How do binary clusters form?

Arnold, Becky; Goodwin, S. P.; Griffiths, Daniel; Parker, R. J.

doi:10.1093/mnras/stx1719

Cited by 23 publications

(30 citation statements)

References 27 publications

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“…The simulation differ only by the initial virial ratio. If 16-05-1 was the true initial condition, IRS 1/2 could be a binary cluster (Rozhavskii et al 1976 Priyatikanto et al 2016;Zhong et al 2019;Bisht et al 2021), which is a common outcome in simulations with these initial conditions (Arnold et al 2017). If 16-03-5 remained as a set of initial conditions consistent with the observations, then IRS 1/2 would have formed with a slightly different initial set-up than S Mon.…”

Section: Implications Of the Results For Both Subregionsmentioning

confidence: 89%

Constraining the initial conditions of NGC 2264 using ejected stars found in Gaia DR2

Schoettler

Parker

Bruijne

2021

Monthly Notices of the Royal Astronomical Society

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Fast, ejected stars have been found around several young star-forming regions, such as the Orion Nebula Cluster (ONC). These ejected stars can be used to constrain the initial density, spatial and kinematic substructure when compared to predictions from N-body simulations. We search for runaway and slower walkaway stars using Gaia DR2 within 100 pc of NGC 2264, which contains subclustered regions around higher-mass OB-stars (S Mon, IRS 1 and IRS 2). We find five runaways and nine walkaways that trace back to S Mon and six runaways and five walkaways that trace back to IRS 1/2 based on their 3D-kinematics. We compare these numbers to a range of N-body simulations with different initial conditions. The number of runaways/walkaways is consistent with initial conditions with a high initial stellar density (∼10 000 M⊙ pc−3), a high initial amount of spatial substructure and either a subvirial or virialised ratio for all subclusters. We also confirm the trajectories of our ejected stars using the data from Gaia EDR3, which reduces the number of runaways from IRS 1/2 from six to four but leaves the number of runaways from S Mon unchanged. The reduction in runaways is due to smaller uncertainties in the proper motion and changes in the parallax/distance estimate for these stars in Gaia EDR3. We find further runaway/walkaway candidates based on proper motion alone in Gaia DR2, which could increase these numbers once radial velocities are available. We also expect further changes in the candidate list with upcoming Gaia data releases.

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Section: Implications Of the Results For Both Subregionsmentioning

confidence: 89%

Constraining the initial conditions of NGC 2264 using ejected stars found in Gaia DR2

Schoettler

Parker

Bruijne

2021

Monthly Notices of the Royal Astronomical Society

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“…In part, this is due to the fact that stars migrate significant distances during the dynamical evo-lution of the simulations (Fig. 6) and swap between groups (see also Arnold et al 2017). The problem of 'bridging' is likely ignored in observational studies if the thresholds for group definition are tuned to each specific region at a given time, rather than being automated as we have done here.…”

Section: Discussionmentioning

confidence: 99%

“…Interestingly, Arnold et al (2017) find a similar result when examining the formation of binary star clusters -two clusters orbiting a common centre of massfrom initially supervirial, substructured star-forming regions like those in this paper. Arnold et al (2017) find that the stars which constitute the components of the binary clusters do not originate in the same location as their fellow constituents, making it impossible to predict where a star will end up during the evolution of a supervirial star-forming region.…”

Section: Supervirial (Expanding) Star-forming Regionsmentioning

confidence: 99%

“…Again, the colours of groups identified at later snapshots are not correlated with the colours of the groups identified at t = 0 Myr. These initial conditions (D = 2.0 and α vir = 1.5) often lead to the formation of a binary cluster (Arnold et al 2017), and this happens in more than 50 per cent of the realisations of this set of initial conditions.…”

Section: Varying the Initial Degree Of Substructurementioning

confidence: 99%

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Evolution of spatio-kinematic structures in star-forming regions: are Friends of Friends worth knowing?

Parker

Wright

2018

Monthly Notices of the Royal Astronomical Society

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The Friends of Friends algorithm identifies groups of objects with similar spatial and kinematic properties, and has recently been used extensively to quantify the distributions of gas and stars in young star-forming regions. We apply the Friends of Friends algorithm to N-body simulations of the dynamical evolution of subvirial (collapsing) and supervirial (expanding) star-forming regions. We find that the algorithm picks out a wide range of groups (1-25) for statistically identical initial conditions, and cannot distinguish between subvirial and supervirial regions in that we obtain similar mode and median values for the number of groups it identifies. We find no correlation between the number of groups identified initially and either the initial or subsequent spatial and kinematic tracers of the regions' evolution, such as the amount of spatial substructure, dynamical mass segregation, or velocity dispersion. We therefore urge caution in using the Friends of Friends algorithm to quantify the initial conditions of star formation.

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“…Such substructures can be characterised using the fractal substructure parameter (e.g., Goodwin & Whitworth 2004;Daffern-Powell & Parker 2020). Such clumpy initial structures of star clusters were seen to trigger the formation of binary star clusters (see Arnold et al 2017), through the mechanism (see de la Fuente Marcos & de la Fuente Marcos 2010). Such mechanism is thought to form binary star clusters, as identified by Dieball et al (2002), de la Fuente Marcos & de la Fuente Marcos (2009), and Palma et al (2016).…”

Section: Introductionmentioning

confidence: 99%

The Formation of Binary Star Clusters in the Milky Way and Large Magellanic Cloud

Darma,

Arifyanto,

Kouwenhoven

2021

Preprint

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Recent observations of young embedded clumpy clusters and statistical identifications of binary star clusters have provided new insights into the formation process and subsequent dynamical evolution of star clusters. The early dynamical evolution of clumpy stellar structures provides the conditions for the origin of binary star clusters. Here, we carry out 𝑁-body simulations in order to investigate the formation of binary star clusters in the Milky Way and in the Large Magellanic Cloud (LMC). We find that binary star clusters can form from stellar aggregates with a variety of initial conditions. For a given initial virial ratio, a higher degree of initial substructure results in a higher fraction of binary star clusters. The number of binary star clusters decreases over time due to merging or dissolution of the binary system. Typically, ∼ 45% of the aggregates evolve into binary/multiple clusters within 𝑡 = 20 Myr in the Milky Way environment, while merely ∼ 30% survives beyond 𝑡 = 50 Myr, with separations 50 pc. On the other hand, in the LMC, ∼ 90% of the binary/multiple clusters survive beyond 𝑡 = 20 Myr and the fraction decreases to ∼ 80% at 𝑡 = 50 Myr, with separations 35 pc. Multiple clusters are also rapidly formed for highly-substructured and expanding clusters. The additional components tend to detach and the remaining binary star cluster merges. The merging process can produce fast rotating star clusters with mostly flat rotation curves that speed up in the outskirts.

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How do binary clusters form?

Cited by 23 publications

References 27 publications

Constraining the initial conditions of NGC 2264 using ejected stars found in Gaia DR2

Constraining the initial conditions of NGC 2264 using ejected stars found in Gaia DR2

Evolution of spatio-kinematic structures in star-forming regions: are Friends of Friends worth knowing?

The Formation of Binary Star Clusters in the Milky Way and Large Magellanic Cloud

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