The cold gas content of bulgeless dwarf galaxies
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abstract
We present an analysis of the neutral hydrogen (HI) properties of a fully
cosmological hydrodynamical dwarf galaxy, run with varying simulation
parameters. As reported by Governato et al. (2010), 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 HI
distribution and kinematics of this simulated bulgeless disk 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, turbulence),
and the power spectrum of structure within the cold interstellar medium 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 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 SMC. We
conclude that unavoidable limitations remain due to the unresolved physics of
star formation and feedback within pc-scale molecular clouds.
