IN SITU FORMATION OF SgrA* STARS VIA DISK FRAGMENTATION: PARENT CLOUD PROPERTIES AND THERMODYNAMICS
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abstract
The formation of the massive young stars surrounding SgrA* is still an open
question. In this paper, we simulate the infall of a turbulent molecular cloud
towards the Galactic Center (GC). We adopt two different cloud masses (4.3x10^4
and 1.3x10^5 solar masses). We run five simulations: the gas is assumed to be
isothermal in four runs, whereas radiative cooling is included in the fifth
run. In all the simulations, the molecular cloud is tidally disrupted, spirals
towards the GC, and forms a small, dense and eccentric disk around SgrA*. With
high resolution simulations, we follow the fragmentation of the gaseous disk.
Star candidates form in a ring at ~0.1-0.4 pc from the super-massive black hole
(SMBH) and have moderately eccentric orbits (~0.2-0.4), in good agreement with
the observations. The mass function of star candidates is top-heavy only if the
local gas temperature is high (>~100 K) during the star formation and if the
parent cloud is sufficiently massive (>~10^5 solar masses). Thus, this study
indicates that the infall of a massive molecular cloud is a viable scenario for
the formation of massive stars around SgrA*, provided that the gas temperature
is kept sufficiently high (>~100 K).
