Aspect ratio dependence of the free-fall time for non-spherical symmetries

Andy Pon, Jesús A. Toalá, Doug Johnstone, Enrique Vázquez-Semadeni, Fabian Heitsch, Gilberto C. Gómez

Resultado de la investigación: Contribución a una revistaArtículo

40 Citas (Scopus)

Resumen

We investigate the collapse of non-spherical substructures, such as sheets and filaments, which are ubiquitous in molecular clouds. Such non-spherical substructures collapse homologously in their interiors but are influenced by an edge effect that causes their edges to be preferentially accelerated. We analytically compute the homologous collapse timescales of the interiors of uniform-density, self-gravitating filaments and find that the homologous collapse timescale scales linearly with the aspect ratio. The characteristic timescale for an edge-driven collapse mode in a filament, however, is shown to have a square-root dependence on the aspect ratio. For both filaments and circular sheets, we find that selective edge acceleration becomes more important with increasing aspect ratio. In general, we find that lower dimensional objects and objects with larger aspect ratios have longer collapse timescales. We show that estimates for star formation rates, based upon gas densities, can be overestimated by an order of magnitude if the geometry of a cloud is not taken into account.

Idioma originalInglés
Número de artículo145
PublicaciónAstrophysical Journal
Volumen756
N.º2
DOI
EstadoPublicada - 10 sep 2012

Huella dactilar

free fall
symmetry
aspect ratio
filaments
timescale
substructures
edge effect
gas density
star formation rate
molecular clouds
geometry
causes
estimates
gas

Citar esto

Pon, Andy ; Toalá, Jesús A. ; Johnstone, Doug ; Vázquez-Semadeni, Enrique ; Heitsch, Fabian ; Gómez, Gilberto C. / Aspect ratio dependence of the free-fall time for non-spherical symmetries. En: Astrophysical Journal. 2012 ; Vol. 756, N.º 2.
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Aspect ratio dependence of the free-fall time for non-spherical symmetries. / Pon, Andy; Toalá, Jesús A.; Johnstone, Doug; Vázquez-Semadeni, Enrique; Heitsch, Fabian; Gómez, Gilberto C.

En: Astrophysical Journal, Vol. 756, N.º 2, 145, 10.09.2012.

Resultado de la investigación: Contribución a una revistaArtículo

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AU - Pon, Andy

AU - Toalá, Jesús A.

AU - Johnstone, Doug

AU - Vázquez-Semadeni, Enrique

AU - Heitsch, Fabian

AU - Gómez, Gilberto C.

PY - 2012/9/10

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N2 - We investigate the collapse of non-spherical substructures, such as sheets and filaments, which are ubiquitous in molecular clouds. Such non-spherical substructures collapse homologously in their interiors but are influenced by an edge effect that causes their edges to be preferentially accelerated. We analytically compute the homologous collapse timescales of the interiors of uniform-density, self-gravitating filaments and find that the homologous collapse timescale scales linearly with the aspect ratio. The characteristic timescale for an edge-driven collapse mode in a filament, however, is shown to have a square-root dependence on the aspect ratio. For both filaments and circular sheets, we find that selective edge acceleration becomes more important with increasing aspect ratio. In general, we find that lower dimensional objects and objects with larger aspect ratios have longer collapse timescales. We show that estimates for star formation rates, based upon gas densities, can be overestimated by an order of magnitude if the geometry of a cloud is not taken into account.

AB - We investigate the collapse of non-spherical substructures, such as sheets and filaments, which are ubiquitous in molecular clouds. Such non-spherical substructures collapse homologously in their interiors but are influenced by an edge effect that causes their edges to be preferentially accelerated. We analytically compute the homologous collapse timescales of the interiors of uniform-density, self-gravitating filaments and find that the homologous collapse timescale scales linearly with the aspect ratio. The characteristic timescale for an edge-driven collapse mode in a filament, however, is shown to have a square-root dependence on the aspect ratio. For both filaments and circular sheets, we find that selective edge acceleration becomes more important with increasing aspect ratio. In general, we find that lower dimensional objects and objects with larger aspect ratios have longer collapse timescales. We show that estimates for star formation rates, based upon gas densities, can be overestimated by an order of magnitude if the geometry of a cloud is not taken into account.

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