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On the physical mechanisms governing the cloud lifecycle in the Central Molecular Zone of the Milky Way

Jeffreson, SMR, Kruijssen, JMD, Krumholz, MR and Longmore, SN (2018) On the physical mechanisms governing the cloud lifecycle in the Central Molecular Zone of the Milky Way. Monthly Notices of the Royal Astronomical Society. ISSN 0035-8711

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Abstract

We apply an analytic theory for environmentally-dependent molecular cloud lifetimes to the Central Molecular Zone of the Milky Way. Within this theory, the cloud lifetime in the Galactic centre is obtained by combining the time-scales for gravitational instability, galactic shear, epicyclic perturbations and cloud-cloud collisions. We find that at galactocentric radii ∼45-120 pc, corresponding to the location of the ‘100-pc stream’, cloud evolution is primarily dominated by gravitational collapse, with median cloud lifetimes between 1.4 and 3.9 Myr. At all other galactocentric radii, galactic shear dominates the cloud lifecycle, and we predict that molecular clouds are dispersed on time-scales between 3 and 9 Myr, without a significant degree of star formation. Along the outer edge of the 100-pc stream, between radii of 100 and 120 pc, the time-scales for epicyclic perturbations and gravitational free-fall are similar. This similarity of time-scales lends support to the hypothesis that, depending on the orbital geometry and timing of the orbital phase, cloud collapse and star formation in the 100-pc stream may be triggered by a tidal compression at pericentre. Based on the derived time-scales, this should happen in approximately 20 per cent of all accretion events onto the 100-pc stream.

Item Type: Article
Additional Information: This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record S M R Jeffreson, J M D Kruijssen, M R Krumholz, S N Longmore; On the physical mechanisms governing the cloud lifecycle in the Central Molecular Zone of the Milky Way, Monthly Notices of the Royal Astronomical Society, , sty1154, https://doi.org/10.1093/mnras/sty1154 is available online at: http://dx.doi.org/S M R Jeffreson, J M D Kruijssen, M R Krumholz, S N Longmore; On the physical mechanisms governing the cloud lifecycle in the Central Molecular Zone of the Milky Way, Monthly Notices of the Royal Astronomical Society, , sty1154, https://dx.doi.org/10.1093/mnras/sty1154
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:
Date Deposited: 11 May 2018 09:18
Last Modified: 16 Sep 2018 18:16
DOI or Identification number: 10.1093/mnras/sty1154
URI: http://researchonline.ljmu.ac.uk/id/eprint/8638

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