Bulgeless dwarf galaxies and dark matter cores from supernova-driven outflows

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Abstract

For almost two decades the properties of ‘dwarf’ galaxies have challenged the cold dark matter (CDM) model of galaxy formation1. Most observed dwarf galaxies consist of a rotating stellar disk2 embedded in a massive dark-matter halo with a near-constant-density core3. Models based on the dominance of CDM, however, invariably form galaxies with dense spheroidal stellar bulges and steep central dark-matter profiles4,5,6, because low-angular-momentum baryons and dark matter sink to the centres of galaxies through accretion and repeated mergers7. Processes that decrease the central density of CDM halos8 have been identified, but have not yet reconciled theory with observations of present-day dwarfs. This failure is potentially catastrophic for the CDM model, possibly requiring a different dark-matter particle candidate9. Here we report hydrodynamical simulations (in a framework10 assuming the presence of CDM and a cosmological constant) in which the inhomogeneous interstellar medium is resolved. Strong outflows from supernovae remove low-angular-momentum gas, which inhibits the formation of bulges and decreases the dark-matter density to less than half of what it would otherwise be within the central kiloparsec. The analogues of dwarf galaxies—bulgeless and with shallow central dark-matter profiles—arise naturally in these simulations.

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Figure 1: The observable properties of simulated galaxy DG1.
Figure 2: The SDSS i -band radial light profile of the simulated dwarf galaxy DG1 at z = 0.
Figure 3: The rotation curve of the simulated dwarf compared to that measured for a real galaxy.
Figure 4: A comparison between the angular momentum distribution of the stellar disk and the dark-matter halo in the simulated galaxy DG1.

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Acknowledgements

We acknowledge discussions with L. Blitz, A. Kravtsov, J. Primack, I. Trujillo and V. Wild. We thank R. Swaters and the THINGS team for sharing some of their data with us. L.M. and C.B. thank the Kavli Institute for Theoretical Physics at the University of California, Santa Barbara, for hospitality during the early stages of this work. F.G. and P.M. thank the computer support people at Nasa Advanced Supercomputing, TERAGRID, ARSC and UW, where the simulations were run.

Author Contributions F.G. provided the scientific leadership, designed the numerical experiments, wrote the paper and led the analysis and interpretation of the simulations. C.B. and A.B. performed part of the analysis. C.B., L.M., A.B., B.W. and P.M. helped with the interpretation and the writing of the manuscript. J.W., T.Q. and G.S. developed GASOLINE, the code used for the simulations. P.J. developed the analysis code SUNRISE. G.R. performed the kinematical analysis of the simulations.

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Correspondence to F. Governato.

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Supplementary information

Supplementary Information

This file contains Supplementary Methods and Data, Supplementary Tables 1-2, Supplementary Notes, Supplementary References, Supplementary Figures 1-4 with Legends and the Legend for Supplementary Movie 1. (PDF 1154 kb)

Supplementary Movie 1

The movie shows the evolution of the gas density in the region where galaxy DG2 forms, from shortly after the Big Bang to the present time (see Supplementary Information file for full Legend). (MOV 21555 kb)

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Governato, F., Brook, C., Mayer, L. et al. Bulgeless dwarf galaxies and dark matter cores from supernova-driven outflows. Nature 463, 203–206 (2010) doi:10.1038/nature08640

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