2011MNRAS.412.1755L

Spectral observations of molecular line profiles reveal the so-called `blue profiles' for double-peaked molecular spectral 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 show that these unexplained `red profiles' can be signatures of global self-similar 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 1.2, 0.85 and 0.45 mm from FeSt 1-457 are also predicted.