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Information about Giant Diffuse Galaxy

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The cluster of galaxies known as Abell S0740, taken by NASA's Hubble telescope. It is around 450 million light years away
A giant diffuse galaxy is a supermassive, elliptical galaxy that is usually located in the centre of a cluster of galaxies. The term is often contracted to cD galaxies[1] or BCGs (for brightest cluster galaxies).[2] Giant diffuse galaxies are on average about 10 times more luminous than "regular" galaxies, and many times larger than a normal elliptical galaxy - some having diameters of over 6 million light years (the Milky Way, in contrast, is thought to be only around 100 thousand light years across).<ref name="curious" /> Giant diffuse galaxies are usually the largest galaxies in their respective clusters.

Growth

cD galaxies are believed to grow larger by accreting or merging with other galaxies,<ref name="curious" /> and this "cannibalising" of smaller galaxies has actually been observed. Because giant diffuse galaxies exist at the centres of galaxy clusters, there are many galaxies to "feed" on. This mode of growth leads to the overwhelming diameter and luminosity of the cDs.<ref name="curious" /> However, there is usually a perimeter around the cD galaxy in which no smaller galaxies exist, because they have already been accreted. There are always remains of "eaten" galaxies, appearing as a diffuse halo of gas and dust.<ref name="curious" /> This halo can be up to 3 million light years in diameter.[3]

Dynamic friction

Dynamic friction is the catalytic factor in the formation of the cD galaxy at the centre of a cluster.[4] This process begins when the motion of a large galaxy in a cluster attracts smaller galaxies into a wake behind it. This trail of smaller galaxies effectively slows the large galaxy, and, losing kinetic energy, it will gradually fall towards 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.<ref name="astro" /> A giant diffuse galaxy will result from this accumulation.<ref name="astro" /> The nuclei of merged galaxies often remain recognizable long after the mergers.

See also

References

1. ^ T. Matthews, W. W. Morgan, M. Schmidt (1964 ). "A Discussion of Galaxies Identified With Radio Sources". The Astrophysical Journal 140 : 35-49. Retrieved on 2007-04-03. 
2. ^ Curious About Astronomy?. Retrieved on 28 March, 2007.
3. ^ Cosmos: The SAO Encyclopedia: cD galaxies. Retrieved on 29 March, 2007.
4. ^ cD galaxies and cannibalism. Retrieved on 29 March, 2007.
elliptical galaxy is a galaxy belonging to one of the three main classes of galaxy originally described by Edwin Hubble in his 1936 work “The Realm of the Nebulae”[1] and, as such, forms part of the Hubble sequence.
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A galaxy (from the Greek root γαλαξίας, meaning "milky", a reference to our own Milky Way) is a massive, gravitationally bound system consisting of stars, an interstellar medium of gas and dust, and dark matter.
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Galaxy groups and clusters are the largest gravitationally-bound objects. 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
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Brightest cluster galaxies (BCGs) are the brightest and most massive galaxies in the universe, emitting purely photospheric light. They are generally elliptical galaxies which lie close to the host galaxy cluster kinematic centre, and except for those undergoing major mergers, they
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Luminous may refer to:
  • Luminosity, a scientific term referring to different things depending on the field in which it is used
  • Luminous (story collection), a short story collection by Greg Egan
  • Luminous paint, paint that glows in the dark

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1 light-year =
SI units
01015 m 01012 km
Astronomical units
0103 AU 0 pc
US customary / Imperial units
01015 ft 01012 mi
A light-year or lightyear (symbol:
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Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias) sometimes referred to simply as "the Galaxy"), is a barred spiral galaxy that lies with the Local Group of galaxies
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Galaxy mergers can happen when two (or more) galaxies collide. It is the most violent type of galaxy interaction. While this does not involve stars or star systems actually colliding, due to the vast distances between stars in most circumstances, the gravitational interactions
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Gas is one of the four major states of matter, consisting of freely moving atoms or molecules without a definite shape. Compared to the solid and liquid states of matter a gas has lower density and a lower viscosity.
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Dust is a general name for minute solid particles with diameters less than 500 micrometers. On Earth, dust occurs in the atmosphere from various sources; soil dust lifted up by wind, volcanic eruptions, and pollution are some examples.
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Dynamical friction is a term in astrophysics related to loss of momentum and kinetic energy of moving bodies through a gravitational interaction with surrounding matter in space.
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kinetic energy of an object is the extra energy which it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its current velocity.
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STAR is an acronym for:

Organizations:
  • Society for Telescopy, Astronomy, and Radio, a non-profit astronomy club in New Jersey
  • Special Tasks and Rescue or Special Tactics and Response, synonyms for SWAT

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Gas is one of the four major states of matter, consisting of freely moving atoms or molecules without a definite shape. Compared to the solid and liquid states of matter a gas has lower density and a lower viscosity.
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Dust is a general name for minute solid particles with diameters less than 500 micrometers. On Earth, dust occurs in the atmosphere from various sources; soil dust lifted up by wind, volcanic eruptions, and pollution are some examples.
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In astrophysics and cosmology, dark matter is hypothetical matter of unknown composition that does not emit or reflect enough electromagnetic radiation to be observed directly, but whose presence can be inferred from gravitational effects on visible matter.
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This is a list of notable galaxies.
  • Abell 1835 IR1916
  • AM 0644-741
  • Andromeda Galaxy (M31/NGC 224)
  • Andromeda I
  • Antennae Galaxies (NGC 4038/NGC 4039)
  • Aquarius Dwarf
  • Black Eye Galaxy (M64/NGC 4826)
  • Bode's Galaxy (M81/NGC 3031)

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