Searching for shocks in high-mass starless clump candidates

Abstract

In order to search for shocks in the very early stage of star formation, we performed single-point surveys of SiO J=1-0, 2-1 and 3-2 lines and the H${}_2$CO $2_{12}-1_{11}$ line toward a sample of 100 high-mass starless clump candidates (SCCs) by using the Korean VLBI Network (KVN) 21-m radio telescopes. The detection rates of the SiO J=1-0, 2-1, 3-2 lines and the H${}_2$CO line are $31.0\%$, $31.0\%$, $19.5\%$ and $93.0\%$, respectively. Shocks seem to be common in this stage of massive star formation. The widths of the observed SiO lines (full width at zero power (FWZP)) range from 3.4 to 55.1 km s${}^{-1}$. A significant fraction ($\sim 29\%$) of the detected SiO spectra have broad line widths (FWZP $>20km{s}^{-1}$), which are very likely associated with fast shocks driven by protostellar outflows. This result suggests that about one third of the SiO-detected SCCs are not really starless but protostellar. On the other hand, about 40$\%$ of the detected SiO spectra show narrow line widths (FWZP<10 $km{s}^{-1}$) probably associated with low-velocity shocks which are not necessarily protostellar in origin. The estimated SiO column densities are mostly $0.31-4.32\times 10^{12}c{m}^{-2}$. Comparing the SiO column densities derived from SiO J=1-0 and 2-1 lines, we suggest that the SiO molecules in the SCCs may be in the non-LTE condition. The SiO abundances to H${}_2$ are usually $0.20-10.92\times 10^{-10}$.

19 pages, 13 figures

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Cited by in corpus (8)

• Kinetic temperature of massive star-forming molecular clumps measured with formaldehyde IV. The ALMA view of N113 and N159W in the LMC
• A global view on star formation: The GLOSTAR Galactic plane survey VIII. Formaldehyde absorption in Cygnus~X
• A survey of SiO $J=$ 1 -- 0 emission toward massive star-forming regions
• SiO Outflows in the Most Luminous and Massive Protostellar Sources of the Southern Sky
• Star Formation in Extreme Environments: A 200 pc High Velocity Gas Stream in the Galactic Centre
• Spatial distributions and kinematics of shocked and ionized gas in M17
• Different molecular filament widths as tracers of accretion onto filaments
• Origins of the shocks in high-mass starless clump candidates