Radiation Hydrodynamics Simulations of Spherical Protostellar Collapse for Very Low Mass Objects

Abstract

We perform radiation hydrodynamical simulations of protostellar collapse in spherical symmetry, with a special focus on very low-mass objects, i.e. brown dwarfs and sub-brown dwarfs. The inclusion of a realistic equation of state that includes the effect of hydrogen dissociation allows for a modeling of the complete process from the beginning of the collapse until the formation of the protostar. We solve the frequency-dependent radiative transfer equation without any diffusion approximation, using realistic dust and gas opacities. Our results show that the properties of the protostar are essentially independent of the initial conditions, which had previously only been confirmed for higher mass ranges. For very low mass initial conditions, however, we find that the first core phase of the collapse shows some significant differences in the time evolution, with the first core lifetime increasing dramatically because of the reduced accretion rate from the surrounding envelope. We consider the observational implications of this. We also investigate the opposite case of a collapse without any first core phase, which may occur for very unstable initial conditions. In the appendix, we describe a severe numerical problem that causes an unphysical expansion after the formation of the protostar, which may affect other attempts at similar calculations of self-gravitational collapse. We explain the origin of the unphysical behavior and present a solution that can be used in similar investigations.

Accepted to ApJ

References in corpus (14)

• Filamentary structure of star-forming complexes
• The properties of brown dwarfs and low-mass hydrogen-burning stars formed by disc fragmentation
• Inefficient star formation through turbulence, magnetic fields and feedback
• Radiation Magnetohydrodynamic Simulations of Protostellar Collapse: Non-Ideal Magnetohydrodynamic Effects and Early Formation of Circumstellar Disks
• Can non-ideal magnetohydrodynamics solve the magnetic braking catastrophe?
• Effects of Ohmic and ambipolar diffusion on the formation and evolution of the first cores, protostars and circumstellar discs
• Exposed Long-lifetime First-core: A New Model of First Cores Based on Radiation Hydrodynamics
• The First Jet in the Universe: Protostellar Jets from the First Stars
• Chemical tracers of episodic accretion in low-mass protostars
• Revealing the dynamics of Class 0 protostellar discs with ALMA
• Chemical and physical characterization of collapsing low-mass prestellar dense cores
• A grid of 1D low-mass star formation collapse models
• Multigroup radiation hydrodynamics with flux-limited diffusion and adaptive mesh refinement
• A fast and accurate method of radiation hydrodynamics calculation in spherical symmetry

Cited by in corpus (4)

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• A low-velocity bipolar outflow from a deeply embedded object in Taurus revealed by the Atacama Compact Array
• A centrally concentrated sub-solar mass starless core in the Taurus L1495 filamentary complex
• Insights into the first and second hydrostatic core stages from numerical simulations