paper

The Modelling of Feedback Processes in Cosmological Simulations of Disk Galaxy Formation

arXiv:0909.4167

Abstract

We present a systematic study of stellar feedback processes in simulations of disk galaxy formation. Using a dark matter halo with properties similar to the ones for the Milky Way's stellar halo, we perform a comparison of different methods of distributing energy related to feedback processes to the surrounding gas. A most promising standard model is applied to halos spanning a range of masses in order to compare the results to disk galaxy scaling relations. With few exceptions we find little or no angular momentum deficiency for our galaxies and a good agreement with the angular momentum-size relation. Our galaxies are in good agreement with the baryonic Tully-Fisher relation and the slope of the photometric Tully-Fisher relation is reproduced. We find a zero-point offset of 0.7 to 1 magnitudes, depending on the employed IMF. We also study our standard feedback model in combination with additional physical processes like a UV background, kinetic feedback, a delayed energy deposition as expected for type Ia supernovae, mass return and metal-dependent cooling. Only a combination of effects yields a real improvement of the resulting galaxy by reducing the bulge, while including metal-dependent cooling increases the bulge again. We find that in general the stellar mass fraction of our galaxies is too high. In an ad-hoc experiment we show that an removal of the bulge could reconcile this. However, the fit of the Tully-Fisher relation can only be improved by delaying the star formation, but not suppressing it completely. Our models do not seem to be efficient enough to achieve either effect. We conclude that disk formation is a complex, highly interconnected problem and we expect a solution to come from a combination of small effects.

arXiv comment21 pages, 27 figures, submitted to MNRAS

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