstractions?


EDIT: Interesting new find on the subject. Laniakea Supercluster.


@AlexeyBobrick is correct. To add to his answer:

The scale of galaxy clusters are on the order of ~1Mpc (~3.14 Million light years in size), and are therefore much smaller than the cosmological horizon.

The cosmological principle is extraordinarily important for cosmologists, and makes the assumption about the universe's global properties (which turn out to be really good assumptions, so far):

  1. Homogeneity on the scale of about 100 Mpc. This means that one would see very little change in density within a bubble of radiua 100 Mpc as you move said bubble around the universe.
  2. Isotropy means that there is no preferred directions to look. No matter where you look, you should see roughly the same picture of the universe.

As for how these clusters are generated (addressing the title of your question), large N-body simulations are run over the age of the universe from different sets of initial conditions (this is where different models and assumptions come into it). These are dark matter only simulations and involve only the force of gravity. Some people are including electromagnetic interactions in their code, but it's far from being the norm, and are really only important on small scales, i.e. - inner regions of galaxies and clusters. These simulations can contain upwards of ~10 billion dark matter particles.


No, the structures are not of the size of the observable Universe. In fact modern cosmolgical models rely on the Universe being homogeneous over scales above $100 extrm{Mpc}$. This is an observational fact, which serves as a base for the so-called cosmological principle. See also a wiki article on large-scale structure, where the scale is mentioned in the section "End of Greatness".

The scale corresponds to a few hundred million light years. The largest structures, therefore, are clearly way smaller than the size of the observable Universe, which is of order of ten billion light years.

Note, that because it takes time for the light to reach us, the current size of the Universe we observe is larger than its apparent size due to cosmological expansion.


Super star cluster

A super star cluster (SSC) is a very massive young open cluster that is thought to be the precursor of a globular cluster. [1] These clusters are referred to as "super" due to the fact that they are relatively more luminous and contain more mass than other young star clusters. [2] The SSC, however, does not have to physically be larger than other clusters of lower mass and luminosity. [3] They typically contain a very large number of young, massive stars that ionize a surrounding HII region or a so-called "Ultra dense HII regions (UDHIIs)" in the Milky Way Galaxy [4] as well as in other galaxies (however, SSCs do not always have to be inside an HII region). An SSC's HII region is in turn surrounded by a cocoon of dust. In many cases, the stars and the HII regions will be invisible to observations in certain wavelengths of light, such as the visible spectrum, due to high levels of extinction. As a result, the youngest SSCs are best observed and photographed in radio and infrared. [5] SSCs, such as Westerlund 1 (Wd1), have been found in the Milky Way Galaxy. [6] However, most have been observed in farther regions of the universe. In the galaxy M82 alone, 197 young SSCs have been observed and identified using the Hubble Space Telescope. [7]

Generally, SSCs have been seen to form in the interactions between galaxies and in regions of high amounts of star formation with high enough pressures to satisfy the properties needed for the formation of a star cluster. [2] These regions can include newer galaxies with much new star formation, dwarf starburst galaxies, [8] arms of a spiral galaxy that have a high star formation rate, and in the merging of galaxies. In an Astronomical Journal published in 1996, using pictures taken in the ultraviolet (UV) spectrum by the Hubble Space Telescope of star-forming rings in five different barred galaxies, numerous star clusters were found in clumps within the rings which had high rates of star formation. These clusters were found to have masses of about 10 3 > M to 10 5 > M, ages of about 100 Myr, and radii of about 5 pc, and are thought to evolve into globular clusters later in their lifetimes. [9] These properties match those found in SSCs.


How are Galaxy Super Clusters Generated - Astronomy

Superclusters

The Lynx Arc Supercluster

The Lynx Arc Supercluster is the furthest from us found to date, and is about 3.7 Gpc away. Thus we are seeing it as it was when the Universe was only about 2 billion years old, while it is thought to be around 13.7 billion years old now. Here is an artists impression of the Lynx Arc. It is behind the Lynx Cluster of galaxies, which is around 1.7 Gpc away, though not in any way connected to it as it is much further away. They are both named after the constellation, the Lynx, in which they are seen. You can see the Lynx Arc in this picture (right click to enlarge) of the Lynx Cluster as a smeared red streak that I have arrowed. In fact we see it gravitationally lensed by an intermediate cluster of galaxies which is why it appears as a streak.

The Lynx Arc contains around one million extremely hot, young, blue stars, and is about one million times brighter than the Orion Nebula. The light we see is predominantly ultraviolet light from these hot stars that has been red-shifted after travelling 12 billion light-years to reach us. This level of intensity of ultra-violet could come only from stars that are very large and hot, with surface temperatures around 80,000º K. This is about twice the temperature of the hottest stars that form today, and is due to the star comprising hydrogen and helium with the density of heavier elements being only about 5% the value for the Sun. Of course this means that with masses several hundred times that of the Sun, they burn much hotter and last for a much shorter life span possibly one or two million years compared to a star like the Sun that has a lifespan of around 10 billion years.

The Great Attractor
The Shapley Supercluster


Also Known as the Shapley Concentration, it lies approximately 200 Mpc away in the direction of Centaurus, and contains at least 25 clusters of galaxies, and has the mass of approximately 10,000 Milky Way galaxies, concentrated in a volume of space comparable to our own Virgo Supercluster. It is the largest known concentration of matter in the nearby Universe. To produce the observed motion of the Local Group, the mass needed at the Shapley distance is more than 10 17 solar masses. The highest estimate for the mass of the Shapley that I have found is 5 x 10 16 solar masses. This would provide less than 50% of the gravitational force necessary. The map to the left shows the location of the Shapley Concentration with respect to the Milky Way galaxy. The direction of the motion of the Local Group is toward the "zone of Avoidance", a large volume of dust within the Milky Way that obscures our vision. Thus, optical astronomy is of little use, and detection of galaxies and clusters relies on X-ray astronomy. As this technique improves, we should find more about what lies beyond Shapley, and explain these anomalies.

While Shapley first identified the region as being abnormally rich in galaxies back in the 1930s, it was not formally recognized as a supercluster until the 1980s, and named the Shapley Supercluster in 1989.

Abell 3558, also known as Shapley 8, is the largest cluster in the Shapley Concentration, and one of the richest clusters known. It is so large, that it seems itself to comprise a number of distinct groups of galaxies. There are two other particularly large clusters Abell 3559 and Abell 3660. Many astronomers believe that we have yet to see the full scale of the Shapley, and it may turn out to be much larger than it seems.


How are Galaxy Super Clusters Generated - Astronomy

Context: Superclusters are the largest systems in the Universe to give us information about the very early Universe. Our present series of papers is devoted to the study of the properties of superclusters of galaxies from the 2dF Galaxy Redshift survey.
Aims: We use catalogues of superclusters of galaxies from the 2dF Galaxy Redshift Survey to compare the properties of rich and poor superclusters. In particular, we study the properties of galaxies (spectral types, colours, and luminosities) in superclusters.
Methods: We compare the distribution of densities in rich and poor superclusters, and the properties of galaxies in high and low-density regions of rich superclusters, in poor superclusters, and in the field. In superclusters and in the field, we also compare the properties of galaxies in groups, and the properties of those galaxies which do not belong to any group.
Results: We show that in rich superclusters the values of the luminosity density smoothed on a scale of 8 h -1 Mpc are higher than in poor superclusters: the median density in rich superclusters is δ ≈ 7.5 and in poor superclusters δ ≈ 6.0. Rich superclusters contain high-density cores with densities δ > 10, while in poor superclusters such high-density cores are absent. The properties of galaxies in rich and poor superclusters and in the field are different: the fraction of early type, passive galaxies in rich superclusters is slightly higher than in poor superclusters, and is the lowest among the field galaxies. Most importantly, in high-density cores of rich superclusters (δ > 10), there is an excess of early type, passive galaxies in groups and clusters, as well as among those which do not belong to any group. The main galaxies of superclusters have a rather limited range of absolute magnitudes. The main galaxies of rich superclusters have higher luminosities than those of poor superclusters and of groups in the field.
Conclusions: .Our results show that both the local (group/cluster) environments and global (supercluster) environments influence galaxy morphologies and their star formation activity.


How are Galaxy Super Clusters Generated - Astronomy

On the largest scales, the Universe consists of voids and filaments making up the cosmic web. Galaxy clusters are located at the knots in this web, at the intersection of filaments. Clusters grow through accretion from these large-scale filaments and by mergers with other clusters and groups. In a growing number of galaxy clusters, elongated Mpc-sized radio sources have been found 1,2 . Also known as radio relics, these regions of diffuse radio emission are thought to trace relativistic electrons in the intracluster plasma accelerated by low-Mach-number shocks generated by cluster-cluster merger events 3 . A long-standing problem is how low-Mach-number shocks can accelerate electrons so efficiently to explain the observed radio relics. Here, we report the discovery of a direct connection between a radio relic and a radio galaxy in the merging galaxy cluster Abell 3411-3412 by combining radio, X-ray and optical observations. This discovery indicates that fossil relativistic electrons from active galactic nuclei are re-accelerated at cluster shocks. It also implies that radio galaxies play an important role in governing the non-thermal component of the intracluster medium in merging clusters.


Ancient history

As Saraswati is so far away and its light takes time to reach us, studying it allows us to look back in time to when the universe was only about 10 billion years old.

“Since a structure of this vastness will only grow extremely slowly, taking many billions of years, it carries with it a sort of record of the entire history of its formation,” says Bagchi. As the Saraswati supercluster was formed relatively early, it could give us a unique opportunity to characterise the early universe and probe the tiny fluctuations that expanded after the big bang to form the largest structures.

With more observations, Bagchi hopes that we will also be able to use the supercluster to probe the interactions between dark matter, which helps clump galaxies together with its gravity, and dark energy, which causes space to expand and the galaxies to spread apart. The Saraswati supercluster was formed in an era when it is thought that dark energy was just starting to accelerate the universe’s expansion, making it a product of the delicate balance between dark energy and dark matter.

“This is how we will make a discovery of whether the standard model of cosmology is wrong, which is one of the most important discoveries we can possibly make,” says J. Richard Bond at the University of Toronto in Canada. “The arena where that plays out will be on these large scales.”


60-Second Astro News: Infant Superclusters and Wavering Gamma Rays

By: Christopher Crockett October 19, 2018 0

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In astronomy news this week: A gargantuan supercluster of galaxies lurks in the early universe, while data from the Fermi telescope hint at two supermassive black holes locked in a gravitational dance.

A Colossal Galaxy Supercluster in the Early Universe

A galaxy proto-supercluster nicknamed Hyperion is the most massive structure known at such a remote time and distance — about 2.7 billion years after the Big Bang. This visualization of Hyperion is based on real data.
L. Calçada(ESO) / O. Cucciati et al. 2018

The most massive structures in the universe are superclusters, complex webs of galaxies spanning hundreds of millions of light-years. Now, researchers have identified what may be a gargantuan predecessor to modern superclusters. The discovery could help astronomers better understand how these behemoths arose and evolved into the cosmic beasts around us today.

The light from this proto-supercluster takes about 11 billion years to reach Earth, so astronomers see it as it was roughly 2.8 billion years after the Big Bang. The discoverers nicknamed it Hyperion, after one of the Titans from Greek mythology. Seven galaxy clusters, ranging in mass from 10 trillion to 270 trillion Suns, appear linked together by filaments of galaxies across roughly 20 million billion billion cubic light-years of space. The entire ensemble is about as massive as 4.6 quadrillion suns.

While this isn’t the first galaxy cluster seen in the early universe, none are as massive or as sprawling as this one.

Olga Cucciati (National Institute for Astrophysics, Bologna, Italy) and colleagues discovered the adolescent supercluster in data from the VIMOS (Visible Multi-Object Spectrograph) Ultra Deep Survey, a project to obtain redshifts of roughly 10,000 faint galaxies using the Very Large Telescope in Chile.

The team’s results will appear in Astronomy & Astrophysics and can be found on the astronomy preprint arXiv.

Wobbly Gamma Rays from a Far-Flung Galaxy

A pair of supermassive black holes whipping around one another could explain recurring fluctuations in gamma rays coming from the heart of a remote galaxy.

In 2015, researchers working with NASA’s Fermi Gamma-ray Space Telescope detected hints of a periodic modulation of gamma rays emitted by a galaxy designated PG 1553+113, which sits nearly 5 billion light-years away. Now, by analyzing 10 years of Fermi data, astronomers confirm that something is causing the intensity of those gamma rays to waver every 2.2 years. What’s more, the gamma-ray vacillation matches similar changes seen in visible light, X rays, and radio waves.

Stefano Ciprini (Italian Space Agency, Rome) and colleagues announced their finding at an October 17th press conference.

All this radiation is likely being generated by blazing gas swirling around a pair of supermassive black holes, the researchers argue. As the black holes orbit each other, fountains of gamma rays precess, alternately pointing towards us and then leaning away. The researchers do caution, however, that this interpretation is just one possibility. However, if a pair of supermassive black holes does live in this galaxy, it could be a good target for the European Space Agency’s eLISA satellite, a gravitational-wave detector scheduled to launch in 2034.

Gamma-ray brightness from galaxy PG 1553+113 exhibits a 2.2-year period (purple) that matches fluctuations in visible light (white).
S. Ciprini et al. 2018


Galaxy Cluster

A grouping of galaxies. The Milky Way belongs to a small cluster known as the Local Group, but other clusters can contain hundreds or thousands of galaxies. Clusters of galaxies, in turn, can group together to form superclusters.

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Featured Images

Radio Programs

Super Clusters Super star clusters in a nearby galaxy December 8, 2020

Sculptor Galaxies A galaxy with a dark void December 7, 2020

Andromeda Galaxies The orderly Andromeda galaxies October 12, 2018

Void Galaxy A galaxy that’s on its own September 8, 2018

Coma Galaxies Gluing together clusters of galaxies May 11, 2018

On the Move Tugging at the Milky Way February 13, 2018

Eridanus Cluster Galaxy clusters in the southern sky January 14, 2018

Seyfert’s Sextet Illumination in a dark sky September 28, 2017

Virgo Cluster Galaxies that hang out together April 18, 2017

Galaxies Galore Uncovering a whole bunch of galaxies February 13, 2017

Local Supercluster “Nesting” the structure of the universe January 13, 2017

Local Group II The Milky Way’s galactic entourage January 10, 2017

Local Group Our galactic neighborhood January 9, 2017

Dark Matters Lighting up the darkness December 16, 2016

Lacy Galaxies Finding big but hazy galaxies March 31, 2016

Coma Cluster A bright but dark galaxy cluster March 30, 2016


Planet Facts

. It may have formed over many years. Galaxies could be formed from ten to thousands of galaxies. Galaxy clusters seem to be a group or plenty of galaxies joined together by mutual pull of gravity. There are irregular galaxy clusters and regular galaxy clusters.

Irregular galaxy clusters have lesser masses and absence of a well-defined center. Regular galaxy clusters have a well defined core and a spherical shape.

A galaxy cluster also has large structures. These are superclusters, the great attractor, and voids, sheets and filaments. Superclusters may have huge mass, approximately ten million billion suns. The great attractor shows enormous motions with peculiar velocities. The voids, sheets and filaments show a bubbly appearance that its galaxies are situated to sheets and filaments.

Just recently, scientists have discovered the most distant galaxy cluster they could find. They named this galaxy cluster, SXDF-XCLJ0218-0510.

Knowing about galaxy cluster is important because it tells a lot of stories about the universe. It lets us know about the environment that nurtured the formation of galaxies. If you are curious about the universe and its structure, you must learn of its components like the galaxy clusters. It helps you understand the universe itself.

Galaxy Clusters


How are Galaxy Super Clusters Generated - Astronomy

Several reasons suggest clusters of galaxies as potential sources of energetic γ radiation. Present models include γ-rays produced hadronically via p-p-interactions of Cosmic rays with the ICM, originating from a secondary population of relativistic electrons or generated as a result of large scale cosmological structure formation. Quantitative estimates, however, remain uncertain by orders of magnitude, but are generally close or below the detection threshold of the EGRET telescope. Only recently, correlation studies have been performed between Abell clusters and unidentified or unresolved EGRET sources. We have reassessed the situation by studying a flux-limited sample of nearby X-ray bright galaxy clusters in the EGRET data between 1991 and 2000. We are only able to report upper limits for 58 individual clusters, also their cumulative overlay yielded only an upper limit of ∼6×10 -9 cm -2 s -1 for E>100 MeV. We compare our results with model predictions on the high-energy γ-ray emission from galaxy clusters and contrast it with recently proposed associations between γ-ray sources and galaxy clusters.


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