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Abstract: We examine metal and entropy content in galaxy groups having T X~0.5-2 keV incosmological hydrodynamic simulations. Our simulations include awell-constrained prescription for galactic outflows following momentum-drivenwind scalings, and a sophisticated chemical evolution model. Our simulationwith no outflows reproduces observed iron abundances in X-ray emitting gas, butthe oxygen abundance is too low; including outflows yields iron and oxygenabundances in good agreement with data. X-ray measures of O-Fe primarilyreflect metal distribution mechanisms into hot gas, not the ratio of Type Ia toType II supernovae within the group. Iron abundance increases by x2 from z=1-0independent of group size, consistent with that seen in clusters, while O-Fedrops by ~30%. Core entropy versus temperature is elevated over self-similarpredictions regardless of outflows due to radiative cooling removinglow-entropy gas, but outflows provide an additional entropy contribution below1 keV. This results in a noticeable break in the L X-T X relation below 1 keV,as observed. Importantly, outflows serve to reduce the stellar content ofgroups to observed levels. Radial profiles from simulations are in broadagreement with observations, but there remain non-trivial discrepancies thatmay reflect an excess of late-time star formation in central group galaxies inour simulations. Our model with outflows suggests a connection between physicalprocesses of galaxy formation and both pre-heating and enrichment in intragroupgas, though more definitive conclusions must await a model that simultaneouslysuppresses cooling flows as observed.



Author: Romeel Davé, Benjamin D. Oppenheimer, Suresh Sivanandam Arizona

Source: https://arxiv.org/







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