'The Brick' is not a brick: A comprehensive study of the structure and dynamics of the Central Molecular Zone cloud G0.253+0.016

Henshaw, JD; Ginsburg, A; Haworth, TJ; Longmore, SN; Kruijssen, JMD; Mills, EAC; Sokolov, V; Walker, DL; Barnes, AT; Contreras, Y; Bally, J; Battersby, C; Beuther, H; Butterfield, N; Dale, JE; Henning, T; Jackson, JM; Kauffmann, J; Pillai, T; Ragan, S; Riener, M; Zhang, Q

'The Brick' is not a brick: A comprehensive study of the structure and dynamics of the Central Molecular Zone cloud G0.253+0.016

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Henshaw, JD, Ginsburg, A, Haworth, TJ, Longmore, SN, Kruijssen, JMD, Mills, EAC, Sokolov, V, Walker, DL, Barnes, AT, Contreras, Y, Bally, J, Battersby, C, Beuther, H, Butterfield, N, Dale, JE, Henning, T, Jackson, JM, Kauffmann, J, Pillai, T, Ragan, S et al (2019) 'The Brick' is not a brick: A comprehensive study of the structure and dynamics of the Central Molecular Zone cloud G0.253+0.016. Monthly Notices of the Royal Astronomical Society, 485 (2). pp. 2457-2485. ISSN 0035-8711

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Publisher URL: https://doi.org/10.1093/mnras/stz471

Abstract

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.

Item Type:	Article
Additional Information:	This article has been accepted for publications in Monthly Notices of the Royal Astronomical Society ©: 2019 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Uncontrolled Keywords:	astro-ph.GA; astro-ph.GA
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Divisions:	Astrophysics Research Institute
Publisher:	Oxford University Press
Related URLs:	http://arxiv.org/abs/1902.02793v1
Date of acceptance:	4 February 2019
Date of first compliant Open Access:	18 February 2019
Date Deposited:	18 Feb 2019 09:31
Last Modified:	04 Sep 2021 01:59
URI:	https://researchonline.ljmu.ac.uk/id/eprint/10170

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