TY - JOUR
T1 - Failed and delayed protostellar outflows with high-mass accretion rates
AU - Machida, Masahiro N.
AU - Hosokawa, Takashi
N1 - Funding Information:
This research used the computational resources of the HPCI system provided by the Cyber Science Center at Tohoku University, the Cybermedia Center at Osaka University, and the Earth Simulator at JAMSTEC through the HPCI System Research Project (Project ID: hp180001, hp190035, and hp200004). Simulations reported in this paper were also performed by 2019 and 2020 Koubo Kadai on the Earth Simulator (NEC SX-ACE) at JAMSTEC. This study was supported by JSPS KAKENHI Grants (JP17H02869, JP17H06360, JP17K05387, JP17KK0096: MM, JP17H01102, JP19H01934: TH).
Publisher Copyright:
© 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
PY - 2020/12/1
Y1 - 2020/12/1
N2 - The evolution of protostellar outflows is investigated under different mass accretion rates in the range ∼10−5-10−2 M yr−1 with 3D magnetohydrodynamic simulations. A powerful outflow always appears in strongly magnetized clouds with B0 > B0,cr = 10−4(Mcl/100 M) G, where Mcl is the cloud mass. When a cloud has a weaker magnetic field, the outflow does not evolve promptly with a high-mass accretion rate. In some cases with moderate magnetic fields B0 slightly smaller than B0, cr, the outflow growth is suppressed or delayed until the infalling envelope dissipates and the ram pressure around the protostellar system is significantly reduced. In such an environment, the outflow begins to grow and reaches a large distance only during the late accretion phase. On the other hand, the protostellar outflow fails to evolve and is finally collapsed by the strong ram pressure when a massive (> 100 M) initial cloud is weakly magnetized with B0 < 100 μG. The failed outflow creates a toroidal structure that is supported by magnetic pressure and encloses the protostar and disc system. Our results indicate that high-mass stars form only in strongly magnetized clouds, if all high-mass protostars possess a clear outflow. If we would observe either very weak or no outflow around evolved protostars, it means that strong magnetic fields are not necessarily required for high-mass star formation. In any case, we can constrain the high-mass star formation process from observations of outflows.
AB - The evolution of protostellar outflows is investigated under different mass accretion rates in the range ∼10−5-10−2 M yr−1 with 3D magnetohydrodynamic simulations. A powerful outflow always appears in strongly magnetized clouds with B0 > B0,cr = 10−4(Mcl/100 M) G, where Mcl is the cloud mass. When a cloud has a weaker magnetic field, the outflow does not evolve promptly with a high-mass accretion rate. In some cases with moderate magnetic fields B0 slightly smaller than B0, cr, the outflow growth is suppressed or delayed until the infalling envelope dissipates and the ram pressure around the protostellar system is significantly reduced. In such an environment, the outflow begins to grow and reaches a large distance only during the late accretion phase. On the other hand, the protostellar outflow fails to evolve and is finally collapsed by the strong ram pressure when a massive (> 100 M) initial cloud is weakly magnetized with B0 < 100 μG. The failed outflow creates a toroidal structure that is supported by magnetic pressure and encloses the protostar and disc system. Our results indicate that high-mass stars form only in strongly magnetized clouds, if all high-mass protostars possess a clear outflow. If we would observe either very weak or no outflow around evolved protostars, it means that strong magnetic fields are not necessarily required for high-mass star formation. In any case, we can constrain the high-mass star formation process from observations of outflows.
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U2 - 10.1093/mnras/staa3139
DO - 10.1093/mnras/staa3139
M3 - Article
AN - SCOPUS:85097022755
VL - 499
SP - 4490
EP - 4514
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 3
ER -