Research

To date, I have performed analyses of integral-field spectroscopic observations of a variety of galaxy types. Such data allows us to uncover the stellar populations and ionised gas properties of observed galaxies. Through dynamical modelling, we may also analyse the galaxies' mass contents (dark and stellar) as well as the orbital motions of the galaxies' stars. All of these measurements allow us to narrow down  the likely formation histories of these galaxies, furthering our understanding of how different galaxy types form and evolve.

To see my papers on ADS, click here.

Gas-phase abundances in star-forming galaxies

Star-forming galaxies are filled with bright ionised gas, which has been enriched with heavy elements by successive stellar generations. Modern spectroscopic datasets allow us to map gas properties across galaxies for large galaxy samples, providing much information on galaxies' chemical structures. Studying galaxies' chemistry in this way provides much insight into how galaxies form and evolve

I am largely using data from the MaNGA integral-field survey to perform this research. So far, I have found a striking mass-size trend for both gas-phase metallicity gradients and Nitrogen abundance gradients: for a wide range in galaxy stellar masses, more extended galaxies display gradients for their size than more compact galaxies at a given stellar mass. This behaviour is not readily apparent if we consider gradients as functions of only mass or size individually; thus, mass and size should be considered together in order to obtain the full picture. For gas metallicities, I have also found that local relations amongst galaxy regions, such as the stellar density-metallicity relation, can predict the mass-size trend in a qualitative sense. This suggests that gas metallicity gradients can be understood largely in terms of local trends. 

Within extended lower-mass galaxies, I have found in addition that gas metallicity actually trends more tightly with galactocentric radius then with local stellar surface density. Such galaxies, it should be noted, also typically display steep metallicity gradients overall. I argued these findings to be consistent with such galaxies having experienced smooth accretion histories, producing steep metallicity gradients over time.

Milky Way analogs

Our position within the Milky Way offers a unique opportunity to study galaxy evolution on small scales, allowing observations of such things as single stars and individual gas clouds. At the same time, our place within the Milky Way's disk makes it comparatively difficult to calculate integrated quantities such as galaxy optical colour. Thus, it is difficult to relate the Milky Way to the wider galaxy population. In turn, it remains challenging to make use of the full wealth of information contained within the Milky Way galaxy. 

Milky Way Analogs offer an ideal solution in this area, by allowing us to visualise how the Milky Way may appear to an external observer. To this end, I am studying the properties of various selected "analog" samples. By comparing and contrasting these samples, I can consider what sample selection strategies lead to the most stringent constraints on the Milky Way, as well as considering whether the Milky Way is in any way unusual in its properties.

I employed data from the MaNGA survey to carry out this work.  The rich information encoded within the MaNGA spectra allow to measure various properties of analogs' stellar and gaseous contents, both integrated over the observed field of view and also as functions of position. At the same time, I employed various wide-field galaxy catalogs to select complimentary samples of analogs, to better understand how the Milky Way - along with the neighbouring Andromeda - compares to the wider population of galaxies in the local Universe.

Early-type galaxies

"Early-type" galaxies are those galaxies that lie within the Elliptical and Lenticular regions on the classic Hubble tuning fork diagram. Unlike Spiral galaxies such as our own Milky Way, these galaxies show little to no evidence of ongoing star-formation and so lack the bright spiral arms that give Spiral galaxies their name. Early-type galaxies are believed to represent the end-stages of galaxies' evolution; thus, understanding them is crucial  if we are to construct a complete picture of how galaxies change over time.

To further our understanding of early-type galaxy evolution, I worked with a sample of twelve such galaxies observed on the Mitchell Spectrograph at McDonald Observatory, Texas. I studied the galaxies' gas and stellar population out to approximately three half-light radii, allowing me to analyse the regions of the galaxies' where dynamical timescales were long and where evidence of recent mergers would be expected to be preserved. 

My work on early-type galaxies is the topic of my doctoral thesis, which can be found here.