Statistics – Computation
Scientific paper
Dec 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001phdt........17s&link_type=abstract
Thesis (PhD). IOWA STATE UNIVERSITY, Source DAI-B 62/06, p. 2758, Dec 2001, 111 pages.
Statistics
Computation
2
Scientific paper
Late-type spiral galaxies share many universal properties. One school of thought proposes that this universality arises from common initial conditions at the formation of these galaxies. The initial conditions are frozen out once the disks have formed, thus accounting for common structure among disk galaxies. However, observations over the last decade suggest that most galaxies have had one or more encounters with other galaxies and that these interactions disturb their structures significantly. One solution to this paradox suggests that disks have a preferred hydrodynamic state and that some processes regulates these disks to that state. This self-regulation may occur during the initial disk formation and carry on through the life of the disk bringing it back to its preferred state even after an interaction has pushed it far from equilibrium. The interstellar medium of disk galaxies experience broad spectrum heating from supernovae, stellar winds and intense UV fluxes from young star clusters that drive turbulent flows and produce multiple thermal phases. Star formation processes from which these young stars arise are regulated by the heat and exchange of phases that they produce. While these star formation processes are effective locally, the overall thermohydrodynamic self- regulation must act globally to account for the large scale universal structure observed in disks. Study of these global regulatory processes is an important step to understanding the formation and evolution of large scale structure in disk galaxies. This dissertation describes our analytic and computational thermohydrodynamic models of gas disks with star formation feedback. The models suggest a number of results that are in accord with observation, as well as some novel predictions. The analytic model suggests the existence of opposing radial flows and a difference in rotational velocity between cold clouds in the midplane and warm and hot gas above and below the midplane. The heating and cooling balance in the analytic model also requires a star formation rate that is similar to the Schmidt Law. The computational models produce steady states with spiral structures that depend on the amount and location of the star formation.
Smith Daniel Carlton
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