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| pages = 207
| pages = 207
| bibcode = 2002IAUS..207..745G
| bibcode = 2002IAUS..207..745G
|arxiv = astro-ph/0109052 }}</ref> These clusters are referred to as "super" due to the fact that they are relatively more luminous and contain more mass than other young star clusters.<ref name=":0">{{Cite journal|last=Johnson|first=Kelsey|year=|title=The Properties of Super Star Clusters In A Sample of Starburst Galaxies|url=https://pdfs.semanticscholar.org/998f/66fe062452fb32657a42a06c4818c2d5dd64.pdf|journal=|volume=|pages=|via=}}</ref> The SSC, however, does not have to physically be larger that other clusters of lower mass and luminosity.<ref name=":1">{{Cite journal|last=de Grijs|first=Richard|year=|title="Super" Star Clusters|url=http://astro-expat.info/deGrijsJD11.pdf|journal=|volume=|pages=|via=}}</ref> They typically contain a very large number of [[T Tauri Star|young]], [[OB star|massive stars]] that ionize a surrounding [[H II region]], similar to the [[Milky Way|Milky Way Galaxy]]'s so-called "Ultra dense H II regions (UDHIIs)".<ref name="kobulnicky99">{{cite journal
|arxiv = astro-ph/0109052 }}</ref> These clusters are referred to as "super" due to the fact that they are relatively more luminous and contain more mass than other young star clusters.<ref name=":0">{{Cite journal|last=Johnson|first=Kelsey|year=|title=The Properties of Super Star Clusters In A Sample of Starburst Galaxies|url=https://pdfs.semanticscholar.org/998f/66fe062452fb32657a42a06c4818c2d5dd64.pdf|journal=|volume=|pages=|via=}}</ref> The SSC, however, does not have to physically be larger that other clusters of lower mass and luminosity.<ref name=":1">{{Cite journal|last=de Grijs|first=Richard|year=|title="Super" Star Clusters|url=http://astro-expat.info/deGrijsJD11.pdf|journal=|volume=|pages=|via=}}</ref> They typically contain a very large number of [[T Tauri Star|young]], [[OB star|massive stars]] that ionize a surrounding [[H II region|HII region]] (however, SSC's do not always have to be inside an HII region), similar to the [[Milky Way|Milky Way Galaxy]]'s so-called "Ultra dense HII regions (UDHIIs)".<ref name="kobulnicky99">{{cite journal
| last = Kobulnicky
| last = Kobulnicky
| first = Henry A.
| first = Henry A.
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| bibcode = 1999ApJ...527..154K
| bibcode = 1999ApJ...527..154K
| doi = 10.1086/308075
| doi = 10.1086/308075
|arxiv = astro-ph/9907233 }}</ref> An SSC's [[H II region]] is in turn surrounded by a cocoon of [[cosmic dust|dust]]. In many cases, the stars and the H II regions will be invisible to optical observations due to high levels of [[extinction (astronomy)|extinction]]. As a result, the youngest SSCs are best observed in [[radio astronomy|radio]] and [[infrared astronomy|infrared]].<ref name="johnson04">{{cite journal
|arxiv = astro-ph/9907233 }}</ref> An SSC's [[H II region]] is in turn surrounded by a cocoon of [[cosmic dust|dust]]. In many cases, the stars and the HII regions will be invisible to optical observations due to high levels of [[extinction (astronomy)|extinction]]. As a result, the youngest SSCs are best observed in [[radio astronomy|radio]] and [[infrared astronomy|infrared]].<ref name="johnson04">{{cite journal
| author = Johnson
| author = Johnson
| date = 2004
| date = 2004
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| volume = 527
| volume = 527
| bibcode = 2004ASPC..322..339J
| bibcode = 2004ASPC..322..339J
|arxiv = astro-ph/0405125 }}</ref> SSCs, such as Westerlund 1 (Wd1), have been found in the Milky Way,<ref>{{Cite news|url=http://www.universetoday.com/10360/super-star-cluster-discovered-in-our-own-milky-way/|title=Super Star Cluster Discovered in Our Own Milky Way - Universe Today|date=2005-03-22|access-date=2017-02-10|language=en-US|newspaper=Universe Today}}</ref> however, most have been observed in farther regions of the universe. Specifically, SSCs have been seen to form in the interactions between galaxies and regions of high amounts of star formation with high enough pressures to satisfy the properties needed for a star cluster to form.<ref name=":0" />
|arxiv = astro-ph/0405125 }}</ref> SSCs, such as Westerlund 1 (Wd1), have been found in the Milky Way,<ref>{{Cite news|url=http://www.universetoday.com/10360/super-star-cluster-discovered-in-our-own-milky-way/|title=Super Star Cluster Discovered in Our Own Milky Way - Universe Today|date=2005-03-22|access-date=2017-02-10|language=en-US|newspaper=Universe Today}}</ref> however, most have been observed in farther regions of the universe.


Specifically, SSCs have been seen to form in the interactions between galaxies and regions of high amounts of star formation with high enough pressures to satisfy the properties needed for a star cluster to form.<ref name=":0" /> These regions can include newer galaxies, such as dwarf [[Starburst galaxy|starburst galaxies]]<ref>{{Cite journal|last=Hunter|first=Deidre A.|last2=O'Connell|first2=Robert W.|year=|title=The Star Clusters in the Starburst Irregular Galaxy NGC 1569|url=|journal=The Astronomical Journal|volume=20|pages=2383-2401|doi=10.1086/316810|via=}}</ref>, arms of a spiral galaxy that have a high star formation rate, and in the merging of galaxies. In an Astronomical Journal published in 1996, using pictures taken in the UV spectrum by the Hubble Space Telescopes of star-forming rings in five different barred galaxies, numerous star clusters were found in clumps within the rings which had high rates of star formation. It was found that these clusters had masses of about <math>10^3</math>M<sub>☉</sub> to <math>10^5</math>M<sub>☉</sub>, ages of about 100 Myr, and radii of about 5 pc, and are though to evolve into globular clusters later in their lifetimes.<ref>{{Cite journal|last=Maoz|first=D.|last2=Barth|first2=A. J.|last3=Sternberg|first3=A.|last4=Filippenko|first4=A. V.|last5=Ho|first5=L. C.|last6=Macchetto|first6=F. D.|last7=Rix|first7=H.-W.|last8=Schneider|first8=D. P.|date=1996-06-01|title=Hubble Space Telescope Ultraviolet Images of Five Circumnuclear Star-Forming Rings|url=http://adsabs.harvard.edu/abs/1996AJ....111.2248M|journal=The Astronomical Journal|volume=111|pages=2248|doi=10.1086/117960|issn=0004-6256}}</ref> These are the properties of SSC's.

== Characteristics and Properties ==
The typical characteristics of SSCs:
The typical characteristics of SSCs:
* Large [[electron]] [[Density|densities]] <math>n_e=10^3</math>–<math>10^6</math> cm<math>^{-3}</math>
* Large [[electron]] [[Density|densities]] <math>n_e=10^3</math>–<math>10^6</math> cm<math>^{-3}</math> (this is a property of the HII region associated with the SSC)
* [[Pressure]]s <math>P/</math>[[Boltzmann's constant|<math>k_b</math>]]<math>=10^7</math>–<math>10^{10}</math> [[Kelvin|K]] cm<math>^{-3}</math>.<ref name="johnson04" />
* [[Pressure]]s <math>P/</math>[[Boltzmann's constant|<math>k_b</math>]]<math>=10^7</math>–<math>10^{10}</math> [[Kelvin|K]] cm<math>^{-3}</math>.<ref name="johnson04" /> (this is a property of the HII region associated with the SSC)
* Mass <math>\gtrsim</math> <math>10^5</math>M<sub>☉</sub><ref name=":0" />
* Mass <math>\gtrsim</math> <math>10^5</math>M<sub>☉</sub><ref name=":0" />
* Radius ≈ 5 pc ≈ <math>10^{19}</math> cm<ref name=":0" />
* Radius ≈ 5 pc ≈ <math>10^{19}</math> cm<ref name=":0" />
* Age ≈ 100 Myr<ref name=":0" /> (Although other sources state that observed SSCs have an age of 1 Gyr<ref name=":1" />)
* Age ≈ 100 Myr<ref name=":0" /> (Although other sources state that observed SSCs have an age of 1 Gyr<ref name=":1" />)

== Hubble Space Telescope Contributions ==
Given the relatively small size of SSC's compared to their host galaxies, astronomers have had trouble finding them in the past due to the limited resolution of the telescopes at the time. With the introduction of the [[Hubble Space Telescope|Hubble Space Telescope (HST)]] in the 1990's, finding SSC's as well as other astronomical objects became much easier thanks to the higher resolution of the HST (angular resolution of ~1/10 arcsecond<ref>{{Cite web|url=https://www.spacetelescope.org/about/faq/|title=FAQ - Frequently Asked Questions|last=information@eso.org|website=www.spacetelescope.org|language=en|access-date=2017-03-18}}</ref>). This not only allowed astronomers to see SSC's, but also allowed for them to measure their properties as well as the properties of the individual stars within the SSC. Recently, a massive star, Westerlund 1-26, was discovered in the SSC Westerlund 1 in the Milky Way. The radius of this star is thought to larger than the radius of Jupiter's orbit around the Sun.<ref>{{Cite web|url=http://www.upi.com/Science_News/2017/03/10/Hubble-finds-young-super-star-cluster-giant-star/3391489160736/|title=Hubble finds young super star cluster, giant star|last=Wallace|first=Amy|date=March 10, 2017|website=UPI|archive-url=|archive-date=|dead-url=|access-date=}}</ref>


==List==
==List==
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| [[Westerlund 1]] (Wd1)
| [[Westerlund 1]] (Wd1)
| [[Milky Way|Milky Way Galaxy]]
| [[Milky Way|Milky Way Galaxy]]
| First SSC discovered in the [[Milky Way|Milky Way Galaxy]].
| First SSC discovered in the [[Milky Way|Milky Way Galaxy]]. This SSC was discovered by the HST.
| <ref>{{cite journal|doi=10.1051/0004-6361:20042413|title=On the massive stellar population of the super star cluster Westerlund 1|journal=Astronomy and Astrophysics|volume=434|issue=3|pages=949|year=2005|last1=Clark|first1=J. S.|last2=Negueruela|first2=I.|last3=Crowther|first3=P. A.|last4=Goodwin|first4=S. P.|bibcode=2005A&A...434..949C|arxiv = astro-ph/0504342 }}</ref>
| <ref>{{cite journal|doi=10.1051/0004-6361:20042413|title=On the massive stellar population of the super star cluster Westerlund 1|journal=Astronomy and Astrophysics|volume=434|issue=3|pages=949|year=2005|last1=Clark|first1=J. S.|last2=Negueruela|first2=I.|last3=Crowther|first3=P. A.|last4=Goodwin|first4=S. P.|bibcode=2005A&A...434..949C|arxiv = astro-ph/0504342 }}</ref>
|[[File:Westerlund 1.jpg|alt=Westerlund 1|center|thumb|Westerlund 1]]
|[[File:Westerlund 1.jpg|alt=Westerlund 1|center|thumb|Westerlund 1]]

Revision as of 23:54, 18 March 2017

A super star cluster (SSC) is a very massive young open cluster that is thought to be the precursor of a globular cluster.[1] These clusters are referred to as "super" due to the fact that they are relatively more luminous and contain more mass than other young star clusters.[2] The SSC, however, does not have to physically be larger that other clusters of lower mass and luminosity.[3] They typically contain a very large number of young, massive stars that ionize a surrounding HII region (however, SSC's do not always have to be inside an HII region), similar to the Milky Way Galaxy's so-called "Ultra dense HII regions (UDHIIs)".[4] An SSC's H II region is in turn surrounded by a cocoon of dust. In many cases, the stars and the HII regions will be invisible to optical observations due to high levels of extinction. As a result, the youngest SSCs are best observed in radio and infrared.[5] SSCs, such as Westerlund 1 (Wd1), have been found in the Milky Way,[6] however, most have been observed in farther regions of the universe.

Specifically, SSCs have been seen to form in the interactions between galaxies and regions of high amounts of star formation with high enough pressures to satisfy the properties needed for a star cluster to form.[2] These regions can include newer galaxies, such as dwarf starburst galaxies[7], arms of a spiral galaxy that have a high star formation rate, and in the merging of galaxies. In an Astronomical Journal published in 1996, using pictures taken in the UV spectrum by the Hubble Space Telescopes of star-forming rings in five different barred galaxies, numerous star clusters were found in clumps within the rings which had high rates of star formation. It was found that these clusters had masses of about M☉ to M☉, ages of about 100 Myr, and radii of about 5 pc, and are though to evolve into globular clusters later in their lifetimes.[8] These are the properties of SSC's.

Characteristics and Properties

The typical characteristics of SSCs:

  • Large electron densities – cm (this is a property of the HII region associated with the SSC)
  • Pressures – K cm.[5] (this is a property of the HII region associated with the SSC)
  • Mass M☉[2]
  • Radius ≈ 5 pc ≈ cm[2]
  • Age ≈ 100 Myr[2] (Although other sources state that observed SSCs have an age of 1 Gyr[3])

Hubble Space Telescope Contributions

Given the relatively small size of SSC's compared to their host galaxies, astronomers have had trouble finding them in the past due to the limited resolution of the telescopes at the time. With the introduction of the Hubble Space Telescope (HST) in the 1990's, finding SSC's as well as other astronomical objects became much easier thanks to the higher resolution of the HST (angular resolution of ~1/10 arcsecond[9]). This not only allowed astronomers to see SSC's, but also allowed for them to measure their properties as well as the properties of the individual stars within the SSC. Recently, a massive star, Westerlund 1-26, was discovered in the SSC Westerlund 1 in the Milky Way. The radius of this star is thought to larger than the radius of Jupiter's orbit around the Sun.[10]

List

Name Galaxy Comments Notes Pictures
Westerlund 1 (Wd1) Milky Way Galaxy First SSC discovered in the Milky Way Galaxy. This SSC was discovered by the HST. [11]
Westerlund 1
Westerlund 1
NGC 3603 Milky Way Galaxy [12]
\NGC 3603
NGC 3603
R136 Large Magellanic Cloud (LMC) The prototype SSC [13]
R136 (Located in the Tarantula Nebula)
R136 (Located in the Tarantula Nebula)
NGC 1569 A1 and A2 NGC 1569 Galaxy contains two SSCs [14]
NGC 1569
NGC 1569

References

  1. ^ Gallagher; Grebel (2002). "Extragalactic Star Clusters: Speculations on the Future". Extragalactic Star Clusters, IAU Symposium. 207: 207. arXiv:astro-ph/0109052. Bibcode:2002IAUS..207..745G. {{cite journal}}: Unknown parameter |last-author-amp= ignored (|name-list-style= suggested) (help)
  2. ^ a b c d e Johnson, Kelsey. "The Properties of Super Star Clusters In A Sample of Starburst Galaxies" (PDF). {{cite journal}}: Cite journal requires |journal= (help)
  3. ^ a b de Grijs, Richard. ""Super" Star Clusters" (PDF). {{cite journal}}: Cite journal requires |journal= (help)
  4. ^ Kobulnicky, Henry A.; Johnson, Kelsey E. (1999). "Signatures of the Youngest Starbursts: Optically Thick Thermal Bremsstrahlung Radio Sources in Henize 2-10". ApJ. 527 (1): 154–166. arXiv:astro-ph/9907233. Bibcode:1999ApJ...527..154K. doi:10.1086/308075. {{cite journal}}: Unknown parameter |last-author-amp= ignored (|name-list-style= suggested) (help)
  5. ^ a b Johnson (2004). "Extragalactic Ultracompact HII Regions: Probing the Birth Environments of Super Star Clusters". ASP Conference Series. 527: 322. arXiv:astro-ph/0405125. Bibcode:2004ASPC..322..339J.
  6. ^ "Super Star Cluster Discovered in Our Own Milky Way - Universe Today". Universe Today. 2005-03-22. Retrieved 2017-02-10.
  7. ^ Hunter, Deidre A.; O'Connell, Robert W. "The Star Clusters in the Starburst Irregular Galaxy NGC 1569". The Astronomical Journal. 20: 2383–2401. doi:10.1086/316810.
  8. ^ Maoz, D.; Barth, A. J.; Sternberg, A.; Filippenko, A. V.; Ho, L. C.; Macchetto, F. D.; Rix, H.-W.; Schneider, D. P. (1996-06-01). "Hubble Space Telescope Ultraviolet Images of Five Circumnuclear Star-Forming Rings". The Astronomical Journal. 111: 2248. doi:10.1086/117960. ISSN 0004-6256.
  9. ^ information@eso.org. "FAQ - Frequently Asked Questions". www.spacetelescope.org. Retrieved 2017-03-18.
  10. ^ Wallace, Amy (March 10, 2017). "Hubble finds young super star cluster, giant star". UPI. {{cite web}}: Cite has empty unknown parameter: |dead-url= (help)
  11. ^ Clark, J. S.; Negueruela, I.; Crowther, P. A.; Goodwin, S. P. (2005). "On the massive stellar population of the super star cluster Westerlund 1". Astronomy and Astrophysics. 434 (3): 949. arXiv:astro-ph/0504342. Bibcode:2005A&A...434..949C. doi:10.1051/0004-6361:20042413.
  12. ^ Fukui, Y.; Ohama, A.; Hanaoka, N.; Furukawa, N.; Torii, K.; Dawson, J. R.; Mizuno, N.; Hasegawa, K.; Fukuda, T.; Soga, S.; Moribe, N.; Kuroda, Y.; Hayakawa, T.; Kawamura, A.; Kuwahara, T.; Yamamoto, H.; Okuda, T.; Onishi, T.; Maezawa, H.; Mizuno, A. (2014). "Molecular Clouds Toward the Super Star Cluster Ngc 3603; Possible Evidence for a Cloud-Cloud Collision in Triggering the Cluster Formation". The Astrophysical Journal. 780: 36. arXiv:1306.2090. Bibcode:2014ApJ...780...36F. doi:10.1088/0004-637X/780/1/36.
  13. ^ Massey, Philip; Hunter, Deidre A. (1998). "Star Formation in R136: A Cluster of O3 Stars Revealed by Hubble Space Telescope Spectroscopy". The Astrophysical Journal. 493: 180. Bibcode:1998ApJ...493..180M. doi:10.1086/305126.
  14. ^ Hunter, Deidre A.; O'Connell, Robert W.; Gallagher, J. S.; Smecker-Hane, Tammy A. (2000). "The Star Clusters in the Starburst Irregular Galaxy NGC 1569". The Astronomical Journal. 120 (5): 2383. arXiv:astro-ph/0009280. Bibcode:2000AJ....120.2383H. doi:10.1086/316810.
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