High-resolution simulations of clump–clump collisions using SPH with particle splitting期刊界 All Journals 搜尽天下杂志传播学术成果专业期刊搜索期刊信息化学术搜索

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High-resolution simulations of clump–clump collisions using SPH with particle splitting

Authors:	S Kitsionas A P Whitworth

Institution:	Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany;Institute of Astronomy &Astrophysics, National Observatory of Athens, I. Metaxa and V. Pavlou, GR-15236 P. Penteli, Greece;School of Physics &Astronomy, Cardiff University, PO Box 913, 5 The Parade, Cardiff CF24 3AA

Abstract:	We investigate, by means of numerical simulations, the phenomenology of star formation triggered by low-velocity collisions between low-mass molecular clumps. The simulations are performed using a smoothed particle hydrodynamics code which satisfies the Jeans condition by invoking on-the-fly particle splitting. Clumps are modelled as stable truncated (non-singular) isothermal, i.e. Bonnor–Ebert, spheres. Collisions are characterized by M ₀ (clump mass), b (offset parameter, i.e. ratio of impact parameter to clump radius) and (Mach number, i.e. ratio of collision velocity to effective post-shock sound speed). The gas subscribes to a barotropic equation of state, which is intended to capture (i) the scaling of pre-collision internal velocity dispersion with clump mass, (ii) post-shock radiative cooling and (iii) adiabatic heating in optically thick protostellar fragments. The efficiency of star formation is found to vary between 10 and 30 per cent in the different collisions studied and it appears to increase with decreasing M ₀, and/or decreasing b , and/or increasing . For b < 0.5 collisions produce shock-compressed layers which fragment into filaments. Protostellar objects then condense out of the filaments and accrete from them. The resulting accretion rates are high, , for the first . The densities in the filaments, , are sufficient that they could be mapped in NH₃ or CS line radiation, in nearby star formation regions.

Keywords:	accretion accretion discs hydrodynamics methods: numerical binaries: general stars: formation ISM: clouds

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