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- Farias Osses, Juan Pablo, 1987, et al.
(författare)
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Gas expulsion in highly substructured embedded star clusters
- 2018
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 476:4, s. 5341-5357
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the response of initially substructured, young, embedded star clusters to instantaneous gas expulsion of their natal gas. We introduce primordial substructure to the stars and the gas by simplistically modelling the star formation process so as to obtain a variety of substructure distributed within our modelled star-forming regions. We show that, by measuring the virial ratio of the stars alone (disregarding the gas completely), we can estimate how much mass a star cluster will retain after gas expulsion to within 10 per cent accuracy, no matter how complex the background structure of the gas is, and we present a simple analytical recipe describing this behaviour. We show that the evolution of the star cluster while still embedded in the natal gas, and the behaviour of the gas before being expelled, is crucial process that affect the time-scale on which the cluster can evolve into a virialized spherical system. Embedded star clusters that have high levels of substructure are subvirial for longer times, enabling them to survive gas expulsion better than a virialized and spherical system. By using a more realistic treatment for the background gas than our previous studies, we find it very difficult to destroy the young clusters with instantaneous gas expulsion. We conclude that gas removal may not be the main culprit for the dissolution of young star clusters.
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| 2. |
- Farias Osses, Juan Pablo, 1987, et al.
(författare)
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On the formation of runaway stars BN and x in the Orion Nebula Cluster
- 2018
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 612
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Tidskriftsartikel (refereegranskat)abstract
- We explore scenarios for the dynamical ejection of stars BN and x from source I in the Kleinmann-Low nebula of the Orion Nebula Cluster (ONC), which is important because it is the closest region of massive star formation. This ejection would cause source I to become a close binary or a merger product of two stars. We thus consider binary-binary encounters as the mechanism to produce this event. By running a large suite of N-body simulations, we find that it is nearly impossible to match the observations when using the commonly adopted masses for the participants, especially a source I mass of 7 M-circle dot. The only way to recreate the event is if source I is more massive, that is, similar to 20 M-circle dot. However, even in this case, the likelihood of reproducing the observed system is low. We discuss the implications of these results for understanding this important star-forming region.
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| 3. |
- Farias Osses, Juan Pablo, 1987
(författare)
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Th Dynamics of Star Cluster Formation
- 2018
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A major question in astrophysics is how star clusters form. These objects are important, since they are the birth sites of most stars, perhaps including our own Sun. There are different theoretical models of cluster formation and our main goal is to examine how they may affect the dynamical evolution of the stars in the system, including those stars that are ejected from the cluster. In particular, we set up cluster formation models with global initial conditions of the Turbulent Clump Model, which has been proposed as a description of gas structures within molecular clouds. We then investigate how global star formation efficiency from such a natal gas clump, overall clump density, degree of primordial mass segregation, degree of primordial binarity and binary population properties affect the subsequent dynamical evolution. In a second paper, after a major code development that allows modeling of gradual star formation, we investigate how the rate of star cluster formation affects its dynamical evolution, which is the first time such a study has been conducted for realistic clusters that have realistic binary properties. We show througth this thesis that star clusters that formed fast, i.e., during about one free-fall time, show quite different properties than star clusters that forms in a slow quasi-equilibirum fashion. Quickly-formed clusters tend to expand much faster compared to slow-formed clusters, thus requiring higher initial densities to agree with observations. Creation of the runaway stellar population is also sensitive to the rate of cluster formation. Future directions of this work, adding greater degrees of realism are also discussed. Finally, we carry out an example study of how the observed properties of a particular set of runaway stars can constrain properties of the dynamical ejection event, with implications for the closest region of massive star formation in the Orion Nebula Cluster.
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