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Information about Brightest Cluster Galaxy

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 lie at the bottom of the cluster potential well and close to the X-ray peak emission.

Their small variance in luminosity, abundance and bright apparent magnitude make them excellent standard candles for distance determination.

Formation scenarios for BCGs include:
  • Cooling flow—Star formation from the central cooling flow in high density cooling centres of X-ray cluster halos.
The study of accretion populations in BCGs carried out by McNamara and O’Connell (1989) has cast doubt over this theory and Motl et al. (2004) have since seen no evidence of cooling flows in radiative cooling clusters. The two remaining theories exhibit healthier prospects. It is possible to differentiate the cannibalism model from the merging model by considering the formation period of the BCGs. In the cannibalism model, there are numerous small galaxies present in the evolved cluster, whereas in the merging model, a hierarchical cosmological model is expected due to the collapse of clusters. The origin of the merging model is much earlier than the previous two.

BCGs are divided into various classes of galaxies: giant ellipticals (gE), D galaxies and cD galaxies, defined by Matthews, Morgan and Schmidt (1964). cD and D both exhibit an extended diffuse envelope surrounding an elliptical-like nucleus akin to regular ellipticals (Tonry 1987), the light profile of BCGs is described by a de Vaucouleurs surface brightness law (de Vaucouleurs 1948).

Sources

  • de Vaucouleurs, G. 1948 Annales d'Astrophysique, vol. 11, p.247
  • Dubinski, J. 1998 The Astrophysical Journal, vol. 502, p.141
  • Matthews, T., Morgan, W. W., & Schmidt, M. 1964 The Astrophysical Journal, vol. 140, p.35
  • McNamara, B. R. & O'Connell, R. W. 1989 The Astronomical Journal, vol. 98, p.2018
  • Motl, Patrick M.; Burns, Jack O.; Loken, Chris; Norman, Michael L., & Bryan, Greg 2004 The Astrophysical Journal, vol. 606, p.635
  • Tonry, J. L. 1987 International Astronomical Union Symposium, vol. 127, p.89
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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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The Universe is defined as the summation of all particles and energy that exist and the space-time in which all events occur. Based on observations of the portion of the Universe that is observable, physicists attempt to describe the whole of space-time, including all matter and
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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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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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Luminosity has different meanings in several different fields of science.

In photometry and color imaging

Main article: luminance
In photometry, luminosity
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The apparent magnitude (m) of a celestial body is a measure of its brightness as seen by an observer on Earth, normalized to the value it would have in the absence of the atmosphere.
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A cooling flow[1] occurs according to the theory that the intracluster medium (ICM) in the centres of galaxy clusters should be rapidly cooling at the rate of tens to thousands of solar masses per year.
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X-rays (or Röntgen rays) are a form of electromagnetic radiation with a wavelength in the range of 10 to 0.01 nanometers, corresponding to frequencies in the range 30 PHz to 30 EHz. X-rays are primarily used for diagnostic radiography and crystallography.
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The term galactic halo is used to denote an extended, roughly spherical component of a galaxy, which extends beyond the main, visible component. It can refer to any of several distinct components which share these properties:
  • the galactic spheroid (stars)

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Interacting galaxies (Colliding galaxies) are the result of one galaxy's gravity disturbing another galaxy. An example of minor interaction is a satellite galaxy disturbing the primary galaxy's spiral arms.
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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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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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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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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).
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Gérard Henri de Vaucouleurs (April 25, 1918–October 7, 1995) was a French astronomer.

Biography

Born in Paris, he had an early interest in amateur astronomy and received his undergraduate degree in 1939 at the Sorbonne in that city.
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Surface brightness is a concept used in astronomy when describing extended astronomical objects such as galaxies and nebulae.

General description

The apparent magnitude of an astronomical object is generally given as an integrated value - if a galaxy is quoted as having a
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