Formation and dissolution of leaky clusters

Pfalzner, Susanne

doi:10.1051/0004-6361/201117777

Cited by 37 publications

(94 citation statements)

References 29 publications

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“…Our objects are found in the gap between the samples of embedded and exposed clusters studied by Pfalzner (2011); however, our results do not confirm the mass-radius or density-radius dependences suggested by her. In fact, we verified that massive clusters from Pfalzner (2011) are distributed in two groups.…”

Section: Summary Of the Results And Conclusioncontrasting

confidence: 99%

“…4c). However, the distribution of our clusters, as well as LL03 data, does not agree with the mass vs. density relation proposed by Pfalzner (2009Pfalzner ( , 2011. As suggested in Sect.…”

Section: Volumetric Densitycontrasting

confidence: 85%

“…To discuss whether these differences could be interpreted as a formation condition, as proposed by Adams et al (2006), or differently if they are related to a time sequence, as suggested by Pfalzner (2011), we compare the relations between mass and radius. Figure 4c shows that our sample has the same dependence as is obtained by fitting the LL03 data: M = 118 R 1.3 .…”

Section: Massmentioning

confidence: 99%

“…Figure 4c shows that our sample has the same dependence as is obtained by fitting the LL03 data: M = 118 R 1.3 . Figure 4c also displays the data of the "leaky" massive clusters studied by Pfalzner (2011), who proposes that these objects would be the ending of a time sequence. However, the massradius dependence M ∼ 359 R 1.7 , which Pfalzner (2011) used to illustrate the suggested time sequence, is steeper than the distribution of LL03 clusters.…”

Section: Massmentioning

confidence: 99%

“…Depending on size and density, a bimodal distribution is found for the cluster size as a function of age. Based on the mass-radius and density-radius dependence observed in the sample from LL03, Pfalzner (2011) proposes a scenario of sequential formation of "leaky" (exposed) massive clusters. On the other hand, unlike the time sequence proposed by Pfalzner (2011), the relations of cluster properties can be interpreted as formation condition (Adams et al 2006;Adams 2010).…”

Section: Introductionmentioning

confidence: 99%

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Characterisation of young stellar clusters

Santos-Silva

Gregorio-Hetem

2012

A&A

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Aims. Several embedded clusters are found in the Galaxy. Depending on the formation scenario, most of them can evolve to unbounded groups that are dissolved within 10 Myr to 20 Myr. A systematic study of young stellar clusters that show distinct characteristics provides interesting information on the evolutionary phases during the pre-main sequence. To identify and to understand these phases we performed a comparative study of 21 young stellar clusters. Methods. Near-infrared data from 2MASS were used to determine the structural and fundamental parameters based on surface stellar density maps, radial density profile, and colour-magnitude diagrams. The cluster members were selected according to their membership probability, which is based on the statistical comparison with the cluster proper motion. Additional members were selected on the basis of a decontamination procedure that was adopted to distinguish field stars found in the direction of the cluster area. Results. We obtained age and mass distributions by comparing pre-main sequence models with the position of cluster members in the colour-magnitude diagram. The mean age of our sample is ∼5 Myr, where 57% of the objects is found in the 4-10 Myr range of age, while 43% is <4 Myr old. Their low E(B − V) indicate that the members are not suffering high extinction (A V < 1 mag), which means they are more likely young stellar groups than embedded clusters. Relations between structural and fundamental parameters were used to verify differences and similarities that could be found among the clusters. The parameters of most of the objects show the same trends or correlations. Comparisons with other young clusters show similar relations among mass, radius, and density. Our sample tends to have larger radius and lower volumetric density than embedded clusters. These differences are compatible with the mean age of our sample, which we consider intermediate between the embedded and the exposed phases of the stellar clusters evolution.

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Section: Summary Of the Results And Conclusioncontrasting

confidence: 99%

“…4c). However, the distribution of our clusters, as well as LL03 data, does not agree with the mass vs. density relation proposed by Pfalzner (2009Pfalzner ( , 2011. As suggested in Sect.…”

Section: Volumetric Densitycontrasting

confidence: 85%

Section: Massmentioning

confidence: 99%

Section: Massmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Characterisation of young stellar clusters

Santos-Silva

Gregorio-Hetem

2012

A&A

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Role of Gas Dynamical Friction in the Evolution of Embedded Stellar Clusters

Indulekha¹

2013

J Astrophys Astron

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Two puzzles associated with open clusters have attracted a lot of attention -their formation, with densities and velocity dispersions that are not too different from those of the star forming regions in the Galaxy, given that the observed Star Formation Efficiencies (SFE) are low and, the mass segregation observed / inferred in some of them, at ages significantly less than the dynamical relaxation times in them. Gas dynamical friction has been considered before as a mechanism for contracting embedded stellar clusters, by dissipating their energy. This would locally raise the SFE which might then allow bound clusters to form. Noticing that dynamical friction is inherently capable of producing mass segregation, since here, the dissipation rate is proportional to the mass of the body experiencing the force, we explore further, some of the details and implications of such a scenario, vis-a-vis observations. Making analytical approximations, we obtain a boundary value for the density of a star forming clump of given mass, such that, stellar clusters born in clumps which have densities higher than this, could emerge bound after gas loss. For a clump of given mass and density, we find a critical mass such that, sub-condensations with larger masses than this could suffer significant segregation within the clump.

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Early evolution of the birth cluster of the solar system

Pfalzner

2012

A&A

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Context. The solar system was most likely born in a star cluster containing at least 1000 stars. It is highly probable that this cluster environment influenced various properties of the solar system such as its chemical composition, size, and the orbital parameters of some of its constituting bodies. Aims. In the Milky Way, clusters with more than 2000 stars only form in two types -starburst clusters and leaky clusters -, each following a unique temporal development in the mass-radius plane. The aim is here to determine the encounter probability in the range relevant to solar system formation for starburst or leaky cluster environments as a function of cluster age. Methods. N-body methods were used to investigate the cluster dynamics and the effect of gravitational interactions between cluster members on young solar-type stars surrounded by discs. Results. Using the now available knowledge of the cluster density at a given cluster age we demonstrate that in starburst clusters the central densities over the first 5 Myr are so high (initially >10 5 M pc −3 ) that hardly any discs with solar system building potential would survive this phase. This makes starburst clusters an unlikely environment for the formation of our solar system. Instead it is highly probable that the solar system formed in a leaky cluster (often classified as OB association). We demonstrate that an encounter determining the characteristic properties existing in our solar systems most likely happened very early on (<2 Myr) in its formation history and that after 5 Myr the likelihood of a solar-type star experiencing such an encounter in a leaky cluster is negligible even if it was still part of the bound remnant. This explains why the solar system could develop and maintain its high circularity later in its development.

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Formation and dissolution of leaky clusters

Cited by 37 publications

References 29 publications

Characterisation of young stellar clusters

Characterisation of young stellar clusters

Role of Gas Dynamical Friction in the Evolution of Embedded Stellar Clusters

Early evolution of the birth cluster of the solar system

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