'The Brick' is not a brick: a comprehensive study of the structure and dynamics of the central molecular zone cloud G0.253+0.016. Issue 2 (17th February 2019)

• Record Type: Journal Article
• Authors: Henshaw, J D; Ginsburg, A; Haworth, T J; Longmore, S N; Kruijssen, J M D; Mills, E A C; Sokolov, V; Walker, D L; Barnes, A T; Contreras, Y; Bally, J; Battersby, C; Beuther, H; Butterfield, N; Dale, J E; Henning, T; Jackson, J M; Kauffmann, J; Pillai, T; Ragan, S; Riener, M; Zhang, Q
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 485:Issue 2(2019)
• Page Start: 2457
• Page End: 2485
• Publication Date: 2019-02-17
• Subjects: turbulence -- stars: formation -- ISM: clouds -- ISM: kinematics and dynamics -- ISM: structure -- galaxy: centre; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stz471
• Languages: English
• ISSNs: 0035-8711

Abstract

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 that 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, $\sigma _{v_{\mathrm{ los}}, {\rm 1D}}=4.4\pm 2.1$ km s −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 $\sigma _{v_{\mathrm{ los}}, {\rm 1D}}/\sigma _{v_{\mathrm{ pos}}, {\rm 1D}}\sim 1.2\pm 0.3$ . 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 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.