The Spatial Distribution of Stars in Open Clusters

Sánchez, Néstor; Alfaro, E. J.

doi:10.1088/0004-637x/696/2/2086

Cited by 124 publications

(143 citation statements)

References 48 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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“…Information in the two positional dimensions has been used by many people to quantify the structure of star forming regions and star clusters, and to understand how this structure evolves over time (e.g., Cartwright & Whitworth, 2004;Sánchez & Alfaro, 2009). To better understand this evolution we also need to study what is happening in the kinematic subspace during this evolution.…”

Section: The Kinematics Of Young Stars In Star Clusters and Ob Associmentioning

confidence: 99%

Star formation in the Gaia era

Wright

2016

A&G

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The European Space Agency's Gaia space telescope, launched in 2013, aims to measure the positions, parallaxes, and proper motions of a billion stars in our Galaxy and throughout the Local Group. In doing so it will include hundreds of thousands of young stars in star forming regions, star clusters and OB associations. This will provide us with an unprecedented view of the role of dynamics in the star formation process and the evolution of young star clusters. Data from this ambitious mission is expected very soon, with the first data release scheduled for 2016. This review discusses the current state of our understanding of the kinematics of star formation and how the community can best prepare for Gaia data.

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“…9). But the main drawback of this method is that simple analytical fits are not always a good representation of the star distribution in open clusters (Sánchez & Alfaro 2009). The radius defined by fitting a density profile may be useful in analyzing and comparing the properties of several clusters systematically, but great care must be taken when using these model-dependent definitions to estimate the "true" cluster radius.…”

Section: Cluster Radius and Optimal Sampling Radiusmentioning

confidence: 99%

Cluster radius and sampling radius in the determination of cluster membership probabilities

Sánchez¹,

Vicente²,

Alfaro³

2010

A&A

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We analyze the dependence of the membership probabilities obtained from kinematical variables on the radius of the field of view around open clusters (the sampling radius, R s ). From simulated data, we show that optimal discrimination between cluster members and non-members is achieved when the sampling radius is very close to the cluster radius. At higher R s values, more field stars tend to be erroneously assigned as cluster members. From real data of two open clusters (NGC 2323 and NGC 2311), we infer that the number of identified cluster members always increases with increasing R s . However, there is a threshold value R s,opt above which the identified cluster members are severely contaminated by field stars and the effectiveness of membership determination is relatively small. This optimal sampling radius is 14 arcmin for NGC 2323 and 13 arcmin for NGC 2311. We discuss the reasons for this behavior and the relationship between cluster radius and optimal sampling radius. We suggest that, independently of the method used to estimate membership probabilities, several tests using different sampling radius should be performed to evaluate possible biases.

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The Spatial Distribution of Stars in Open Clusters

Cited by 124 publications

References 48 publications

The spatial distribution of stars in open clusters

The spatial distribution of stars in open clusters

Star formation in the Gaia era

Cluster radius and sampling radius in the determination of cluster membership probabilities

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