Dynamical Mass Segregation on a Very Short Timescale

Allison, Richard J.; Goodwin, S. P.; Parker, R. J.; Grijs, Richard de; Zwart, Simon F. Portegies; Kouwenhoven, M. B. N.

doi:10.1088/0004-637x/700/2/l99

Cited by 256 publications

(358 citation statements)

References 42 publications

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“…Since star/cluster formation happens in a dynamic environment [6,2,28] it may be impossible to define what will become a stellar cluster in these early stages, as the final object that remains bound is simply the dynamically mixed part of a larger, initially hierarchical, distribution. In this scenario a cluster can only be clearly defined above the surrounding distribution once it is dynamically evolved where t age /t cross > 1, as defined by Gieles & Portegies Zwart 2010.…”

Section: Discussionmentioning

confidence: 99%

Do All Stars in the Solar Neighbourhood Form in Clusters?

Bressert

Bastian

Gutermuth

2011

Star Clusters in the Era of Large Surveys

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We present a global study of low mass, young stellar object (YSO) surface densities (Σ ) in nearby (< 500 pc) star forming regions based on a comprehensive collection of Spitzer Space Telescope surveys. We show that the distribution of YSO surface densities is a smooth distribution, being adequately described by a lognormal function from a few to 10 3 YSOs per pc 2 , with a peak at ∼ 22 stars pc −2 . The observed lognormal Σ is consistent with predictions of hierarchically structured starformation at scales below 10 pc, arising from the molecular cloud structures. We do not find evidence for multiple discrete modes of star-formation (e.g. clustered and distributed). Comparing the observed Σ distribution to previous Σ threshold definitions of clusters show that they are arbitrary. We find that only a low fraction (< 26%) of stars are formed in dense environments where their formation/evolution (along with their circumstellar disks and/or planets) may be affected by the close proximity of their low-mass neighbours.

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Section: Discussionmentioning

confidence: 99%

Do All Stars in the Solar Neighbourhood Form in Clusters?

Bressert

Bastian

Gutermuth

2011

Star Clusters in the Era of Large Surveys

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“…Compared with the time scale on which mass segregation occurs in the simulations of McMillan et al (2007) and Allison et al (2009) the present setup leads to an equally rapid evolution. This indicates that in fact subvirial initial conditions might be the dominant dynamical driver of rapid mass segregation in young star clusters.…”

Section: Resultsmentioning

confidence: 43%

“…We 390 C. Olczak, R. Spurzem, Th. Henning use the Nbody6-GPU code Aarseth (2003) to model the dynamics of these numerical models and analyze the degree of mass segregation, Λ MST , via a minimum spanning tree algorithm as described by Allison et al (2009).…”

Section: Numerical Setupmentioning

confidence: 99%

“…Spurzem & Takahashi 1995;Khalisi et al 2007) occurs rapid enough to account for the observed mass segregation, recent investigations have focused on how substructure in stellar systems can accelerate this process (McMillan et al 2007;Allison et al 2009;Moeckel & Bonnell 2009, see also (Aarseth & Hills 1972)). However, all these works have simulated the evolution under subvirial initial conditions.…”

Section: Introductionmentioning

confidence: 99%

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Rapid mass segregation in young star clusters without substructure?

2010

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Abstract. The young star clusters we observe today are the building blocks of a new generation of stars and planets in our Galaxy and beyond. Despite their fundamental role we still lack knowledge about the initial conditions under which star clusters form and the impact of these often harsh environments on the formation and evolution of their stellar and substellar members.We present recent results showing that mass segregation in realistic models of young star clusters occurs very quickly for subvirial spherical systems without substructure. This finding is a critical step to resolve the controversial debate on mass segregation in young star clusters and provides strong constraints on their initial conditions. The rapid concentration of massive stars is usually associated with strong gravitational interactions early on during cluster evolution and the subsequent formation of multiple systems and ejection of stars.

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“…Mass segregation to the center of the cluster could be primordial or dynamical: the most massive stars can be concentrated at or near the center or migrate into the center of the cluster due to two-body interactions. Allison et al (2009) describe an ensemble of simulations of cool, clumpy (fractal) clusters and they show that during the early life of such a cluster often mass segregation takes place on timescales far shorter than expected A27, page 12 of 13 from simple models. The results of these N-body simulations look quite similar to the current situation in IRAS 06084-0611.…”

Section: Discussionmentioning

confidence: 99%

Sequential star formation in IRAS 06084-0611 (GGD 12-15)

Maaskant

Bik

Waters

et al. 2011

A&A

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Context. The formation and early evolution of high-and intermediate-mass stars towards the main sequence involves the interplay of stars in a clustered and highly complex environment. To obtain a full census of this interaction, the Formation and Early evolution of Massive Stars (FEMS) collaboration studies a well-selected sample of 10 high-mass star-forming regions. Aims. In this study we examine the stellar content of the high-mass star-forming region centered on IRAS 06084-0611 in the Monoceros R2 cloud. Methods. Using the near-infrared H-and K-band spectra from the VLT/SINFONI instrument on the ESO Very Large Telescope (VLT) and photometric near-infrared NTT/SOFI, 2MASS and Spitzer/IRAC data, we were able to determine the spectral types for the most luminous stars in the cluster. Results. Two very young and reddened massive stars have been detected by SINFONI: a massive young stellar object (YSO) consistent with an early-B spectral type and a Herbig Be star. Furthermore, stars of spectral type G and K are detected while still in the Pre-Main Sequence (PMS) phase. We derive additional properties such as temperatures, extinctions, radii and masses. We present a Hertzsprung-Russell diagram and find most objects having intermediate masses between ∼1.5-2.5 M . For these stars we derive a median cluster age of ∼4 Myr. Conclusions. Using Spitzer/IRAC data we confirm earlier studies that the younger class 0/I objects are centrally located while the class II objects are spread out over a larger area, with rough scale size radii of ∼0.5 pc and ∼1.25 pc respectively. Moreover, the presence of a massive YSO, an ultracompact H ii region and highly reddened objects in the center of the cluster suggest a much younger age of <1 Myr. A possible scenario for this observation would be sequential star formation along the line of sight; from a cluster of intermediate-mass to high-mass stars.

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Dynamical Mass Segregation on a Very Short Timescale

Cited by 256 publications

References 42 publications

Do All Stars in the Solar Neighbourhood Form in Clusters?

Do All Stars in the Solar Neighbourhood Form in Clusters?

Rapid mass segregation in young star clusters without substructure?

Sequential star formation in IRAS 06084-0611 (GGD 12-15)

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