tokens: mixes with nearby gas, producing a sharp peak in the PDF at the high metallicity end. More efficient diffusion tends to push this peak to lower metallicities. This trend is produced by enriched gas losing its metals more rapidly. However, this also depends on the recent star formation history, and is not a monotonic trend with diffusion strength. This peak is not present in Nodiff. Instead, there is a high-metallicity tail, consisting of the small number of particles that have been enriched by very many feedback events. The difference between the metal distributions has no clear impact on the distribution of cooling times, presumably because the number of particles in the high-metallicity tail is small. In general, the gas properties of Shear do not seem to stand out as particularly distinct among the other simulations. The differences between the simulations thus appears to depend only on the strength of diffusion, even when the diffusion coefficient is calculated in different ways. This suggests that diffusion can be accurately calibrated by adjusting the pre-factor, and that it is not necessary to introduce a more complex method for calculating the diffusion coefficient. 3.3. Spatial Distribution of Metals The spatial distribution of metals at t = 750 Myr is plotted in the second column of Figures 3 and 4 . This distribution is strongly affected by the choice of diffusion algorithm. Without any diffusion, the metal distribution is very clumpy as there is no mechanism to smooth out the metals. Highly metal-enriched particles can therefore move over large distances without losing their metals. Metal-rich gas in the Nodiff model at clearly has a large vertical extent, while Disp is more localized (Figure 4 ). We have plotted the mean metallicity, and [O/Fe], in vertical and radial bins in Figure 7 at intervals of 250 Myr to examine more clearly the difference between the diffusion algorithms. The radial metallicity bins are annuli that extend 2 kpc above and below the disk plane, and the vertical metallicity bins are pillboxes of radius 5 kpc. While many observed dwarf galaxies appear to have flat or near-flat metallicity gradients (Crnojević et al. 2010 ; Koleva et al. 2011 ), all of our simulations show significant slopes. This is likely a result of our feedback being weak, resulting in gas (and hence star formation) that is centrally concentrated. Stronger feedback at higher resolution can produce more distributed star formation ( K14 ). This dependence on feedback means that the simulated spatial distributions of metals can not be directly compared with observations, but only compared with other models with similar feedback strength. Figure 7. Metallicity distributions at t = 250, 500, 750, and 1000 Myr (from top to bottom). First column: metallicity as a function of height above the disk plane. Second column: Metallicity as a function of radius. Third column: [O/Fe] as a function of height above the disk plane. Fourth column: [O/Fe]
ner_tags: O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O