2011/03/31 by Kazunari Iwasaki, Shu-ichiro Inutsuka, Shu‐ichiro Inutsuka +1 · 1 citation
Mathematics · Physics and Astronomy · #Astro and Planetary Science #Astrophysics and Star Formation Studies #Boundary (topology) #Boundary value problem #Classical mechanics #Cosmology and Gravitation Theories #Discontinuity (linguistics) #Geometry #Gravitation #Materials science #Mathematical analysis #Mathematics #Mechanics #Perturbation (astronomy) #Physics #Shell (structure) #Shock (circulatory) #Shock front #Shock wave #Statistical physics #astro-ph.GA #astro-ph.SR
paper · pdf · doi:10.1088/0004-637x/733/1/16
13 pages, 13 figures, to be published in the Astrophysical Journal
openalex publication_date 2011/04/27 · arxiv created 2011/05/02 · arxiv updated 2015/05/27 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We perform a linear perturbation analysis of expanding shells driven by expansions of H ii regions. The ambient gas is assumed to be uniform. As an unperturbed state, we develop a semi-analytic method for deriving the time evolution of the density profile across the thickness. It is found that the time evolution of the density profile can be divided into three evolutionary phases: deceleration-dominated, intermediate, and self-gravity-dominated phases. The density peak moves relatively from the shock front to the contact discontinuity as the shell expands. We perform a linear analysis taking into account the asymmetric density profile obtained by the semi-analytic method, and imposing the boundary conditions for the shock front and the contact discontinuity while the evolutionary effect of the shell is neglected. It is found that the growth rate is enhanced compared with previous studies based on the thin-shell approximation. This is due to the boundary effect of the contact discontinuity and asymmetric density profile that were not taken into account in previous works.