A method for computing selfgravitating gas flows with radiation

Tscharnuter, W. M.; Winkler, Karl-Heinz A.

doi:10.1016/0010-4655(79)90111-5

Cited by 131 publications

(70 citation statements)

References 10 publications

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“…An excellent solution has been found by Tscharnuter and Winkler [30] for nonrelativistic hydrodynamics. We extend this approach to general relativistic hydrodynamics and define the viscous tensor…”

Section: Shock Waves and Artificial Viscositymentioning

confidence: 73%

Conservative general relativistic radiation hydrodynamics in spherical symmetry and comoving coordinates

2001

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The description of general relativistic radiation hydrodynamics in spherical symmetry is presented in natural coordinate choices. For hydrodynamics, comoving coordinates are chosen and the momentum phase space for the radiation particles is described in comoving frame four momenta. We also investigate a description of the momentum phase space in terms of particle impact parameter and energy at infinity and derive a simple approximation to the general relativistic Boltzmann equation. Further developed are, however, the exact equations in comoving coordinates since the description of the interaction between matter and radiation particles is best described in the closely related orthonormal basis comoving with the fluid elements. We achieve a conservative and concise formulation of radiation hydrodynamics that is well suited for numerical implementation by a variety of methods. The contribution of radiation to the general relativistic jump conditions at shock fronts is discussed and artificial viscosity is consistently included in the derivations in order to support approaches relying on this option.

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Section: Shock Waves and Artificial Viscositymentioning

confidence: 73%

Conservative general relativistic radiation hydrodynamics in spherical symmetry and comoving coordinates

2001

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“…The β-viscosity is a mechanical analog and an extension of the α-viscosity (Shakura & Sunyaev 1973) modeled according to the thermal properties of the disk. In addition we use the artificial tensor viscosity introduced by Tscharnuter & Winkler (1979) to broaden the emerging shock fronts. The respective kinematic viscosity reads…”

Section: Angular Momentum Transport and Viscositymentioning

confidence: 99%

Protostellar collapse of rotating cloud cores

Schönke

Tscharnuter

2011

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Aims. We investigate the influence of turbulent viscosity on the collapse of a rotating molecular cloud core with axial symmetry, in particular, on the first and second collapse phase, as well as the evolution of the second (protostellar) core during its first accretion period. By using extensive numerical calculations, we monitor the intricate interactions between the newly formed protostar and the surrounding accretion disk (the first core) in which the star is embedded. Methods. We use a grid-based radiation-hydrodynamics code with a spatial grid designed to meet the high resolution required to study the second core. The radiative transfer is treated in the flux-limited diffusion approximation. A slightly supercritical Bonnor-Ebert sphere of 1 M and uniform rotation according to a fixed centrifugal radius of 100 AU serves as the initial condition without exception. In a parameter study, we vary the β-viscosity driving the angular momentum transport. Results. Without viscosity (β = 0), a highly flattened accretion disk forms that fragments into several "cold" rings. For β = 10 −4 , a single "warm" ring forms that undergoes collapse due to hydrogen dissociation. For β = 10 −3 , ring formation is suppressed completely. The second collapse proceeds on the local thermal timescale, which is in contrast to the current view of a generally dynamical second collapse. During the first accretion period of the second core, the first core heats up globally and, as a consequence, a nearly spherical outflow occurs, destroying the structure of the former accretion disk completely. Finally, for β = 10 −2 , we see the classical dynamical second collapse and a shorter but more rapid accretion phase. The impact on the surrounding accretion disk is even more pronounced. We follow the resulting massive outflow up to several kyr after the second collapse, where the central parts (R < 0.7 AU) are now cut out and replaced with an appropriate inner boundary condition. Matter is found to turn back to the center at a radius of 500 AU after about 4 kyr and to reach the protostar again after approximately 7 kyr. The results suggest that the star formation process consists of short and rapid accretion phases (lasting on the order of 100 yr) between long and quiet outflow periods (lasting several kyr).

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“…It has been well established that the molecular gas experiences different thermal regimes from isothermal to adiabatic during the earliest phase of the collapse via the coupling between gas, dust, and radiation (e.g. Larson 1969;Tscharnuter & Winkler 1979;Masunaga et al 1998).…”

Section: Introductionmentioning

confidence: 99%

Physical and radiative properties of the first-core accretion shock

Commerçon

Audit

Chabrier

et al. 2011

A&A

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Context. Radiative shocks play a dominant role in star formation. The accretion shocks on first and second Larson cores involve radiative processes and are thus characteristic of radiative shocks. Aims. In this study, we explore the formation of the first Larson core and characterize the radiative and dynamical properties of the accretion shock, using both analytical and numerical approaches. Methods. We developed both numerical radiation-hydrodynamics calculations and a semi-analytical model that characterize radiative shocks in various physical conditions, for radiating or barotropic fluids. Then, we performed 1D spherical collapse calculations of the first Larson core, using a grey approximation for the opacity of the material. We considered three different models for radiative transfer: the barotropic approximation, the flux limited diffusion approximation, and the more complete M1 model. We investigate the characteristic properties of the collapse and of the first core formation. Comparison between the numerical results and our semianalytical model for radiative shocks shows that the latter reproduces the core properties obtained with the numerical calculations quite well. Results. The accretion shock on the first Larson core is found to be supercritical; i.e., the post and pre-shock temperatures are equal, implying that all the accretion shock energy on the core is radiated away. The shock properties are described well by the semianalytical model. The flux-limited diffusion approximation is found to agree quite well with the results based on the M1 model of radiative transfer, and is thus appropriate for studying the star formation process and allows a tractable and relatively correct treatment of radiative transfer in multidimensional radiation-hydrodynamics calculations. In contrast, the barotropic approximation does not correctly describe the thermal properties of the gas during the collapse.

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A method for computing selfgravitating gas flows with radiation

Cited by 131 publications

References 10 publications

Conservative general relativistic radiation hydrodynamics in spherical symmetry and comoving coordinates

Conservative general relativistic radiation hydrodynamics in spherical symmetry and comoving coordinates

Protostellar collapse of rotating cloud cores

Physical and radiative properties of the first-core accretion shock

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