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RADIO GALAXIES.
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Explanations & hypotheses for these galaxies.... More...
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Paper Abstract:
Explanations & hypotheses for these galaxies.
Paper Introduction:
Cygnus A is the best known of the group of dumbbell galaxies. It consists of two nuclei in a common halo. It could be an extreme case of double galaxies. Galaxies are often radio sources. Cygnus A is so-called because of the constellation in which it is located. The galaxies at the center of radio star Cygnus A are photographed with the 200-inch telescope. These galaxies are practically at the limit of present optical observation. However, they are one of the strongest radio sources in the sky. Minkowski interprets Cygnus A as two galaxies, of about 100 billion stars each, in head-on collision - a catastrophe of tremendous magnitude. A different interpretation is that these two galaxies are the fragments of one original galaxy undergoing fission, that is, blowing apart in an explosion that must be just as violent as Minkowski's
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Some of the emission lines can be identified with forbiddenlines of various atoms. Examples: Cygnus A and Centaurus A. Englewood Cliffs: New Jersey: Prentice-Hall, 1962.Reddish, Vincent. Galaxies and Cosmology. Graham Smith at Cambridge obtained the firstaccurate radio position and sent his result to Walter Baade at the Mt.Wilson and Palomar Observatories. 149.Van Nostrand's Scientific Encyclopedia (Princeton: D. Thehypothesis of instability of some clusters of galaxies - radio galaxiessuch as this one might be single originally, possessing enormous andunexplained energy that is tearing them apart. Galaxies, Nuclei and Quasars. A number of ratio sources opticallyidentified with star-like objects in the sky. New York: Harper & Row, 1965.Lequeux, J. 146.Ibid., p. Normal Radio Quasar GalaxiesOptical Power (ergs/sec) 1 44 1 44 1 44Radio Power (ergs/sec) 1 38 1 43 1 44 At present it is hypothesized that these strange objects have shortlives, probably on the order of 1 5 years and that they are very strongemitters in the radio and visible regions and that they are probably smallgas clouds with low surface density.[viii] A Radio Galaxy. Any galaxy that exceeds thisradio power is considered to be a radio galaxy. The astonishing fact emerged that as muchenergy was being emitted in the form of radio waves as in the form ofvisible light. If Cygnus A is a singlegalaxy undergoing fission, it may be similar to Virgo A, which is ejectingmaterial that continue to emit radio waves for some time and mighteventually accumulate in a large plume far from the galaxy.[iii] The breakthrough came with the optical identification of Cygnus A,the first known radio source. Thefirst explanation that they are two galaxies in collision is no longeracceptable. Their visual spectrum is characterized by broad emission lines,thermal high radiation, very small linear diameters and variablebrightness. 36-37.Paul Hodge, Galaxies and Cosmology (New York: McGraw-Hill BookCo., 1966), pp. It has been suggestedthat the source of the energy may be gravitational. Further identifications also appeared to supportthe collision hypothesis, the sources associated with the galaxy NGC 5128in Centarus and NGC 12975, Minkowski found the gas to be moving at highspeeds, up to 3 km sec-1, relative to the stellar background belonging tothe elliptical, and this seemed to give support to the idea of a highvelocity collision.[iv] Many hypotheses exist for the explanation of radio galaxies. Twoother explanations relate to supernovae and gravitational collapse. Lequeux, Structure and Evolution of Galaxies (New York:Gordon and Breach Science Publishers, 1969), pp. It could be an extreme case ofdouble galaxies. Their spectrum ischaracterized by a non-thermal component, probably due to synchrontonradiation. Accretion doesnot work in general. Galaxies are often radio sources.[i] Cygnus A is so-called because of the constellation in which it is located.[ii] Thegalaxies at the center of radio star Cygnus A are photographed with the 2 -inch telescope. Cygnus A, a particularly luminous galaxy and a radiosource, has a total optical luminosity of 4 x 1 44 ergs/sec, of which abouthalf is contributed by emission lines. 116.Page, pp. Baade immediately made the now famousidentification with what seemed like a pair of colliding galaxies, distantsome half billion light-years. 1 4.----------------------- 8 94-95.Thorton Page, et al., Stars and Galaxies (Englewood Cliffs, NJ:Prentice-Hall, Inc., 1962), p. However, they are one of the strongest radio sourcesin the sky. Structure and Evolution of Galaxies. The amounts of energy theyemit in radio and light waves are more than can be generated by theconversion of matter to energy by nuclear reactions. Another that radio galaxies are antimatter is improbable asanti-matter is not generally believed to exist in space. Van Nostrand Co., Inc., 1968.-----------------------J. Shklovsky saidthat Cygnus A most likely was a generically related double galaxy. The radiation from radiogalaxies can go as high as 1 37 watts. Itconsists of two nuclei in a common halo. Any normal galaxy emits up to about 1 32 watts inthe radio wavelength between 1 MH2-1 6H2. The gravitational energy released insuch a collapse can be very considerable.[v] Some Strong Radio Sources[vi] Optical Radio Radio OpticalDistanceName Description Luminosity Diameter Diameter MpcVirgo Elliptical 5 x 1 41 1 ' 1 ' 11(M87) galaxy (ergs/sec) (3 " jet) (2 " jet) with "jet" from nucleusFornax A SO galaxy 6 x 1 4 3 ' 15' 1 (NGC with dust (double) 1316) lanes and outer ringCent- Peculiar 8 x 1 4 1 o 2 ' 4arus A Spiral (mul-(NGC tiple) 5128)Perseus Complex 1 42 4' 2' 7 A SO (with(NGC 1 " 1275) core)Hydra A Large SO 2 x 1 43 5 " '5 21 galaxyHercules Large SO 1.5 x 1 44 11 ' '2 61 A galaxy (double) with dust lanes and outer wispsCygnus A Double 5 x 1 44 1 6" 2" 22 galaxy (double)3 C 48 Quasi- 5 x 1 44 less than less than 11 stellar 1" "5 fluctua- tions in brightness The total amount of energy radiated by a normal luminous galaxy isabout 1 43 ergs/sec. This has not been proven.Related to supernova-rich nucleus is the hypothesis that stars of highmass, such as 1 6 solar mass, form in the galaxy's nucleus and then evolverapidly until their nuclei collapse. 1474.Vincent Reddish, Evolution of the Galaxies (Edinburgh andLondon: Oliver and Boyd, 1967), p. The radio emission from Cygnus A,for comparison, is 3 x 1 44 ergs/sec. The opticalcounterpart of radio source Cygnus A is a pair of overlapping bright spotscentered two inches apart and surrounded by a large dim halo. 1453.Ibid., p. Cygnus A is the best known of the group of dumbbell galaxies. A different interpretation is that these two galaxies are thefragments of one original galaxy undergoing fission, that is, blowing apartin an explosion that must be just as violent as Minkowski's collision.Neither interpretation has been proved as yet. These galaxies are practically at the limit of presentoptical observation. That galaxies are in the process of formation fromintergalactic material cannot apply to the majority of radio galaxies.Magnetic energy might be released if spiral arms wind up so tightly thatdischarges occur in the center. The emission lines in many of their objectsexhibit very large red shifts. He also found lines of more stripped atoms, for example,NeV, showing that the system contained a great deal of hot gas. Edinburgh and London: Oliver and Boyd, 1967.Van Nostrand's Scientific Encyclopedia. We do not knowwhether the quasars are young or old objects - the birth of new galaxies orthe death of old ones.[x] Endnotes BibliographyHodge, Paul W. Ifstars are very densely packed in the nucleus of a galaxy, then a supernovaexplosion there might set off a chain reaction. Theappearance was interpreted at first as two colliding galaxies that hadinterpenetrated until their centers were only a few light years apart. In 196 , I. Stars and Galaxies. This requires large angular momentum andconsiderable gas, neither of which is present in all radio galaxies. Minkowski found a considerable fraction of the light was inemission lines, such as the 3727 line of OII and the doublet of OIII at4959 and 5 7A. A number of radio sources havecharacteristics so much alike that they may represent a class of ratherfrequent occurrence. Theheating process was taken at that time to come from the collision of thetwo apparent galaxies. Thecollision hypothesis for this and similar galaxies was favorably receivedby most astronomers until 196 when it began improbable that such strongemissions could be produced by collision. VanNostrand Co., Inc., 1968), p. During recentyears very powerful radio emissions have been discovered to be coming fromsome very distant galaxies of small angular diameter - their images onphotographs are almost as small as those of stars, and they have beencalled quasi-stellar radio sources of quasars. 128-129.Fred Hoyle, Galaxies, Nuclei and Quasars (New York: Harper andRow, 1965), pp. New York: Gordon and Breach Science Publishers, 1969.Page, Thorton, et al. Exampleof an irregular galaxy is M82, source of intensive non-thermalradiation.[ix] In one respect the future of galaxies is uncertain. The range of emitted energies atradio wavelengths is from 1 4 to 1 45 ergs/sec for various objects.[vii] Quasi-stellar radio objects. Their objects have great optical and radiopower. Princeton: D. 151-152.Ibid., p. Severalgalaxies in the early stages of explosion are already recognized. Minkowski interprets Cygnus A as two galaxies, of about 1 billion stars each, in head-on collision - a catastrophe of tremendousmagnitude. S. New York: McGraw-Hill Book Co., 1966.Hoyle, Fred. Evolution of the Galaxies. They might be splittinginto a pair of galaxies with the production of intense radiation.
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