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RCW 120: a possible case of hit and run, elucidated by multitemperature dust mapping

Marsh, K. A. and Whitworth, A. P. (2019) RCW 120: a possible case of hit and run, elucidated by multitemperature dust mapping. Monthly Notices of the Royal Astronomical Society, 483 (1). pp. 352-358. ISSN 0035-8711. doi:10.1093/mnras/sty3186.

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We present resolution-enhanced images of warm dust at multiple temperatures and opacity index values in the star-forming bubble/H II region, RCW 120. The image set, representing a four-dimensional hypercube of differential column density, was obtained using our Bayesian procedure, PPMAP. The cool peripheral material (∼16–22 K) exhibits ragged clumpy structure as noted previously by others. However, at higher temperatures (≲26 K) the geometry changes dramatically, showing a bubble boundary which is accurately circular in projection, except for the previously reported opening in the north. Comparison with Spitzer 8 μμm data suggests that the ∼26–30 K dust seen by Herschel resides in the photodissociation region (PDR) surrounding the H II region. Its projected radial profile is consistent with that of a spherical shell, thus arguing against previous suggestions of cylindrical or planar geometry. The inferred geometry is, in fact, consistent with previous interpretations of the H II region as a classical Strömgren sphere, except for the fact that the ionizing star (CD −38∘..∘11636; O8V) is displaced by more than half a radius from its geometric centre. None of the previously published models has satisfactorily accounted for that displacement. It could, however, be explained by proper motion of the O star at ∼2–4 km s^(−1) since its formation, possibly due to a cloud–cloud collision. We suggest that the current spherical bubble constitutes the fossilized remnant of the initial expansion of the H II region following the formation of the star, which now continues to flee its formation site.

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URLURL TypeDescription Paper
Marsh, K. A.0000-0003-0107-7803
Alternate Title:RCW 120: A possible case of hit and run, elucidated by multi temperature dust mapping
Additional Information:© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2018 November 19. Received 2018 November 14; in original form 2018 September 24. Published: 26 November 2018. We thank the referee for helpful comments. We also gratefully acknowledge the support of a consolidated grant (ST/K00926/1) from the UK Science and Technology Funding Council. This work was performed using the computational facilities of the Advanced Research Computing at Cardiff (ARCCA) Division, Cardiff University. It has used data from the European Space Agency (ESA) mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC, ( Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. The work is based, in part, on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with National Aeronautics and Space Administration (NASA).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Science and Technology Facilities Council (STFC)ST/K00926/1
Gaia Multilateral AgreementUNSPECIFIED
Subject Keywords:stars: early-type – stars: formation – ISM: bubbles – dust, extinction – ISM: individual objects (RCW 120) –HII regions
Issue or Number:1
Record Number:CaltechAUTHORS:20190411-133103217
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Official Citation:K A Marsh, A P Whitworth, RCW 120: a possible case of hit and run, elucidated by multitemperature dust mapping, Monthly Notices of the Royal Astronomical Society, Volume 483, Issue 1, February 2019, Pages 352–358,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:94664
Deposited By: Tony Diaz
Deposited On:11 Apr 2019 22:20
Last Modified:16 Nov 2021 17:06

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