No CrossRef data available.
Published online by Cambridge University Press: 03 August 2017
Galaxy disks are observed to be young, dynamically cold, and centrifugally supported. These properties suggest that they formed in a quiescent dynamical context, reached their current configuration while still gaseous, and have been relatively undisturbed since formation. This situation can be understood if disks grow by the cooling of a gaseous atmosphere within a quasi-equilibrium dark halo. A simple version of this model can be combined with results from numerical simulations of halo formation to provide quantitative explanations for the Tully-Fisher relation, for the typical sizes of disks, and for their star formation history. A viable model seems to require stellar winds and supernovae to heat the gaseous halos of spirals via a galactic fountain. Such models predict observable X-ray halos, and suggest that continued infall replenishes the gas consumed by star formation in late-type galaxies.