Polar-ring galaxy: Difference between revisions
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[[Image:NGC 4650A I HST2002.jpg|right|thumb|140px|[[NGC 4650A]], an example of a polar-ring galaxy. Credit:[[Hubble Space Telescope]]/[[NASA]]/[[ESA]].]] | |||
[[Image:NGC 4650A I HST2002.jpg|right|thumb|140px|[[NGC 4650A]] | |||
A '''polar-ring galaxy''' is a type of [[galaxy]] in which an outer ring of gas and stars rotates over the poles of the galaxy.<ref name="binneymerrifield1998">{{cite book | A '''polar-ring galaxy''' is a type of [[galaxy]] in which an outer ring of gas and stars rotates over the poles of the galaxy.<ref name="binneymerrifield1998">{{cite book | ||
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| publisher=Princeton University Press | | publisher=Princeton University Press | ||
| location=Princeton, New Jersey | | location=Princeton, New Jersey | ||
| id=ISBN 0-691-00402-1}}</ref> | | id=ISBN 0-691-00402-1}}</ref> These polar rings are thought to form when two galaxies [[gravitational interaction|gravitationally interact]] with each other. One possibility is that a material is tidally stripped from a passing galaxy to produce the polar ring seen in the polar-ring galaxy. The other possibility is that a smaller galaxy collides orthogonally with the larger galaxy, with the smaller galaxy effectively forming the polar ring structure.<ref name="schweizeretal1983">{{cite journal | ||
| author= B. C. Whitmore, | | author=F. Schweizer, B. C. Whitmore, V. C. Rubin | ||
| title= | | title=Colliding and merging galaxies. II - S0 galaxies with polar rings | ||
| journal=Astronomical Journal | | journal=Astronomical Journal | ||
| year= | | year=1983 | ||
| volume= | | volume=88 | ||
| pages= | | pages=909-925 | ||
| url=http://adsabs.harvard.edu/abs/ | | url=http://adsabs.harvard.edu/abs/1983AJ.....88..909S}}</ref> | ||
The first four galaxies that were identified as polar-ring galaxies were [[NGC 2685]],<ref name="schectergunn1978">{{cite journal | The first four galaxies that were identified as polar-ring galaxies were [[NGC 2685]],<ref name="schectergunn1978">{{cite journal | ||
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| volume=88 | | volume=88 | ||
| pages=909-925 | | pages=909-925 | ||
| url=http://adsabs.harvard.edu/abs/1983AJ.....88..909S}}</ref> and [[ESO 415 -G26]].<ref name="whitmoreetal1987" /> While these galaxies have been extensively studied, many other polar-ring galaxies have since been identified.<ref name="whitmoreetal1990"/> | | url=http://adsabs.harvard.edu/abs/1983AJ.....88..909S}}</ref> and [[ESO 415 -G26]].<ref name="whitmoreetal1987" /> While these galaxies have been extensively studied, many other polar-ring galaxies have since been identified.<ref name="whitmoreetal1990">{{cite journal | ||
| author= B. C. Whitmore, R. A. Lucas, D. B. McElroy, T. Y. Steiman-Cameron, P. D. Sackett, R. P. Olling | |||
| title=New observations and a photographic atlas of polar-ring galaxies | |||
| journal=Astronomical Journal | |||
| year=1990 | |||
| volume=100 | |||
| pages=1489-1522, 1721-1755 | |||
| url=http://adsabs.harvard.edu/abs/1990AJ....100.1489W}}</ref> Polar rings may be found around 0.5% of all nearby [[lenticular galaxies]], and it is possible that 5% of lenticular galaxies may have had polar rings at some point during their lifetimes.<ref name="whitmoreetal1990"/> | |||
==References== | ==References== | ||
Revision as of 09:31, 11 May 2007
A polar-ring galaxy is a type of galaxy in which an outer ring of gas and stars rotates over the poles of the galaxy.[1] These polar rings are thought to form when two galaxies gravitationally interact with each other. One possibility is that a material is tidally stripped from a passing galaxy to produce the polar ring seen in the polar-ring galaxy. The other possibility is that a smaller galaxy collides orthogonally with the larger galaxy, with the smaller galaxy effectively forming the polar ring structure.[2]
The first four galaxies that were identified as polar-ring galaxies were NGC 2685,[3] NGC 4650A,[4][5] A 0136 -0801,[2] and ESO 415 -G26.[5] While these galaxies have been extensively studied, many other polar-ring galaxies have since been identified.[6] Polar rings may be found around 0.5% of all nearby lenticular galaxies, and it is possible that 5% of lenticular galaxies may have had polar rings at some point during their lifetimes.[6]
References
- ↑ James Binney, Michael Merrifield (1998). Galactic Astronomy. Princeton, New Jersey: Princeton University Press. ISBN 0-691-00402-1.
- ↑ 2.0 2.1 F. Schweizer, B. C. Whitmore, V. C. Rubin (1983). "Colliding and merging galaxies. II - S0 galaxies with polar rings". Astronomical Journal 88: 909-925. http://adsabs.harvard.edu/abs/1983AJ.....88..909S.
- ↑ P. L. Schecter, J. E. Gunn (1978). "NGC 2685 - Spindle or pancake". Astronomical Journal 83: 1360-1362. http://adsabs.harvard.edu/abs/1978AJ.....83.1360S.
- ↑ J. L. Sérsic (1967). "Southern Peculiar Galaxies III". Zeitschrift für Astrophysik 67: 306-311. http://adsabs.harvard.edu/abs/1967ZA.....67..306S.
- ↑ 5.0 5.1 B. C. Whitmore, D. B. McElroy, F. Schweizer (1987). "The shape of the dark halo in polar-ring galaxies". Astrophysical Journal 314: 439-456. http://adsabs.harvard.edu/abs/1987ApJ...314..439W.
- ↑ 6.0 6.1 B. C. Whitmore, R. A. Lucas, D. B. McElroy, T. Y. Steiman-Cameron, P. D. Sackett, R. P. Olling (1990). "New observations and a photographic atlas of polar-ring galaxies". Astronomical Journal 100: 1489-1522, 1721-1755. http://adsabs.harvard.edu/abs/1990AJ....100.1489W.