The dynamical evolution of Taurus-Auriga-type aggregates

Kroupa, Pavel; Bouvier, J.

doi:10.1046/j.1365-2966.2003.06645.x

Cited by 74 publications

(104 citation statements)

References 44 publications

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“…The normalization is performed by dividing the given binary frequencies by the initial binary frequency and allows direct comparison of the evolution of the binary frequencies for simulations with different initial binary frequencies. As expected from previous studies (Kroupa 1995a;Kroupa & Bouvier 2003;Parker et al 2009), dynamical evolution reduces the binary frequency with time in all simulations. This can be explained by the destruction of wide binary systems by means of three body encounters (see Kroupa 1995a,b, for more details).…”

Section: Resultssupporting

confidence: 67%

“…Theoretical studies of the evolution of binary populations are unaffected by from this shortcoming but usually also use this simple observable for reasons of comparison with observational data (see for example Kroupa 1995a; Kroupa & Bouvier 2003;Ivanova et al 2005;Hurley et al 2007;Sollima 2008). If we also do this here, we obtain the result described by Fig.…”

Section: Resultsmentioning

confidence: 99%

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Evolution of the binary population in young dense star clusters

Kaczmarek

Olczak

Pfalzner

2011

A&A

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Context. Field stars are not always single stars, but can often be found in bound double systems. Since binary frequencies in the birth places of stars, young embedded clusters, are sometimes even higher than on average the question arises of how binary stars form in young dense star clusters and how their properties evolve to those observed in the field population. Aims. We assess, the influence of stellar dynamical interactions on the primordial binary population in young dense cluster environments. Methods. We perform numerical N-body simulations of the Orion nebula cluster like star cluster models including primordial binary populations using the simulation code nbody6 ++ . Results. We find two remarkable results that have yet not been reported: The first is that the evolution of the binary frequency in young dense star clusters is independent predictably of its initial value. The time evolution of the normalized number of binary systems has a fundamental shape. The second main result is that the mass of the primary star is of vital importance to the evolution of the binary. The more massive a primary star, the lower the probability that the binary is destroyed by gravitational interactions. This results in a higher binary frequency for stars more massive than 2 M compared to the binary frequency of lower mass stars. The observed increase in the binary frequency with primary mass is therefore most likely not due to differences in the formation process but can be entirely explained as a dynamical effect. Conclusions. Our results allow us to draw conclusions about the past and the future number of binary systems in young dense star clusters and demonstrate that the present field stellar population has been influenced significantly by its natal environments.

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Section: Resultssupporting

confidence: 67%

Section: Resultsmentioning

confidence: 99%

Evolution of the binary population in young dense star clusters

Kaczmarek

Olczak

Pfalzner

2011

A&A

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“…The small amount of dynamical evolution expected to occur in Taurus will take place very early on (≤10 5 yr), when the initial protostellar aggregates still have a density of order 10 3 stars pc −3 (Kroupa & Bouvier 2003). Disruptive encounters between protostellar systems at this stage may result in the decreasing multiplicity fraction we observe in Taurus during the Class I phase on a timescale of ∼10 5 yr (Table 4).…”

Section: Confrontation With Model Predictionsmentioning

confidence: 93%

Multiple protostellar systems

Duchêne

Bouvier²,

Bontemps

et al. 2004

A&A

112

147

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Abstract. We performed a deep infrared imaging survey of 63 embedded young stellar objects (YSOs) located in the Taurus and Ophiuchus clouds to search for companions. The sample includes Class I and flat infrared spectrum protostellar objects. We find 17 companions physically bound to 15 YSOs with angular separations in the range 0.8-10 (110-1400 AU) and derive a companion star fraction of 23 ± 9% and 29 ± 7% for embedded YSOs in Taurus and Ophiuchus, respectively, about twice as large as that found among G dwarfs in the solar neighborhood. Therefore, binary and multiple protostellar systems are a very frequent outcome of the fragmentation of prestellar cores. In spite of different properties of the clouds and especially of the prestellar cores, the fraction of wide companions, 27 ± 6% for the combined sample, is identical in the two star-forming regions. This suggests that the frequency and properties of wide multiple protostellar systems are not very sensitive to specific initial conditions. Comparing the companion star fraction of the youngest YSOs still surrounded by extended envelopes to that of more evolved YSOs, we find evidence for a possible evolution of the fraction of wide multiple systems, which seems to decrease by a factor of about two on a timescale of ∼10 5 yr. For the first time it is possible to confront the result of a multiplicity survey of a nearly complete population of embedded YSOs at an age of ∼10 5 yr to numerical simulations of molecular cloud collapse which, after a few free fall times, reach this evolutionary stage. Somewhat contrary to model predictions, we do not find evidence for a sub-clustering of embedded sources at this stage on a scale of a few 100 AU that could be related to the formation of small-N protostellar clusters. Possible interpretations of this discrepancy are discussed.

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“…All of Taurus has more than 300 known members and the stellar density in each of its groups is, with 1 − 10 stars pc −3 , very low (Luhman et al 2009). The N-body models of Kroupa & Bouvier (2003b) show that Taurus-Auriga like arrangements are largely unevolved and in particular that the binary properties should be similar to those at birth, with some dynamical evolution . Taurus exhibits a paucity of high-mass young stars (Kenyon et al 2008) and was originally proposed to be deficient in low-mass stars (Briceño et al 2002) as well.…”

Section: The Stellar and Substellar Population Inmentioning

confidence: 99%

Using binary statistics in Taurus-Auriga to distinguish between brown dwarf formation processes

Marks¹,

Martín

Béjar

et al. 2017

A&A

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Context. Whether brown dwarfs (BDs) form just as stars directly from the gravitational collapse of a molecular cloud core ("star-like") or whether BDs and some very low-mass stars (VLMSs) constitute a separate population which form alongside stars comparable to the population of planets, e.g. through circumstellar disk ("peripheral") fragmentation, is one of the key questions of the star-formation problem. Aims. For young stars in Taurus-Auriga the binary fraction has been shown to be large with little dependence on primary mass above ≈ 0.2M⊙, while for BDs it is < 10%. Here we investigate a case in which BDs in Taurus formed dominantly, but not exclusively, through peripheral fragmentation, which naturally results in low binary fractions. The decline of the binary frequency in the transition region between star-like formation and peripheral formation is modelled. Methods. A dynamical population synthesis model is employed in which stellar binary formation is universal with a large binary fraction close to unity. Peripheral objects form separately in circumstellar disks with a distinctive initial mass function (IMF), own orbital parameter distributions for binaries and a low binary fraction according to observations and expectations from smoothed particle hydrodynamics (SPH) and grid-based computations. A small amount of dynamical processing of the stellar component is accounted for as appropriate for the low-density Taurus-Auriga embedded clusters. Results. The binary fraction declines strongly in the transition region between star-like and peripheral formation, exhibiting characteristic features. The location of these features and the steepness of this trend depend on the masslimits for star-like and peripheral formation. Such a trend might be unique to low density regions like Taurus which host dynamically largely unprocessed binary populations in which the binary fraction is large for stars down to M-dwarfs and low for BDs. Conclusions. The existence of a strong decline in the binary fraction -primary mass diagram will become verifiable in future surveys on BD and VLMS binarity in the Taurus-Auriga star forming region. It is a test of the (non-)continuity of star formation along the mass-scale, the separateness of the stellar and BD populations and the dominant formation channel for BDs and BD binaries in regions of low stellar density hosting dynamically unprocessed populations.

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The dynamical evolution of Taurus-Auriga-type aggregates

Cited by 74 publications

References 44 publications

Evolution of the binary population in young dense star clusters

Evolution of the binary population in young dense star clusters

Multiple protostellar systems

Using binary statistics in Taurus-Auriga to distinguish between brown dwarf formation processes

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