Anemic galaxy

An anemic galaxy is a type of spiral galaxy characterized by a low contrast between its spiral arms and its disk.

NGC 4921 by HST
NGC 4921, a typical anemic galaxy.
NGC 4569 is also an example of an anemic galaxy.

Origin of the term

The term was coined in 1976 by the Canadian astronomer Sidney van den Bergh to classify galaxies that are an intermediate form between the gas-rich, star-forming spiral galaxies and the gas-poor, inactive lenticular galaxies[1]


Anemic galaxies not only show spiral arms of low contrast but also a low content and density of neutral hydrogen (the raw material needed to form stars),[2][3] redder colours than a normal spiral, fewer H II regions, and thus a low star formation activity.[3]

At first it was believed their molecular hydrogen content was similar to that of a normal spiral,[4] but subsequent studies have shown that a number of them are deficient in molecular gas.[5]

Anemic galaxies should not be confused with galaxies with red colors due to a low star formation activity but which show a normal content of neutral gas, as is the case of the Andromeda Galaxy.[6][7]


As most galaxies of this type are present in rich galaxy clusters, it has been proposed that this may be one of the reasons that converts normal spirals into anemic ones. Studies of spiral galaxies in the nearby Virgo cluster have shown not only how, unlike in isolated spiral galaxies, in most cases their neutral gas and star formation are truncated within their optical disks, in some cases quite severely,[8][9] but also how star formation activity in them is lower than on spirals outside clusters,:[9] this means that processes that take place in galaxy clusters as interactions with the intracluster medium like ram-pressure stripping and/or interactions with other neighboring galaxies are responsible of the origin of anemic galaxies, stripping the normal spirals of their gas, increasing in some cases their star formation activity, and thus in the end quenching the latter as their gas is exhausted and not replenished.[10] Spiral galaxies may have become anemic ones by exhausting their supply of gas via star formation activity.[3]

An anemic galaxy's most probable fate is to lose their remaining gas and star formation, becoming similar to a lenticular galaxy: it therefore is likely that most lenticular galaxies in clusters, are former spiral galaxies.[10]

Passive spiral galaxies

Passive spiral galaxies (also known as passive spirals) are a type of spiral galaxy located in rich galaxy clusters at high redshifts that present spiral structure, but little or no star formation,[11] in some cases hidden by dust and concentrated within its innermost regions.[12] Often, they seem too to have few or no massive (>20 solar masses) stars.[12]

According to computer simulations, they are systems on the way to becoming a lenticular galaxy as they have lost the hydrogen that is assumed to be present in the haloes of spiral galaxies and that replenishes them with new gas to form stars.[13]

While they share at least some properties with anemic galaxies,[14] its relationship with them is unclear:[13] they may be a more advanced stage on the evolution of a spiral galaxy to become a lenticular than the anemic galaxies[15] or passive spirals and anemic galaxies may be the same type of object, their difference is that the former are much farther away than the latter.[16]


NGC 4921 in the Coma Cluster and Messier 90 in the Virgo Cluster are examples of this type of galaxy;[1] however, most spiral galaxies of the latter are more or less deficient in gas.[2]


  1. ^ a b Bergh, S. (1976). "A new classification system for galaxies". The Astrophysical Journal. 206: 883–887. Bibcode:1976ApJ...206..883V. doi:10.1086/154452. Part 1.
  2. ^ a b Chamaraux, P.; Balkowski, C.; Gerard, E. (1980). "The H I deficiency of the Virgo cluster spirals". Astronomy & Astrophysics. 83 (1–2): 38–51. Bibcode:1980A&A....83...38C.
  3. ^ a b c Elmegreen, D.M.; Elmegreen, B.G.; Frogel, J.A; Eskridge, P.B.; Pogge, R.W.; Gallagher, A.; Iams, J. (2002). "Arm Structure in Anemic Spiral Galaxies". The Astronomical Journal. 124 (2): 777–781. arXiv:astro-ph/0205105. Bibcode:2002AJ....124..777E. doi:10.1086/341613.
  4. ^ Bergh, S. (1991). "What are anemic galaxies?". Publications of the Astronomical Society of the Pacific. 103: 390–391. Bibcode:1991PASP..103..390V. doi:10.1086/132832.
  5. ^ Fumagalli, M.; Krumholz, M.R.; Prochaska, J.X; Gavazzi, G.; Boselli, A. (2009). "Molecular Hydrogen Deficiency in H I-poor Galaxies and its Implications for Star Formation". The Astrophysical Journal. 697 (2): 1811–1821. arXiv:0903.3950. Bibcode:2009ApJ...697.1811F. doi:10.1088/0004-637X/697/2/1811.
  6. ^ Davidge, T. J.; Connachie, A. W.; Fardal, M. A.; Fliri, J.; Valls-Gabaud, D.; Chapman, S. C.; Lewis, G. F.; Rich, R. M. (2012). "The Recent Stellar Archeology of M31—The Nearest Red Disk Galaxy". The Astrophysical Journal. 751 (1): 74. arXiv:1203.6081. Bibcode:2012ApJ...751...74D. doi:10.1088/0004-637X/751/1/74. article 74.
  7. ^ Schommer, R. A.; Bothun, G. D. (1983). "Very red, yet H I rich galaxies". The Astronomical Journal. 88: 577–582. Bibcode:1983AJ.....88..577S. doi:10.1086/113346.
  8. ^ Chung, A.; Van Gorkom, J.H.; Kenney, J.F.P.; Crowl, Hugh; Vollmer, B. (2009). "VLA Imaging of Virgo Spirals in Atomic Gas (VIVA). I. The Atlas and the H I Properties". The Astronomical Journal. 138 (6): 1741–1816. Bibcode:2009AJ....138.1741C. doi:10.1088/0004-6256/138/6/1741.
  9. ^ a b Koopmann, R.; Kenney, J. D. P. (2004). "Hα Morphologies and Environmental Effects in Virgo Cluster Spiral Galaxies". The Astrophysical Journal. 613 (2): 866–885. arXiv:astro-ph/0406243. Bibcode:2004ApJ...613..866K. doi:10.1086/423191.
  10. ^ a b Boselli, A.; Gavazzi, G. (2006). "Environmental Effects on Late-Type Galaxies in Nearby Clusters". The Publications of the Astronomical Society of the Pacific. 118 (842): 517–559. arXiv:astro-ph/0601108. Bibcode:2006PASP..118..517B. doi:10.1086/500691.
  11. ^ Moran, S. M.; Ellis, R. S.; Treu, T.; Treu, T.; Salim, S.; Rich, R. M.; Smith, G. P.; Kneib, J. P. (2006). "GALEX Observations of ``Passive Spirals in the Cluster Cl 0024+17: Clues to the Formation of S0 Galaxies". The Astrophysical Journal. 641 (2): L97–L100. arXiv:astro-ph/0603182. Bibcode:2006ApJ...641L..97M. doi:10.1086/504078.
  12. ^ a b Bekki, K.; Couch, W. J (2010). "Origin of optically passive spiral galaxies with dusty star-forming regions. Outside-in truncation of star formation?". Monthly Notices of the Royal Astronomical Society. 408 (1): L11–L15. arXiv:1007.2532. Bibcode:2010MNRAS.408L..11B. doi:10.1111/j.1745-3933.2010.00917.x.
  13. ^ a b Bekki, K.; Couch, W. J.; Shioya, Y. (2002). "Passive Spiral Formation from Halo Gas Starvation: Gradual Transformation into S0s". The Astrophysical Journal. 577 (2): 651–657. arXiv:astro-ph/0206207. Bibcode:2002ApJ...577..651B. doi:10.1086/342221.
  14. ^ Goto, T.; Okamura, S.; Sekiguchi, M.; Bernardi, M.; Brinkmann, J.; Gómez, P. L.; Harvanek, M.; Kleinman, S.; Krzesinky, J.; Long, D. (2003). "The Environment of Passive Spiral Galaxies in the SDSS". Publications of the Astronomical Society of Japan. 55 (4): 757–770. arXiv:astro-ph/0301303. Bibcode:2003PASJ...55..757G. doi:10.1093/pasj/55.4.757.
  15. ^ Crowl, H. H.; Kenney, J. D. P. (2008). "The Stellar Populations of Stripped Spiral Galaxies in the Virgo Cluster". The Astronomical Journal. 136 (4): 1623–1644. arXiv:0807.3747. Bibcode:2008AJ....136.1623C. doi:10.1088/0004-6256/136/4/1623.
  16. ^ Wolf, C.; Aragón-Salamanca, A.; Balogh, M.; Barden, M.; Bell, E. F.; Gray, M. E.; Peng, C. Y.; Bacon, D.; Barazza, F. D.; Böhm, A. (2009). "Optically-Passive Spirals: the Missing Link in Gradual Star Formation Suppression upon Cluster Infall". The Starburst-AGN Connection. ASP Conference Series , proceedings of the conference held 27–31 October 2008, at Shanghai Normal University, Shanghai, China. San Francisco: Astronomical Society of the Pacific. 408: 248. arXiv:0906.0306. Bibcode:2009ASPC..408..248W.
Coma Filament

Coma Filament is a galaxy filament. The filament contains the Coma Supercluster of galaxies and forms a part of the CfA2 Great Wall.

Lynx–Ursa Major Filament

Lynx–Ursa Major Filament (LUM Filament) is a galaxy filament.The filament is connected to and separate from the Lynx–Ursa Major Supercluster.

Messier 58

Messier 58 (also known as M58 and NGC 4579) is an intermediate barred spiral galaxy with a weak inner ring structure located within the constellation Virgo, approximately 68 million light-years away from Earth. It was discovered by Charles Messier on April 15, 1779 and is one of four barred spiral galaxies that appear in Messier's catalogue. M58 is one of the brightest galaxies in the Virgo Cluster. From 1779 it was arguably (though unknown at that time) the farthest known astronomical object until the release of the New General Catalogue in the 1880s and even more so the publishing of redshift values in the 1920s.

Messier 90

Messier 90 (also known as M90 and NGC 4569) is an intermediate spiral galaxy exhibiting a weak inner ring structure about 60 million light-years away in the constellation Virgo. It was discovered by Charles Messier in 1781.

Messier 91

Messier 91 (also known as NGC 4548 or M91) is a barred spiral galaxy located in the Coma Berenices constellation and is part of the Virgo Cluster of galaxies. M91 is about 63 million light-years away from the earth. It was the last of a group of eight nebulae discovered by Charles Messier in 1781.

Originally M91 was a missing Messier object in the catalogue as the result of a bookkeeping mistake by Messier. It was not until 1969 that amateur astronomer William C. Williams realized that M91 was NGC 4548, which was documented by William Herschel in 1784 (according to other sources, however, the nearby spiral galaxy NGC 4571 was also considered as a candidate for Messier 91 by him.)

NGC 3883

NGC 3883 is a large low surface brightness spiral galaxy located about 330 million light-years away in the constellation Leo. NGC 3883 has a prominent bulge but does host an AGN. The galaxy also has flocculent spiral arms in its disk. It was discovered by astronomer William Herschel on April 13, 1785 and is a member of the Leo Cluster.

NGC 4216

NGC 4216 is a metal-rich intermediate spiral galaxy located not far from the center of the Virgo Cluster of galaxies, roughly 55 million light-years away. It is seen nearly edge-on.

NGC 4450

NGC 4450 is a spiral galaxy in the constellation Coma Berenices.

NGC 4580

NGC 4580 is an unbarred spiral galaxy located about 70 million light-years away in the constellation Virgo. NGC 4580 is also classified as a LINER galaxy. It was discovered by astronomer William Herschel on February 2, 1786 and is a member of the Virgo Cluster.

NGC 4689

NGC 4689 is a spiral galaxy located about 54 million light-years away in the constellation of Coma Berenices. NGC 4689 is also classified as a LINER galaxy. NGC 4689 is inclined at an angle of about 36° which means that the galaxy is seen almost face-on to the Earth's line of sight. NGC 4689 was discovered by astronomer William Herschel on April 12, 1784. The galaxy is a member of the Virgo Cluster.

Perseus–Pegasus Filament

Perseus–Pegasus Filament is a galaxy filament containing the Perseus-Pisces Supercluster and stretching for roughly a billion light years (or over 300/h Mpc). Currently, it is considered to be one of the largest known structures in the universe. This filament is adjacent to the Pisces–Cetus Supercluster Complex.

Radio Galaxy Zoo

Radio Galaxy Zoo (RGZ) is an internet crowdsourced citizen science project that seeks to locate supermassive black holes in distant galaxies. It is hosted by the web portal Zooniverse. The scientific team want to identify black hole/jet pairs and associate them with the host galaxies. Using a large number of classifications provided by citizen scientists they hope to build a more complete picture of black holes at various stages and their origin. It was initiated in 2010 by Ray Norris in collaboration with the Zooniverse team, and was driven by the need to cross-identify the millions of extragalactic radio sources that will be discovered by the forthcoming Evolutionary Map of the Universe survey. RGZ is now led by scientists Julie Banfield and Ivy Wong. RGZ started operations on 17 December 2013.

Ursa Major Filament

Ursa Major Filament is a galaxy filament. The filament is connected to the CfA Homunculus, a portion of the filament forms a portion of the "leg" of the Homunculus.

Active nuclei
Energetic galaxies
Low activity
See also

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