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Abstract: We use high resolution 2D hydrodynamic simulations to study the formation ofspiral substructure in the gaseous disk of a galaxy. The obtained gaseousresponse is driven by a self-consistent non-axisymmetric potential obtainedfrom an imposed spiral mass distribution. We highlight the importance ofultraharmonic resonances in generating these features. The temporal evolutionof the system is followed with the parallel ZEUS-MP code, and we follow thesteepening of perturbations induced by the spiral potential until large-scaleshocks emerge. These shocks exhibit bifurcations that protrude from the gaseousarms and continue to steepen until new shocks are formed. When the contributionfrom the spiral potential relative to the axisymmetric background is increasedfrom our default value, spurs protrude from the main arms after severalrevolutions of the gaseous disk. Such spurs overlap on top of theaforementioned shocks. These results support the hypothesis that a complicatedgaseous response can coexist with an orderly spiral potential term, in thesense that the underlying background potential can be smooth yet drive agaseous response that is far more spatially complex.

Autor: Miguel A. Yáñez, Michael L. Norman, Marco A. Martos, John C. Hayes


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