CD銀河

cD銀河^[1](type-cD galaxy^[2], cD-type galaxy^[3], cD galaxy^[1]^[4])は、銀河の形態分類の1つであり、Dタイプの巨大楕円銀河の一部である。恒星の巨大な銀河ハローを持つ^[5]。しばしば銀河団の中心近くで見られる^[6]。supergiant ellipticals^[7]またはcentral dominant galaxies^[8]としても知られる。

cD銀河は、Dタイプ銀河とともにヤーキス分類による分類である^[9]。"c"は、銀河が非常に大きいことを示しており、"D"は銀河が拡散して見えることを示している^[10]。逆生して、"cD"はしばしばcentral Dominant galaxyを意味するのにも用いられる^[8]。cD銀河は最も大きい銀河と考えられている^[11]^[12]。

cD銀河は、レンズ状銀河や楕円銀河に似ているが、それより何倍も大きく、半径100万光年を超える巨大な包を持つものもある^[13]。低表面輝度の包を伴った楕円状に見える^[14]。現在は、cD銀河は銀河の合体の結果であると考えられている^[15]。いくつかのcD銀河は複数の銀河核を持つ^[16]。cD銀河は、しばしば銀河団のbrightest cluster galaxy(BCG)になるのが見られる銀河の1つである^[17]。多くの化石銀河群の銀河はcD BCG銀河に似ており、cD銀河は化石銀河群の生成の結果であり、その後化石銀河群の周りに新しいクラスタが蓄積したものだという説もある^[18]。しかし、cD銀河自体は化石銀河群と異なり散在銀河としては見られない^[14]。cD銀河は、BCGの約20%を占める^[14]。

cD銀河は、銀河団の中心に落ち込む銀河の融合により成長すると信じられている。この説は、1965年にHerbert J. Roodが提唱した^[19]。この「共食い」成長モデルで、銀河の圧倒的な大きさと明るさが説明できる^[20]。銀河団で2番目に明るい銀河は、「捕食されている」と考えられる^[21]。「食べられた」銀河の残骸は、ガスや塵の拡散した銀河ハローとして見えることがあり^[20]、この銀河ハローの直径は300万光年にも達する^[15]。cD銀河は、銀河団の質量に依り、12.5ビリアル半径内のバリオンの合計質量のうち、単独で1-7%を占めると推定されている^[22]。

力学的摩擦

銀河団の中心でのcD銀河の形成には、力学的摩擦が重要な役割を果たすと信じられている^[23]。この過程は、銀河団中での大きな銀河の動きが小さな銀河や暗黒物質をその後流に引き付ける時に始まる。この高密度領域は大きな銀河の後ろを流れ、定常的な重力を及ぼし、速度を低下させる。運動エネルギーを失うと、大きな銀河は徐々に銀河団の中心に向かって落ち込む。一度そうなると、大きな銀河の恒星、ガス、塵、暗黒物質やそれを追いかける銀河も加わり、同じ運命を辿る^[24]。超巨大で拡散した楕円銀河は、この蓄積に由来する^[25]。融合銀河の中心は長期間認識できる状態で残るため、cD銀河には複数の「核」があるように見える^[26]。

ESO 383-76 - シャプレー超銀河団を構成するAbell3571の中心。有効半径において既知の最大の銀河 (長軸直径:1,764,000光年短軸直径:882,000光年)^[27]
NGC 1275^[28]
NGC 6166^[29]
IC 1101 - 既知の最も大きな銀河の一つ^[30]^[31]^[32]。近年の観測では距離が修正された結果、有効半径(長軸直径:553,200光年、短軸直径:403,300光年)、銀河ハローの直径200万光年とされる。^[33]
M87 - おとめ座銀河団の中心
NGC 1399 - ろ座銀河団
NGC 4889
NGC 6086
QSO 0957 - 最初に同定された重力レンズ天体

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[3]
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[4]
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[7]
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[13]
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[14]
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[15]
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[16]
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[18]
Universe Today, "How Do Fossil Galaxy Clusters Form so Quickly?", Fraser Cain, 27 April 2006 (accessed 15 April 2010)
[19]
Rood, Herbert J. (1965). The Dynamics of the Coma Cluster of Galaxies (PhD thesis). The University of Michigan. Bibcode:1965PhDT.........3R。
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[23]
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[24]
Merritt, David (January 1984). “Relaxation and tidal stripping in rich clusters of galaxies. II. Evolution of the luminosity distribution”. The Astrophysical Journal 276: 26-37. Bibcode: 1984ApJ...276...26M. doi:10.1086/161590.
[25]
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[26]
Merritt, David (May 1984). “The nature of multiple-nucleus cluster galaxies”. The Astrophysical Journal 280: L5-8. Bibcode: 1984ApJ...280L...5M. doi:10.1086/184257.
[27]
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[29]
Nature, "FIGURE 3. The entropy of the intracluster medium in spherical shells of radius r." 9 July 2009, ISSN 0028-0836 ; EISSN 1476-4687 ; (accessed 15 April 2010)
[30]
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[31]
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[32]
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[33]
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PDF - "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)
PDF - "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)

[ox-1] [1]
『オックスフォード天文学辞典』（初版第1刷）朝倉書店、180頁。ISBN 4-254-15017-2。

[2] [2]
Sidereal Times, June 2002, page 3

[3] [3]
Proceedings of PATRAS 2008, page 59

[4] [4]
Galaxy Clusters, Jan Hartlap, page 3

[5] [5]
Surface Photometry and the Structure of Elliptical Galaxies, "Chapter 11. cD and Brightest Cluster Galaxies", John Kormendy, S. Djorgovski, 1989

[6] [6]
A Dictionary of Astronomy, "cD galaxy"^{[リンク切れ]} (accessed 14 April 2010)

[7] [7]
encyclopedia.com "supergiant elliptical"

[UoCoGd-8] [8]
"Uncertainties on Clusters of Galaxies Distances", C. Adami, M.P. Ulmer, 18 July 2000, arXiv:astro-ph/0007265 (accessed 14 April 2010)

[9] [9]
An Atlas of DRAGNs, "Glossary", J. P. Leahy, 15 March 1997 (accessed 14 April 2010)

[10] [10]
Global Telescope Network, "Types of Galaxies" アーカイブ 2010年7月16日 - ウェイバックマシン, Kevin McLin, 14 April 2010 (accessed 14 April 2010)

[11] [11]
Universe Today, "What is the Largest Galaxy?", Fraser Cain (accessed 14 April 2010)

[12] [12]
EurekAlert, "Scientists observe largest explosion in space", Andrea Gibson, 5 January 2005 (accessed 15 April 2010)

[13] [13]
Encyclopadia Britannica, "cD-galaxy" (accessed 14 April 2010)

[ICyese-cD-14] [14]
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)

[cosmos-sao-CDgalaxies-15] [15]
COSMOS - The SAO Encyclopedia of Astronomy, "CD Galaxies", Swinburne University of Technology (accessed 14 April 2010)

[16] [16]
Internet Encyclopedia of Science, "D galaxy", David Darling (accessed 14 April 2010)

[17] [17]
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)

[18] [18]
Universe Today, "How Do Fossil Galaxy Clusters Form so Quickly?", Fraser Cain, 27 April 2006 (accessed 15 April 2010)

[19] [19]
Rood, Herbert J. (1965). The Dynamics of the Coma Cluster of Galaxies (PhD thesis). The University of Michigan. Bibcode:1965PhDT.........3R。

[curious-20] [20]
“Curious About Astronomy?”. 28 March 2007閲覧。

[21] [21]
Hausman, M. J.; Ostriker, J. P. (November 1977). “Cannibalism among the galaxies - Dynamically produced evolution of cluster luminosity functions”. The Astrophysical Journal Letters 217: L125-L128. Bibcode: 1977ApJ...217L.125O. doi:10.1086/182554.

[Vikhlinin-22] [22]
Section 8 of Vikhlinin, A.; Kravtsov, A.; Forman, W.; Jones, C.; Markevitch, M.; Murray, S. S.; Van Speybroeck, L. (April 2006). “Chandra Sample of Nearby Relaxed Galaxy Clusters: Mass, Gas Fraction, and Mass-Temperature Relation” (PDF). The Astrophysical Journal (Chicago, Illinois, USA: University of Chicago Press) 640 (2): 691-709. arXiv:astro-ph/0507092. Bibcode: 2006ApJ...640..691V. doi:10.1086/500288 March 12, 2012閲覧。.

[DM1983-23] [23]
Merritt, David (January 1983). “Relaxation and tidal stripping in rich clusters of galaxies. I. Evolution of the mass distribution”. The Astrophysical Journal 264: 24-48. Bibcode: 1983ApJ...264...24M. doi:10.1086/160571.

[DM1984-24] [24]
Merritt, David (January 1984). “Relaxation and tidal stripping in rich clusters of galaxies. II. Evolution of the luminosity distribution”. The Astrophysical Journal 276: 26-37. Bibcode: 1984ApJ...276...26M. doi:10.1086/161590.

[DM1985-25] [25]
Merritt, David (February 1985). “Relaxation and tidal stripping in rich clusters of galaxies. III. Growth of a massive central galaxy”. The Astrophysical Journal 289: 18-32. Bibcode: 1985ApJ...289...18M. doi:10.1086/162860.

[26] [26]
Merritt, David (May 1984). “The nature of multiple-nucleus cluster galaxies”. The Astrophysical Journal 280: L5-8. Bibcode: 1984ApJ...280L...5M. doi:10.1086/184257.

[27] [27]
“Results for object ESO 383- G 076 (ESO 383-G 076)”. NASA/IPAC Extragalactic Database. National Aeronautics and Space Administration, California Institute of Technology. 2023年3月23日閲覧。

[28] [28]
Nature, "FIGURE 4. Optical, radio and X-ray images of the Perseus cluster." 9 July 2009, ISSN 0028-0836 ; EISSN 1476-4687 ; (accessed 15 April 2010)

[29] [29]
Nature, "FIGURE 3. The entropy of the intracluster medium in spherical shells of radius r." 9 July 2009, ISSN 0028-0836 ; EISSN 1476-4687 ; (accessed 15 April 2010)

[30] [30]
Science, "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

[31] [31]
Ellensburg Daily Record, "Galaxy Found", United Press International, 27 October 1990, p.16

[32] [32]
Lodi News-Sentinel, "Giant Galaxy Discovered", UPI, 26 October 1990, pg.9

[33] [33]
“NED results for object IC 1101”. NASA/IPAC Extragalactic Database. National Aeronautics and Space Administration, California Institute of Technology.. 2023年3月23日閲覧。

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CD銀河

力学的摩擦

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CD銀河

力学的摩擦

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cD銀河

成長

cD銀河の例

出典

関連文献