Research

Galaxy dynamics is the study of how stars, gas, dust, and dark matter move under gravity and collectively shape a galaxy. I use it to investigate how disc galaxies form, how their central structures evolve, and how the Milky Way acquired the structure that we observe today.

My research combines numerical simulations with astrometric, photmetric, and time-domain observations. By comparing models of isolated galaxies and cosmological simulations with data from facilities and surveys such as Gaia, the Hubble Space Telescope (HST), the Vera C. Rubin Observatory, APOGEE, and LAMOST, I study both the physical mechanisms that drive galaxy evolution and the observable signatures they leave in different stellar populations.

Bars, box/peanut bulges, and secular evolution

Much of my work focuses on the slow internal, or secular, processes that reshape galaxies over billions of years. Bars redistribute material and angular momentum through a disc and can build vertically extended box/peanut bulges. Seen from the appropriate angle, these structures produce the X-shaped morphology observed in the central Milky Way and many external galaxies.

An important part of this research is kinematic fractionation: stellar populations with different random motions can respond differently when a bar forms, producing population-dependent structure and kinematics without requiring separate formation mechanisms. My first paper used an isolated barred-galaxy model to study the proper-motion rotation curves of differently aged stars in the Milky Way bulge. The model reproduced qualitative trends observed with HST and predicted where age-dependent signatures and forbidden velocities could be detected with future observations from HST and Rubin. My ongoing work extends this approach to the kinematic moments of stellar populations across barred galaxies.

The Milky Way bulge and its stellar populations

The Galactic bulge contains overlapping structures and populations whose motions, chemistry, and spatial distributions record the Milky Way’s formation history. I contribute to work that combines these dimensions to distinguish the signatures of the bar, box/peanut bulge, and more spheroidal components.

This includes studying the chemical and spatial variation of the bulge’s velocity ellipsoids, which describe the direction and dispersion of stellar motions across the bulge. I have also worked on three-dimensional and kinematic maps of RR Lyrae stars as tracers of the Galactic bar and on evidence for coexisting spherical and X-shaped bulge populations. Together, these projects test how stellar populations of different ages and chemical compositions respond to the Milky Way’s bar.

Variable stars and time-domain surveys

Pulsating variable stars provide distances, ages, and dynamical information that make them powerful probes of Galactic structure. My research uses RR Lyrae and Mira variables to map the Milky Way and to prepare for the volume and cadence of data from the Vera C. Rubin Observatory.

A recent pilot study of Rubin early alerts tested RR Lyrae candidates from several existing surveys using early multi-band Rubin light curves. In work currently under review, I use data-driven selection of Mira candidates in Gaia to investigate how the age distribution of the bulge traces its peanut-shaped structure. I also contribute to planning how Rubin can work with the Nancy Grace Roman Space Telescope and other facilities to increase their combined scientific return and explore the Roman Galactic Plane Survey.

Bar and bulge formation in a cosmological context

Idealised simulations allow individual dynamical mechanisms to be isolated, while cosmological simulations place those mechanisms within a realistic history of gas accretion, star formation, and mergers. My research uses the TNG50 run of the IllustrisTNG simulation to study a statistical population of barred galaxies.

Our analysis of box/peanut bulges in TNG50 connected their formation to the age and strength of galactic bars, galaxy downsizing, and merger history. This comparison between simulated and observed populations helps identify which galaxy properties determine whether a bar develops a box/peanut bulge, while also revealing the effects of numerical resolution and excessive dynamical heating in cosmological models.

The structure and evolution of the Milky Way disc

My interests also extend beyond the central bulge to the wider Galactic disc. By combining stellar ages and kinematics from APOGEE, LAMOST, and Gaia with N-body and hydrodynamical simulations, our recent work identified a U-shaped stellar age profile in the Milky Way. The location of its minimum marks the break, or edge, of the star-forming disc at roughly 11-12 kiloparsecs from the Galactic centre. The result links a decline in outer-disc star formation with the radial migration of stars and demonstrates how dynamics can connect the present-day distribution of stellar ages to the long-term evolution of the disc.