Super star cluster

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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 called "super" because 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 than 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 or a so-called "Ultra dense HII region (UDHII)" in the Milky Way Galaxy [4] or in other galaxies (however, SSCs do not always have to be inside an HII region). An SSC's HII region is in turn surrounded by a cocoon of dust. In many cases, the stars and the HII regions will be invisible to observations in certain wavelengths of light, such as the visible spectrum, due to high levels of extinction. As a result, the youngest SSCs are best observed and photographed in radio and infrared. [5] SSCs, such as Westerlund 1 (Wd1), have been found in the Milky Way Galaxy. [6] However, most have been observed in farther regions of the universe. In the galaxy M82 alone, 197 young SSCs have been observed and identified using the Hubble Space Telescope. [7]

Contents

Generally, SSCs have been seen to form in the interactions between galaxies and in regions of high amounts of star formation with high enough pressures to satisfy the properties needed for the formation of a star cluster. [2] These regions can include newer galaxies with much new star formation, dwarf starburst galaxies, [8] 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 ultraviolet (UV) spectrum by the Hubble Space Telescope 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. These clusters were found to have masses of about M☉ to M☉, ages of about 100 Myr, and radii of about 5 pc, and are thought to evolve into globular clusters later in their lifetimes. [9] These properties match those found in SSCs.

Characteristics and properties

The typical characteristics and properties of SSCs:

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 ground-based and space telescopes at the time. With the introduction of the Hubble Space Telescope (HST) in the 1990s, 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 [10] ). This has 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 be larger than the radius of Jupiter's orbit around the Sun. [11] Essentially, the HST searches the night sky, specifically nearby galaxies, for star clusters and "dense stellar objects" to see if any have the properties similar to that of a SSC or an object that would, in its lifetime, evolve into a globular cluster. [3]

List of SSC's

NameContained
in Galaxy		CommentsRefs / NotesPictures
Westerlund 1 (Wd1) Milky Way Galaxy First SSC discovered in the Milky Way Galaxy. This SSC was discovered by Bengt Westerlund in 1961. [12]
Westerlund 1 Westerlund 1.jpg
Westerlund 1
NGC 3603 Milky Way Galaxy Candidate for SSC [13]
NGC 3603 Stellar nursery NGC 3603.jpg
NGC 3603
NGC 2070 Large Magellanic Cloud (LMC)Candidate for SSC
NGC 2070 The Tarantula Nebula (30 Doradus or NGC 2070).jpg
NGC 2070
R136 Large Magellanic Cloud (LMC)The prototype SSC, inside NGC 2070 [14]
R136 (Located in the Tarantula Nebula) Grand star-forming region R136 in NGC 2070 (captured by the Hubble Space Telescope).jpg
R136 (Located in the Tarantula Nebula)
NGC 346 Small Magellanic Cloud (SMC)May be a SSC [15]
NGC 346 Ngc346.jpg
NGC 346
NGC 1569 A1 and A2 (NGC 1569 A) NGC 1569 Clusters A1 and A2 formed SSC A [16]
NGC 1569 NGC 1569.jpg
NGC 1569
NGC 1569 B NGC 1569 It contains older population of red giants and red supergiants [17]
NGC 1569 Starburst in a Dwarf Irregular Galaxy.jpg
NGC 1569
NGC 5253's central SSC NGC 5253 It is very dusty, and is the site of ongoing star formation. Particularly rich in O-type stars, containing at least 7,000.
NGC 5253 A Peculiar Compact Blue Dwarf Galaxy.jpg
NGC 5253

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<span class="mw-page-title-main">Globular cluster</span> Spherical collection of stars

A globular cluster is a spheroidal conglomeration of stars. Globular clusters are bound together by gravity, with a higher concentration of stars towards their centers. They can contain anywhere from tens of thousands to many millions of member stars. Their name is derived from Latin globulus. Globular clusters are occasionally known simply as "globulars".

<span class="mw-page-title-main">H II region</span> Large, low-density interstellar cloud of partially ionized gas

An H II region or HII region is a region of interstellar atomic hydrogen that is ionized. It is typically in a molecular cloud of partially ionized gas in which star formation has recently taken place, with a size ranging from one to hundreds of light years, and density from a few to about a million particles per cubic centimetre. The Orion Nebula, now known to be an H II region, was observed in 1610 by Nicolas-Claude Fabri de Peiresc by telescope, the first such object discovered.

<span class="mw-page-title-main">Tarantula Nebula</span> H II region in the constellation Dorado

The Tarantula Nebula is a large H II region in the Large Magellanic Cloud (LMC), forming its south-east corner.

<span class="mw-page-title-main">Messier 61</span> Galaxy in the constellation Virgo

Messier 61 is an intermediate barred spiral galaxy in the Virgo Cluster of galaxies. It was first discovered by Barnaba Oriani on May 5, 1779, six days before Charles Messier discovered the same galaxy. Messier had observed it on the same night as Oriani but had mistaken it for a comet. Its distance has been estimated to be 45.61 million light years from the Milky Way Galaxy. It is a member of the M61 Group of galaxies, which is a member of the Virgo II Groups, a series of galaxies and galaxy clusters strung out from the southern edge of the Virgo Supercluster.

<span class="mw-page-title-main">Sombrero Galaxy</span> Galaxy in the constellation Virgo

The Sombrero Galaxy is a peculiar galaxy of unclear classification in the constellation borders of Virgo and Corvus, being about 9.55 megaparsecs from the Milky Way galaxy. It is a member of the Virgo II Groups, a series of galaxies and galaxy clusters strung out from the southern edge of the Virgo Supercluster. It has an isophotal diameter of approximately 29.09 to 32.32 kiloparsecs, making it slightly bigger in size than the Milky Way.

<span class="mw-page-title-main">Dwarf galaxy</span> Small galaxy composed of up to several billion stars

A dwarf galaxy is a small galaxy composed of about 1000 up to several billion stars, as compared to the Milky Way's 200–400 billion stars. The Large Magellanic Cloud, which closely orbits the Milky Way and contains over 30 billion stars, is sometimes classified as a dwarf galaxy; others consider it a full-fledged galaxy. Dwarf galaxies' formation and activity are thought to be heavily influenced by interactions with larger galaxies. Astronomers identify numerous types of dwarf galaxies, based on their shape and composition.

<span class="mw-page-title-main">Sculptor Galaxy</span> Intermediate spiral galaxy in the constellation Sculptor

The Sculptor Galaxy is an intermediate spiral galaxy in the constellation Sculptor. The Sculptor Galaxy is a starburst galaxy, which means that it is currently undergoing a period of intense star formation.

<span class="mw-page-title-main">NGC 6946</span> Galaxy in the constellations Cepheus & Cygnus

NGC 6946, sometimes referred to as the Fireworks Galaxy, is a face-on intermediate spiral galaxy with a small bright nucleus, whose location in the sky straddles the boundary between the northern constellations of Cepheus and Cygnus. Its distance from Earth is about 25.2 million light-years or 7.72 megaparsecs, similar to the distance of M101 in the constellation Ursa Major. Both were once considered to be part of the Local Group, but are now known to be among the dozen bright spiral galaxies near the Milky Way but beyond the confines of the Local Group. NGC 6946 lies within the Virgo Supercluster.

<span class="mw-page-title-main">NGC 3603</span> Open cluster in the constellation Carina

NGC 3603 is a nebula situated in the Carina–Sagittarius Arm of the Milky Way around 20,000 light-years away from the Solar System. It is a massive H II region containing a very compact open cluster HD 97950.

<span class="mw-page-title-main">NGC 1569</span> Galaxy in the constellation Camelopardalis

NGC 1569 is a dwarf irregular galaxy in Camelopardalis. The galaxy is relatively nearby and consequently, the Hubble Space Telescope can easily resolve the stars within the galaxy. The distance to the galaxy was previously believed to be only 2.4 Mpc. However, in 2008 scientists studying images from Hubble calculated the galaxy's distance at nearly 11 million light-years away, about 4 million light-years farther than previously thought, meaning it is a member of the IC 342 group of galaxies.

<span class="mw-page-title-main">NGC 4214</span> Galaxy in the constellation Canes Venatici

NGC 4214 is a dwarf barred irregular galaxy located around 10 million light-years away in the constellation Canes Venatici. NGC 4214 is a member of the M94 Group.

<span class="mw-page-title-main">NGC 4536</span> Spiral galaxy in the constellation Virgo

NGC 4536 is an intermediate spiral galaxy in the constellation Virgo located about 10° south of the midpoint of the Virgo cluster. However, it is not considered a member of the cluster. Rather, it is a member of the M61 Group of galaxies, which is a member of the Virgo II Groups, a series of galaxies and galaxy clusters strung out from the southern edge of the Virgo Supercluster. The morphological classification in the De Vaucouleurs system is SAB(rs)bc, which indicates it is a weakly barred spiral galaxy with a hint of an inner ring structure plus moderate to loosely wound arms. It does not have a classical bulge around the nucleus.

<span class="mw-page-title-main">NGC 2366</span> Galaxy in the constellation Camelopardalis

NGC 2366 is a Magellanic barred irregular dwarf galaxy located in the constellation Camelopardalis.

<span class="mw-page-title-main">NGC 4449</span> Galaxy in the constellation Canes Venatici

NGC 4449, also known as Caldwell 21, is an irregular Magellanic type galaxy in the constellation Canes Venatici, being located about 13 million light-years away. It is part of the M94 Group or Canes Venatici I Group that is relatively close to the Local Group hosting our Milky Way galaxy.

<span class="mw-page-title-main">NGC 3256</span> Peculiar galaxy in the constellation Vela

NGC 3256 is a peculiar galaxy formed from the collision of two separate galaxies in the constellation of Vela. NGC 3256 is located about 100 million light-years away and belongs to the Hydra–Centaurus Supercluster complex. NGC 3256 provides a nearby template for studying the properties of young star clusters in tidal tails. The system hides a double nucleus and a tangle of dust lanes in the central region. The telltale signs of the collision are two extended luminous tails swirling out from the galaxy. The tails are studded with a particularly high density of star clusters. NGC 3256 is the most luminous galaxy in the infrared spectrum located within z 0.01 from Earth.

<span class="mw-page-title-main">NGC 7469</span> Galaxy located in the constellation Pegasus

NGC 7469 is an intermediate spiral galaxy in the constellation of Pegasus. NGC 7469 is located about 200 million light-years away from Earth, which means, given its apparent dimensions, that NGC 7469 is approximately 90,000 light-years across. It was discovered by William Herschel on November 12, 1784.

<span class="mw-page-title-main">NGC 541</span> Galaxy in the constellation Cetus

NGC 541 is a lenticular galaxy located in the constellation Cetus. It is located at a distance of circa 230 million light years from Earth, which, given its apparent dimensions, means that NGC 541 is about 130,000 light years across. It was discovered by Heinrich d'Arrest on October 30, 1864. It is a member of the Abell 194 galaxy cluster and is included in the Atlas of Peculiar Galaxies in the category galaxies with nearby fragments. NGC 541 is a radio galaxy of Fanaroff-Riley class I, also known as 3C 40A.

<span class="mw-page-title-main">NGC 545</span> Galaxy in the constellation Cetus

NGC 545 is a lenticular galaxy located in the constellation Cetus. It is located at a distance of circa 250 million light years from Earth, which, given its apparent dimensions, means that NGC 545 is about 180,000 light years across. It was discovered by William Herschel on October 1, 1785. It is a member of the Abell 194 galaxy cluster and is included along with NGC 547 in the Atlas of Peculiar Galaxies.

<span class="mw-page-title-main">NGC 4299</span> Spiral galaxy in the constellation Virgo

NGC 4299 is a featureless spiral galaxy located about 55 million light-years away in the constellation Virgo. It was discovered by astronomer William Herschel on March 15, 1784 and is a member of the Virgo Cluster.

<span class="mw-page-title-main">NGC 4800</span> Galaxy in constellation Canes Venatici

NGC 4800 is an isolated spiral galaxy in the constellation Canes Venatici, located at a distance of 95 megalight-years from the Milky Way. It was discovered by William Herschel on April 1, 1788. The morphological classification of this galaxy is SA(rs)b, indicating a spiral galaxy with no visual bar at the nucleus (SA), an incomplete ring structure (rs), and moderately-tightly wound spiral arms (b). The galactic plane is inclined to the line of sight by an angle of 43°, and the long axis is oriented along a position angle of 25°. There is a weak bar structure at the nucleus that is visible in the infrared.

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.
  2. 1 2 3 4 5 Johnson, Kelsey (2001). "The Properties of Super Star Clusters In A Sample of Starburst Galaxies" (PDF). Bibcode:2001PhDT.......182J. S2CID   117321058. Archived from the original (PDF) on 2017-02-27.{{cite journal}}: Cite journal requires |journal= (help)
  3. 1 2 3 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". Astrophysical Journal. 527 (1): 154–166. arXiv: astro-ph/9907233 . Bibcode:1999ApJ...527..154K. doi:10.1086/308075. S2CID   15431678.
  5. 1 2 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. ↑ Melo, V. P.; Muñoz-Tuñón, C.; Maíz-Apellániz, J.; Tenorio-Tagle, G. (2005-01-01). "Young Super Star Clusters in the Starburst of M82: The Catalog". The Astrophysical Journal. 619 (1): 270. arXiv: astro-ph/0409750 . Bibcode:2005ApJ...619..270M. doi:10.1086/426421. ISSN   0004-637X. S2CID   16452890.
  8. ↑ Hunter, Deidre A.; O'Connell, Robert W. (2000). "The Star Clusters in the Starburst Irregular Galaxy NGC 1569". The Astronomical Journal. 20 (5): 2383–2401. arXiv: astro-ph/0009280 . Bibcode:2000AJ....120.2383H. doi:10.1086/316810. S2CID   6445978.
  9. ↑ 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. arXiv: astro-ph/9604012 . Bibcode:1996AJ....111.2248M. doi:10.1086/117960. ISSN   0004-6256. S2CID   12241545.
  10. ↑ "FAQ - Frequently Asked Questions". www.spacetelescope.org. Retrieved 2017-03-18.
  11. ↑ Wallace, Amy (March 10, 2017). "Hubble finds young super star cluster, giant star". UPI.
  12. ↑ 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. S2CID   119042919.
  13. ↑ 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 (1): 36. arXiv: 1306.2090 . Bibcode:2014ApJ...780...36F. doi:10.1088/0004-637X/780/1/36. S2CID   53118305.
  14. ↑ 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 (1): 180–194. Bibcode:1998ApJ...493..180M. doi: 10.1086/305126 .
  15. ↑ Sabbi, E.; Nota, A.; Cignoni, M.; Degl'Innocenti, S.; De Marchi, G.; Gallagher, J. S.; Panagia, N.; Prada Moroni, P. G.; Romaniello, M.; Smith1, L. J.; Sirianni, M.; Tosi, M. (2011). "NGC 346: Tracing the Evolution of a Super Star Cluster". Stellar Clusters & Associations: A Ria Workshop on Gaia: 244–249. Bibcode:2011sca..conf..244S.
  16. ↑ 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. S2CID   6445978.
  17. ↑ 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. S2CID   6445978.
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