Gas expulsion in highly substructured embedded star clusters

Farias, J. P.; Fellhauer, M.; Smith, Rory; Domínguez, Raimundo; Dabringhausen, J.

doi:10.1093/mnras/sty597

Cited by 34 publications

(50 citation statements)

References 66 publications

(100 reference statements)

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“…The situation becomes even more complicated due to effects of cloud and star cluster structure. Simulations indicate that spatial decoupling between gas and stars (Dale et al 2015) and highly substructured spatial distributions of stars (Farias et al 2018) will attenuate the effect of gas expulsion on a stellar system. Other factors such as dynamical ejection of massive stars from very dense clusters have also been identified as possible contributors to cluster mass loss leading to cluster expansion (Pfalzner & Kaczmarek 2013).…”

Section: Expectations From Simulationsmentioning

confidence: 99%

Kinematics in Young Star Clusters and Associations with Gaia DR2

Kuhn

Hillenbrand

Sills

et al. 2019

ApJ

350

385

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The Gaia mission has opened a new window into the internal kinematics of young star clusters at the sub-km s −1 level, with implications for our understanding of how star clusters form and evolve. We use a sample of 28 clusters and associations with ages from ∼1-5 Myr, where lists of members are available from previous X-ray, optical, and infrared studies. Proper motions from Gaia DR2 reveal that at least 75% of these systems are expanding; however, rotation is only detected in one system. Typical expansion velocities are on the order of ∼0.5 km s −1 , and in several systems, there is a positive radial gradient in expansion velocity. Systems that are still embedded in molecular clouds are less likely to be expanding than those that are partially or fully revealed. One-dimensional velocity dispersions, which range from 1 1D s = to 3 km s −1 , imply that most of the stellar systems in our sample are supervirial and that some are unbound. In star-forming regions that contain multiple clusters or subclusters, we find no evidence that these groups are coalescing, implying that hierarchical cluster assembly, if it occurs, must happen rapidly during the embedded stage.

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Section: Expectations From Simulationsmentioning

confidence: 99%

Kinematics in Young Star Clusters and Associations with Gaia DR2

Kuhn

Hillenbrand

Sills

et al. 2019

ApJ

350

385

View full text Add to dashboard Cite

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“…Stars are not randomly distributed within the GMCs, but are formed hierarchically within the densest molecular cores at the intersections of the gas filaments (e.g. Smith et al 2011Smith et al , 2013Farias et al 2015;Lee & Goodwin 2016;Farias et al 2018). The non-star-forming gas is expelled outward gradually rather than instantaneously (Geyer & Burkert 2001;Smith et al 2013) and is preferentially channelled through low-density holes and tunnels rather than being removed homogeneously.…”

Section: Bound Fraction Of Model Clustersmentioning

confidence: 99%

“…Stars are formed at the intersections of gas filaments and assembled into different subclusters hierarchically. Previous works have explored some of the above complications using different physical and numerical methods, including analytical models (Hills 1980;Mathieu 1983;Adams 2000;Boily & Kroupa 2003a;Kruijssen 2012;Parmentier & Pfalzner 2013), pure N-body simulations (Tutukov 1978;Lada et al 1984;Boily & Kroupa 2003b;Goodwin & Bastian 2006;Baumgardt & Kroupa 2007;Smith et al 2011;Farias et al 2018), and hydrodynamic simulations (Bonnell et al 2011;Girichidis et al 2012;Moeckel et al 2012;Fujii & Portegies Zwart 2016;Gavagnin et al 2017). Recent efforts have been made to include various relevant physical processes in hydrodynamic simulations (e.g.…”

Section: Introductionmentioning

confidence: 99%

Disruption of giant molecular clouds and formation of bound star clusters under the influence of momentum stellar feedback

Vogelsberger

Marinacci

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Energetic feedback from star clusters plays a pivotal role in shaping the dynamical evolution of giant molecular clouds (GMCs). To study the effects of stellar feedback on the star formation efficiency of the clouds and the dynamical response of embedded star clusters, we perform a suite of isolated GMC simulations with star formation and momentum feedback subgrid models using the moving-mesh hydrodynamics code AREPO. The properties of our simulated GMCs span a wide range of initial mass, radius, and velocity configurations. We find that the ratio of the final stellar mass to the total cloud mass, int , scales strongly with the initial cloud surface density and momentum feedback strength. This correlation is explained by an analytic model that considers force balancing between gravity and momentum feedback. For all simulated GMCs, the stellar density profiles are systematically steeper than that of the gas at the epochs of the peaks of star formation, suggesting a centrally concentrated stellar distribution. We also find that star clusters are always in a sub-virial state with a virial parameter ∼ 0.6 prior to gas expulsion. Both the sub-virial dynamical state and steeper stellar density profiles prevent clusters from dispersal during the gas removal phase of their evolution. The final cluster bound fraction is a continuously increasing function of int . GMCs with star formation efficiency smaller than 0.5 are still able to form clusters with large bound fractions.

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“…An alternative mechanism for the velocity structure presenting "Hubble-like" flows, which has being unforeseen in the literature is the possibility that the removal of mass due to the expansion of the H II region not only removes the gravitational potential, as has being studied previously (e.g., Smith et al 2013;Farias et al 2018), but it actually flips it up, generating a cusp at the position of the H II region, and moving away the potential well to the outside. This reversal of the gravitational field shape will add an outward acceleration to the stars in the clusters.…”

Section: -Orimentioning

confidence: 99%

Flipping-up the field: gravitational feedback as a mechanism for young clusters dispersal

Zamora-Avilés

Ballesteros-Paredes

Hernández

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Recent analyses of Gaia data have provided direct evidence that most young stellar clusters are in a state of expansion, with velocities of the order of ∼ 0.5 km s −1 . Traditionally, expanding young clusters have been pictured as entities that became unbound due to the lack of gravitational binding once the gas from the parental cloud that formed the cluster has been expelled by the stellar radiation of the massive stars in the cluster. In the present contribution we used radiation-magnetohydrodynamic numerical simulations of molecular cloud formation and evolution to understand how stellar clusters form and disperse. We found that the ionising feedback from the newborn massive stars expels the gas from the collapse centre, flipping-up the gravitational potential as a consequence of the mass removal from the inside-out. Since neither the parental clouds, nor the formed shells are distributed symmetrically around the H II region, net forces pulling out the stars are present, accelerating them towards the edges of the cavity. We call this mechanism "gravitational feedback", in which the gravity from the expelled gas appears to be the crucial mechanism producing unbound clusters that expand away from their formation centre in an accelerated way in young stellar clusters. This mechanism naturally explains the "Hubble flow-like" expansion observed in several young clusters.

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Gas expulsion in highly substructured embedded star clusters

Cited by 34 publications

References 66 publications

Kinematics in Young Star Clusters and Associations with Gaia DR2

Kinematics in Young Star Clusters and Associations with Gaia DR2

Disruption of giant molecular clouds and formation of bound star clusters under the influence of momentum stellar feedback

Flipping-up the field: gravitational feedback as a mechanism for young clusters dispersal

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