The centres of M83 and the Milky Way: opposite extremes of a common star formation cycle

Daniel Callanan, Steven N. Longmore, J. M. Diederik Kruijssen, Andreas Schruba, Adam Ginsburg, Mark R. Krumholz, Nate Bastian, Joao Alves, Jonathan D. Henshaw, Johan H. Knapen, Melanie Chevance

In the centres of the Milky Way and M83, the global environmental

properties thought to control star formation are very similar. However,

M83's nuclear star formation rate (SFR), as estimated by synchrotron and

H-alpha emission, is an order of magnitude higher than the Milky Way's.

To understand the origin of this difference we use ALMA observations of

HCN (1-0) and HCO+ (1-0) to trace the dense gas at the size scale of

individual molecular clouds (0.54", 12pc) in the inner ~500 pc of M83,

and compare this to gas clouds at similar resolution and galactocentric

radius in the Milky Way. We find that both the overall gas distribution

and the properties of individual clouds are very similar in the two

galaxies, and that a common mechanism may be responsible for instigating

star formation in both circumnuclear rings. Given the considerable

similarity in gas properties, the most likely explanation for the order

of magnitude difference in SFR is time variability, with the Central

Molecular Zone (CMZ) currently being at a more quiescent phase of its

star formation cycle. We show M83's SFR must have been an order of

magnitude higher 5-7 Myr ago. M83's `starburst' phase was highly

localised, both spatially and temporally, greatly increasing the

feedback efficiency and ability to drive galactic-scale outflows. This

highly dynamic nature of star formation and feedback cycles in galaxy

centres means (i) modeling and interpreting observations must avoid

averaging over large spatial areas or timescales, and (ii) understanding

the multi-scale processes controlling these cycles requires comparing

snapshots of a statistical sample of galaxies in different evolutionary


Department of Astrophysics
External organisation(s)
Liverpool John Moores University (LJMU), Harvard University, Ruprecht-Karls-Universität Heidelberg, Max-Planck-Institut für extraterrestrische Physik, National Radio Astronomy Observatory, Australian National University, ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Max-Planck-Institut für Astronomie, Instituto de Astrofísica de Canarias, Universidad de La Laguna
Monthly Notices of the Royal Astronomical Society
Publication date
Peer reviewed
Austrian Fields of Science 2012
103004 Astrophysics
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