Dark matter in dwarf irregular galaxies, DDO 210 and DDO 169

It has been proposed that dwarf irregular galaxies can be separated into two classes based on their formation mechanism; that they are the result of the collapse of a primordial gas cloud or that they are the product of condensation of gas in the tidal tails of interacting galaxies. Simulations of galaxy interactions indicate that one can differentiate between these two scenarios by the dark matter content, with a low dark matter content indicating a fossil tidal dwarf. The purpose of this dissertation was to explore the dark matter distribution of two dwarf irregular galaxies using optical and neutral atomic hydrogen data. For DDO 210, the method of mass-modelling was used to determine its dark matter. About 64% of the galaxy mass was calculated to be in the form of dark matter and hence it is unlikely to be a fossil tidal dwarf. The method of mass-modelling could not be used for DDO 169 as the galaxy shows evidence of being tidally disrupted and hence, has a disturbed velocity field. Instead, the suggestion that dark matter might be responsible for a pressure anomaly in DDO 169 was tested to determine its dark matter content. According to this method, a pressure anomaly does exist but without a concrete value for the scale-height, it is unclear whether the anomaly is due to the presence of dark matter. Hence one cannot say how much dark matter might actually be present in DDO 169. A rotation curve would be required to do this. ^

Asterisms

ASTERISMS is a collection of lyric poetry that seeks to express a sense of awe for the natural world by exploring themes of science, art, and the self. By combining physics and metaphysics, scientific terminology and musings on love, ASTERISMS argues that these seemingly-disparate fields of knowledge can harmonize in unexpected ways. In its style, the collection draws from the works of Dorianne Laux, Pablo Neruda, and Annie Dillard. Most of the poems are written in free-version and are tied together by images of astronomy and wilderness, both modern and prehistoric. Poems about classical music appear as interludes meant to complement others concerned with science and technology, as music too has its own invented language. Like asterisms - ancient inventions meant to personalize the expansive mystery of the night sky - this collection seeks to admire, if not completely understand, our place in the natural world and cosmos beyond.