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- Volume 80 - Année 2011
- Radiation-MHD models of elephant trunks and globules in HII regions
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Radiation-MHD models of elephant trunks and globules in HII regions
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Abstract
We study the formation and evolution of pillars of dense gas, known as elephant trunks, at the boundaries of H II regions, formed by shadowing of ionising radiation by dense clumps. The effects of magnetic fields on this process are investigated using 3D radiation-magnetohydrodynamics simulations. For a simulation in which an initially uniform magnetic field of strength |B|≈ 50 micro-G is oriented perpendicular to the radiation propagation direction, the field is swept into alignment with the pillar during its dynamical evolution, in agreement with observations of the “Pillars of Creation” in M16, and of some cometary globules. This effect is significantly enhanced when the simulation is re-run with a weaker field of ≈ 18 micro-G. A stronger field with |B| ≈ 160 micro-G is sufficient to prevent this evolution completely, also significantly affecting the photoionisation process. Using a larger simulation domain it is seen that the pillar formation models studied in Mackey & Lim (2010) ultimately evolve to cometary structures in the absence of dense gas further from the star.
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Acerca de: Jonathan Mackey
Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Ireland, and Argelander Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany, jmackey@astro.uni-bonn.de
Acerca de: Andrew J. Lim
Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Ireland