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Published November 2011 | Accepted Version + Published
Journal Article Open

The cold gas content of bulgeless dwarf galaxies

Abstract

We present an analysis of the neutral hydrogen (H i) properties of a fully cosmological hydrodynamical dwarf galaxy, run with varying simulation parameters. As reported by Governato et al., the high-resolution, high star formation density threshold version of this galaxy is the first simulation to result in the successful reproduction of a (dwarf) spiral galaxy without any associated stellar bulge. We have set out to compare in detail the H i distribution and kinematics of this simulated bulgeless disc with what is observed in a sample of nearby dwarfs. To do so, we extracted the radial gas density profiles, velocity dispersion (e.g. velocity ellipsoid and turbulence) and the power spectrum of structure within the cold interstellar medium (ISM) from the simulations. The highest resolution dwarf, when using a high-density star formation threshold comparable to densities of giant molecular clouds, possesses bulk characteristics consistent with those observed in nature, though the cold gas is not as radially extended as that observed in nearby dwarfs, resulting in somewhat excessive surface densities. The lines-of-sight velocity dispersion radial profiles have values that are in good agreement with the observed dwarf galaxies, but due to the fact that only the streaming velocities of particles are tracked, a correction to include the thermal velocities can lead to profiles that are quite flat. The ISM power spectra of the simulations appear to possess more power on smaller spatial scales than that of the Small Magellanic Cloud. We conclude that unavoidable limitations remain due to the unresolved physics of star formation and feedback within parsec-scale molecular clouds.

Additional Information

© 2011 The Authors Monthly. Notices of the Royal Astronomical Society © 2011 RAS. Accepted 2011 July 14. Received 2011 June 15; in original form 2010 September 2. Article first published online: 31 Aug 2011. We wish to thank the THINGS team for their insights and access to their exceptional data set, in addition to a number of helpful discussions with F. Governato, A. Pontzen, D. Kawata and A. Burkert and comments from the referee which led to a vastly improved manuscript. BKG and CBB acknowledge the support of the UK's Science & Technology Facilities Council (ST/F002432/1). KP acknowledges the support of STFC through its PhD Studentship programme (ST/F007701/1). RJT acknowledges support from NSERC, CFI, the CRC program and NSRIT. KP and BKG acknowledge visitor support from Saint Mary's University. We thank the DEISA consortium, cofunded through EU FP6 project RI-031513 and the FP7 project RI-222919, for support within the DEISA Extreme Computing Initative, and the UK's National Cosmology Supercomputer (COSMOS), NASA's Advanced Supercomputing Division, Tera-Grid, the Arctic Region Supercomputing Center, and the University of Central Lancashire's High Performance Computing Facility.

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Published - Pilkington2011p16547Mon_Not_R_Astron_Soc.pdf

Accepted Version - 1107.2922.pdf

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