Streaming motions and kinematic distances to molecular clouds
Abstract
We present high-resolution smoothed particle hydrodynamics simulations of a region of gas flowing in a spiral arm and identify dense gas clouds to investigate their kinematics with respect to a Milky Way model. We find that, on average, the gas in the arms can have a net radial streaming motion of vR ≈ -9 km s-1 and rotate approximate to 6 km s-1 slower than the circular velocity. This translates to average peculiar motions towards the Galaxy centre and opposite to Galactic rotation. These results may be sensitive to the assumed spiral arm perturbation, which is ≈ 3 per cent of the disc potential in our model. We compare the actual distance and the kinematic estimate and we find that streaming motions introduce systematic offsets of ≈ 1 kpc. We find that the distance error can be as large as ± 2 kpc, and the recovered cloud positions have distributions that can extend significantly into the inter-arm regions. We conclude that this poses a difficulty in tracing spiral arm structure in molecular cloud surveys.
Citation
Fox , F G R & Bonnell , I A 2018 , ' Streaming motions and kinematic distances to molecular clouds ' , Monthly Notices of the Royal Astronomical Society , vol. 474 , no. 2 , pp. 2028-2038 . https://doi.org/10.1093/mnras/stx2866
Publication
Monthly Notices of the Royal Astronomical Society
Status
Peer reviewed
ISSN
0035-8711Type
Journal article
Description
FGR-F and IAB gratefully acknowledge support from the ERC Advanced Grant ECOGAL project, grant agreement 291227, funded by the European Research Council under ERC-2011-ADG.Collections
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