Velocity distribution of collapsing starless cores, L694-2 and L1197

Abstract

In an attempt to understand the dynamics of collapsing starless cores, we have onducted a detailed investigation of the velocity fields of two collapsing cores, L694-2 and L1197, with high spatial resolution HCN J=1-0 maps and Monte Carlo radiative transfer alculation. It is found that infall motion is most active in the middle and outer layers outside the central density-flat region, while both the central and outermost parts of the cores are static or exhibit slower motion. Their peak velocities are 0.28 km s^{-1} for L694-2 and 0.20 km s^{-1$ for L1197, which could not be found in simple models. These velocity fields are roughly consistent with the gravitational collapse models of the isothermal core; However, the velocity gradients inside the peak velocity position are steeper than those of the models. Our results also show that the density distributions are ~ r^{-2.5} and ~ r^{-1.5} in the outer part for L694-2 and L1197, respectively. HCN abundance relative to H_2 is spatially almost constant in L694-2 with a value of 7.0 X 10^{-9}, while for L1197, it shows a slight inward increase from 1.7 X 10^{-9} to 3.5 X 10^{-9}.

accepted in ApJ

References in corpus (9)

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• Abundance of HCN and its C and N isotopologues in L1498
• Molecular line profiles as diagnostics of protostellar collapse: modelling the `blue asymmetry' in inside-out infall
• L1506: a prestellar core in the making
• Molecular Line Profiles from Contracting Dense Cores
• The Evolution of Density Structure of Starless and Protostellar Cores
• On the internal dynamics of starless cores: stability of starless cores with internal motions and collapse dynamics
• Chemical constraints on the dynamical evolution of the cold core L694
• Why do some cores remain starless ?
• The effects of a compressive velocity pulse on a collapsing turbulent clump