External links
- "The Morphs" Durham University, United Kingdom
The Morphs collaboration was a coordinated study to determine the morphologies of galaxies in distant clusters and to investigate the evolution of galaxies as a function of environment and epoch. Eleven clusters were examined and a detailed ground-based and space-based study was carried out.
The project was begun in 1997 based upon the earlier observations by two groups [1] [2] using data from images derived from the pre-refurbished Hubble Space Telescope. It was a collaboration of Alan Dressler and Augustus Oemler Jr., at Observatory of the Carnegie Institute of Washington, Warrick J. Couch at the University of New South Wales, Richard Ellis at Caltech, Bianca Poggianti at the University of Padua, Amy Barger at the University of Hawaii's Institute for Astronomy, Harvey Butcher at ASTRON, and Ray M. Sharples and Ian Smail at Durham University. Results were published through 2000.
The collaboration sought answers to the differences in the origins of the various galaxy types — elliptical, lenticular, and spiral. The studies found that elliptical galaxies were the oldest and formed from the violent merger of other galaxies about two to three billion years after the Big Bang. Star formation in elliptical galaxies ceased about that time. On the other hand, new stars are still forming in the spiral arms of spiral galaxies. Lenticular galaxies (SO) are intermediate between the first two. They contain structures similar to spiral arms, but devoid of the gas and new stars of the spiral galaxies. Lenticular galaxies are the prevalent form in rich galaxy clusters, which suggests that spirals may be transformed into lenticular galaxies as time progresses. The exact process may be related to high galactic density, or to the total mass in a rich cluster's central core. The Morphs collaboration found that one of the principal mechanisms of this transformation involves the interaction among spiral galaxies, as they fall toward the core of the cluster.
The Inamori Magellan Areal Camera and Spectrograph (IMACS) Cluster Building Survey is the follow-on project to the Morphs collaboration. [3]
A galaxy is a system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity. The word is derived from the Greek galaxias (γαλαξίας), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. Galaxies, averaging an estimated 100 billion stars, range in size from dwarfs with less than a hundred million stars, to the largest galaxies known – supergiants with one hundred trillion stars, each orbiting its galaxy's center of mass. Most of the mass in a typical galaxy is in the form of dark matter, with only a few percent of that mass visible in the form of stars and nebulae. Supermassive black holes are a common feature at the centres of galaxies.
The Hubble sequence is a morphological classification scheme for galaxies published by Edwin Hubble in 1926. It is often colloquially known as the Hubble tuning-fork diagram because the shape in which it is traditionally represented resembles a tuning fork. It was invented by John Henry Reynolds and Sir James Jeans.
An elliptical galaxy is a type of galaxy with an approximately ellipsoidal shape and a smooth, nearly featureless image. They are one of the four main classes of galaxy described by Edwin Hubble in his Hubble sequence and 1936 work The Realm of the Nebulae, along with spiral and lenticular galaxies. Elliptical (E) galaxies are, together with lenticular galaxies (S0) with their large-scale disks, and ES galaxies with their intermediate scale disks, a subset of the "early-type" galaxy population.
Spiral galaxies form a class of galaxy originally described by Edwin Hubble in his 1936 work The Realm of the Nebulae and, as such, form part of the Hubble sequence. Most spiral galaxies consist of a flat, rotating disk containing stars, gas and dust, and a central concentration of stars known as the bulge. These are often surrounded by a much fainter halo of stars, many of which reside in globular clusters.
The Virgo Cluster is a large cluster of galaxies whose center is 53.8 ± 0.3 Mly away in the constellation Virgo. Comprising approximately 1,300 member galaxies, the cluster forms the heart of the larger Virgo Supercluster, of which the Local Group is a member. The Local Group actually experiences the mass of the Virgo Supercluster as the Virgocentric flow. It is estimated that the Virgo Cluster's mass is 1.2×1015M☉ out to 8 degrees of the cluster's center or a radius of about 2.2 Mpc.
A lenticular galaxy is a type of galaxy intermediate between an elliptical and a spiral galaxy in galaxy morphological classification schemes. It contains a large-scale disc but does not have large-scale spiral arms. Lenticular galaxies are disc galaxies that have used up or lost most of their interstellar matter and therefore have very little ongoing star formation. They may, however, retain significant dust in their disks. As a result, they consist mainly of aging stars. Despite the morphological differences, lenticular and elliptical galaxies share common properties like spectral features and scaling relations. Both can be considered early-type galaxies that are passively evolving, at least in the local part of the Universe. Connecting the E galaxies with the S0 galaxies are the ES galaxies with intermediate-scale discs.
Centaurus A is a galaxy in the constellation of Centaurus. It was discovered in 1826 by Scottish astronomer James Dunlop from his home in Parramatta, in New South Wales, Australia. There is considerable debate in the literature regarding the galaxy's fundamental properties such as its Hubble type and distance. NGC 5128 is one of the closest radio galaxies to Earth, so its active galactic nucleus has been extensively studied by professional astronomers. The galaxy is also the fifth-brightest in the sky, making it an ideal amateur astronomy target. It is only visible from the southern hemisphere and low northern latitudes.
Galaxy morphological classification is a system used by astronomers to divide galaxies into groups based on their visual appearance. There are several schemes in use by which galaxies can be classified according to their morphologies, the most famous being the Hubble sequence, devised by Edwin Hubble and later expanded by Gérard de Vaucouleurs and Allan Sandage. However, galaxy classification and morphology are now largely done using computational methods and physical morphology.
Messier 32 is a dwarf "early-type" galaxy about 2,650,000 light-years (810,000 pc) from the Solar System, appearing in the constellation Andromeda. M32 is a satellite galaxy of the Andromeda Galaxy (M31) and was discovered by Guillaume Le Gentil in 1749.
Messier 85 is a lenticular galaxy, or elliptical galaxy for other authors, in the Coma Berenices constellation. It is 60 million light-years away, and it is estimated to be 125,000 light-years across.
Messier 89 is an elliptical galaxy in the constellation Virgo. It was discovered by Charles Messier on March 18, 1781. M89 is a member of the Virgo Cluster of galaxies.
Amy J. Barger is an American astronomer and Henrietta Leavitt Professor of Astronomy at the University of Wisconsin–Madison. She is considered a pioneer in combining data from multiple telescopes to monitor multiple wavelengths and in discovering distant galaxies and supermassive black holes, which are outside of the visible spectrum. Barger is an active member of the International Astronomical Union.
A dwarf spiral galaxy is the dwarf version of a spiral galaxy. Dwarf galaxies are characterized as having low luminosities, small diameters, low surface brightnesses, and low hydrogen masses. The galaxies may be considered a subclass of low-surface-brightness galaxies.
IC 1101 is a class S0 supergiant (cD) lenticular galaxy at the center of the Abell 2029 galaxy cluster. It has an isophotal diameter at about 123.65 to 169.61 kiloparsecs. It possesses a diffuse core which is the largest known core of any galaxy to date, and contains a supermassive black hole, one of the largest discovered. The galaxy is located at 354.0 megaparsecs from Earth. The galaxy was discovered on 19 June 1790, by the British astronomer William Herschel.
Harvey Raymond Butcher III is an astronomer who has made significant contributions in observational astronomy and instrumentation which have advanced understanding of the formation of stars and of the universe. He received a B.Sc. in Astrophysics from the California Institute of Technology in 1969, where he contributed to the development of advanced infrared spectrometry applied in the first survey of the sky at infrared wavelengths.
The Butcher–Oemler Effect is a scientific hypothesis suggesting the cores of galaxy clusters at intermediate redshift contain a larger fraction of blue galaxies than do the cores of low redshift clusters. The claim was first put forward by Harvey Butcher and Augustus Oemler in a 1978 Astrophysical Journal paper.
Alan Michael Dressler is an American astronomer at the Carnegie Institution for Science of Washington, D.C. Among his works is the popularization Voyage To The Great Attractor: Exploring Intergalactic Space.
Warrick John Couch is an Australian professional astronomer. He is currently a professor at Swinburne University of Technology in Melbourne. He was previously the Director of Australia's largest optical observatory, the Australian Astronomical Observatory (AAO). He was also the president of the Australian Institute of Physics (2015–2017), and a non-executive director on the Board of the Giant Magellan Telescope Organization. He was a founding non-executive director of Astronomy Australia Limited.
The following outline is provided as an overview of and topical guide to galaxies:
