Examples of PhD projects available

An overview

There will be several PhD positions open for application with a deadline of December 1, 2021. For details of the application procedure see this page. The positions are available in all the research areas in which the Observatory is active. This page will give a broad overview of possible research projects . However, research in different areas is possible and not all projects that might be offered are listed. The faculty research interests provides more background information.

  • Project Title: Oxygen-bearing species as probes of the shocked and radiation-driven gas in high redshift galaxies.
    Supervisors: Paul van der Werf and Serena Viti

    This PhD project will make use of a comprehensive set of oxygen-bearing molecular species to trace and characterize the physical conditions and kinematics of the neutral and ionised “cold” gas in outflows at high redshifts. The project will first concentrate on the analysis and reduction of multi-line, spatially resolved H2O observations of 5 high-z galaxies, most with matching OH+ and H2O+ data, with a simple LTE/LVG analysis in order to broadly constrain the physical and energetic characteristic of the galaxies. This will then be followed by a substantial modelling effort, using and adapting in-house chemical and radiative transfer models to the high redshift environment. The student will systematically model the various energetic processes, individually as well as in concomitance, in order to first determine key molecular species and transitions that can be used as possibly unique tracers of each of the processes that are present and shape high-redshift ULIRGs. The results from their modelling work will be then used to fit the observations with the ultimate aims of (i) disentangling the shocked gas from the radiatively dominated gas; (ii) determining the physical conditions of the shocks and their origin; (iii) characterizing the radiation fields; (iv) determining mass outflow rates (based on abundances derived from the modelling) and local conditions in the outflowing gas.

  • Project title: Unravelling the formation histories of distant quiescent galaxies using ultra-deep spectroscopy
    Supervisor: Mariska Kriek

    One of the most remarkable discoveries from the past two decades in extra-galactic astronomy is the finding of a large population of high-redshift galaxies with very low star formation rates. The existence of these quiescent galaxies has yet to be explained, largely due to the difficulty of obtaining high-quality spectra. To remedy this situation, we have executed the Heavy Metal survey with the Keck I Telescope and obtained ultra-deep spectra of 20 quiescent galaxies at 1.3<z<2.3. We have also been awarded a Cycle 1 JWST/NIRSpec program to obtain even deeper spectra of a sample of 16 quiescent galaxies at 1.0<z<2.5. Combined, these programs yield the first statistical sample of 1.0<z<2.5 quiescent galaxies with robust stellar ages, stellar metallicities, chemical abundance patterns, and (resolved) stellar kinematics. These unprecedented measurements will provide novel insights into the star-forming, transitional, and quiescent phase of distant quiescent galaxies. We have an opening for a PhD student to become involved in the analysis of this unique dataset.

  • Project Title: Investigating stellar winds and coronal mass ejections with numerical simulations
    Supervisor: Aline Vidotto

    Outflows from low-mass stars come in the form of quiescent winds and bursty ejecta (coronal mass ejections or CMEs). As these outflows propagate through the interplanetary medium, they interact with any orbiting exoplanet and cause a pressure confinement around (otherwise freely) expanding atmospheres of exoplanets. Presently, there has been no systematic study that quantifies how realistic stellar outflow conditions of low-mass stars affect atmospheric evaporation in close-in exoplanets.

    What this project is about: The group led by Aline Vidotto has on opening for a PhD student to work on the modelling of stellar winds and CMEs. The PhD student will employ state-of-the-art 3D models of the injection and propagation of a CME through the background stellar wind. By comparing the simulation results with observations, the project will constrain the most realistic stellar CME scenario, allowing us to assess how the quiescent wind conditions are changed due to episodic mass ejections and for how long.

    The project within the ASTROFLOW team: The student will be part of the ASTROFLOW team, funded by an ERC Consolidator grant. This project will connect to the team's work by providing the physical quantities that will be used to determine the response of planetary evaporation on the impact of a CME.

  • Project Title: he formation of galaxies and the evolution of the intergalactic medium
    Supervisor: Prof. Joop Schaye

    The group led by Joop Schaye has an opening for a PhD student to work on simulations of the formation of galaxies and/or the evolution of the intracluster and intergalactic media. Possible projects include the development and analysis of new simulations, varying from large volumes for observational cosmology to high-resolution models of small volumes. Comparisons with observations are foreseen. The PhD student will become part of an international team.

  • Project Title: Unravelling the physics of particle acceleration and magnetic fields in distant galaxy clusters
    Supervisors: Reinout van Weeren, Huub Röttgering

    Galaxy clusters form by violent mergers with other galaxy clusters and groups. Radio observations of clusters have revealed the existence of large megaparsec-size, diffuse synchrotron emitting sources. The synchrotron radiation implies the existence of cosmic rays and magnetic fields. With their enormous extent, these radio sources trace the largest particle accelerators in the Universe. The LOFAR group of Dr. Reinout van Weeren and Prof. Huub Röttgering has a PhD project to work on shocks, turbulence, and magnetic fields in distant clusters. LOFAR is the world's most powerful low-frequency telescope and ideally suited to study merging galaxy clusters. Making use of subarcsecond resolution LOFAR imaging, the applicant will study massive distant clusters in large areas surveys and the more common less massive clusters in ultra-deep surveys. In addition, the recently started LOFAR decametre sky survey will be utilized to uncover the mysterious cluster fossil plasma. The work will involve the data reduction, analysis, interpretation, and publication of the LOFAR observations.

  • Project Title: How do complex organic molecules form in space?
    Supervisor: Serena Viti

    Complex organic molecules (COMs) are molecules with more than six atoms in their structure containing at least one carbon atom. Numerous COMs have been detected towards comets, in the interstellar medium of our Galaxy, and even in extragalactic environments. Among them, oxygen-bearing and nitrogen-bearing COMs have attracted much interest in recent years because of their role in prebiotic chemistry. Several efforts (experimental and theoretical) are being made to understand the chemistry of these species in various interstellar environments but a complete picture of how, when and where these COMs form and get destroyed is not yet available.

    With the aid of techniques developed in the information sciences, machine learning and statistical disciplines, we propose an interdisciplinary project that tackles one of the fundamental problems in Astrochemistry: the determination of the most likely reactions that lead to complex organic molecules as a function of the physical environment in the interstellar medium. Specifically, the student will devise and apply a novel combination of statistical and neural networks techniques (e.g. Bayesian statistical techniques, Monte Carlo sampling methods and Neural Networks) to perform large scale astrochemical models, involving large datasets of gas- and surface-phase chemical reactions, to derive the physical and chemical conditions under which every surface chemical reaction is viable. The calculations will simultaneously investigate the paths and efficiencies of formation and destruction of chemical reactions for many different complex molecules that we now routinely find in star forming regions, over a large physical (densities, temperatures, radiation fields, and cosmic ray ionization rates) and chemical (rate coefficients) parameter space, and determine if, where and under what conditions they can form in space.

  • Project Title: Quasars in a Neutral Universe.
    Supervisor: Joe Hennawi

    Description: This project focuses on the application and implementation of machine learning methods to facilitate making precision cosmological measurements from high redshift quasars that will be discovered by the upcoming Euclid satellite and observed with the about to be launched James Webb Space Telescope.

  • Project Title: Adaptive Correction of Optical Wave Phase and Amplitude distortions
    Supervisors: Prof. Niek Doelman, Prof. Christoph Keller

    Optical waves propagating through atmospheric turbulence experience random fluctuations on both the amplitude and phase of the electric field. For long, outdoor propagation ranges this may lead to significant beam spread, beam wander and irradiance fluctuations at a receiving telescope.

    Adaptive correction of both wave phase and amplitude distortions can be a powerful approach to reduce the detrimental impact of atmospheric turbulence on the optical beam. This correction is based on real-time measurements of the wave distortion. In its classical form, Adaptive Optics - as currently implemented at large-aperture astronomical telescopes - aims at correcting the wavefront phase-only.

    The main challenge in this research project is to correct for wave phase and amplitude errors. This would lead for instance to reduced fading in Free Space Optical Communication channels. Alternatively in the direct imaging of exo-planets, it would enable to reach higher contrast levels.

    The research study (with openings for 2 PhD students) includes: real-time sensing of wavefield distortions, tomography of atmospheric turbulence profiles and multiple-deformable mirror configurations. Outdoor field tests for the verification of the adaptive correction strategies are foreseen.

    This research is part of the NWO-funded Perspective program Optical Wireless Superhighways. In this program new concepts and technologies for broadband and secure data communication are developed. A total of 15 PhD researchers, distributed over 9 research groups from 5 Dutch universities are joining forces with 16 knowledge institutes and industries to explore these opportunities at all length scales: ranging from ultra-long links between satellites, to short links within indoor rooms.

  • Project Title: Linking chemistry and physics in the planet-forming zones of disks
    Supervisors: E.F. van Dishoeck, M. McClure, M.R. Hogerheijde

    Two PhD positions are available to observationally study planet formation in protoplanetary disks with the flagship James Webb Space Telescope (JWST), tracking the evolution of gas and ices from young to mature disks. The PhD students will be fully integrated in international teams that have privileged access to several hundred hours of JWST guaranteed and open observing time with the MIRI and NIRSPEC spectrometers. One PhD student will focus on the chemistry of simple and more complex molecules in the gas and ice in disks that will ultimately form planets. The second PhD student will combine JWST and ALMA data to uncover the physical structure of the inner planet-zones of disks and connect the observed chemistry to structures such as dust traps, which may be the cradles of proto-planets. The positions are financed by A-ERC grant MOLDISK.

  • Isotopes in exoplanet atmospheres (funding is pending)
    Supervisor: I. Snellen

    Understanding when, where, and how planets form is one of the main objectives of the field of extrasolar planets. An important observational avenue is to identify specific properties of exoplanets, such as the chemical constituencies of their atmospheres, that can be linked to their birth-place in proto-planetary disks. Isotope-ratios could be just that, with fractionation processes that depend on the location in the protoplanetary disk, resulting in changes in the observed abundances of minor isotopes in planet atmospheres. Indeed, we recently detected for the first time 13CO in the atmosphere of a young super-Jupiter (Zhang et al. Nature, 2021). The planet appears enriched in 13C by approximately a factor two with respect to the local interstellar medium.

    This PhD project is ideally timed since CRIRES+, a new state-of-the-art spectrograph, is available now at the European Very Large Telescope - perfectly suited for isotope observations. The candidate will determine the 13CO ratios for hot giant planets on close-in orbits and of young super- Jupiters, addressing important questions: Are the minor-isotope abundance deviations as seen in the first super-Jupiters part of a trend, or not? If so, does this level of enrichment depend on planet properties such as their current orbital location or planetary mass? Do close-in gas giants break with these trends? Also, are there any other isotopologues we can access, such as those involving oxygen or deuterium? There are so many exciting things to do. This is the first step on a new route in exoplanet research.

  • Measuring cosmological model parameters from large-scale structure simulations
    Supervisor: Matthieu Schaller, Henk Hoekstra, Joop Schaye and Koen Kuijken

    Description: Numerical simulations are playing a crucial role in the process of analyzing and understanding the data coming from cosmological probes utilizing weak lensing, strong lensing or galaxy clustering, such as Euclid (launch in 2022). This project focuses on developing, running, and analyzing suites of large-scale structure simulations then generating observables and inferring cosmological parameters from within the simulations. Modern statistical tools and machine learning techniques will later be used to construct realistic counter-parts to upcoming surveys that can be used by the observational teams to extract information out of their data. This project involves using some of the largest existing simulations and mixes theory with numerical work whilst keeping an eye out for observational methods. The PhD student will become part of an international team and will contribute to the Euclid consortium.

    Other projects related to developing, running, or analyzing state-of-the-art cosmological hydrodynamical simulations can also be discussed.

    This project is partially funded by the Lorentz Institute for theoretical physics.

  • Project Title: Characterising the Early Build-up of Massive Star-Forming Galaxies with ALMA + JWST
    Supervisors: Rychard Bouwens, Jacqueline Hodge, Paul van der Werf

    When do the first massive galaxies in the universe build up their mass? Addressing this question has not been easy due to the lack of sensitive spectroscopy and mid-IR photometry for galaxies in the first billion years of the universe. Fortunately, thanks to the launch of the James Webb Space Telescope (JWST) and several ambitious on-going observing programs with the Atacama Large Millimeter Array (ALMA), we are on the brink of a revolution in our understanding of early build-up of massive galaxies. One of the most important of these observing programs is an on-going ALMA Cycle-7 Large Program Leiden University is leading to identify especially massive interstellar medium (ISM) reservoirs in the first 850 Myr of the Universe. Already >25 such ISM reservoirs have been identified from this program and its pilots, more than quadrupling numbers from prior programs. As exciting as these results are, the bulk of the science will come from a suite of follow-up observations from ALMA, JWST, the Jansky Very Large Array, Keck, and the Very Large Telescope. These data will allow for the first significant characterization of the mass build-up in massive galaxies in the early Universe, while probing obscured star formation rates, gas motions, merger rates, and physical conditions. We have an opening for a PhD student to take a leading role in the analysis of this exciting data set.

  • Project Title: Radio loud AGN and the study of the epoch of reionisation
    Supervisor: Huub Rottgering

    Constraining when and how the Universe made a phase transition from neutral to almost completely ionised remains a paramount goal of modern astrophysics. Powerful high-redshift radio galaxies and radio-loud quasars are important laboratories for studying this important phase. In the epoch of reionisation (z > 6), these radio-loud galaxies, the likely progenitors of brightest cluster galaxies, will significantly influence their environment on Mpc scales. They would also be unique beacons against which absorption by the neutral gas that pervaded the very early Universe can be seen in the HI 21cm line. The WEAVE-LOFAR survey will obtain about 1 million optical spectra and has been designed to identify the most suitable candidates to pursue for such deep HI absorption observations. In addition, Euclid will likely detect tens of radio-loud quasars at z > 7. Making use of LOFAR’s high angular and spectral resolution, the unfolding of the reionisation will be studied on the important kpc scales. These are inaccessible to ‘classical’ experiments that are limited to searching for HI fluctuations on tens of Mpc scales. This study will have profound consequences for our understanding of the epoch of reionisation.

    The PhD students will be involved in the selection of extremely distant radio loud AGN, making use of the surveys with LOFAR, WEAVE and Euclid. Initially an important element will be working with the WEAVE data and later on followup of good candidates with LOFAR spectroscopy.