TY - JOUR
T1 - Accretion phase of star formation in clouds with different metallicities
AU - Machida, Masahiro N.
AU - Nakamura, Teppei
N1 - Publisher Copyright:
© 2015 The Authors.
Copyright:
Copyright 2015 Elsevier B.V., All rights reserved.
PY - 2015/1/20
Y1 - 2015/1/20
N2 - The main accretion phase of star formation is investigated in clouds with different metallicities in the range 0 ≤ Z ≤Z⊙, resolving the protostellar radius. Starting from a near-equilibrium prestellar cloud, we calculate the cloud evolution up to ~100 yr after the first protostar forms. Star formation differs considerably between clouds with lower (Z ≤ 10-4 Z⊙) and higher (Z > 10-4 Z⊙) metallicities. Fragmentation frequently occurs and many protostars appear without a stable circumstellar disc in lower-metallicity clouds. In these clouds, although protostars mutually interact and some are ejected from the cloud centre,many remain as a small stellar cluster. In contrast, higher-metallicity clouds produce a single protostar surrounded by a nearly stable rotation-supported disc. In these clouds, although fragmentation occasionally occurs in the disc, the fragments migrate inwards and finally fall on to the central protostar. The difference in cloud evolution is due to different thermal evolutions and mass accretion rates. The thermal evolution of the cloud determines the emergence and lifetime of the first core. The first core develops prior to the formation of a protostar in higher-metallicity clouds, whereas no (obvious) first core appears in lower-metallicity clouds. The first core evolves into a circumstellar disc with a spiral pattern, which effectively transfers the angular momentum outwards and suppresses frequent fragmentation. In lower-metallicity clouds, the higher mass accretion rate increases the disc surface density within a very short time, rendering the disc unstable to self-gravity and inducing vigorous fragmentation.
AB - The main accretion phase of star formation is investigated in clouds with different metallicities in the range 0 ≤ Z ≤Z⊙, resolving the protostellar radius. Starting from a near-equilibrium prestellar cloud, we calculate the cloud evolution up to ~100 yr after the first protostar forms. Star formation differs considerably between clouds with lower (Z ≤ 10-4 Z⊙) and higher (Z > 10-4 Z⊙) metallicities. Fragmentation frequently occurs and many protostars appear without a stable circumstellar disc in lower-metallicity clouds. In these clouds, although protostars mutually interact and some are ejected from the cloud centre,many remain as a small stellar cluster. In contrast, higher-metallicity clouds produce a single protostar surrounded by a nearly stable rotation-supported disc. In these clouds, although fragmentation occasionally occurs in the disc, the fragments migrate inwards and finally fall on to the central protostar. The difference in cloud evolution is due to different thermal evolutions and mass accretion rates. The thermal evolution of the cloud determines the emergence and lifetime of the first core. The first core develops prior to the formation of a protostar in higher-metallicity clouds, whereas no (obvious) first core appears in lower-metallicity clouds. The first core evolves into a circumstellar disc with a spiral pattern, which effectively transfers the angular momentum outwards and suppresses frequent fragmentation. In lower-metallicity clouds, the higher mass accretion rate increases the disc surface density within a very short time, rendering the disc unstable to self-gravity and inducing vigorous fragmentation.
UR - http://www.scopus.com/inward/record.url?scp=84925426347&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84925426347&partnerID=8YFLogxK
U2 - 10.1093/mnras/stu2633
DO - 10.1093/mnras/stu2633
M3 - Article
AN - SCOPUS:84925426347
VL - 448
SP - 1405
EP - 1429
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 2
ER -