Galaxy groups and clusters are the largest known gravitationally bound objects to have arisen thus far in the process of cosmic structure formation. They form the densest part of the large-scale structure of the Universe . In models for the gravitational formation of structure with cold dark matter , the smallest structures collapse first and eventually build the largest structures, clusters of galaxies. Clusters are then formed relatively recently between 10 billion years ago and now. Groups and clusters may contain ten to thousands of individual galaxies. The clusters themselves are often associated with larger, non-gravitationally bound, groups called superclusters .
26-658: (Redirected from Groups ) [REDACTED] The present page holds the title of a primary topic , and an article needs to be written about it. It is believed to qualify as a broad-concept article . It may be written directly at this page or drafted elsewhere and then moved to this title. Related titles should be described in Group , while unrelated titles should be moved to Group (disambiguation) . [REDACTED] [REDACTED] Look up group in Wiktionary,
52-435: A Buddhist concept of five material and mental factors that take part in the rise of craving and clinging Science and technology [ edit ] Mathematics [ edit ] Group (mathematics) , a set together with a binary operation satisfying certain algebraic conditions Chemistry [ edit ] Functional group , a group of atoms which provide some property to a molecule Group (periodic table) ,
78-435: A Buddhist concept of five material and mental factors that take part in the rise of craving and clinging Science and technology [ edit ] Mathematics [ edit ] Group (mathematics) , a set together with a binary operation satisfying certain algebraic conditions Chemistry [ edit ] Functional group , a group of atoms which provide some property to a molecule Group (periodic table) ,
104-566: A category of car allowed to compete in auto racing Army group Militia groups Rebel groups Terrorist groups Group (military unit) , an air force formation Corporate group , a group of affiliated companies Group psychotherapy , sometimes colloquially known as "group" Musical ensemble See also [ edit ] All pages with titles containing Group Affiliation (disambiguation) Association (disambiguation) Class (disambiguation) Grouping (disambiguation) Grup (disambiguation) Grupp ,
130-566: A category of car allowed to compete in auto racing Army group Militia groups Rebel groups Terrorist groups Group (military unit) , an air force formation Corporate group , a group of affiliated companies Group psychotherapy , sometimes colloquially known as "group" Musical ensemble See also [ edit ] All pages with titles containing Group Affiliation (disambiguation) Association (disambiguation) Class (disambiguation) Grouping (disambiguation) Grup (disambiguation) Grupp ,
156-497: A classification category in the International Code of Nomenclature for Cultivated Plants Galaxy groups and clusters , in cosmology Group (firearms) , the grouping of shots from a firearm Language group, a unit of classification within a Language family Other uses [ edit ] Breed Groups (dog) , the group or category to which breeds of dogs are assigned by kennel clubs Group (auto racing) ,
182-429: A classification category in the International Code of Nomenclature for Cultivated Plants Galaxy groups and clusters , in cosmology Group (firearms) , the grouping of shots from a firearm Language group, a unit of classification within a Language family Other uses [ edit ] Breed Groups (dog) , the group or category to which breeds of dogs are assigned by kennel clubs Group (auto racing) ,
208-535: A column in the periodic table of chemical elements Computing and the Internet [ edit ] Group (computing) , a collection of users or other objects Group (database) Group (online social networking) Usenet newsgroup Google Groups Yahoo! Groups Facebook groups Other uses in science and technology [ edit ] Group (stratigraphy) , in geology, consisting of formations or rock strata Cultivar group , in biology,
234-479: A column in the periodic table of chemical elements Computing and the Internet [ edit ] Group (computing) , a collection of users or other objects Group (database) Group (online social networking) Usenet newsgroup Google Groups Yahoo! Groups Facebook groups Other uses in science and technology [ edit ] Group (stratigraphy) , in geology, consisting of formations or rock strata Cultivar group , in biology,
260-534: A group whose members share the same social identity Tribal group , a group whose members share the same tribal identity Organization , an entity that has a collective goal and is linked to an external environment Peer group , an entity of three or more people with similar age, ability, experience, and interest Social science [ edit ] In-group and out-group Primary, secondary, and reference groups Social group Collectives Philosophy and religion [ edit ] Khandha ,
286-534: A group whose members share the same social identity Tribal group , a group whose members share the same tribal identity Organization , an entity that has a collective goal and is linked to an external environment Peer group , an entity of three or more people with similar age, ability, experience, and interest Social science [ edit ] In-group and out-group Primary, secondary, and reference groups Social group Collectives Philosophy and religion [ edit ] Khandha ,
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#1732764803314312-412: A surname List of animal names , including collective nouns for groups of animals Set (disambiguation) Syndicate The Group (disambiguation) Union (disambiguation) Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title Group . If an internal link led you here, you may wish to change the link to point directly to
338-412: A surname List of animal names , including collective nouns for groups of animals Set (disambiguation) Syndicate The Group (disambiguation) Union (disambiguation) Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title Group . If an internal link led you here, you may wish to change the link to point directly to
364-641: Is known as dark matter and its nature is unknown. In a typical cluster perhaps only 5% of the total mass is in the form of galaxies, maybe 10% in the form of hot X-ray emitting gas and the remainder is dark matter. Brownstein and Moffat use a theory of modified gravity to explain X-ray cluster masses without dark matter. Observations of the Bullet Cluster are the strongest evidence for the existence of dark matter; however, Brownstein and Moffat have shown that their modified gravity theory can also account for
390-497: The basis of scaling laws that they followed. According to this paper, galaxy aggregations less massive than 8 × 10 solar masses are classified as galaxy groups. Clusters are larger than groups, although there is no sharp dividing line between the two. When observed visually, clusters appear to be collections of galaxies held together by mutual gravitational attraction. However, their velocities are too large for them to remain gravitationally bound by their mutual attractions, implying
416-423: The free dictionary. A group is a number of persons or things that are located, gathered, or classed together. Groups of people [ edit ] Cultural group , a group whose members share the same cultural identity Ethnic group , a group whose members share the same ethnic identity Religious group (disambiguation) , a group whose members share the same religious identity Social group ,
442-423: The free dictionary. A group is a number of persons or things that are located, gathered, or classed together. Groups of people [ edit ] Cultural group , a group whose members share the same cultural identity Ethnic group , a group whose members share the same ethnic identity Religious group (disambiguation) , a group whose members share the same religious identity Social group ,
468-548: The 💕 (Redirected from Group (disambiguation) ) [REDACTED] The present page holds the title of a primary topic , and an article needs to be written about it. It is believed to qualify as a broad-concept article . It may be written directly at this page or drafted elsewhere and then moved to this title. Related titles should be described in Group , while unrelated titles should be moved to Group (disambiguation) . [REDACTED] [REDACTED] Look up group in Wiktionary,
494-429: The galaxies by roughly a factor of two. However, this is still not enough mass to keep the galaxies in the cluster. Since this gas is in approximate hydrostatic equilibrium with the overall cluster gravitational field, the total mass distribution can be determined. It turns out the total mass deduced from this measurement is approximately six times larger than the mass of the galaxies or the hot gas. The missing component
520-422: The intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Group&oldid=1243788867 " Category : Disambiguation pages Hidden categories: Disambiguation pages to be converted to broad concept articles Short description is different from Wikidata All article disambiguation pages All disambiguation pages Group (disambiguation) From Misplaced Pages,
546-434: The intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Group&oldid=1243788867 " Category : Disambiguation pages Hidden categories: Disambiguation pages to be converted to broad concept articles Short description is different from Wikidata All article disambiguation pages All disambiguation pages Galaxy groups and clusters Groups of galaxies are
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#1732764803314572-590: The most common structures of galaxies in the universe, comprising at least 50% of the galaxies in the local universe. Groups have a mass range between those of the very large elliptical galaxies and clusters of galaxies. Our own galaxy, the Milky Way , is contained in the Local Group of more than 54 galaxies. In July 2017 S. Paul, R. S. John et al. defined clear distinguishing parameters for classifying galaxy aggregations as ‘galaxy groups’ and ‘clusters’ on
598-408: The presence of either an additional invisible mass component, or an additional attractive force besides gravity. X-ray studies have revealed the presence of large amounts of intergalactic gas known as the intracluster medium . This gas is very hot, between 10 K and 10 K, and hence emits X-rays in the form of bremsstrahlung and atomic line emission . The total mass of the gas is greater than that of
624-576: The properties of the cluster. Clusters of galaxies have been found in surveys by a number of observational techniques and have been studied in detail using many methods: Clusters of galaxies are the most recent and most massive objects to have arisen in the hierarchical structure formation of the Universe and the study of clusters tells one about the way galaxies form and evolve. Clusters have two important properties: their masses are large enough to retain any energetic gas ejected from member galaxies and
650-446: The smallest aggregates of galaxies. They typically contain no more than 50 galaxies in a diameter of 1 to 2 megaparsecs (Mpc)(see 10 m for distance comparisons). Their mass is approximately 10 solar masses . The spread of velocities for the individual galaxies is about 150 km/s. However, this definition should be used as a guide only, as larger and more massive galaxy systems are sometimes classified as galaxy groups. Groups are
676-527: The thermal energy of the gas within the cluster is observable within the X-Ray bandpass. The observed state of gas within a cluster is determined by a combination of shock heating during accretion, radiative cooling, and thermal feedback triggered by that cooling. The density , temperature , and substructure of the intracluster X-Ray gas therefore represents the entire thermal history of cluster formation. To better understand this thermal history one needs to study
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