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What controls star formation in the central 500 pc of the Galaxy?

Kruijssen, JMD, Longmore, SN, Elmegreen, BG, Murray, N, Bally, J, Testi, L and Kennicutt, RC (2014) What controls star formation in the central 500 pc of the Galaxy? Monthly Notices of the Royal Astronomical Society, 440 (4). pp. 3370-3391. ISSN 0035-8711

1303.6286v3.pdf - Accepted Version

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The star formation rate (SFR) in the Central Molecular Zone (CMZ, i.e. the central 500 pc) of the Milky Way is lower by a factor of ≥10 than expected for the substantial amount of dense gas it contains, which challenges current star formation theories. In this paper, we quantify which physical mechanisms could be responsible. On scales larger than the disc scaleheight, the low SFR is found to be consistent with episodic star formation due to secular instabilities or possibly variations of the gas inflow along the Galactic bar. The CMZ is marginally Toomre-stable when including gas and stars, but highly Toomre-stable when only accounting for the gas, indicating a low condensation rate of self-gravitating clouds. On small scales, we find that the SFR in the CMZ may be caused by an elevated critical density for star formation due to the high turbulent pressure. The existence of a universal density threshold for star formation is ruled out. The H I–H2 phase transition of hydrogen, the tidal field, a possible underproduction of massive stars due to a bottom-heavy initial mass function, magnetic fields, and cosmic ray or radiation pressure feedback also cannot individually explain the low SFR. We propose a self-consistent cycle of star formation in the CMZ, in which the effects of several different processes combine to inhibit star formation. The rate-limiting factor is the slow evolution of the gas towards collapse – once star formation is initiated it proceeds at a normal rate. The ubiquity of star formation inhibitors suggests that a lowered central SFR should be a common phenomenon in other galaxies. We discuss the implications for galactic-scale star formation and supermassive black hole growth, and relate our results to the star formation conditions in other extreme environments.

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 MNRAS (June 1, 2014) 440 (4): 3370-3391 is available online at: http://dx.doi.org/10.1093/mnras/stu494
Uncontrolled Keywords: 0201 Astronomical And Space Sciences
Subjects: Q Science > QB Astronomy
Divisions: Astrophysics Research Institute
Publisher: Oxford University Press
Related URLs:
Date Deposited: 08 Jun 2016 09:34
Last Modified: 04 Sep 2021 12:50
DOI or ID number: 10.1093/mnras/stu494
URI: https://researchonline.ljmu.ac.uk/id/eprint/3727
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