THE COLLAPSE OF TURBULENT CORES AND RECONNECTION DIFFUSION

Autor(es)

Leao, M. R. M. ^{[1, 2]} ; Dal Pino, E. M. De Gouveia ^[1] ; Santos-Lima, R. ^[1] ; Lazarian, A. ^[3]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, BR-05508090 Sao Paulo - Brazil

^[2] Univ Estadual Campinas, Inst Matemat Estat & Comp Cient, BR-13083859 Campinas, SP - Brazil

^[3] Univ Wisconsin, Dept Astron, Madison, WI 53706 - USA

• Tipo de documento: Artigo Científico
• Fonte: ASTROPHYSICAL JOURNAL; v. 777, n. 1 NOV 1 2013.
• Citações Web of Science: 20

Resumo

In order for a molecular cloud clump to form stars, some transport of magnetic flux is required from the denser internal regions to the outer regions; otherwise, this can prevent the gravitational collapse. Fast magnetic reconnection, which takes place in the presence of turbulence, can induce a process of reconnection diffusion that has been elaborated on in earlier theoretical works. We have named this process turbulent reconnection diffusion, or simply RD. This paper continues our numerical study of this process and its implications. In particular, we extend our studies of RD in cylindrical clouds and consider more realistic clouds with spherical gravitational potentials (from embedded stars); we also account for the effects of the gas self-gravity. We demonstrate that, within our setup reconnection, diffusion is efficient. We have also identified the conditions under which RD becomes strong enough to make an initially subcritical cloud clump supercritical and induce its collapse. Our results indicate that the formation of a supercritical core is regulated by a complex interplay between gravity, self-gravity, the magnetic field strength, and nearly transonic and trans-Alfvenic turbulence; therefore, it is very sensitive to the initial conditions of the system. In particular, self-gravity helps RD and, as a result, the magnetic field decoupling from the collapsing gas becomes more efficient compared with the case of an external gravitational field. Our simulations confirm that RD can transport magnetic flux from the core of collapsing clumps to the envelope, but only a few of them become nearly critical or supercritical sub-Alfvenic cores, which is consistent with the observations. Furthermore, we have found that the supercritical cores built up in our simulations develop a predominantly helical magnetic field geometry that is also consistent with recent observations. Finally, we have also evaluated the effective values of the turbulent RD coefficient in our simulations and found that they are much larger than the numerical diffusion coefficient, especially for initially trans-Alfvenic clouds, thus ensuring that the detected magnetic flux removal is due to the action of turbulent RD rather than numerical diffusivity. (AU)

• Processo FAPESP: 09/54006-4 - Um cluster de computadores para o Departamento de Astronomia do IAG-USP e para o Núcleo de Astrofísica da UNICSUL
• Beneficiário: Elisabete Maria de Gouveia Dal Pino
• Modalidade de apoio: Auxílio à Pesquisa - Programa Equipamentos Multiusuários
• Processo FAPESP: 07/04551-0 - Turbulência no meio intergaláctico e a origem e evolução dos campos magnéticos cósmicos
• Beneficiário: Reinaldo Santos de Lima
• Modalidade de apoio: Bolsas no Brasil - Doutorado Direto
• Processo FAPESP: 06/50654-3 - Investigação de fenômenos de altas energias e plasmas astrofísicos: teoria, observação e simulações numéricas
• Beneficiário: Elisabete Maria de Gouveia Dal Pino
• Modalidade de apoio: Auxílio à Pesquisa - Temático