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Structure and Expansion Law of HII Regions in structured Molecular Clouds | | Manuel Zamora-Avilés
; Enrique Vázquez-Semadeni
; Ricardo F. González
; José Franco
; Steven N. Shore
; Lee W. Hartmann
; Javier Ballesteros-Paredes
; Robi Banerjee
; Bastian Körtgen
; | | Date: |
5 Mar 2019 | | Abstract: | We present radiation-magnetohydrodynamic simulations aimed at studying
evolutionary properties of HII regions in turbulent, magnetised, and collapsing
molecular clouds formed by converging flows in the warm neutral medium. We
focus on the structure, dynamics and expansion laws of these regions. Once a
massive star forms in our highly structured clouds, its ionising radiation
eventually stops the accretion (through filaments) toward the massive
star-forming regions. The new over-pressured HII regions push away the dense
gas, thus disrupting the more massive collapse centres. Also, because of the
complex density structure in the cloud, the HII regions expand in a hybrid
manner: they virtually do not expand toward the densest regions (cores), while
they expand according to the classical analytical result towards the rest of
the cloud, and in an accelerated way, as a blister region, towards the diffuse
medium. Thus, the ionised regions grow anisotropically, and the ionising stars
generally appear off-centre of the regions. Finally, we find that the
hypotheses assumed in standard HII-region expansion models (fully embedded
region, blister-type, or expansion in a density gradient) apply simultaneously
in different parts of our simulated HII regions, producing a net expansion law
($R propto t^alpha$, with $alpha$ in the range of 0.93-1.47 and a mean value
of $1.2 pm 0.17$) that differs from any of those of the standard models. | | Source: | arXiv, 1903.1644 | | Services: | Forum | Review | PDF | Favorites | |
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