scholarly journals Chemical variation in molecular cloud cores in the Orion A Cloud. III

2014 ◽  
Vol 66 (6) ◽  
pp. 119 ◽  
Author(s):  
Satoshi Ohashi ◽  
Ken'ichi Tatematsu ◽  
Minho Choi ◽  
Miju Kang ◽  
Tomofumi Umemoto ◽  
...  
Keyword(s):  
Molecular Cloud ◽  
Chemical Variation ◽  
Cloud Cores

scholarly journals Chemical Variation in Molecular Cloud Cores in the Orion A Cloud

2010 ◽  
Vol 62 (6) ◽  
pp. 1473-1482 ◽  
Author(s):  
Ken'ichi Tatematsu ◽  
Tomoya Hirota ◽  
Ryo Kandori ◽  
Tomofumi Umemoto
Keyword(s):  
Molecular Cloud ◽  
Chemical Variation ◽  
Cloud Cores

scholarly journals Chemical variation in molecular cloud cores in the Orion A cloud. II.

2014 ◽  
Vol 66 (1) ◽  
pp. 16 ◽  
Author(s):  
Ken'ichi Tatematsu ◽  
Satoshi Ohashi ◽  
Tomofumi Umemoto ◽  
Jeong-Eun Lee ◽  
Tomoya Hirota ◽  
...  
Keyword(s):  
Molecular Cloud ◽  
Chemical Variation ◽  
Cloud Cores

scholarly journals Aperture synthesis CS and 98 GHz continuum observations of protostellar IRAS sources in Taurus

1991 ◽  
Vol 147 ◽  
pp. 353-356
Author(s):  
N. Ohashi ◽  
R. Kawabe ◽  
M. Hayashi ◽  
M. Ishiguro
Keyword(s):  
Molecular Cloud ◽  
Total Mass ◽  
T Tauri Stars ◽  
Continuum Emission ◽  
Beam Size ◽  
Dust Grains ◽  
Dynamical Mass ◽  
T Tauri ◽  
Cloud Cores ◽  
The Continuum

The CS (J = 2 — 1) line and 98 GHz continuum emission have been observed for 11 protostellar IRAS sources in the Taurus molecular cloud with resolutions of 2.6″−8.8″ (360 AU—1200 AU) using the Nobeyama Millimeter Array (NMA). The CS emission is detected only toward embedded sources, while the continuum emission from dust grains is detected only toward visible T Tauri stars except for one embedded source, L1551-IRS5. This suggests that the dust grains around the embedded sources do not centrally concentrate enough to be detected with our sensitivity (∼4 m Jy r.m.s), while dust grains in disks around the T Tauri stars have enough total mass to be detected with the NMA. The molecular cloud cores around the embedded sources are moderately extended and dense enough to be detected in CS, while gas disks around the T Tauri are not detected because the radius of such gas disks may be smaller than 70 (50 K/Tex) AU. These results imply that the total amount of matter within the NMA beam size must increase when the central objects evolve into T Tauri stars from embedded sources, suggesting that the compact and highly dense disks around T Tauri stars are formed by the dynamical mass accretion during the embedded protostar phase.

scholarly journals The Structure of Cold Molecular Cloud Cores

2004 ◽  
Vol 221 ◽  
pp. 43-50
Author(s):  
D. Ward-Thompson ◽  
D. J. Nutter ◽  
J. M. Kirk ◽  
P. André
Keyword(s):  
Molecular Cloud ◽  
Initial Conditions ◽  
Current Knowledge ◽  
Current Debate ◽  
Core Density ◽  
Density Profiles ◽  
Cloud Cores ◽  
Protostellar Collapse ◽  
The Magnetic Field ◽  
Equilibrium Status

A brief summary is presented of our current knowledge of the structure of cold molecular cloud cores that do not contain protostars, sometimes known as starless cores. The most centrally condensed starless cores are known as pre-stellar cores. These cores probably represent observationally the initial conditions for protostellar collapse that must be input into all models of star formation. The current debate over the nature of core density profiles is summarised. A cautionary note is sounded over the use of such profiles to ascertain the equilibrium status of cores. The magnetic field structure of pre-stellar cores is also briefly discussed.

scholarly journals Star–disc alignment in the protoplanetary discs: SPH simulation of the collapse of turbulent molecular cloud cores

2020 ◽  
Vol 492 (4) ◽  
pp. 5641-5654 ◽  
Author(s):  
Daisuke Takaishi ◽  
Yusuke Tsukamoto ◽  
Yasushi Suto
Keyword(s):  
Time Scale ◽  
Molecular Cloud ◽  
Three Dimensional ◽  
Gravitational Energy ◽  
Circumstellar Envelope ◽  
Rotation Axes ◽  
Particle Hydrodynamics ◽  
Disc Rotation ◽  
Cloud Cores ◽  
Sph Simulation

ABSTRACT We perform a series of three-dimensional smoothed particle hydrodynamics (SPH) simulations to study the evolution of the angle between the protostellar spin and the protoplanetary disc rotation axes (the star–disc angle ψsd) in turbulent molecular cloud cores. While ψsd at the protostar formation epoch exhibits broad distribution up to ∼130°, ψsd decreases (≲ 20°) in a time-scale of ∼104 yr. This time-scale of the star–disc alignment, talignment, corresponds basically to the mass doubling time of the central protostar, in which the protostar forgets its initial spin direction due to the mass accretion from the disc. Values of ψsd both at t = 102 yr and t = 105 yr after the protostar formation are independent of the ratios of thermal and turbulent energies to gravitational energy of the initial cloud cores: α = Ethermal/|Egravity| and γturb = Eturbulence/|Egravity|. We also find that a warped disc is possibly formed by the turbulent accretion flow from the circumstellar envelope.

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