Widespread SiO and CH3OH emission in Filamentary Infrared Dark Clouds

Abstract

Infrared-Dark Clouds (IRDCs) are cold, dense regions of high (optical and infrared) extinction, believed to be the birthplace of high-mass stars and stellar clusters. The physical mechanisms leading to the formation of these IRDCs are not completely understood and it is thus important to study their molecular gas kinematics and chemical content to search for any signature of the IRDCs formation process. Using the 30m-diameter antenna at the Instituto de Radioastronomía Milimétrica, we have obtained emission maps of dense gas tracers (H${}^{13}$CO${}^{+}$ and HN${}^{13}$C) and typical shock tracers (SiO and CH${}_3$OH) toward three IRDCs, G028.37+00.07, G034.43+00.24 and G034.77-00.55 (clouds C, F and G, respectively). We have studied the molecular gas kinematics in these clouds and, consistent with previous works toward other IRDCs, the clouds show complex gas kinematics with several velocity-coherent sub-structures separated in velocity space by a few km s${}^{-1}$. Correlated with these complex kinematic structures, widespread (parsec-scale) emission of SiO and CH${}_3$OH is present in all the three clouds. For clouds C and F, known to be actively forming stars, widespread SiO and CH${}_3$OH is likely associated with on-going star formation activity. However, for cloud G, which lacks either 8 $\mu$m or 24 $\mu$m sources and 4.5 $\mu$m H${}_2$ shock-excited emission, the detected widespread SiO and CH${}_3$OH emission may have originated in a large-scale shock interaction, although a scenario involving a population of low-mass stars driving molecular outflows cannot be fully ruled out.

23 pages, 12 figures. Accepted for publication in MNRAS

References in corpus (1)

• 15N Fractionation in Infrared-Dark Cloud Cores

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• Molecular line signatures of cloud-cloud collisions
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• Extended HNCO, SiO, and HC${}_3$N emission in 43 southern star-forming regions
• Different molecular filament widths as tracers of accretion onto filaments
• Searching for Molecular Jets from High-Mass Protostars
• ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions -- XIX. The origin of SiO emission
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