Outflow detection in a 70 $\mu$m dark high-mass core
  We present observations towards a high-mass ($\rm >40\,M_{\odot}$), low luminosity ($\rm <10\,L_{\odot}$) $\rm 70\,\mu$m dark molecular core G 28.34 S-A at 3.4 mm, using the IRAM 30 m telescope and the NOEMA interferometer. We report the detection of $\rm SiO$ $J=\rm 2\rightarrow1$ line emission, which is spatially resolved in this source at a linear resolution of $\sim$0.1 pc, while the 3.4 mm continuum image does not resolve any internal sub-structures. The SiO emission exhibits two W-E oriented lobes centring on the continuum peak. Corresponding to the red-shifted and blue-shifted gas with velocities up to $\rm 40\,km\,s^{-1}$ relative to the quiescent cloud, these lobes clearly indicate the presence of a strong bipolar outflow from this $\rm 70\,\mu$m dark core, a source previously considered as one of the best candidates of "starless" core. Our SiO detection is consistent with ALMA archival data of $\rm SiO$ $J=\rm 5\rightarrow4$, whose high-velocity blue-shifted gas reveals a more compact lobe spatially closer to the dust center. This outflow indicates that the central source may be in an early evolutionary stage of forming a high-mass protostar. We also find that the low-velocity components (in the range of $\rm V_{lsr}$$\rm_{-5}^{+3}\,km\,s^{-1}$) have an extended, NW-SE oriented distribution. Discussing the possible accretion scenarios of the outflow-powering young stellar object, we argue that the molecular line emission and the molecular outflows may provide a better indication of the accretion history when forming young stellar object, than that from a snapshot observations of the present bolometric luminosity. This is particularly significant for the cases of episodic accretion, which may occur during the collapse of the parent molecular core. 
S. Feng, H. Beuther, Q. Zhang, H. B. Liu, Z. Zhang, K. Wang, K. Qiu
astro-ph.GA