The formation of a bound star cluster: from the orion nebula cluster to the pleiades

By Pavel Kroupa, S. Aarseth, J. Hurley. 2000

346 citations recorded by the source corpus.

Summary Direct N-body calculations are presented of the formation of Galactic clusters using GasEx, which is a variant of the code Nbody6. The calculations focus on the possible evolution of the Orion Nebula Cluster (ONC) by assuming that the embedded OB stars explosively drove out 2/3 of its mass in the form of gas about 0.4 Myr ago. A bound cluster forms readily and survives for 150 Myr despite additional mass loss from the large number of massive stars, and the Galactic tidal field. This is the very first time that cluster formation is obtained under such realistic conditions. The cluster contains about 1/3 of the initial 10 4 stars, and resembles the Pleiades Cluster to a remarkable degree, implying that an ONC-like cluster may have been a precursor of the Pleiades. This scenario predicts the present expansion velocity of the ONC, which will be measurable by upcoming astrometric space missions. These missions should also detect the original Pleiades members as an associated expanding young Galactic-field sub-population. The results arrived at here suggest that Galactic clusters form as the nuclei of expanding OB associations. The results have wide implications, also for the formation of globular clusters and the Galactic field and halo stellar populations. In view of this, the distribution of binary orbital periods and the mass function within and outside the model ONC and Pleiades is quantified, finding consistency with observational constraints. Advanced mass segregation is evident in one of the ONC models. The calculations show that the primordial binary population of both clusters could have been much the same as is observed in the Taurus–Auriga star forming region. The computations also demonstrate that the binary proportion of brown dwarfs is depleted significantly for all periods, whereas massive stars attain a high binary fraction.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/b8e5706aa7b3447063e1cf2b19cb83aba3a2a039

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Citations in the corpus

The stellar and sub-stellar IMF of simple and composite populations (2011, methodology): “Assuming the Star-Like Hypothesis to hold, Kroupa et al. (2001, 2003) perform N -body calculations of ONC- and Taurus-Auriga-like stellar aggregates to predict the semi-major-axis distribution functions of BD–BD, star–BD and star–star binaries.”
Formation of Globular Clusters in Hierarchical Cosmology (2003, background): “Within such cores, star clusters form with a locally high efficiency (Geyer & Burkert 2001; Kroupa et al. 2001; Kroupa & Boily 2002), M Mg k 0:5; ð1Þ which is required in order to produce gravitationally bound clusters.”
Inverse dynamical population synthesis: Constraining the initial conditions of young stellar clusters by studying their binary populations (2012, background): “4 in Marks et al. 2011) and/or expulsion of gas (Kroupa et al. 2001).”
Gravitational N-Body Simulations (2003, neutral): “The collision hypothesis was put on a firmer footing by Leonard & Linnell [1992] who concluded that collisions of such stars can only account for about 10% of the observed objects in M67 and NGC 188.”
The Birth Environment of the Solar System (2010, background): “Only relatively large bound clusters, those with N ≥ 1000, are expected to live that long (Binney & Tremaine 1987, Kroupa et al. 2001, Lamers et al. 2005).”
The Variation of Integrated Star Initial Mass Functions among Galaxies (2005, background): “While these are important constraints, it is clear that such clusters are already heavily dynamically evolved (Kroupa et al. 2001).”
The relation between the most-massive star and its parental star cluster mass (2009, background): “…the star clusters should still be embedded in their natal gas cloud or at least be very young, such that gas expulsion would not have effected them strongly (Lada et al. 1984; Goodwin 1997; Kroupa et al. 2001; Goodwin & Bastian 2006; Weidner et al. 2007; Pellerin et al. 2006; Bastian & Goodwin”
THE LONG-TERM EVOLUTION OF THE GALACTIC DISK TRACED BY DISSOLVING STAR CLUSTERS (2010, background): “They are either the innermost remnants of clusters that lost most of their members and produced only a small bound core (e.g. Kroupa et al. 2001), or they are clusters that remained bound because they had star formation efficiencies significantly higher than the typical 10 − 30% (Lada & Lada 2003).”
Slow Star Formation in Dense Gas: Evidence and Implications (2006, background): “At the other extreme, Bonnell et al. (2003) argue that star clusters form from gas clumps at densities of 5 ; 104 cm 3 that undergo a free-fall collapse in which at least 30% of their mass is converted into stars (Kroupa et al. 2001), so star formation should be rapid at this density or higher.”
THE ROLE OF STELLAR FEEDBACK IN THE FORMATION OF GALAXIES (2007, background): “Then, we get a runaway bubble, which proceeds to blowing away all gas (Kroupa et al. 2001).”