Formation of Star Clusters in the Large Magellanic Cloud and Small Magellanic Cloud. I. Preliminary Results on Cluster Formation from Colliding Gas Clouds

Bekki, Kenji; Beasley, Michael A.; Forbes, Duncan A.; Couch, Warrick J.

doi:10.1086/381171

Cited by 50 publications

(60 citation statements)

References 34 publications

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“…Real cluster formation processes from SCCs are more complicated than the present model describes. For example, the observed large fraction of binary clusters in the LMC (e.g., Bhatia & Hatzidimitriou 1988) can not be simply explained by the present model, and it can be better explained by other cluster formation models based on GMC collisions (e.g., Bekki et al 2004a). Thus we need to discuss these other issues related to cluster formation in our future papers.…”

Section: Sccmentioning

confidence: 62%

Globular cluster formation with multiple stellar populations from hierarchical star cluster complexes

Bekki¹

2017

Mon. Not. R. Astron. Soc.

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Most old globular clusters (GCs) in the Galaxy are observed to have internal chemical abundance spreads in light elements. We discuss a new GC formation scenario based on hierarchical star formation within fractal molecular clouds. In the new scenario, a cluster of bound and unbound star clusters ('star cluster complex', SCC) that have a power-law cluster mass function with a slope (β) of 2 is first formed from a massive gas clump developed in a dwarf galaxy. Such cluster complexes and β = 2 are observed and expected from hierarchical star formation. The most massive star cluster ('main cluster'), which is the progenitor of a GC, can accrete gas ejected from asymptotic giant branch (AGB) stars initially in the cluster and other low-mass clusters before the clusters are tidally stripped or destroyed to become field stars in the dwarf. The SCC is initially embedded in a giant gas hole created by numerous supernovae of the SCC so that cold gas outside the hole can be accreted onto the main cluster later. New stars formed from the accreted gas have chemical abundances that are different from those of the original SCC. Using hydrodynamical simulations of GC formation based on this scenario, we show that the main cluster with the initial mass as large as [2 − 5] × 10 5 M ⊙ can accrete more than 10 5 M ⊙ gas from AGB stars of the SCC. We suggest that merging of hierarchical star cluster complexes can play key roles in stellar halo formation around GCs and self-enrichment processes in the early phase of GC formation.

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Section: Sccmentioning

confidence: 62%

Globular cluster formation with multiple stellar populations from hierarchical star cluster complexes

Bekki¹

2017

Mon. Not. R. Astron. Soc.

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“…However, we have to admit that the radial velocity difference between the two clusters is on the high side and indicates only a marginal possibility for the binary nature. On the other hand, the uncertainties in masses and in velocities do not exclude this possibility, in particular in view of the recent simulations of Bekki et al (2004), who concluded that bound star clusters can be formed within the centers of two colliding clouds provided that the relative velocities of these clouds are between 10 and 60 km s À1 . Measurements of more accurate velocities and better constraints on the masses are necessary together with more sophisticated modeling to confirm or reject the binary nature of our target.…”

Section: Discussionmentioning

confidence: 96%

“…Measurements of more accurate velocities and better constraints on the masses are necessary together with more sophisticated modeling to confirm or reject the binary nature of our target. Several authors have discussed observations and models of binary stellar clusters (e.g., Icke & Alcaino 1988;Bhatia & Hatzidimitriou 1988;Sugimoto & Makino 1989;Makino et al 1991;Gilmozzi et al 1994;van den Bergh 1996;de Oliveira et al 2000;Ballabh & Alladin 2000;Thurl & Johnston 2000;Dieball et al , 2002Bekki et al 2004). In particular, Dieball et al (2002) made a statistical study of all the binary and multiple clusters in the LMC, concluding that the formation of binary clusters by tidal capture is not likely because of the low probability of close encounters of star clusters, and thus the even lower probability of tidal capture.…”

Section: Discussionmentioning

confidence: 99%

The Most Exciting Massive Binary Cluster in NGC 5128: Clues to the Formation of Globular Clusters

Minniti

Rejkuba

Funes

et al. 2004

ApJ

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Very Large Telescope images in BVI are used to identify the ionizing source centered on Sersic 13, the largest H ii region of the giant nearby galaxy NGC 5128, with log L H ¼ 39:6 ergs s À1 . This ionizing source turns out to be a close pair of bright and blue star cluster candidates. Spectroscopy obtained with the Magellan I telescope confirms that these are massive young clusters physically associated with the giant H ii region Sersic 13. The spectra of both clusters show prominent Wolf-Rayet-type emission features and prominent lines of H i and He ii, indicative of a very young age (t % a few ; 10 6 yr). Their luminosities make each of them at least as luminous as the massive young cluster R136 in 30 Doradus in the LMC, and their individual masses are estimated to be 1 7:5 ð Þ; 10 5 M . In addition, the projected separation of the cluster pair is 42 pc. The measured velocity difference between the clusters is small, ÁV ¼ 49 AE 21 km s À1 , and within 2 of the expected orbital velocity V orb ¼ 5 12 km s À1 if they are bound. Dynamical models predict that binary clusters with these properties would merge in a short timescale of a few orbital periods, P ¼ 20 50 ð Þ; 10 6 yr. The discovery of this binary cluster suggests that mergers of young massive clusters could lead to the formation of the most massive globular clusters, such as ! Cen in our Galaxy and G1 in M31. Alternatively, if they are not gravitationally bound these objects would individually evolve into two normal globular clusters.

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“…They may also be the final products of multiple mergers of smaller clusters. Coformation scenarios have been suggested by Article published by EDP Sciences Fujimoto & Kumai (1997) and Bekki et al (2004). Objects formed are genetic pairs and therefore true binaries if bound.…”

Section: Double or Binary: Formation Channelsmentioning

confidence: 99%

“…Nevertheless, Subramaniam et al (1995) were able to identify a number of additional candidates, concluding that about 8% of open clusters may be actual binaries, challenging the traditional view. In spite of this result, it is still emphasized (see, e.g., Dieball & Grebel 1998;Bekki et al 2004) that the number of cluster pairs in the Milky Way is small compared to that in the Clouds. This is usually interpreted as supporting evidence for the higher formation efficiency of bound stellar groups in the Clouds.…”

Section: Introductionmentioning

confidence: 99%

Double or binary: on the multiplicity of open star clusters

Marcos¹,

Marcos²

2009

A&A

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Context. Observations indicate that the fraction of potential binary star clusters in the Magellanic Clouds is about 10%. In contrast, it is widely accepted that the binary cluster frequency in the Galaxy disk is much lower. Aims. Here we investigate the multiplicity of clusters in the Milky Way disk to either confirm or disprove this dearth of binaries. Methods.We quantify the open cluster multiplicity using complete, volume-limited samples from WEBDA and NCOVOCC. Results. At the Solar Circle, at least 12% of all open clusters appear to be experiencing some type of interaction with another cluster; i.e., are possible binaries. As in the Magellanic Clouds, the pair separation histogram hints at a bimodal distribution. Nearly 40% of identified pairs are probably primordial. Most of the remaining pairs could be undergoing some type of close encounter, perhaps as a result of orbital resonances. Confirming early theoretical predictions, the characteristic time scale for destruction of bound pairs in the disk is 200 Myr, or one galactic orbit. Conclusions. Our results show that the fraction of possible binary clusters in the Galactic disk is comparable to that in the Magellanic Clouds.

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Formation of Star Clusters in the Large Magellanic Cloud and Small Magellanic Cloud. I. Preliminary Results on Cluster Formation from Colliding Gas Clouds

Cited by 50 publications

References 34 publications

Globular cluster formation with multiple stellar populations from hierarchical star cluster complexes

Globular cluster formation with multiple stellar populations from hierarchical star cluster complexes

The Most Exciting Massive Binary Cluster in NGC 5128: Clues to the Formation of Globular Clusters

Double or binary: on the multiplicity of open star clusters

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