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March 29 (4:00PM) in the 2nd Floor Conference Room in Dearborn Speaker: Kostas Tassis (KICP - Univ of Chicago) “Are galactic winds shaping the properties of dwarf galaxies?” Nearby dwarf galaxies exhibit tight correlations between their global stellar and dynamical properties, such as circular velocity, mass-to-light ratio, stellar mass, surface brightness, and metallicity. Such correlations are often attributed to gas or metal-rich outflows driven by supernova feedback. Using high-resolution cosmological simulations of high-z galaxies with and without energy feedback, as well as analytic chemical evolution modeling, we investigate whether the observed correlations can arise without supernova-driven outflows. We find that the simulated dwarf galaxies exhibit correlations similar to those observed as early as z~10 even when feedback is explicitly turned off. We conclude that correlations in simulated galaxies arise due to the increasingly inefficient conversion of gas into stars in low-mass dwarf galaxies rather than mass loss in winds. We also show that the decrease of the observed effective yield in low-mass objects, often used as an indicator of gas and metal outflows, can be reasonably reproduced in our simulations without outflows. We show that this trend can arise if a significant fraction of metals in small galaxies is spread to the outer regions of the galaxy halos outside the stellar extent via mixing. In this case the effective yield can be significantly underestimated if only metals within the stellar radius are taken into account. |