List of galaxy groups and clusters explained

This article lists some galaxy groups and galaxy clusters.

Defining the limits of galaxy clusters is imprecise as many clusters are still forming. In particular, clusters close to the Milky Way tend to be classified as galaxy clusters even when they are much smaller than more distant clusters.

Clusters exhibiting strong evidence of dark matter

Some clusters exhibiting strong evidence of dark matter.

Galaxy clusterNotes
Bullet ClusterIn this collision between two clusters of galaxies, the stars pass between each other unhindered, while the hot, diffuse gas experiences friction and is left behind between the clusters. The gas dominates the visible mass budget of the clusters, being several times more massive than all the stars. Yet the regions with the stars show more gravitational lensing than the gas region, indicating that they are more massive than the gas. Some dark (since we don't see it), collision-less (or it would have been slowed, like the gas) matter is inferred to be present to account for the extra lensing around otherwise low-mass regions.[1]
Abell 520This is actually a collision between two galaxy clusters. The galaxies and the dark matter seems to have separated out into separate dark and light cores.[2]
Abell 2142A collision between two massive, X-ray luminous galaxy clusters.
Cl 0024+17
(ClG 0024+16, ZwCl 0024+1652)		This is a recently coalesced merger of galaxy clusters, which has resulted in a ring of dark matter around the galaxies, yet to be redistributed.[3] [4]

Named groups and clusters

This is a list of galaxy groups and clusters that are well known by something other than an entry in a catalog or list, or a set of coordinates, or a systematic designation.

Clusters

Galaxy clusterOrigin of nameNotes
Bullet ClusterThe cluster is named for the merger of two clusters colliding like a bullet.Also has a systematic designation of 1E 0657-56
El GordoNamed for its size, El Gordo ("the fat one") is the biggest cluster found in the distant universe (at its distance and beyond), at the time of discovery in 2011, with a mass of 3 quadrillion suns. The second most massive galaxy cluster next to El Gordo is RCS2 J2327, a galaxy cluster with the mass of 2 quadrillion suns.Also has a systematic designation of ACT-CL J0102-4915.[5] [6] [7]
Musket Ball ClusterNamed in comparison to the Bullet Cluster, as this one is older and slower galaxy cluster merger than the Bullet Cluster.Also has a systematic designation of DLSCL J0916.2+2951.[8]
Pandora's ClusterNamed because the cluster resulted from a collision of clusters, which resulted in many different and strange phenomena.Also has a catalogue entry of Abell 2744.[9]

Groups

Galaxy groupOrigin of nameNotes
Local GroupThe galaxy group that includes the Milky Way.
Bullet GroupNamed in comparison with the Bullet Cluster, being of similar formation, except smaller.Also has a systematic catalogue name SL2S J08544-0121. As of 2014, it was the lowest mass object that showed separation between the concentrations of dark matter and baryonic matter in the object.[10] [11]
Burbidge Chain
Copeland SeptetDiscovered by British astronomer Ralph Copeland in 1874.
Deer Lick GroupCoined by Tom Lorenzin (author of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing") to honor Deer Lick Gap in the mountains of North Carolina, from which he had especially fine views of the galaxy group.Also referred to as the NGC 7331 Group, after the brightest member of the group.[12]
Leo TripletNamed for the fact it contains only three galaxies.This small group of galaxies lies in the constellation Leo.
Markarian's ChainThis stretch of galaxies forms part of the Virgo Cluster.
Robert's QuartetIt was named by Halton Arp and Barry F. Madore, who compiled A Catalogue of Southern Peculiar Galaxies and Associations in 1987.This compact group of galaxies lies 160 million light-years away in the Phoenix constellation.
Seyfert's SextetNamed after its discoverer, Carl Seyfert. At the time it appeared to contain six external nebulae. It is also called the NGC 6027 Sextet, after its brightest member.There are actually only five galaxies in the sextet, and only four galaxies in the compact group. One of the galaxies is an ungravitationally bound background object. The other "galaxy" is instead an extension of the interacting system - a tidal stream caused by the merger. The group is, therefore, more properly called HCG 79; the name refers to the visual collection and not the group. HCG 79 lies 190 million light-years away in the Serpens Caput constellation.
Stephan's Quintet (Stephan's Quartet)Named after its discoverer, Édouard Stephan.There are actually only four galaxies in the compact group, the other galaxy is a foreground galaxy. The group is therefore more properly called HCG 92, because the name refers to a visual collection and not a group. Thus, the real group is also called Stephan's Quartet.
Wild's TripletNamed after the British-born and Australia-based astronomer Paul Wild (1923–2008), who studied the trio in the early 1950s.[13]
Zwicky's Triplet

The major nearby groups and clusters are generally named after the constellation they lie in. Many groups are named after the leading galaxy in the group. This represents an ad hoc systematic naming system.

Groups and clusters visible to the unaided eye

The Local Group contains the largest number of visible galaxies with the naked eye. However, its galaxies are not visually grouped together in the sky, except for the two Magellanic Clouds. The IC342/Maffei Group, the nearest galaxy group, would be visible by the naked eye if it were not obscured by the stars and dust clouds in the Milky Way's spiral arms.

Galaxy groupVisible galaxiesNotes
Local Group5Apart from the Milky Way, only 4 galaxies are visible to the naked eye.
Centaurus A/M83 Group2The Centaurus A galaxy has been spotted with the naked eye by Stephen James O'Meara [14] [15] and M83 has also reportedly been seen with the naked eye.[16]
M81 Group1Only Bode's Galaxy (M81, NGC 3031) is visible to the naked eye.[17] [18]

Firsts

First discoveredNameDateNotes
Galaxy clusterVirgo Cluster1784Discovered by Charles Messier.[20]
Galaxy group
Compact groupThe four brightest members of Stephan's Quintet1877Discovered by Edouard Stephan.
Proto-cluster
Double galaxyMagellanic Cloudsantiquity

Extremes

TitleNameDataNotestime
Most distant galaxy clusterCL J1001+0220redshift z=2.506Announced August 2016.[21]
Nearest galaxy clusterVirgo ClusterThe Virgo Cluster is at the core of the Virgo Supercluster. The Local Group is a member of the supercluster, but not the cluster.
Most distant galaxy group
Nearest galaxy groupLocal Group0 distanceThis is the galaxy group that our galaxy belongs to.
Nearest neighbouring galaxy groupIC 342/Maffei Group
Most distant proto-clusterA2744z7p9ODz=7.88[22]
Nearest proto-cluster
Most distant massive proto-clusterz66ODz=6.585At time of discovery in 2019, the object had 12 members, including Himiko.[23] [24] [25]
Least massive galaxy group
Most massive galaxy clusterRX J1347.5-1145mass= 2.0 ± 0.4 × 1015 MSun
  • distance: z= 0.451
  • LX-ray = 6.0 ± 0.1 × 1045 erg/s
  • temperature: kT = 10.0 ± 0.3 keV
[26] [27]

Closest groups

See also: Virgo Supercluster.

Galaxy group!style="background:#CCCCCC;text-align:center;" width="15%"
DistanceRedshift (z)Recession velocity (km/s)Notes
Local Group- - -Our Galaxy, the Milky Way, belongs to the Local Group.
LGG 104 (IC 342/Maffei Group, IC 342 / Maffei 1 Group, IC 342 Maffei 1-2 Group)0.000868The IC 342/Maffei Group contains two subgroups, the IC 342 subgroup (IC 342 Group) and the Maffei 1 subgroup (Maffei subgroup, Maffei 1 Group, Maffei Group).
M81 Group (NGC 3031 Group)3.5Mpc0.001115[28]
Centaurus A/M83 Group (Centaurus A Group, M83 Group)3.66Mpc0.000999The Centaurus A/M83 Group contains two subgroups, the Centaurus A subgroup (Centaurus A Group, NGC 5128 Group, LGG 344) and the M83 subgroup (M83 Group, NGC 5236 Group, LGG 355).
Sculptor Group (South Polar Group)3.9Mpc
Canes Venatici Group (Canes Venatici I Group, Canes I Group, M94 Group, NGC 4736 Group, LGG 291)4Mpc0.001612
NGC 1023 Group (LGG 70)6.12Mpc0.002926
M101 Group (NGC 5457 Group, LGG 371)7.33Mpc0.001288
NGC 2997 Group (LGG 180)7.66Mpc0.002615
Canes Venatici II Group (Canes II Group)8Mpc
M51 Group (NGC 5194 Group, LGG 347)9.5Mpc0.001850
Leo Triplet (M66 Group, NGC 3627 Group, LGG 231)10.75Mpc0.002207
Leo Group (Leo I Group, M96 Group, NGC 3379 Group, LGG 217)11.66Mpc0.002267
Draco Group12.25Mpc
LGG 396 (NGC 5866 Group, NGC 5907 Group)0.003020
Ursa Major Group (Ursa Major I Group, M109 Group, NGC 3992 Group, NGC 3726 Group, LGG 258)16.88Mpc0.003388
  • Mly represents millions of light-years, a measure of distance.
  • Mpc represents millions of parsecs, a measure of distance (1 Mpc = 3.26 Mly).
  • z represents redshift, a measure of recessional velocity and inferred distance due to cosmological expansion.
    In this very nearby context, however, the observed redshift and recessional velocity are due to the Doppler shifting of the light.
  • Distances are measured from Earth, with Earth being at zero.

Closest clusters

See also: Virgo Supercluster.

Galaxy cluster!style="background:#CCCCCC;text-align:center;" width="12%"
DistanceRedshift (z)Recession velocity (km/s)Notes
Virgo Cluster18Mpc0.0038The Virgo Cluster is at the core of the Virgo Supercluster. The Local Group is a member of the supercluster, but not the cluster.[29]
Fornax Cluster (Abell S 373, AM 0336-353, MCL 52)19Mpc0.0046
Antlia Cluster (Abell S 636)40.7Mpc0.0087Also called the Antlia Group.
Centaurus Cluster (Abell 3526, Cl 1247-4102)52.4 Mpc 0.0110
Hydra Cluster (Hydra I Cluster, Abell 1060, Cl 1034-2716)58.3 Mpc0.0114
Perseus Cluster (Abell 426, NGC 1275 Cluster)0.0179-->
  • Mly represents millions of light-years, a measure of distance.
  • Mpc represents millions of parsecs, a measure of distance.
  • z represents redshift, a measure of recessional velocity and inferred distance due to cosmological expansion.
  • Distances are measured from Earth, with Earth being at zero.

Farthest clusters

Galaxy cluster!style="background:#CCCCCC;text-align:center;" width="15%"
DistanceNotes
No entries yet
  • Mly represents millions of light-years, a measure of distance.
  • Mpc represents millions of parsecs, a measure of distance.
  • z represents redshift, a measure of recessional velocity and inferred distance due to cosmological expansion.
  • Distances are measured from Earth, with Earth being at zero.
Galaxy cluster!style="background:#CCCCCC;text-align:center;"
DateRedshift (z)Recession Velocity
(km/s)		Notes
CL J1001+02202016 - 2.506
CL J1449+0856
(ClG J1449+0856)		2011–20162.07[30] [31] [32]
JKCS 0412009–20111.9
XMMXCS 2215-1738 (XMMXCS 2215.9-1738)2006–20091.45XMM-XCS 2215-1738 was also the most massive early cluster so far discovered.[33] [34]
ISCS J143809+3414192005–20061.41[35] [36]
XMMU J2235.3-255720051.393[37] [38] [39]
RDCS 0848+4453 (RDCS0848.6+4453, RX J0848+4453, ClG 0848+4453)1997–1.276ClG 0848+4453 forms a double-cluster supercluster with RDCS J0849+4452[40] [41]
galaxy cluster around 3C 324 (3C 234 Cluster)1984–1.206At the time, the BCG, 3C324 was the most distant non-quasar galaxy.[42]
Cl 0016+161980 − z=0.54In 1981, this cluster was the most distant cluster studied photometrically.[43] -->
Cl 1305+29521977 − 0.947This was not generally accepted as the redshift for this cluster. This was the first cluster beyond about z~0.5 [44] -->
Cl 1409+5241960–19750.461The measurement of 3C295's redshift in 1960 also defined its cluster's position. 3C 295 was also the most distant galaxy of the time.[45] [46]
Abell 732 (fainter Hydra Cluster Cl 0855+0321)1951–19600.261 000 Attempts at measuring the redshift of the brightest cluster galaxy of this Hydra Cluster had been attempted for years before it had been successfully achieved. The BCG was also the most distant galaxy of the time.[47] [48] [49]
Abell 1930 (Bootes Cluster)1936–19510.1339 000 The BCG of this cluster was also the most distant galaxy of the time.[50]
Gemini Cluster (Abell 568)1932 - 19360.07523 000 The BCG of this cluster was the most distant galaxy at the time.[51]
WH Christie's Leo Cluster1931–193219 700 The BCG of this cluster was the most distant galaxy known at the time.[52] [53] [54]
Baede's Ursa Major Cluster1930–193111 700 The BCG of this cluster was the highest redshift galaxy of the time.[55]
Coma Cluster1929–19300.0267 800 This cluster's distance was determined by one of the NGC objects lying in it, NGC4860.[56]
Pegasus Group (LGG 473, NGC 7619 Group)19290.0123 779 The BCG for this group was used to measure its redshift. Shortly after this was publicized, it was accepted that redshifts were an acceptable measure of inferred distance.[57]
Cetus Group (Holmberg 45, LGG 27)1921–19290.0061 800 NGC 584 (Dreyer 584) was measured for the redshift to this galaxy group.[58] [59] [60]
Virgo Cluster1784–192159 Mly (18 Mpc)
z=0.003		1 200 This was the first noted cluster of "nebulae" that would become galaxies. The first redshifts to galaxies in the cluster were measured in the 1910s. Galaxies were not identified as such until the 1920s. The distance to the Virgo Cluster would have to wait until the 1930s.
  • Mly represents millions of light-years, a measure of distance.
  • Mpc represents millions of parsecs, a measure of distance.
  • z represents redshift, a measure of recessional velocity and inferred distance due to cosmological expansion.
  • Distances are measured from Earth, with Earth being at zero.

Farthest protoclusters

Galaxy protocluster!style="background:#CCCCCC;text-align:center;" width="15%"
DistanceNotes
No entries yet
  • Mly represents millions of light-years, a measure of distance.
  • Mpc represents millions of parsecs, a measure of distance.
  • z represents redshift, a measure of recessional velocity and inferred distance due to cosmological expansion.
  • Distances are measured from Earth, with Earth being at zero.
Galaxy protocluster!style="background:#CCCCCC;text-align:center;"
DateRedshift (z)Notes
BoRG-582012~ 8[73]
COSMOS-AzTEC32011–5.3Located in Sextans, the cluster appears to contain 11 young small galaxies.[74] [75]
Protocluster around radio-galaxy TN J1338-19422002–4.11It was described as the most distant cluster.[76] [77] [78] [79]
Protocluster around 3C 3681982–1.13[80]
  • z represents redshift, a measure of recessional velocity and inferred distance due to cosmological expansion.
  • Distances are measured from Earth, with Earth being at zero.

False clusters

Sometimes clusters are put forward that are not genuine clusters or superclusters. Through the researching of member positions, distances, peculiar velocities, and binding mass, former clusters are sometimes found to be the product of a chance line-of-sight superposition.

Former clusterNotes
Cancer ClusterThe Cancer Cluster was found to be a random assortment of galaxy groups, and not a true cluster.
Coma-Virgo CloudThe early identification of the Coma-Virgo Cloud of Nebulae was actually a mistaken identification due to the superposition of the Virgo Supercluster and Coma Supercluster, and not a Coma-Virgo Supercluster

See also

Lists of groups and clusters

External links

Notes and References

  1. Web site: Galaxy Collision Separates Out the Dark Matter . Universe Today . 2006-08-21.
  2. Web site: Galaxy Cluster Collision Creates a Dark Matter Core. Universe Today . 2007-08-16.
  3. Web site: Ring of Dark Matter Discovered Around a Galaxy Cluster. Universe Today . 2007-05-15.
  4. SIMBAD, "ClG 0024+17"
  5. Web site: Schilling . Govert . 12 January 2012 . When Galaxies Crash . ScienceNOW . https://web.archive.org/web/20120129075039/http://news.sciencemag.org/sciencenow/2012/01/when-galaxies-crash.html . 2012-01-29.
  6. Humongous 'El Gordo' galaxy cluster packs mass of 2 quadrillion stars. Christian Science Monitor. 2012-01-11.
  7. NASA, "El Gordo Galaxy Cluster", 10 January 2012 (accessed 7 July 2012)
  8. Web site: Discovery of the Musket Ball Cluster, a system of colliding galaxy clusters . Science Daily.
  9. ESO, "A Galactic Crash Investigation", 22 June 2011 (accessed 7 July 2012)
  10. Web site: Cosmic collision in the Bullet Group . 6 June 2014 . XMM-Newton . European Space Agency .
  11. 10.1093/mnrasl/slu058 . 2014MNRAS.442L..76G . 1404.5633 . Dark matter–baryons separation at the lowest mass scale: The Bullet Group . Monthly Notices of the Royal Astronomical Society: Letters . 442 . L76–L80 . 2014 . Gastaldello . F. . free . etal .
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  13. Web site: Wild's Triplet . . 13 October 2018.
  14. Web site: Aintno Catalog.
  15. Book: 10.1007/978-1-84628-736-7_4 . 2007 . 157–189 . Inglis . Mike . Astrophysics is Easy! An Introduction for the Amateur Astronomer . Galaxies . Patrick Moore's Practical Astronomy Series . 978-1-85233-890-9 . https://archive.org/details/astrophysicsisea0000ingl/page/157 .
  16. Book: 10.1007/978-1-84628-736-7_4 . Inglis . Mike . Astrophysics is Easy! An Introduction for the Amateur Astronomer . Galaxies . Patrick Moore's Practical Astronomy Series . 157–189 . 2007 . 978-1-85233-890-9 . https://archive.org/details/astrophysicsisea0000ingl/page/157 .
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  18. SEDS, Messier 81
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  28. Hayden Planetarium, Galaxy Clusters and Superclusters
  29. Hayden Planetarium, The 2MASS Galaxies
  30. 1011.1837 . 2011A&A...526A.133G . 10.1051/0004-6361/201016084. A mature cluster with X-ray emission at z= 2.07 . Astronomy & Astrophysics . 526 . A133 . 2011 . Gobat . R. . 39625321 . etal .
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  32. SIMBAD, "ClG J1449+0856"
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  35. NASA - Spitzer Space Telescope, Great Galactic Buddies
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  37. New Scientist, Most distant galaxy cluster yet is revealed, 08:00 02 March 2005
  38. http://www.astro.lsa.umich.edu/~cmullis/research/xmmuj2235/index.html The Most Distant X-ray Massive Galaxy Cluster XMMU J2235.3-2557 z=1.4
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