Radiation Magnetohydrodynamics Simulation of Proto-Stellar Collapse: Two-Component Molecular Outflow

Joos

et al. 2011

A&A

189

216

Context. Stars, and more particularly massive stars, have a drastic impact on galaxy evolution. Yet the conditions in which they form and collapse are still not fully understood. Aims. In particular, the influence of the magnetic field on the collapse of massive clumps is relatively unexplored, it is therefore of great relevance in the context of the formation of massive stars to investigate its impact. Methods. We perform high resolution, MHD simulations of the collapse of one hundred solar masses, turbulent and magnetized clouds, with the adaptive mesh refinement code RAMSES. We compute various quantities such as mass distribution, magnetic field, and angular momentum within the collapsing core and study the episodic outflows and the fragmentation that occurs during the collapse. Results. The magnetic field has a drastic impact on the cloud evolution. We find that magnetic braking is able to substantially reduce the angular momentum in the inner part of the collapsing cloud. Fast and episodic outflows are being launched with typical velocities of the order of 1−3 km s −1 , although the highest velocities can be as high as 20−40 km s −1 . The fragmentation in several objects is reduced in substantially magnetized clouds with respect to hydrodynamical ones by a factor of the order of 1.5−2. Conclusions. We conclude that magnetic fields have a significant impact on the evolution of massive clumps. In combination with radiation, magnetic fields largely determine the outcome of massive core collapse. We stress that numerical convergence of MHD collapse is a challenging issue. In particular, numerical diffusion appears to be important at high density and therefore could possibly lead to an overestimation of the number of fragments.

Section: Discussionmentioning

confidence: 90%

Collapse, outflows and fragmentation of massive, turbulent and magnetized prestellar barotropic cores

Hennebelle

Joos

et al. 2011

A&A

189

216

“…Recent theoretical studies have shown that a low-velocity outflow can be launched during the FHSC stage (e.g., Hennebelle & Fromang 2008;Commerçon et al 2010;Tomida et al 2010b) without the high-velocity outflow that is always present at the SHSC stage (Machida et al 2008). Not only may the morphology and energetics of the outflow help in identifying the cores, but also the chemical composition of the gas in the outflow.…”

Section: Example Of Methodology To Target First Corementioning

confidence: 99%

“…In parallel, enormous work has been put into developing numerical hydrodynamical models that include magnetic fields and radiative transfer (e.g., Price & Bate 2009;Commerçon et al 2010;Tomida et al 2010b) but relatively little has been done in producing synthetic observations that are directly comparable with actual observations. Most of the observables used to confront theory and observation remain statistical in nature, such as the initial mass function (IMF) or the binary distribution, whereas observations report mostly dust continuum and molecular line emission data.…”

Section: Introductionmentioning

confidence: 99%

Synthetic observations of first hydrostatic cores in collapsing low-mass dense cores

Launhardt

Dullemond

et al. 2012

A&A

Context. The low-mass star formation evolutionary sequence is relatively well-defined both from observations and theoretical considerations. The first hydrostatic core is the first protostellar equilibrium object that is formed during the star formation process. Aims. Using state-of-the-art radiation-magneto-hydrodynamic 3D adaptive mesh refinement calculations, we aim to provide predictions for the dust continuum emission from first hydrostatic cores. Methods. We investigated the collapse and the fragmentation of magnetized 1 M prestellar dense cores and the formation and evolution of first hydrostatic cores using the RAMSES code. We used three different magnetization levels for the initial conditions, which cover a wide variety of early evolutionary morphology, e.g., the formation of a disk or a pseudo-disk, outflow launching, and fragmentation. We post-processed the dynamical calculations using the 3D radiative transfer code RADMC-3D. We computed spectral energy distributions and usual evolutionary stage indicators such as bolometric luminosity and temperature. Results. We find that the first hydrostatic core lifetimes depend strongly on the initial magnetization level of the parent dense core. We derive, for the first time, spectral energy distribution evolutionary sequences from high-resolution radiation-magneto-hydrodynamic calculations. We show that under certain conditions, first hydrostatic cores can be identified from dust continuum emission at 24 μm and 70 μm. We also show that single spectral energy distributions cannot help in distinguishing between the formation scenarios of the first hydrostatic core, i.e., between the magnetized and non-magnetized models. Conclusions. Spectral energy distributions are a first useful and direct way to target first hydrostatic core candidates but highresolution interferometry is definitively needed to determine the evolutionary stage of the observed sources.

“…Mihalas & Mihalas 1984;Lowrie et al 2001;Mihalas & Auer 2001;Krumholz et al 2007b). Radiation hydrodynamics (RHD) methods have been developed in grid-based codes (Stone & Norman 1992;Hayes & Norman 2003;Krumholz et al 2007a;Kuiper et al 2010;Sekora & Stone 2010;Tomida et al 2010) and also in smoothed particles hydrodynamics (SPH) codes (Boss et al 2000;Whitehouse & Bate 2006;Stamatellos et al 2007). Most of these studies use the popular flux-limited diffusion approximation (FLD, e.g.…”

Section: Introductionmentioning

confidence: 99%

Radiation hydrodynamics with adaptive mesh refinement and application to prestellar core collapse

Teyssier²,

Audit³

et al. 2011

A&A

160

174

Context. Radiative transfer has a strong impact on the collapse and the fragmentation of prestellar dense cores. Aims. We present the radiation-hydrodynamics (RHD) solver we designed for the RAMSES code. The method is designed for astrophysical purposes, and in particular for protostellar collapse. Methods. We present the solver, using the co-moving frame to evaluate the radiative quantities. We use the popular flux-limited diffusion approximation under the grey approximation (one group of photons). The solver is based on the second-order Godunov scheme of RAMSES for its hyperbolic part and on an implicit scheme for the radiation diffusion and the coupling between radiation and matter. Results. We report in detail our methodology to integrate the RHD solver into RAMSES. We successfully test the method in several conventional tests. For validation in 3D, we perform calculations of the collapse of an isolated 1 M prestellar dense core without rotation. We successfully compare the results with previous studies that used different models for radiation and hydrodynamics. Conclusions. We have developed a full radiation-hydrodynamics solver in the RAMSES code that handles adaptive mesh refinement grids. The method is a combination of an explicit scheme and an implicit scheme accurate to the second-order in space. Our method is well suited for star-formation purposes. Results of multidimensional dense-core-collapse calculations with rotation are presented in a companion paper.