Mathematics – Logic
Scientific paper
Oct 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000phdt.......112a&link_type=abstract
ProQuest Dissertations And Theses; Thesis (Ph.D.)--Harvard University, 2000.; Publication Number: AAT9988517; ISBN: 978059995430
Mathematics
Logic
Scientific paper
This thesis addresses the creation, distribution, and cosmological implications of intergalactic dust and heavy elements ('metals'). Most cosmic metals must have formed in stars in galaxies, yet a significant fraction of all metal lies the in the intergalactic medium (IGM). How these metals escaped their progenitor galaxies is currently an open question, which we address using cosmological N-body/hydrodynamical simulations to which we add prescriptions for the chemical evolution of galaxies and for the ejection of metals into the IGM by dynamical processes, by supernova-driven winds, and by radiation-pressure driven dust efflux. The method provides detailed calculations of the amount and distribution of cosmic metals, and the results demonstrate that winds and radiation pressure---but perhaps not dynamics---might account for most of the intergalactic metal observed, if it was ejected at redshift z ≲ 8 from relatively large galaxies. These and other calculations indicate that unless it is largely destroyed during ejection, a significant level of intergalactic (IG) dust should exist. If this dust reddens attenuated light less than dust in galaxies (perhaps due to selective destruction or galactic retention of very small grains), it could seriously affect recent determinations of the Hubble diagram sing Type Ia supernovae, without having been detected by those observations. Intergalactic dust would also reprocess some diffuse extragalactic background light from optical wavelengths into the far-infrared (FIR), and the expected contribution can be compared to observations of the cosmic microwave (CMB) and FIR backgrounds. This strongly constrains the density of IG dust but does not rule out a cosmologically significant level. Finally, we address the question of whether the entire CMB might be dust emission. Such 'cold big-bang' models have long provided an alternative to the widely accepted hot big-bang models, but have difficulty accounting for the highly thermal nature of the CMB. We estimate the temperature, calculate the evolution, and discuss the anisotropies of a homogeneous radiation background emitted at high redshift by population III objects and thermalized by a mixture of dust types. These calculations are compared in detail to current observations to assess the current viability of cold big-bang models.
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