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. This article is about a celestial body. ... Universe is a word derived from the Old French univers, which in turn comes from the Latin roots unus (one) and versus (a form of vertere, to turn). Physicists concept of the Universe is motivated[] by the attempt to describe the whole of space-time, including all matter and energy... An elliptical galaxy is a type of galaxy in the Hubble sequence characterized by the following physical properties: The giant elliptical galaxy NGC 4881 (the spherical glow at upper left) lies at the edge of the Coma Cluster of Galaxies. ... Galaxy groups and clusters are super-structures in the spread of galaxies of the cosmos. ...

Their small variance in luminosity, abundance and bright apparent magnitude make them excellent standard candles for distance determination. Luminosity has different meanings in several different fields of science. ... // Headline text HEY!! HOW ARE YOU ALL?? Its nice of you to come read this page. ...

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. In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... The galactic halo is a region of space surrounding spiral galaxies, including our galaxy, the Milky Way. ...

• Galactic cannibalism — Galaxies sink to the centre of the cluster due to dynamical friction and tidal stripping.
• Galactic merger — Rapid galactic mergers between several galaxies take place during cluster collapse.

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, where 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. Galactic cannabalism refers to the process by which a large galaxy, through tidal gravitational interactions with a companion, merges with that companion, resulting in a larger, often irregular galaxy. ... 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. ...

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). An elliptical galaxy is a type of galaxy in the Hubble sequence characterized by the following physical properties: The giant elliptical galaxy NGC 4881 (the spherical glow at upper left) lies at the edge of the Coma Cluster of Galaxies. ... Gérard Henri de Vaucouleurs (April 25, 1918–October 7, 1995) was a French-American astronomer. ... Surface brightness is a concept used in astronomy when describing extended astronomical objects such as galaxies and nebulae. ...

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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