Forming Protostars in Molecular Clouds with Shocked Envelope Expansion and Core Collapse

Spectral observations of molecular line profiles reveal the so-called `blue profiles' for double-peaked molecular lines with stronger blue and weaker red peaks as notable features for star-forming cloud core collapses under the self-gravity. In contrast, 25-30 per cent of observed molecular spectral line profiles in star-forming clouds or cores also show the so-called double-peaked `red profiles' with red peaks stronger than blue peaks. Gao & Lou (2010) show that these unexplained `red profiles' can be signatures of global dynamics for envelope expansion with core collapse (EECC) within star-forming molecular clouds or cores. We demonstrate here that spatially-resolved `red profiles' of HCO+ (J=1-0) and CS (J=2-1) molecular transitions from the low-mass star-forming cloud core FeSt 1-457 together with its radial profile of column density inferred from dust extinction observations appear to reveal a self-similar hydrodynamic shock phase for global EECC. Observed spectral profiles of C18O (J=1-0) are also fitted by the same EECC model. For further observational tests, the spatially-resolved profiles of molecular transitions HCO+ (J=3-2) and CS (J=3-2) as well as the radial profiles of (sub)millimetre continuum emissions at three wavelengths of 1.2mm, 0.85mm and 0.45mm from FeSt 1-457 are also predicted.

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