Star formation from non-turbulent gas within globular clusters: Discrete multiple bursts and top-light mass functions

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Abstract

The observed discrete multiple stellar populations and internal abundance spreads in r- and s-process elements within globular clusters (GCs) have been suggested to be explained selfconsistently by discrete star formation (SF) events over a longer time-scale (∼108 yr). We here investigate whether such SF is really possible within GCs using numerical simulations that include effects of dynamical interaction between individual stars and the accumulated gas ('star-gas interaction') on SF. The principal results are as follows. Small gas clouds with densities larger than 1010 atoms cm-3 corresponding to first stellar cores can be developed from gas without turbulence. Consequently, new stars can be formed from the gas with high star formation efficiencies (>0.5) in a burstymanner. However, SF can be suppressed when the gas mass fractions within GCs (fg) are less than a threshold value (fg,th). This fg,th is larger for GCs with lower masses and larger gas discs. Star-gas interaction and gravitational potentials of GCs can combine to suppress the formation of massive stars (i.e. 'top-light' stellar initial mass function). Formation of He-rich stars directly from gas of massive asymptotic giant branch stars is possible in massive GCs due to low fg,th (<0.01). Short bursty SF only for fg> fg,th can be partly responsible for discrete multiple SF events within GCs. We discuss how these results depend on the adopted model assumptions, such as rotating gas discs within GCs.

Original languageEnglish
Pages (from-to)2570-2586
Number of pages17
JournalMonthly Notices of the Royal Astronomical Society
Volume486
Issue number2
DOIs
Publication statusPublished - 1 Jun 2019

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globular clusters
star formation
bursts
gases
gas
stars
stellar cores
asymptotic giant branch stars
interactions
massive stars
gravitational fields
turbulence
timescale
thresholds

Cite this

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title = "Star formation from non-turbulent gas within globular clusters: Discrete multiple bursts and top-light mass functions",
abstract = "The observed discrete multiple stellar populations and internal abundance spreads in r- and s-process elements within globular clusters (GCs) have been suggested to be explained selfconsistently by discrete star formation (SF) events over a longer time-scale (∼108 yr). We here investigate whether such SF is really possible within GCs using numerical simulations that include effects of dynamical interaction between individual stars and the accumulated gas ('star-gas interaction') on SF. The principal results are as follows. Small gas clouds with densities larger than 1010 atoms cm-3 corresponding to first stellar cores can be developed from gas without turbulence. Consequently, new stars can be formed from the gas with high star formation efficiencies (>0.5) in a burstymanner. However, SF can be suppressed when the gas mass fractions within GCs (fg) are less than a threshold value (fg,th). This fg,th is larger for GCs with lower masses and larger gas discs. Star-gas interaction and gravitational potentials of GCs can combine to suppress the formation of massive stars (i.e. 'top-light' stellar initial mass function). Formation of He-rich stars directly from gas of massive asymptotic giant branch stars is possible in massive GCs due to low fg,th (<0.01). Short bursty SF only for fg> fg,th can be partly responsible for discrete multiple SF events within GCs. We discuss how these results depend on the adopted model assumptions, such as rotating gas discs within GCs.",
keywords = "dust, extinction, galaxies: evolution, galaxies: ISM- infrared: galaxies., stars: formation",
author = "Kenji Bekki",
year = "2019",
month = "6",
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doi = "10.1093/mnras/stz999",
language = "English",
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pages = "2570--2586",
journal = "Monthly Notices of the Royal Astronomical Society",
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TY - JOUR

T1 - Star formation from non-turbulent gas within globular clusters

T2 - Discrete multiple bursts and top-light mass functions

AU - Bekki, Kenji

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N2 - The observed discrete multiple stellar populations and internal abundance spreads in r- and s-process elements within globular clusters (GCs) have been suggested to be explained selfconsistently by discrete star formation (SF) events over a longer time-scale (∼108 yr). We here investigate whether such SF is really possible within GCs using numerical simulations that include effects of dynamical interaction between individual stars and the accumulated gas ('star-gas interaction') on SF. The principal results are as follows. Small gas clouds with densities larger than 1010 atoms cm-3 corresponding to first stellar cores can be developed from gas without turbulence. Consequently, new stars can be formed from the gas with high star formation efficiencies (>0.5) in a burstymanner. However, SF can be suppressed when the gas mass fractions within GCs (fg) are less than a threshold value (fg,th). This fg,th is larger for GCs with lower masses and larger gas discs. Star-gas interaction and gravitational potentials of GCs can combine to suppress the formation of massive stars (i.e. 'top-light' stellar initial mass function). Formation of He-rich stars directly from gas of massive asymptotic giant branch stars is possible in massive GCs due to low fg,th (<0.01). Short bursty SF only for fg> fg,th can be partly responsible for discrete multiple SF events within GCs. We discuss how these results depend on the adopted model assumptions, such as rotating gas discs within GCs.

AB - The observed discrete multiple stellar populations and internal abundance spreads in r- and s-process elements within globular clusters (GCs) have been suggested to be explained selfconsistently by discrete star formation (SF) events over a longer time-scale (∼108 yr). We here investigate whether such SF is really possible within GCs using numerical simulations that include effects of dynamical interaction between individual stars and the accumulated gas ('star-gas interaction') on SF. The principal results are as follows. Small gas clouds with densities larger than 1010 atoms cm-3 corresponding to first stellar cores can be developed from gas without turbulence. Consequently, new stars can be formed from the gas with high star formation efficiencies (>0.5) in a burstymanner. However, SF can be suppressed when the gas mass fractions within GCs (fg) are less than a threshold value (fg,th). This fg,th is larger for GCs with lower masses and larger gas discs. Star-gas interaction and gravitational potentials of GCs can combine to suppress the formation of massive stars (i.e. 'top-light' stellar initial mass function). Formation of He-rich stars directly from gas of massive asymptotic giant branch stars is possible in massive GCs due to low fg,th (<0.01). Short bursty SF only for fg> fg,th can be partly responsible for discrete multiple SF events within GCs. We discuss how these results depend on the adopted model assumptions, such as rotating gas discs within GCs.

KW - dust, extinction

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