Probing galaxy evolution through interstellar dust and gas properties

Molecular gas is an important ingredient in galaxy evolution, since it is the fuel of star-formation. This Thesis explores different methods of measuring molecular gas masses in galaxies, and their applicability as a function of global galaxy properties, redshift, and presence of an active galactic nucleus (AGN). While CO(1-0) is the most commonly used emission line tracer of molecular gas for nearby galaxies, higher transitions such as CO(3-2) are more readily accessible for high-redshift galaxies. In order to connect studies at low and high redshift, we investigate which parameters are responsible for variations of the r31 = CO(3-2)/CO(1-0) luminosity line ratio in the local Universe and if the presence of an AGN influences the observed line ratio. Dust emission is often used as a molecular gas tracer in the literature, but to improve its accuracy, we need to know how dust properties change within the galaxy population and to quantify the uncertainties in measuring the dust masses. We study how the dust properties (in particular dust temperature and emissivity index) vary in a sample of ~500 nearby (z < 0.05) galaxies from the JINGLE and HRS surveys and derived scaling relations between the dust properties and other general galaxy properties. Moreover, we explore how the dust properties and scaling relations evolve with redshift using data from the A3COSMOS catalogue. Dust emission in the far-infrared (FIR) is also used to trace star-formation, in particular in the case of AGN, where other star-formation tracers may be more heavily contaminated by the AGN emission. We combine FIR continuum observations with spatially resolved observations of the ionized gas in z ~ 2 AGN and we find no evidence of star-formation suppression due to AGN outflows.