Former Hintze Scholars

Laura Prichard

Laura Prichard was the first Hintze Scholar from October 2014 to March 2018. Laura Prichard completed her thesis in the Spring of 2018. She took up a postdoctoral position with Dr Marc Rafelski at the Space Telescope Science Institute in Baltimore in the Summer of 2018.

Thesis title: The evolution of early-type galaxies

Abstract:
Early-type galaxies (ETGs) are typically thought of as ‘red and dead’ with little to no star formation and old stellar populations. Their detailed kinematics measured locally suggest an interesting array of formation mechanisms and high-redshift observations are starting to reveal a two-phase evolutionary path for the most massive galaxies. In this thesis, I take a combined approach to studying the formation of ETGs. I look to distant quiescent galaxies in one of the densest regions of the early Universe and at the fossil record of a local galaxy to shed light on some of the unsolved mysteries of how ETGs evolved. Using the unique multiplexed instrument, the K-band Multi-Object Spectrograph (KMOS), the evolution of galaxies at both low and high redshift were studied as part of this thesis. I maximised the capabilities of this multi-integral field unit (IFU) near-infrared (NIR) instrument to study different aspects of ETG evolution. With 24 separate IFUs, many quiescent galaxies were efficiently observed in a massive high-redshift cluster as part of the KMOS Cluster Survey. Coupling KMOS spectroscopy with Hubble Space Telescope photometry, I studied the ages, kinematics, and structural properties of the galaxies. I then analysed the detailed properties of a massive local ETG with interesting kinematics, IC 1459. Coupling the NIR IFU data from KMOS with a large mosaic of optical data from the Multi-Unit Spectroscopic Explorer, I was able to study the spatially resolved kinematics, stellar populations, and initial mass function of the galaxy. The work presented in this thesis provides some interesting clues as to the formation of ETGs and possible diversity of their evolutionary paths.

Sergio Martin-Alvarez

Sergio Martin-Alvarez was recruited as a Hintze Scholar in October 2015 and completed his thesis in the Spring of 2019. He took up a postdoctoral position at the Institute of Astronomy in Cambridge in the Summer of 2019.

Thesis title: Magnetic fields in and around galaxies

Abstract:
Magnetic fields are an ubiquitous component of our Universe. They are expected to play an important role in the evolution of many astrophysical systems, from molecular clouds to galaxy clusters. In the case of galaxies, magnetic energy is measured to be in equipartition with thermal and turbulent energies of the interstellar medium. Despite this omnipresence, the origin of cosmic magnetic fields remains an open question, and the precise influence that magnetic fields have in shaping the formation and evolution of galaxies is uncertain.
Using magnetohydrodynamical numerical simulations of both cosmological volumes and high-resolution cosmic zoom-ins on individual galaxies, I explore in this thesis the main mechanisms likely to generate galactic magnetic fields similar to those observed and the role these latter play in shaping galaxies. I present various extensions to existing numerical techniques to account for magnetism in state-of-the-art software employed to simulate galaxies. These culminate in the introduction of a new algorithm that traces magnetic fields generated by different sources separately. In particular, I simulate the formation of a Milky Way-like galaxy, magnetised either through dynamo amplification, a strong primordial magnetic field, or magnetised stellar feedback, demonstrating that each mechanism is capable of producing realistic levels of magnetisation on its own. Jointly tracing primordial and stellar generated fields, I study how they compete to produce the total magnetic field. I find a large degree of interaction, both inside galaxies, where the two components contribute significantly to the magnetic energy budget, and around galaxies, where the magnetic fields pushed out by stellar feedback pollute the primordial magnetic field. In a final set of simulations, I explore how magnetic fields modify the global properties of a galaxy, finding evidence of morphological compression and braking of the rotation of the galaxy by strong magnetisation.

Paul Morris

Paul Morris was recruited as a Hintze Scholar in October 2015 and completed is thesis in November 2019 and began a postdoctoral position with Professor Martin Pohl at DESY-Zeuthen in December 2019.

Thesis title: Variability in gamma-ray sources

Abstract:
Gamma-rays are known to be emitted from some of the most extreme sources in the known Universe. Many of these objects are volatile and variable, and understanding them is the focus of the work contained in this thesis.
One such class of objects which are highly variable in gamma-rays are blazars, which are known to be variable on ~minute timescales at TeV energies. We present a macroscopic emission model to investigate whether magnetic reconnection is a feasible mechanism which can cause this rapid variability, assuming the primary emission mechanism to be synchrotron self-Compton (SSC). We show that in this case reconnection produces synchrotron-dominated flares so in general cannot fit broadband observations, although rapid flares can be produced.
Underlying physical processes occurring in astrophysical sources are believed to relate to the functional forms of the probability distribution function (PDF) of their time-series. Gaussian and lognormal PDFs correspond to linear and multiplicative processes, respectively. By simulating artificial light curves of known PDF functional forms, we prescribe a method for calculating the likelihood that the PDF has been correctly measured, applying this to the blazar PKS2155-304.
In recent years, observations made using the Fermi Large Area Telescope (LAT) have revealed classical novae (CNe) as gamma-ray sources, yet not every optically discovered CNe is a gamma-ray source. Here, we present simulations of an artificial Milky Way population of CNe with optical properties based of those detected in M31 and gamma-ray properties based on the observed sample. We show that observations are consistent with all CNe being gamma-ray sources and predict that all CNe at distances <8 kpc will be detected in gamma-rays.