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How galactic environment regulates star formation

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Abstract
In a new simple model I reconcile two contradictory views on the factors that determine the rate at which molecular clouds form stars-internal structure versus external, environmental influences-providing a unified picture for the regulation of star formation in galaxies. In the presence of external pressure, the pressure gradient set up within a self-gravitating turbulent (isothermal) cloud leads to a non-uniform density distribution. Thus the local environment of a cloud influences its internal structure. In the simple equilibrium model, the fraction of gas at high density in the cloud interior is determined simply by the cloud surface density, which is itself inherited from the pressure in the immediate surroundings. This idea is tested using measurements of the properties of local clouds, which are found to show remarkable agreement with the simple equilibrium model. The model also naturally predicts the star formation relation observed on cloud scales and at the same time provides a mapping between this relation and the closer-to-linear molecular star formation relation measured on larger scales in galaxies. The key is that pressure regulates not only the molecular content of the ISM but also the cloud surface density. I provide a straightforward prescription for the pressure regulation of star formation that can be directly implemented in numerical models. Predictions for the dense gas fraction and star formation efficiency measured on large-scales within galaxies are also presented, establishing the basis for a new picture of star formation regulated by galactic environment.
Keywords
GIANT MOLECULAR CLOUDS, LARGE-MAGELLANIC-CLOUD, GRAVITATING GASEOUS, SPHERES, WHIRLPOOL SURVEY PAWS, NEARBY GALAXIES, MILKY-WAY, FORMATION, EFFICIENCY, INTERSTELLAR-MEDIUM, FORMATION RATES, FORMATION LAW, galaxies: ISM, galaxies: star formation, ISM: clouds, ISM: structure

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Please use this url to cite or link to this publication:

MLA
van der Wel, Sharon Meidt. “How Galactic Environment Regulates Star Formation.” ASTROPHYSICAL JOURNAL, vol. 818, no. 1, 2016.
APA
van der Wel, S. M. (2016). How galactic environment regulates star formation. ASTROPHYSICAL JOURNAL, 818(1).
Chicago author-date
Wel, Sharon Meidt van der. 2016. “How Galactic Environment Regulates Star Formation.” ASTROPHYSICAL JOURNAL 818 (1).
Chicago author-date (all authors)
van der Wel, Sharon Meidt. 2016. “How Galactic Environment Regulates Star Formation.” ASTROPHYSICAL JOURNAL 818 (1).
Vancouver
1.
van der Wel SM. How galactic environment regulates star formation. ASTROPHYSICAL JOURNAL. 2016;818(1).
IEEE
[1]
S. M. van der Wel, “How galactic environment regulates star formation,” ASTROPHYSICAL JOURNAL, vol. 818, no. 1, 2016.
@article{8622267,
  abstract     = {In a new simple model I reconcile two contradictory views on the factors that determine the rate at which molecular clouds form stars-internal structure versus external, environmental influences-providing a unified picture for the regulation of star formation in galaxies. In the presence of external pressure, the pressure gradient set up within a self-gravitating turbulent (isothermal) cloud leads to a non-uniform density distribution. Thus the local environment of a cloud influences its internal structure. In the simple equilibrium model, the fraction of gas at high density in the cloud interior is determined simply by the cloud surface density, which is itself inherited from the pressure in the immediate surroundings. This idea is tested using measurements of the properties of local clouds, which are found to show remarkable agreement with the simple equilibrium model. The model also naturally predicts the star formation relation observed on cloud scales and at the same time provides a mapping between this relation and the closer-to-linear molecular star formation relation measured on larger scales in galaxies. The key is that pressure regulates not only the molecular content of the ISM but also the cloud surface density. I provide a straightforward prescription for the pressure regulation of star formation that can be directly implemented in numerical models. Predictions for the dense gas fraction and star formation efficiency measured on large-scales within galaxies are also presented, establishing the basis for a new picture of star formation regulated by galactic environment.},
  articleno    = {69},
  author       = {van der Wel, Sharon Meidt},
  issn         = {0004-637X},
  journal      = {ASTROPHYSICAL JOURNAL},
  keywords     = {GIANT MOLECULAR CLOUDS,LARGE-MAGELLANIC-CLOUD,GRAVITATING GASEOUS,SPHERES,WHIRLPOOL SURVEY PAWS,NEARBY GALAXIES,MILKY-WAY,FORMATION,EFFICIENCY,INTERSTELLAR-MEDIUM,FORMATION RATES,FORMATION LAW,galaxies: ISM,galaxies: star formation,ISM: clouds,ISM: structure},
  language     = {eng},
  number       = {1},
  pages        = {16},
  title        = {How galactic environment regulates star formation},
  url          = {http://dx.doi.org/10.3847/0004-637X/818/1/69},
  volume       = {818},
  year         = {2016},
}

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