TY - JOUR
T1 - Condition for low-mass star formation in shock-compressed metal-poor clouds
AU - Nakauchi, Daisuke
AU - Omukai, Kazuyuki
AU - Schneider, Raffaella
N1 - Funding Information:
We thank Drs Hide Yajima, Kazu Sugimura, and Gen Chiaki for fruitful discussions. Numerical calculations are performed by the computer cluster, Draco, supported by the Frontier Research Institute for Interdisciplinary Sciences in Tohoku University. This work is supported in part by MEXT/JSPS KAKENHI grants (DN:16J02951, KO:25287040, 17H01102, 17H02869). The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement no. 306476.
Publisher Copyright:
© 2018 The Author(s).
PY - 2018
Y1 - 2018
N2 - Shocks may have been prevalent in the early Universe, associated with virialization and supernova explosions, etc. Here, we study thermal evolution and fragmentation of shockcompressed clouds, by using a one-zone model with detailed thermal and chemical processes. We explore a large range of initial density (1-105 cm-3), metallicity (0-10-2 Z⊙), UV strength (0-500 times Galactic value), and cosmic microwave background temperature (10 and 30 K). Shock-compressed clouds contract isobarically via atomic and molecular line cooling, until self-gravitating clumps are formed by fragmentation. If the metals are only in the gas-phase, the clump mass is higher than ~3M⊙ in any conditions we studied. Although in some cases with a metallicity higher than ~10-3 Z⊙, re-fragmentation of a clump is caused by metal-line cooling, this fragment mass is higher than ~30M⊙. On the other hand, if about half the mass of metals is condensed in dust grains, as in the Galactic interstellar medium, dust cooling triggers re-fragmentation of a clump into subsolar mass pieces, for metallicities higher than ~10-5 Z⊙. Therefore, the presence of dust is essential in low-mass (≳ M⊙) star formation from a shock-compressed cloud.
AB - Shocks may have been prevalent in the early Universe, associated with virialization and supernova explosions, etc. Here, we study thermal evolution and fragmentation of shockcompressed clouds, by using a one-zone model with detailed thermal and chemical processes. We explore a large range of initial density (1-105 cm-3), metallicity (0-10-2 Z⊙), UV strength (0-500 times Galactic value), and cosmic microwave background temperature (10 and 30 K). Shock-compressed clouds contract isobarically via atomic and molecular line cooling, until self-gravitating clumps are formed by fragmentation. If the metals are only in the gas-phase, the clump mass is higher than ~3M⊙ in any conditions we studied. Although in some cases with a metallicity higher than ~10-3 Z⊙, re-fragmentation of a clump is caused by metal-line cooling, this fragment mass is higher than ~30M⊙. On the other hand, if about half the mass of metals is condensed in dust grains, as in the Galactic interstellar medium, dust cooling triggers re-fragmentation of a clump into subsolar mass pieces, for metallicities higher than ~10-5 Z⊙. Therefore, the presence of dust is essential in low-mass (≳ M⊙) star formation from a shock-compressed cloud.
KW - Stars: Population II
KW - Stars: Population III
KW - Stars: formation
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U2 - 10.1093/MNRAS/STY1911
DO - 10.1093/MNRAS/STY1911
M3 - Article
AN - SCOPUS:85055344776
SN - 0035-8711
VL - 480
SP - 1043
EP - 1056
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 1
ER -