Kengo Tomida

RADIATION MAGNETOHYDRODYNAMIC SIMULATIONS OF PROTOSTELLAR COLLAPSE: NONIDEAL MAGNETOHYDRODYNAMIC EFFECTS AND EARLY FORMATION OF CIRCUMSTELLAR DISKS

The transport of angular momentum by magnetic fields is a crucial physical process in formation and evolution of stars and disks. Because the ionization degree in star forming clouds is extremely low, non-ideal magnetohydrodynamic (MHD) effects such as ambipolar diffusion and Ohmic dissipation work strongly during protostellar collapse. These effects have significant impacts in the early phase of star formation as they redistribute magnetic flux and suppress angular momentum transport by magnetic fields. We perform three-dimensional nested-grid radiation magnetohydrodynamic (RMHD) simulations including Ohmic dissipation and ambipolar diffusion. Without these effects, magnetic fields transport angular momentum so efficiently that no rotationally supported disk is formed even after the second collapse. Ohmic dissipation works only in a relatively high density region within the first core and suppresses angular momentum transport, enabling formation of a very small rotationally supported disk after the second collapse. With both Ohmic dissipation and ambipolar diffusion, these effects work effectively in almost the entire region within the first core and significant magnetic flux loss occurs. As a result, a rotationally supported disk is formed even before a protostellar core forms. The size of the disk is still small, about 5 AU at the end of the first core phase, but this disk will grow later as gas accretion continues. Thus the non-ideal MHD effects can resolve the so-called magnetic braking catastrophe while maintaining the disk size small in the early phase, which is implied from recent interferometric observations.

Formation of a keplerian disk in the infalling envelope around l1527 IRS: Transformation from infalling motions to kepler motions

We report Atacama Large Millimeter/submillimeter Array (ALMA) cycle 0 observations of C

RADIATION MAGNETOHYDRODYNAMICS SIMULATION OF PROTO-STELLAR COLLAPSE: TWO-COMPONENT MOLECULAR OUTFLOW

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EXPOSED LONG-LIFETIME FIRST CORE: A NEW MODEL OF FIRST CORES BASED ON RADIATION HYDRODYNAMICS

O (

ALMA OBSERVATIONS OF INFALLING FLOWS TOWARD THE KEPLERIAN DISK AROUND THE CLASS I PROTOSTAR L1489 IRS

J=2-1

Cool and luminous transients from mass-losing binary stars

), SO (

Binary stellar mergers with marginally bound ejecta: excretion discs, inflated envelopes, outflows, and their luminous transients

J_N= 6_5-5_4

EXPLICIT-IMPLICIT SCHEME FOR RELATIVISTIC RADIATION HYDRODYNAMICS

) and 1.3mm dust continuum toward L1527 IRS, a class 0 solar-type protostar surrounded by an infalling and rotating envelope. C

Grand-design Spiral Arms in a Young Forming Circumstellar Disk

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Alma observations of a high-density core in Taurus: Dynamical gas interaction at the possible site of a multiple star formation

O emission shows strong redshifted absorption against the bright continuum emission associated with L1527 IRS, strongly suggesting infall motions in the C