Dust in galaxies throughout cosmic time

• Main Author: Rowlands, Kate
• Published: University of Nottingham 2013
• Subjects: 523.112; QB Astronomy
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.594636

One of the most fundamental observational probes of galaxy evolution is determining the build-up of stellar mass. However, around half of all energy ever emitted from galaxies has been absorbed and reprocessed by dust, which is an end-product of stellar evolution. In order to obtain a more complete understanding of galaxy evolution, sensitive observations in the far-infrared and submillimetre are required where the dust emission peaks. Previous surveys have found galaxies were significantly dustier at earlier times, but the cause of this evolution, and the origin of the dust, are hotly debated topics in astrophysics. With the Herschel Space Observatory, a complete census of the dusty galaxy population has now recently been obtained. In this thesis I investigate the properties of the diverse dusty galaxy population via a panchromatic approach, utilising data from the UV to the submillimetre to study galaxy evolution. Using the first unbiased survey of dust in the local Universe, I explore the properties of galaxies in the local Universe as a function of morphology and highlight particularly interesting populations which are traditionally thought to be passive. The star-formation histories, dust content and environments of dusty early-type galaxies and passive spirals are investigated. I show that dusty early-type galaxies comprise a small minority of the general early-type galaxy population (5.5%), and harbour on average 5.5x10^7 M_sun of dust, which is comparable to that of some spiral galaxies in our sample. I compare these dusty populations to control samples to investigate how these galaxies are different to the general galaxy population. High redshift submillimetre galaxies are the most actively star-forming and dusty galaxies in the Universe. Constraining the properties of these galaxies is important for understanding the evolution of massive galaxies and galaxy evolution models in general. Using panchromatic data from the UV to the submillimetre, I explore the physical properties of a sample of ~250um rest-frame selected galaxies at high redshift, and compare them to dusty galaxies at low redshift selected in a similar way, to investigate the differences in the dusty galaxy populations over cosmic time. I find high redshift dusty galaxies have significantly higher star-formation rates and dust masses than z<0.5 dusty galaxies selected to have a similar stellar mass. Galaxies which are as highly star forming and dusty as those at z~2 are rare in the local Universe. My results support the idea that the most dusty galaxies at high redshift are a heterogeneous population, with around 60% of our sample consistent with secular evolution, and the other 40% of galaxies are starbursting, possibly merger-driven systems. The origin of dust in galaxies at both low and high redshifts presents a challenge to current theories of galaxy evolution. Recent work has revealed a `dust budget crisis', whereby the mass of dust observed in galaxies at low and high redshift cannot be accounted for by stellar mass loss from low-intermediate mass stars. I tackle this challenge using chemical evolution modelling of the high redshift submillimetre galaxies, with a detailed treatment of the star-formation histories and the dust sources and sinks in these galaxies. It is clear that a significant mass of dust must be from supernovae and/or grain growth; however, the origin of dust in high redshift dusty galaxies remains uncertain. I also consider the impact of inflows and outflows of gas, and the effect of changing the IMF on the physical properties of high redshift dusty galaxies.