The formation and early dynamical evolution of bound stellar systems

Lada, Charles J.; Margulis, M.; Dearborn, David S. P.

doi:10.1086/162485

Cited by 334 publications

(364 citation statements)

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“…The second effect that could alter the observed f rac M over time, is gas removal from the central region. When a cluster is formed, the gas left over from the star formation process may be rapidly removed by stellar winds (Lada, Margulis & Dearborn 1984). More recent work, however, suggests that the winds (and later, supernovae) may escape through low density channels formed in a hierarchical ISM (e.g.…”

Section: Gas Removal and Stellar Motionsmentioning

confidence: 99%

Star formation rates from young-star counts and the structure of the ISM across the NGC 346/N66 complex in the SMC★

Hony¹,

Gouliermis²,

Galliano³

et al. 2015

Monthly Notices of the Royal Astronomical Society

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The rate at which interstellar gas is converted into stars, and its dependence on environment, is one of the pillars on which our understanding of the visible Universe is build. We present a comparison of the surface density of young stars (Σ ) and dust surface density (Σ dust ) across NGC 346 (N66) in 115 independent pixels of 6×6 pc 2 . We find a correlation between Σ and Σ dust with a considerable scatter. A power law fit to the data yields a steep relation with an exponent of 2.6±0.2. We convert Σ dust to gas surface density (Σ gas ) and Σ to star formation rate (SFR) surface densities (Σ SFR ), using simple assumptions for the gas-to-dust mass ratio and the duration of star formation. The derived total SFR (4±1·10 −3 M yr −1 ) is consistent with SFR estimated from the H α emission integrated over the H α nebula. On small scales the Σ SFR derived using H α systematically underestimates the count-based Σ SFR , by up to a factor of 10. This is due to ionizing photons escaping the area, where the stars are counted. We find that individual 36 pc 2 pixels fall systematically above integrated disc-galaxies in the Schmidt-Kennicutt diagram by on average a factor of ∼7. The NGC 346 average SFR over a larger area (90 pc radius) lies closer to the relation but remains high by a factor of ∼3. The fraction of the total mass (gas plus young stars) locked in young stars is systematically high (∼10 per cent) within the central 15 pc and systematically lower outside (2 per cent), which we interpret as variations in star formation efficiency. The inner 15 pc is dominated by young stars belonging to a centrally condensed cluster, while the outer parts are dominated by a dispersed population. Therefore, the observed trend could reflect a change of star formation efficiency between clustered and non-clustered star-formation.

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Section: Gas Removal and Stellar Motionsmentioning

confidence: 99%

Star formation rates from young-star counts and the structure of the ISM across the NGC 346/N66 complex in the SMC★

Hony¹,

Gouliermis²,

Galliano³

et al. 2015

Monthly Notices of the Royal Astronomical Society

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“…Tutukov 1978;Lada et al 1984;Goodwin & Bastian 2006;Baumgardt & Kroupa 2007), or by their birth environments (e.g. Kruijssen et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Hierarchical formation of Westerlund 1: a collapsing cluster with no primordial mass segregation?

Gennaro

Goodwin

Parker

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We examine the level of substructure and mass segregation in the massive, young cluster Westerlund 1. We find that it is relatively smooth, with little or no mass segregation, but with the massive stars in regions of significantly higher than average surface density. While an expanding or bouncing-back scenario for the evolution of Westerlund 1 cannot be ruled out, we argue that the most natural model to explain these observations is one in which Westerlund 1 formed with no primordial mass segregation and at a similar or larger size than we now observe.

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“…After 5-10 Myr, 90% of the embedded clusters do not evolve to become bound open clusters, like the Pleiades, but rather disperse into the field (Lada & Lada 2003). This happens because the cluster forms in an unbound state or becomes unbound during a ∼10 Myr timeframe from the dynamical evolution of stars within the cluster (Clark et al 2005;Carpenter 2000;Adams & Myers 2001;Lada & Lada 2003), because of the expulsion of residual gas left over from star formation (e.g., Hills 1980;Lada et al 1984;, because of the tidal heating from nearby giant molecular clouds (Elmegreenalso affects planet formation because of frequent stellar encounters in crowded regions (e.g., Adams & Laughlin 2001;Parker & Quanz 2012), stellar multiplicity through dynamical interactions and the orbital separation distribution of binary systems , and mass segregation towards the cluster core (Parker & Reggiani 2013). A detailed study of dynamical states of clusters in a variety of environments is needed in order to understand the evolution of stellar clusters and the relative importance of these processes.…”

Section: Introductionmentioning

confidence: 99%

TheGaia-ESO Survey: Dynamical analysis of the L1688 region in Ophiuchus

Rigliaco

Wilking

Meyer

et al. 2016

A&A

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The Gaia ESO Public Spectroscopic Survey (GES) is providing the astronomical community with high-precision measurements of many stellar parameters including radial velocities (RVs) of stars belonging to several young clusters and star-forming regions. One of the main goals of the young cluster observations is to study their dynamical evolution and provide insight into their future, revealing whether they will eventually disperse to populate the field rather than evolve into bound open clusters. In this paper we report the analysis of the dynamical state of L1688 in the ρ Ophiuchi molecular cloud using the dataset provided by the GES consortium. We performed the membership selection of the more than 300 objects observed. Using the presence of the lithium absorption and the location in the Hertzspung-Russell diagram, we identify 45 already known members and two new association members. We provide accurate RVs for all 47 confirmed members. A dynamical analysis, after accounting for unresolved binaries and errors, shows that the stellar surface population of L1688 has a velocity dispersion σ ∼ 1.14 ± 0.35 km s −1 that is consistent with being in virial equilibrium and is bound with a ∼80% probability. We also find a velocity gradient in the stellar surface population of ∼1.0 km s −1 pc −1 in the northwest-southeast direction, which is consistent with that found for the pre-stellar dense cores, and we discuss the possibility of sequential and triggered star formation in L1688.

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The formation and early dynamical evolution of bound stellar systems

Cited by 334 publications

References 0 publications

Star formation rates from young-star counts and the structure of the ISM across the NGC 346/N66 complex in the SMC★

Star formation rates from young-star counts and the structure of the ISM across the NGC 346/N66 complex in the SMC★

Hierarchical formation of Westerlund 1: a collapsing cluster with no primordial mass segregation?

TheGaia-ESO Survey: Dynamical analysis of the L1688 region in Ophiuchus

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