The build up of stars and dust in nearby galaxies

• Main Author: Schofield, Simon
• Published: Cardiff University 2016
• Subjects: 523.1; QB Astronomy
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.704915

In this thesis I took a combined sample of dust-selected galaxies (from Clark et al. 2015) and HI-selected galaxies (from De Vis et al. 2016). The dust selected sample contains a large fraction of intriguing galaxies dubbed the ‘Blue And Dusty Gas Rich Sources’ (BADGRS), while the HI selected sources revealed another population of blue and gas rich systems which are instead dust-poor. I investigated whether the unique properties of these galaxies could be explained by variations in their recent star formation activity. I showed that the BADGRS are younger, and have typically experienced more recent bursts of star formation compared to the non-BADGRS. Splitting the sample into dust-rich and dust-poor sources showed that both subpopulations are of similar age, although the dust-rich sources have experienced a burst of star formation more recently. I took the chemical evolution model of Morgan & Edmunds (2003), used more recently used in Rowlands et al. (2014), and updated many of the functions and libraries in line with recent literature. I then produced a suite of models to investigate the dust and metal properties of 425 Herschel sources. These models showed (i) a delayed star formation history is required to match the observed star formation rates; (ii) inflows and outflows are required to explain the observed metallicities at low gas fractions; (iii) a significantly reduced contribution of dust from supernovae is necessary to explain the dust poor sources with high gas fractions. We also showed the dust-to-metal ratio is not definitively constant in all galaxies, and that there is evidence for a decrease in the dust-to-metals ratio towards lower metallicity. This thesis proposes a model in which the dust, gas, metals and stars can be modelled in a consistent and coherent manner, and gains insight into the dust-to-gas evolution at early epochs.