University of Hertfordshire

From the same journal

From the same journal


  • JD-AAM

    Accepted author manuscript, 8.73 MB, PDF document

  • J. D. Henshaw
  • A. Ginsburg
  • T. J. Haworth
  • S. N. Longmore
  • J. M. D. Kruijssen
  • E. A. C. Mills
  • V. Sokolov
  • D. L. Walker
  • A. T. Barnes
  • Y. Contreras
  • J. Bally
  • C. Battersby
  • H. Beuther
  • N. Butterfield
  • James Dale
  • T. Henning
  • J. M. Jackson
  • J. Kauffmann
  • T. Pillai
  • S. Ragan
  • And 2 others
  • M. Riener
  • Q. Zhang
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Original languageEnglish
Pages (from-to)2457–2485
Number of pages29
JournalMonthly Notices of the Royal Astronomical Society
Early online date17 Feb 2019
Publication statusPublished - 1 May 2019


In this paper we provide a comprehensive description of the internal dynamics of G0.253+0.016 (a.k.a. 'the Brick'); one of the most massive and dense molecular clouds in the Galaxy to lack signatures of widespread star formation. As a potential host to a future generation of high-mass stars, understanding largely quiescent molecular clouds like G0.253+0.016 is of critical importance. In this paper, we reanalyse Atacama Large Millimeter Array cycle 0 HNCO $J=4(0,4)-3(0,3)$ data at 3 mm, using two new pieces of software which we make available to the community. First, scousepy, a Python implementation of the spectral line fitting algorithm scouse. Secondly, acorns (Agglomerative Clustering for ORganising Nested Structures), a hierarchical n-dimensional clustering algorithm designed for use with discrete spectroscopic data. Together, these tools provide an unbiased measurement of the line of sight velocity dispersion in this cloud, $\sigma_{v_{los}, {\rm 1D}}=4.4\pm2.1$ kms$^{-1}$, which is somewhat larger than predicted by velocity dispersion-size relations for the Central Molecular Zone (CMZ). The dispersion of centroid velocities in the plane of the sky are comparable, yielding $\sigma_{v_{los}, {\rm 1D}}/\sigma_{v_{pos}, {\rm 1D}}\sim1.2\pm0.3$. This isotropy may indicate that the line-of-sight extent of the cloud is approximately equivalent to that in the plane of the sky. Combining our kinematic decomposition with radiative transfer modelling we conclude that G0.253+0.016 is not a single, coherent, and centrally-condensed molecular cloud; 'the Brick' is not a \emph{brick}. Instead, G0.253+0.016 is a dynamically complex and hierarchically-structured molecular cloud whose morphology is consistent with the influence of the orbital dynamics and shear in the CMZ.


© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.

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