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Angular Distribution Of Interstellar Al-26, Mark D. Leising, Donald D. Clayton
Angular Distribution Of Interstellar Al-26, Mark D. Leising, Donald D. Clayton
Publications
The angular distribution and local concentration of interstellar Al-26 are calculated for five theoretical models of its origin, as a guide for future observations. The models considered relate Al-26 to current star formation (with surface CO density as its indicator), treat Al-26 as a secondary-nucleosynthesis product on seed nuclei with the same metallicity gradient as O, assume the Al-26 ejection rate is proportional to present light output, make Al-26 synthesis depend on total H I + H2 gas density, or assume that Al-26 is formed mainly in novae. The local decay and production rates for the five models are found …
Astration Of Cosmological Deuterium, Donald D. Clayton
Astration Of Cosmological Deuterium, Donald D. Clayton
Publications
Attention is given to the degree of primordial deuterium's astration through the continuous galactic processes of star formation and chemical evolution. Exact analytic solutions are given for galactic chemical evolution when infall of constant composition occurs at a rate, f(t), which is presently defined. Solutions are given for the linear model with instantaneous recycling and with constant return fraction R. The results suggest that Big Bang D/H was at least three times larger than the largest values observed in today's solar neighborhood, and even larger if matter falling into the disk is already astrated.
Galactic Chemical Evolution And Nucleocosmochronology: Analytic Quadratic Models, Donald D. Clayton
Galactic Chemical Evolution And Nucleocosmochronology: Analytic Quadratic Models, Donald D. Clayton
Publications
The author presents a new analytic model of the chemical evolution of the galaxy. Explicit solutions for a gas mass, star mass, metallicity, and radiochronometers are obtained for models with parametrized galactic infall, and for which the star formation rate is proportional to the gas mass. Because all physically interesting observables have a simple explicit dependence on the parameters which themselves map a wide space of physical possibilites, the author suggests adopting this model as a reference standard for studies of chemical evolution.