Abstract
We present an analysis of the role of feedback in shaping the neutral hydrogen (HI) content of simulated disc galaxies. For our analysis, we have used two realisations of two separate Milky Way-like (~L*) discs - one employing a conservative feedback scheme (MUGS), the other significantly more energetic (MaGICC). To quantify the impact of these schemes, we generate zeroth moment (surface density) maps of the inferred HI distribution; construct power spectra associated with the underlying structure of the simulated cold ISM, in addition to their radial surface density and velocity dispersion profiles. Our results are compared with a parallel, self-consistent, analysis of empirical data from THINGS (The HI Nearby Galaxy Survey). Single power-law fits (P~k^gamma) to the power spectra of the stronger-feedback (MaGICC) runs (over spatial scales corresponding to 0.5 kpc to 20 kpc) result in slopes consistent with those seen in the THINGS sample (gamma = -2.5). The weaker-feedback (MUGS) runs exhibit shallower power law slopes (gamma = -1.2). The power spectra of the MaGICC simulations are more consistent though with a two-component fit, with a flatter distribution of power on larger scales (i.e., gamma = -1.4 for scales in excess of 2 kpc) and a steeper slope on scales below 1 kpc (gamma = -5), qualitatively consistent with empirical claims, as well as our earlier work on dwarf discs. The radial HI surface density profiles of the MaGICC discs show a clear exponential behaviour, while those of the MUGS suite are essentially flat; both behaviours are encountered in nature, although the THINGS sample is more consistent with our stronger (MaGICC) feedback runs.
Highlights
The feedback of energy into the interstellar medium (ISM) is a fundamental factor in shaping the morphology, kinematics, and chemistry of galaxies, both in nature and in their simulated analogues (e.g. Thacker & Couchman 2000; Governato et al 2010; Schaye et al 2010; Hambleton et al 2011; Brook et al 2012; Scannapieco et al 2012; Durier & Dalla Vecchia 2012; Hopkins et al 2013, and references therein)
We have presented an analysis of the cold gas and HI content of simulated discs with both ’standard’ (MUGS) and ‘enhanced’ (MaGICC) energy feedback schemes, as well as re-scaled dwarf variants of the massive (MaGICC) simulations
These were generated using their respective zeroth HI moment maps; the weaker feedback associated with McMaster Unbiased Galaxy Survey (MUGS) resulted in very flat radial HI distributions, with sharp cut-offs at galactocentric radii of ∼12−15 kpc, while the stronger feedback associated with MaGICC resulted in HI discs with exponential surface density profiles which were ∼2−3× more extended
Summary
The feedback of energy into the interstellar medium (ISM) is a fundamental factor in shaping the morphology, kinematics, and chemistry of galaxies, both in nature and in their simulated analogues (e.g. Thacker & Couchman 2000; Governato et al 2010; Schaye et al 2010; Hambleton et al 2011; Brook et al 2012; Scannapieco et al 2012; Durier & Dalla Vecchia 2012; Hopkins et al 2013, and references therein). The efficiency and mechanism by which energy from massive stars (both explosive energy deposition from supernovae and pre-explosion radiation energy), cosmic rays, and magnetic fields couple to the ISM can be constrained indirectly via an array of empirical probes, including (but not limited to) stellar halo (Brook et al 2004) and disc (Pilkington et al 2012) metallicity distribution functions, statistical measures of galaxy light compactness, asymmetry, and clumpiness (Hambleton et al 2011), stellar disc age-velocity dispersion relations (House et al 2011), rotation curves and density profiles of dwarf galaxies In Pilkington et al (2011), we explored an alternate means by which to assess the efficacy of energy feedback schemes within a cosmological context: the predicted distribution of structural ‘power’ encoded within the underlying cold gas of late-type dwarf galaxies. Our simulated (dwarf) disc galaxies showed steep ISM power-law spectra, albeit deviating somewhat from the simple, single, power-law seen by Stanimirovic et al
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