TY - GEN
T1 - The role of the first metals in forming the second stars
AU - Smith, Britton
AU - Sigurdsson, Steinn
AU - O'Shea, Brian
AU - Norman, Michael
PY - 2008
Y1 - 2008
N2 - Numerical simulations of the formation of pop III stars suggest that they were much more massive than the pop II and pop I stars observed today. This is due to the collapse dynamics of metal-free gas, which is regulated by the radiative cooling properties of molecular hydrogen. We study how the collapse of gas-clouds is altered by the addition of metals to the star-forming environment. We perform a series of numerical simulations of pre-enriched star-formation at various metallicities using the adaptive mesh refinement, hydrodynamic + N-body code, Enzo. For metallicities below the critical metallicity, Zcr, collapse proceeds nearly identical to the metal-free case, and only massive, singular objects form. For metallicities well above Zcr, efficient cooling rapidly lowers the gas temperature to the temperature of the cosmic microwave background (CMB), which is significantly higher in the distant past. The gas is physically unable to radiatively cool below the CMB temperature, and thus, becomes very thermally stable. For moderately high metallicities, Z≥10-3.5Z⊙, this occurs early in the evolution of the gas-cloud, when the central density is still relatively low. The resulting cloud-cores show little or no fragmentation, and have mass-scales of a few hundred M⊙. On the other hand, if the metallicity is only slightly above Zcr, the cloud slowly cools without ever reaching the CMB temperature. In this case, the minimum cloud temperature is achieved at much higher densities than in the high-metallicity case, resulting in mass-scales of just a few M⊙.
AB - Numerical simulations of the formation of pop III stars suggest that they were much more massive than the pop II and pop I stars observed today. This is due to the collapse dynamics of metal-free gas, which is regulated by the radiative cooling properties of molecular hydrogen. We study how the collapse of gas-clouds is altered by the addition of metals to the star-forming environment. We perform a series of numerical simulations of pre-enriched star-formation at various metallicities using the adaptive mesh refinement, hydrodynamic + N-body code, Enzo. For metallicities below the critical metallicity, Zcr, collapse proceeds nearly identical to the metal-free case, and only massive, singular objects form. For metallicities well above Zcr, efficient cooling rapidly lowers the gas temperature to the temperature of the cosmic microwave background (CMB), which is significantly higher in the distant past. The gas is physically unable to radiatively cool below the CMB temperature, and thus, becomes very thermally stable. For moderately high metallicities, Z≥10-3.5Z⊙, this occurs early in the evolution of the gas-cloud, when the central density is still relatively low. The resulting cloud-cores show little or no fragmentation, and have mass-scales of a few hundred M⊙. On the other hand, if the metallicity is only slightly above Zcr, the cloud slowly cools without ever reaching the CMB temperature. In this case, the minimum cloud temperature is achieved at much higher densities than in the high-metallicity case, resulting in mass-scales of just a few M⊙.
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U2 - 10.1063/1.2905676
DO - 10.1063/1.2905676
M3 - Conference contribution
AN - SCOPUS:42449122223
SN - 9780735405097
T3 - AIP Conference Proceedings
SP - 73
EP - 75
BT - First Stars III
T2 - First Stars III
Y2 - 15 July 2007 through 20 July 2007
ER -