Formation of Turbulent and Magnetized Molecular Clouds via Accretion Flows of H I Clouds

Inoue, Tsuyoshi; Inutsuka, Shu‐ichiro

doi:10.1088/0004-637x/759/1/35

Cited by 151 publications

(199 citation statements)

References 72 publications

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“…Other groups have numerically investigated flow-driven molecular cloud formation including the effects of the TI (e.g. Lim, Falle & Hartquist 2005;Vázquez-Semadini et al 2007;Hennebelle et al 2008;Heitsch, Stone & Hartmann 2009;Ostriker, McKee & Leroy 2010;Van Loo, Falle & Hartquist 2010;Inoue & Inutsuka 2012). This numerical work has included magnetic fields, self-gravity and the TI and has identified the thermal and dynamical instabilities that are responsible for the rapid fragmentation of the nascent cloud, largely through flow-driven scenarios.…”

Section: Formation Models Of Filamentsmentioning

confidence: 99%

Magnetohydrodynamical simulation of the formation of clumps and filaments in quiescent diffuse medium by thermal instability

Wareing

Pittard

Falle

et al. 2016

Mon. Not. R. Astron. Soc.

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We have used the AMR hydrodynamic code, MG, to perform idealised 3D MHD simulations of the formation of clumpy and filamentary structure in a thermally unstable medium without turbulence. A stationary thermally unstable spherical diffuse atomic cloud with uniform density in pressure equilibrium with low density surroundings was seeded with random density variations and allowed to evolve. A range of magnetic field strengths threading the cloud have been explored, from β = 0.1 to β = 1.0 to the zero magnetic field case (β = ∞), where β is the ratio of thermal pressure to magnetic pressure. Once the density inhomogeneities had developed to the point where gravity started to become important, self-gravity was introduced to the simulation. With no magnetic field, clouds and clumps form within the cloud with aspect ratios of around unity, whereas in the presence of a relatively strong field (β = 0.1) these become filaments, then evolve into interconnected corrugated sheets that are predominantly perpendicular to the magnetic field. With magnetic and thermal pressure equality (β = 1.0), filaments, clouds and clumps are formed. At any particular instant, the projection of the 3D structure onto a plane parallel to the magnetic field, i.e. a line of sight perpendicular to the magnetic field, resembles the appearance of filamentary molecular clouds. The filament densities, widths, velocity dispersions and temperatures resemble those observed in molecular clouds. In contrast, in the strong field case β = 0.1, projection of the 3D structure along a line of sight parallel to the magnetic field reveals a remarkably uniform structure.

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Section: Formation Models Of Filamentsmentioning

confidence: 99%

Magnetohydrodynamical simulation of the formation of clumps and filaments in quiescent diffuse medium by thermal instability

Wareing

Pittard

Falle

et al. 2016

Mon. Not. R. Astron. Soc.

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“…Mestel & Paris 1979;Nakano 1990;Basu & Mouschovias 1994, 1995a. In magnetically supercritical clouds, however, cloud collapse and star formation should occur over a short duration ∼ t ff after the star forming cloud forms (Inoue & Inutsuka 2012), where t ff is the freefall timescale for the initial cloud.…”

Section: Environmental Effectsmentioning

confidence: 99%

Different modes of star formation: gravitational collapse of magnetically subcritical cloud

Machida

Higuchi

Okuzumi

2017

Monthly Notices of the Royal Astronomical Society

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Star formation in magnetically subcritical clouds is investigated using a threedimensional non-ideal magneto-hydrodynamics simulation. Since rapid cloud collapse is suppressed until the magnetic flux is sufficiently removed from the initially magnetically subcritical cloud by ambipolar diffusion, it takes ∼ > 5-10 t ff to form a protostar, where t ff is the freefall timescale of the initial cloud. The angular momentum of the star forming cloud is efficiently transferred to the interstellar medium before the rapid collapse begins, and the collapsing cloud has a very low angular momentum. Unlike the magnetically supercritical case, no large-scale low-velocity outflow appears in such a collapsing cloud due to the short lifetime of the first core. Following protostar formation, a very weak highvelocity jet, which has a small momentum and might disappear at a later time, is driven near the protostar, while the circumstellar disc does not grow during the early mass accretion phase. The results show that the star formation process in magnetically subcritical clouds is qualitatively different from that in magnetically supercritical clouds.

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“…Theoretically, it can be addressed by simulations of filament formation in a turbulent medium, where the perturbation is automatically provided at the time of filament formation. However, although many authors have performed such simulations (e.g., Gammie et al 2003;Inoue & Inutsuka 2012;Matsumoto et al 2015;Federrath 2016), none of them have focused on the subsequent collapse of the fragmented cores. To reduce the uncertainty coming from the initial condition, it is important to perform a simulation similar to this work but starting from filament formation in future.…”

Section: Fragmentation Of Filaments Under External Pressurementioning

confidence: 99%

Fates of the dense cores formed by fragmentation of filaments: do they fragment again or not?

Sugimura

Mizuno

Matsumoto

et al. 2017

Monthly Notices of the Royal Astronomical Society

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Fragmentation of filaments into dense cores is thought to be an important step in forming stars. The bar-mode instability of spherically collapsing cores found in previous linear analysis invokes a possibility of re-fragmentation of the cores due to their ellipsoidal (prolate or oblate) deformation. To investigate this possibility, here we perform three-dimensional self-gravitational hydrodynamics simulations that follow all the way from filament fragmentation to subsequent core collapse. We assume the gas is polytropic with index γ, which determines the stability of the bar-mode. For the case that the fragmentation of isolated hydrostatic filaments is triggered by the most unstable fragmentation mode, we find the bar mode grows as collapse proceeds if γ < 1.1, in agreement with the linear analysis. However, it takes more than ten ordersof-magnitude increase in the central density for the distortion to become non-linear. In addition to this fiducial case, we also study non-fiducial ones such as the fragmentation is triggered by a fragmentation mode with a longer wavelength and it occurs during radial collapse of filaments and find the distortion rapidly grows. In most of astrophysical applications, the effective polytropic index of collapsing gas exceeds 1.1 before ten orders-of-magnitude increase in the central density. Thus, supposing the fiducial case of filament fragmentation, re-fragmentation of dense cores would not be likely and their final mass would be determined when the filaments fragment.

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Formation of Turbulent and Magnetized Molecular Clouds via Accretion Flows of H I Clouds

Cited by 151 publications

References 72 publications

Magnetohydrodynamical simulation of the formation of clumps and filaments in quiescent diffuse medium by thermal instability

Magnetohydrodynamical simulation of the formation of clumps and filaments in quiescent diffuse medium by thermal instability

Different modes of star formation: gravitational collapse of magnetically subcritical cloud

Fates of the dense cores formed by fragmentation of filaments: do they fragment again or not?

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