Formation of star clusters with extended main-sequence turn-offs in the Magellanic Clouds: The origin of young stellar objects in older clusters

B. Armstrong, B. Q. For, K. Bekki

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Abstract

We discuss the origin of young stellar objects recently discovered in the central regions of star clusters of the Large Magellanic Cloud by investigating cold-gas accretion on to clusters through our simulation code. First, we discuss the detection of young populations and their correlation with cluster mass and young stellar objects. We show that young populations do not have a mass correlation, but are spatially associated with star clusters. We then create an analytical model of accretion from a giant molecular cloud on to a cluster, and perform numerical simulations of the gas evolution of the Magellanic Clouds during tidal interactions. Our simulations find that interactions between the Magellanic Clouds can greatly increase the amount of H2 available to clusters, allowing some to accrete greater quantities of gas, but cold gas accretion alone cannot explain the presence of extended main-sequence turn-offs in low-mass clusters with young stellar objects. The variation in accretion histories between individual clusters is dramatic. We find the amount accreted is primarily defined by cluster mass and the relative velocity between the cluster and interacting molecular cloud. The gas mass fraction, metallicity, and the strength of the tidal forces are all important parameters. Finally, we explain our results by comparing them with observations and propose observable consequences of our model.

Original languageEnglish
Pages (from-to)3651-3660
Number of pages10
JournalMonthly Notices of the Royal Astronomical Society
Volume481
Issue number3
DOIs
Publication statusPublished - 11 Dec 2018

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star clusters
Magellanic clouds
accretion
gas
young population
cold gas
simulation
molecular clouds
gas evolution
young
gases
metallicity
history
histories
interactions
cold

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title = "Formation of star clusters with extended main-sequence turn-offs in the Magellanic Clouds: The origin of young stellar objects in older clusters",
abstract = "We discuss the origin of young stellar objects recently discovered in the central regions of star clusters of the Large Magellanic Cloud by investigating cold-gas accretion on to clusters through our simulation code. First, we discuss the detection of young populations and their correlation with cluster mass and young stellar objects. We show that young populations do not have a mass correlation, but are spatially associated with star clusters. We then create an analytical model of accretion from a giant molecular cloud on to a cluster, and perform numerical simulations of the gas evolution of the Magellanic Clouds during tidal interactions. Our simulations find that interactions between the Magellanic Clouds can greatly increase the amount of H2 available to clusters, allowing some to accrete greater quantities of gas, but cold gas accretion alone cannot explain the presence of extended main-sequence turn-offs in low-mass clusters with young stellar objects. The variation in accretion histories between individual clusters is dramatic. We find the amount accreted is primarily defined by cluster mass and the relative velocity between the cluster and interacting molecular cloud. The gas mass fraction, metallicity, and the strength of the tidal forces are all important parameters. Finally, we explain our results by comparing them with observations and propose observable consequences of our model.",
keywords = "Galaxies: star clusters: general, Galaxies: star formation, Galaxies: stellar content",
author = "B. Armstrong and For, {B. Q.} and K. Bekki",
year = "2018",
month = "12",
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doi = "10.1093/mnras/sty2445",
language = "English",
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pages = "3651--3660",
journal = "Monthly Notices of the Royal Astronomical Society",
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TY - JOUR

T1 - Formation of star clusters with extended main-sequence turn-offs in the Magellanic Clouds

T2 - The origin of young stellar objects in older clusters

AU - Armstrong, B.

AU - For, B. Q.

AU - Bekki, K.

PY - 2018/12/11

Y1 - 2018/12/11

N2 - We discuss the origin of young stellar objects recently discovered in the central regions of star clusters of the Large Magellanic Cloud by investigating cold-gas accretion on to clusters through our simulation code. First, we discuss the detection of young populations and their correlation with cluster mass and young stellar objects. We show that young populations do not have a mass correlation, but are spatially associated with star clusters. We then create an analytical model of accretion from a giant molecular cloud on to a cluster, and perform numerical simulations of the gas evolution of the Magellanic Clouds during tidal interactions. Our simulations find that interactions between the Magellanic Clouds can greatly increase the amount of H2 available to clusters, allowing some to accrete greater quantities of gas, but cold gas accretion alone cannot explain the presence of extended main-sequence turn-offs in low-mass clusters with young stellar objects. The variation in accretion histories between individual clusters is dramatic. We find the amount accreted is primarily defined by cluster mass and the relative velocity between the cluster and interacting molecular cloud. The gas mass fraction, metallicity, and the strength of the tidal forces are all important parameters. Finally, we explain our results by comparing them with observations and propose observable consequences of our model.

AB - We discuss the origin of young stellar objects recently discovered in the central regions of star clusters of the Large Magellanic Cloud by investigating cold-gas accretion on to clusters through our simulation code. First, we discuss the detection of young populations and their correlation with cluster mass and young stellar objects. We show that young populations do not have a mass correlation, but are spatially associated with star clusters. We then create an analytical model of accretion from a giant molecular cloud on to a cluster, and perform numerical simulations of the gas evolution of the Magellanic Clouds during tidal interactions. Our simulations find that interactions between the Magellanic Clouds can greatly increase the amount of H2 available to clusters, allowing some to accrete greater quantities of gas, but cold gas accretion alone cannot explain the presence of extended main-sequence turn-offs in low-mass clusters with young stellar objects. The variation in accretion histories between individual clusters is dramatic. We find the amount accreted is primarily defined by cluster mass and the relative velocity between the cluster and interacting molecular cloud. The gas mass fraction, metallicity, and the strength of the tidal forces are all important parameters. Finally, we explain our results by comparing them with observations and propose observable consequences of our model.

KW - Galaxies: star clusters: general

KW - Galaxies: star formation

KW - Galaxies: stellar content

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U2 - 10.1093/mnras/sty2445

DO - 10.1093/mnras/sty2445

M3 - Article

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EP - 3660

JO - Monthly Notices of the Royal Astronomical Society

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