type-cD galaxy

The cD-type is a classification in the Yerkes galaxy classification scheme, one of two Yerkes classifications still in common use, along with D-type.An Atlas of DRAGNs, [http://www.jb.man.ac.uk/atlas/gloss.html#cD "Glossary"], J. P. Leahy, 15 March 1997 (accessed 14 April 2010) The "c" in "cD" refers to the fact that the galaxies are very large, hence the adjective supergiant, while the "D" refers to the fact that the galaxies appear diffuse.Global Telescope Network, [http://gtn.sonoma.edu/resources/normal_galaxies/types.php "Types of Galaxies"] {{Webarchive|url=https://web.archive.org/web/20100716001648/http://gtn.sonoma.edu/resources/normal_galaxies/types.php |date=16 July 2010 }}, Kevin McLin, 14 April 2010 (accessed 14 April 2010) A backformation of "cD" is frequently used to indicate "central Dominant galaxy"."Uncertainties on Clusters of Galaxies Distances", C. Adami, M.P. Ulmer, 18 July 2000, {{arxiv|astro-ph/0007265}} (accessed 14 April 2010) cDs are also frequently considered the largest galaxies.Universe Today, [http://www.universetoday.com/guide-to-space/galaxies/what-is-the-largest-galaxy/ "What is the Largest Galaxy?"], Fraser Cain (accessed 14 April 2010)EurekAlert, [http://www.eurekalert.org/pub_releases/2005-01/ou-sol010505.php "Scientists observe largest explosion in space"], Andrea Gibson, 5 January 2005 (accessed 15 April 2010)

cD galaxies are similar to lenticular galaxies (S0) or elliptical galaxies (E#), but many times larger, some having envelopes that exceed one million light years in radius.Encyclopædia Britannica, [http://www.britannica.com/EBchecked/topic/100915/cD-galaxy "cD-galaxy"] (accessed 14 April 2010) They appear elliptical-like, with large low surface brightness envelopes which may belong as much to the galaxy cluster as the cD galaxy. It is currently thought that cDs are the result of galaxy mergers.COSMOS—The SAO Encyclopedia of Astronomy, [http://astronomy.swin.edu.au/cosmos/C/CD+Galaxies "CD Galaxies"], Swinburne University of Technology (accessed 14 April 2010) Some cDs have multiple galactic nuclei.Internet Encyclopedia of Science, [http://www.daviddarling.info/encyclopedia/D/D_galaxy.html "D galaxy"], David Darling (accessed 14 April 2010) cD galaxies are one of the types frequently found to be the brightest cluster galaxy (BCG) of a cluster.IAU Symposium 245, "Star Formation in Bulges from GALEX", Sukyoung K. Yi, 5 September 2007, {{doi|10.1017/S174392130801819X}}, {{arxiv|0709.0177}} (accessed 14 April 2010) Many fossil group galaxies are similar to cD BCG galaxies, leading some to theorize that the cD results from the creation of a fossil group, and then the new cluster accumulating around the fossil group.Universe Today, [http://www.universetoday.com/2006/04/27/how-do-fossil-galaxy-clusters-form-so-quickly/ "How Do Fossil Galaxy Clusters Form so Quickly?"], Fraser Cain, 27 April 2006 (accessed 15 April 2010) However, cDs themselves are not found as field galaxies, unlike fossil groups.Monthly Notices of the Royal Astronomical Society, "Intracluster light and the extended stellar envelopes of cD galaxies: an analytical description", Marc S. Seigar, Alister W. Graham, Helmut Jerjen, July 2007, Volume 378, Issue 4, pp. 1575–1588, {{doi|10.1111/j.1365-2966.2007.11899.x}}, {{bibcode|2007MNRAS.378.1575S}}, {{arxiv|astro-ph/0612229v2}} (accessed 15 April 2010) cDs form around 20% of BCGs.

Massive galaxies such as supergiant elliptical galaxies are important to understanding the evolution of the Universe, because they, along with other large-early type galaxies, account for half of the Universe's stellar mass, contribute a lot to its chemical enrichment and provide clues to the star formation history of the Universe.{{cite journal |last1=Barbosa |first1=C.E. |last2=Spiniello |first2=C. |last3=Arnaboldi |first3=M. |last4=Coccato |first4=L. |last5=Hilker |first5=M. |last6=Richtler |first6=T. |title=A preserved high-z compact progenitor in the heart of NGC 3311 revealed with MUSE 2D stellar population analysis |journal=Astronomy & Astrophysics |date=May 2021 |volume=649 |pages=19 |doi=10.1051/0004-6361/202039809 |arxiv=2012.11609 |bibcode=2021A&A...649A..93B |s2cid=232157305 |doi-access=free }}

cD galaxies are believed to grow via mergers of galaxies that spiral in to the center of a galaxy cluster, a theory first proposed by Herbert J. Rood in 1965.{{Cite thesis |degree=PhD |title=The Dynamics of the Coma Cluster of Galaxies |bibcode=1965PhDT.........3R |last=Rood |first=Herbert J.|date=1965 |publisher=The University of Michigan}} This "cannibalistic" mode of growth leads to the large diameter and luminosity of the cDs.{{Cite web|url=http://curious.astro.cornell.edu/|title=Curious About Astronomy?|access-date=28 March 2007}} The second-brightest galaxy in the cluster is usually under-luminous, a consequence of its having been "eaten".{{Cite journal

| doi = 10.1086/182554

| last1 = Hausman

| first1 = M. J.

| last2 = Ostriker

| first2 = J. P.

| title = Cannibalism among the galaxies—Dynamically produced evolution of cluster luminosity functions

| journal = The Astrophysical Journal Letters

| volume = 217

| pages = L125–L128

| date = November 1977

| bibcode = 1977ApJ...217L.125O| doi-access = free

}} Remains of "eaten" galaxies sometimes appear as a diffuse halo of gas and dust, or tidal streams, or undigested off-center nuclei in the cD galaxy. The envelope or halo may also consist of the "intra-cluster light", originating from stars stripped away from their original galaxy, and it can be up to 3 million light years in diameter. It is estimated that the cD galaxy alone contributes 1–7%, depending on the cluster mass, of the total baryon mass within 12.5 virial radii.Section 8 of {{cite journal

| last1 = Vikhlinin

| first1 = A.

| last2 = Kravtsov

| first2 = A.

| last3 = Forman, W.; Jones, C.; Markevitch, M.; Murray, S. S.; Van Speybroeck, L.

|date=April 2006

| title = Chandra Sample of Nearby Relaxed Galaxy Clusters: Mass, Gas Fraction, and Mass-Temperature Relation

| journal = The Astrophysical Journal

| volume = 640

| issue = 2

| pages = 691–709

| location = Chicago, Illinois, USA

| arxiv = astro-ph/0507092

| bibcode = 2006ApJ...640..691V

| doi = 10.1086/500288

| s2cid = 18940822

}}

Dynamical friction is believed to play an important role in the formation of cD galaxies at the centres of galaxy clusters.

{{Cite journal

| doi = 10.1086/160571

| last = Merritt

| first = David

| author-link = David Merritt

| title = Relaxation and tidal stripping in rich clusters of galaxies. I. Evolution of the mass distribution

| journal = The Astrophysical Journal

| volume = 264

| pages = 24–48

| date = January 1983

| bibcode = 1983ApJ...264...24M}} This process begins when the motion of a large galaxy in a cluster attracts smaller galaxies and dark matter into a wake behind it. This over-density follows behind the larger galaxy and exerts a constant gravitational force on it, causing it to slow down. As it loses kinetic energy, the large galaxy gradually spirals toward the centre of the cluster. Once there, the stars, gas, dust and dark matter of the large galaxy and its trailing galaxies will join with those of other galaxies who preceded them in the same fate.

{{Cite journal

| doi = 10.1086/161590

| last = Merritt

| first = David

| author-link = David Merritt

| title = Relaxation and tidal stripping in rich clusters of galaxies. II. Evolution of the luminosity distribution

| journal = The Astrophysical Journal

| volume = 276

| pages = 26–37

| date = January 1984

| bibcode = 1984ApJ...276...26M| doi-access = free

}} A giant or supergiant diffuse or elliptical galaxy will result from this accumulation.

{{Cite journal

| doi = 10.1086/162860

| last = Merritt

| first = David

| author-link = David Merritt

| title = Relaxation and tidal stripping in rich clusters of galaxies. III. Growth of a massive central galaxy

| journal = The Astrophysical Journal

| volume = 289

| pages = 18–32

| date = February 1985

| bibcode = 1985ApJ...289...18M| doi-access = free

}} The centers of merged or merging galaxies can remain recognizable for long times, appearing as multiple "nuclei" of the cD galaxy.{{Cite journal

| doi = 10.1086/184257

| last = Merritt

| first = David

| author-link = David Merritt

| title = The nature of multiple-nucleus cluster galaxies

| journal = The Astrophysical Journal

| volume = 280

| pages = L5–8

| date = May 1984

| bibcode = 1984ApJ...280L...5M| doi-access = free

}}

Type-cD galaxies are also used to define clusters. A galaxy cluster with a cD at its centre is termed a "cD cluster" or "cD galaxy cluster" or "cD cluster of galaxies".[http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1971PASP...83..313R&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf PDF], "'Tuning Fork' Classification of Rich Clusters of Galaxies", Herbert J.Rood, Gummuluru N. Sastry, June 1971, {{doi|10.1086/129128}}, {{bibcode|1971PASP...83..313R}} (accessed 14 April 2010)

• 3C 401
• Abell 1201 BCG
• Abell 1413 BCG
• ESO 383-76, the large central galaxy of Abell 3571
• Holmberg 15A (home to one of the largest black holes currently known)
• IC 1101, the large central galaxy of the massive cluster Abell 2029.Science, [http://www.sciencemag.org/cgi/content/abstract/250/4980/539 "The Central Galaxy in Abell 2029: An Old Supergiant"], Juan M. Uson, Stephen P. Boughn, and Jeffrey R. Kuhn, 26 October 1990, Vol. 250, no. 4980, pp. 539–540, {{doi|10.1126/science.250.4980.539}}"Galaxy Found", Ellensburg Daily Record, United Press International, 27 October 1990, p. 16Lodi News-Sentinel, "Giant Galaxy Discovered", UPI, 26 October 1990, p. 9
• Messier 87, the central galaxy in the Virgo Cluster
• NeVe 1, the host galaxy of the Ophiuchus Supercluster eruption event, the most energetic outburst known.
• NGC 1399 in the Fornax Cluster
• NGC 4889, is also known as the Caldwell 35, a supergiant galaxy, a class-4 elliptical galaxy, it is the brightest within Caldwell Objects in the constellation Coma Berenices
• NGC 6086
• NGC 6166Nature, [http://www.nature.com/nature/journal/v460/n7252/fig_tab/nature08135_F3.html "FIGURE 3. The entropy of the intracluster medium in spherical shells of radius r."] 9 July 2009, {{ISSN|0028-0836}} ; E-{{ISSN|1476-4687}} ; (accessed 15 April 2010)
• Perseus ANature, [http://www.nature.com/nature/journal/v460/n7252/fig_tab/nature08135_F4.html "FIGURE 4. Optical, radio and X-ray images of the Perseus cluster."] 9 July 2009, {{ISSN|0028-0836}} ; E-{{ISSN|1476-4687}} ; (accessed 15 April 2010)
• QSO 0957, the first identified gravitationally lensed object

• Elliptical galaxy (E#)
• Giant elliptical galaxy (gE)
• Lenticular galaxy (S0, SA0, SAB0, SB0, E9)
• Seyfert galaxy
• Type-D galaxy
• List of largest galaxies - a broader list containing type-cD galaxies, arranged by size.

{{Reflist}}

• [http://nedwww.ipac.caltech.edu/level5/Morgan2/paper.pdf PDF]—[http://nedwww.ipac.caltech.edu/level5/Morgan2/frames.html "A Preliminary Classification of the Forms of Galaxies According to Their Stellar Population"], W. W. Morgan, Yerkes Obeservatory, 1958, {{doi|10.1086/127415}}, {{bibcode|1959PASP...71..394M}} (PASP 70)
• [https://arxiv.org/abs/astro-ph/0612229 "Intracluster light and the extended stellar envelopes of cD galaxies: an analytical description"], Marc S. Seigar, Alister W. Graham, Helmut Jerjen, July 2007 {{doi|10.1111/j.1365-2966.2007.11899.x}}, {{bibcode|2007MNRAS.378.1575S}}, {{arxiv|astro-ph/0612229v2}} (MNRAS 07/2007)

{{Galaxy}}

{{DEFAULTSORT:Type-Cd Galaxy}}

Category:Galaxy morphological types