Evolving structures of star-forming clusters

Schmeja, S.; Klessen, Ralf S.

doi:10.1051/0004-6361:20054464

Cited by 116 publications

(180 citation statements)

References 41 publications

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“…Our results support the idea that stars in newly born clusters likely follow the fractal patterns of their parent molecular clouds, and that they eventually evolve towards more centrally concentrated structures (see Schmeja & Klessen 2006;Schmeja et al 2008Schmeja et al , 2009Sánchez et al 2007aSánchez et al , 2009). However, this seems to be only an overall trend.…”

Section: Discussionsupporting

confidence: 85%

The spatial distribution of stars in open clusters

Sánchez¹,

Alfaro²

2009

Proc. IAU

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Abstract. We study the internal spatial structure of 16 open clusters in the Milky Way spanning a wide range of ages. For this, we use the minimum-spanning-tree method (the Q parameter, which enables one to classify the stellar distribution as either radially or fractally clustered), King-profile fitting, and the correlation dimension (Dc ) for those clusters with fractal patterns. On average, clusters with fractal-like structure are younger than those exhibiting radial stellardensity profiles. There is a significant correlation between Q and the cluster age measured in crossing-time units. For fractal clusters, there is a significant correlation between fractal dimension and age. These results support the idea that stars in newly born clusters likely follow the fractal patterns of their parent molecular clouds, and eventually evolve towards more centrally concentrated structures. However, stellar clusters as old as ∼ 100 Myr can exist that have not totally destroyed their fractal structure. Finally, we have found the intriguing result that the lowest fractal dimensions obtained for the open clusters seem to be considerably smaller than the average value measured in Galactic molecular cloud complexes.

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Section: Discussionsupporting

confidence: 85%

The spatial distribution of stars in open clusters

Sánchez¹,

Alfaro²

2009

Proc. IAU

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“…As a proxy for mass segregation we extend the method M Λ MST developed by Allison et al (2009b) (see also Cartwright & Whitworth 2004;Schmeja & Klessen 2006). In summary, the authors use the minimum spanning tree (MST), the graph which connects all vertices within a given sample with the lowest possible sum of edges and no closed loops (Gower & Ross 1969).…”

Section: Geometrical Minimum Spanning Tree γ Mstmentioning

confidence: 99%

A highly efficient measure of mass segregation in star clusters

Olczak

Spurzem

Henning

2011

A&A

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Context. Investigations of mass segregation are of vital interest for the understanding of the formation and dynamical evolution of stellar systems on a wide range of spatial scales. A consistent analysis requires a robust measure among different objects and well-defined comparison with theoretical expectations. Various methods have been used for this purpose but usually with limited significance, quantifiability, and application to both simulations and observations. Aims. We aim at developing a measure of mass segregation with as few parameters as possible, robustness against peculiar configurations, independence of mass determination, simple implementation, stable algorithm, and that is equally well adoptable for data from either simulations or observations. Methods. Our method is based on the minimum spanning tree (MST) that serves as a geometry-independent measure of concentration.Compared to previous such approaches we obtain a significant refinement by using the geometrical mean as an intermediate-pass. Results. The geometrical mean boosts the sensitivity compared to previous applications of the MST. It thus allows the detection of mass segregation with much higher confidence and for much lower degrees of mass segregation than other approaches. The method shows in particular very clear signatures even when applied to small subsets of the entire population. We confirm with high significance strong mass segregation of the five most massive stars in the Orion nebula cluster (ONC). Conclusions. Our method is the most sensitive general measure of mass segregation so far and provides robust results for both data from simulations and observations. As such it is ideally suited for tracking mass segregation in young star clusters and to investigate the long standing paradigm of primordial mass segregation by comparison of simulations and observations.

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“…We used the Cartwright & Whitworth (2004) definition of cluster radius, R c , as the distance between the mean position of all cluster members and the most distant sources. Following Schmeja & Klessen (2006) the area A of the cluster was estimated using the convex hull (the minimal convex set containing the set of points X in a real vector space V) of the data points. The convex hull radius, R h , is defined as the radius of a circle with an area equal to the area A of the convex hull of the data points.…”

Section: Grouping Propertiesmentioning

confidence: 99%

“…The convex hull radius, R h , is defined as the radius of a circle with an area equal to the area A of the convex hull of the data points. Schmeja & Klessen (2006) describe the elongation measure ξ as: ξ = R c /R h . Notes.…”

Section: Grouping Propertiesmentioning

confidence: 99%

Planckearly results. XXIII. The first all-sky survey of Galactic cold clumps

Ade¹,

Aghanim²,

Arnaud³

et al. 2011

A&A

154

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We present the statistical properties of the Cold Clump Catalogue of Planck Objects (C3PO), the first all-sky catalogue of cold objects, in terms of their spatial distribution, dust temperature, distance, mass, and morphology. We have combined Planck and IRAS data to extract 10 342 cold sources that stand out against a warmer environment. The sources are distributed over the whole sky, including in the Galactic plane, despite the confusion, and up to high latitudes (>30 • ). We find a strong spatial correlation of these sources with ancillary data tracing Galactic molecular structures and infrared dark clouds where the latter have been catalogued. These cold clumps are not isolated but clustered in groups. Dust temperature and emissivity spectral index values are derived from their spectral energy distributions using both Planck and IRAS data. The temperatures range from 7 K to 19 K, with a distribution peaking around 13 K. The data are inconsistent with a constant value of the associated spectral index β over the whole temperature range: β varies from 1.4 to 2.8, with a mean value around 2.1. Distances are obtained for approximately one third of the objects. Most of the detections lie within 2 kpc of the Sun, but more distant sources are also detected, out to 7 kpc. The mass estimates inferred from dust emission range from 0.4 M to 2.4 × 10 5 M . Their physical properties show that these cold sources trace a broad range of objects, from low-mass dense cores to giant molecular clouds, hence the "cold clump" terminology. This first statistical analysis of the C3PO reveals at least two colder populations of special interest with temperatures in the range 7 to 12 K: cores that mostly lie close to the Sun; and massive cold clumps located in the inner Galaxy. We also describe the statistics of the early cold core (ECC) sample that is a subset of the C3PO, containing only the 915 most reliable detections. The ECC is delivered as a part of the Planck Early Release Compact Source Catalogue (ERCSC).

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Evolving structures of star-forming clusters

Cited by 116 publications

References 41 publications

The spatial distribution of stars in open clusters

The spatial distribution of stars in open clusters

A highly efficient measure of mass segregation in star clusters

Planckearly results. XXIII. The first all-sky survey of Galactic cold clumps

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