EPoS Contribution
EPoS Contribution
Molecular Evolutions in the First Hydrostatic Core Stage Adapting Three-Dimensional Radiation Hydrodynamics Simulations

Kenji Furuya
Kobe Univ., Kobe, Japan
First hydrostatic cores are key objects to understand star formation processes; they fragment and form binaries (Matsumoto & Hanawa 2003), drive bipolar molecular outflows (Tomisaka 2002), and their outer regions might directly evolve to circumstellar disks, while the central regions collapse to form protostars (Machida et al. 2010; Bate 2010). While their dynamical evolutions have been well studied, their chemical compositions remain unrevealed. Unveiling chemistry in the first core stages is important; (i) to find observational tracers (ii) to reveal the initial compositions of circumstellar disks. In this presentation, we report the molecular evolution that develops as star formation proceeds from molecular cloud cores to the first hydrostatic cores in three spatial dimensions. We performed radiation hydrodynamics simulations in order to trace fluid parcels, in which molecular evolution is investigated, using a gas-phase and grain-surface reaction network model. We derived the spatial distributions of molecular abundances and column densities in the cloud core harboring the first cores. We found that the total of gas and ice abundances of many species are set in cold regions (10 K), and remain unaltered until the temperature reaches ~500 K. Then the gas abundances in the warm envelope and outer layers of the first core (T < 500 K) are mainly determined via the sublimation of ice-mantle species. Above 500 K, the abundant molecules start to be destroyed mainly via collisional dissociation, and simple molecules, such as CO, H2O and N2 are reformed. On the other hand, some molecules are effectively formed at high temperature; carbon-chains, such as C2H2 and cyanopolyynes, are formed at the temperature of > 800 K. We also found that large organic molecules, such as CH3OH and HCOOCH3, are associated with the first core (r < 10 AU). We propose that these large organic molecules can be good tracers of the first cores.
Y. Aikawa, Kobe Univ., Japan
K. Tomida, TGUAS/NAOJ, Japan
T, Matsumoto, Hosei Univ., Japan
K, Saigo, NAOJ, Japan
K, Tomisaka, NAOJ, Japan
F, Hersant, Univ. Bordeaux, France
V, Wakelam, Univ. Bordeaux, France