Examples of PhD projects available
An overview
There are currently several PhD positions open for application with a deadline of December 15, 2012. 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 gives 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 and the general overview of the research at the Observatory provide more background information.
- Galaxy formation: The group led by Joop Schaye has an opening for a PhD student to work on observations and/or simulations of the formation of galaxies and the evolution of the intergalactic medium. The observational project concerns the analysis of guaranteed time observations with the MUSE integral field spectrograph on the VLT to study the gaseous environments of galaxies. Possible theoretical projects include the analysis of the EAGLE simulation, a ground-breaking cosmological, hydrodynamical simulation using more than 10 billion particles. The PhD student will become part of an international team.
- Constraints on Reionization and Distant Clusters, Observational:
Extragalactic Observational Research with the Dutch-European radio telescope LOFAR: The Dutch-European radio telescope LOFAR will open up the last unexplored window of the electromagnetic spectrum for astrophysical studies and make important contributions to our knowledge of the formation of structure in the universe. PhD positions with Huub Rottgering are available on the following three topics:- Forming massive galaxies at the epoch of reionisation. LOFAR will detect radio galaxies at unprecedented distances close to or even at the epoch when the universe makes a phase transition from neutral to ionised. LOFAR radio spectroscopy targeting associated neutral hydrogen 21 cm absorption would, for the first time, determine physical characteristics of the gas at this crucial epoch. Studies of these galaxies will constrain models of how massive galaxies and associated massive black holes are formed.
- Diffuse synchrotron emission associated with the first bound clusters of galaxies. Currently, diffuse radio synchrotron sources are known in about 50 nearby massive galaxy clusters. LOFAR has the potential to detect many thousands of these systems, up to an epoch when the first bound clusters appear. Studies of the associated shock waves produced by cluster mergers and magnetic field properties of the cluster gas will constrain models of the formation of galaxy clusters.
- Starbursting galaxies. LOFAR will detect radio emission from millions of star-forming galaxies at an epoch at which the bulk of galaxy formation is believed to occur. In combination with infrared surveys, this will enable studies of how the physics of star formation differs between high and low density regions in the universe.
- Physics and chemistry of the interstellar medium: The
interstellar medium plays a key role in the evolution of the Milky Way
and other galaxies. It is the repository of the ashes of earlier
generations of stars and the birthplace of future
generations. Molecules and small dust grains play an active role in
this evolution. Moreover, their emission can be used to probe the
characteristics of the region and the processes therein. Key questions
in this field are the role of molecules and dust in the processes that
drive the evolution of galaxies, the organic inventory of space
particularly regions of star and planet formation, and the growth of
dust in protoplanetary disks.
Leiden Observatory has an active program in the physics and chemistry of the interstellar medium, combining observational studies - mainly in the infrared and sub-millimeter - with space based (Spitzer Space Telescope & Herschel Space Observatory) with ground based (Very Large Telescope) observations and laboratory studies. The focus is on the lifecycle of interstellar gas and dust in the Milky Way during its sojourn from its stellar injection sites such as Asymptotic Giant Branch Stars and supernovae, through the turbulent cloud and inter cloud phases of the interstellar medium, to its final incorporation into newly formed stars and planetary systems. One focus of these studies is on the composition, origin, and evolution of large Polycyclic Aromatic Hydrocarbon molecules and their role in the interstellar medium. Another focus is on the related topic of the characteristics of stardust grains and their evolution in the interstellar medium. There are direct links to other groups in Leiden Observatory, to other groups in Holland through the Dutch Astrochemistry Network, and to several groups at the international level.
The ISM group currently has some ten graduate and master students and five postdocs. Within this group there are opportunities for graduate student(s) in the general area described above, under the general direction of Xander Tielens. Requirements are a broad interest in and good understanding of the physics and chemistry of the interstellar medium, background and experience in observational, experimental, or theoretical techniques relevant to this research area and a willingness to interact across scientific disciplines. While students work on their own PhD projects, good interaction with others in the group will be key to success.
- Solid-state Laboratory Astrophysics -- Forming complex molecules
in space: This PhD research project concerns the simulation of
the chemical processes that take place on the surfaces of dust grains
in star- and planet-forming regions in interstellar space. This
research project will make use of fully operational state-of-the-art
UHV surface science experiments in which interstellar ice analogues at
temperatures of 10-90 K are bombarded with atoms and/or UV radiation
(see www.laboratory-astrophysics.eu for more information).
The focus within this PhD project will be on nitrogen-containing
molecules. The laboratory experiments are directly linked to
astronomical observations on complex organic molecules from the
Atacama Large Millimeter Array (ALMA). The research will be directed by
Prof. E.F. van Dishoeck
and Prof. H. Linnartz.
We are looking for an enthusiastic person with a background in
instrumentation, experimental physics, physical chemistry, surface
science or laboratory based astrophysics.
- Molecules in the comet-forming zones of protoplanetary disks
The Atacama Large Millimeter Array (ALMA) opens up the
possibility to study in detail the physical and chemical structure of
disks around young stars in which planets may be forming. This PhD
project will use ALMA data to determine the chemical inventory of
molecules in the 10-30 AU region of the disk in which planets and icy
bodies such as comets are expected to form. A related aim of the
project is to delineate the processes and physical conditions that led
to the observed molecules. Ultimately, comparison with cometary comae
provides insight into the conditions in the disk out of which our own
solar system formed. The research will be supervised by Prof. E.F. van Dishoeck and Dr. M.R. Hogerheijde.
- Theoretical and/or Observational Studies of Hypervelocity Stars: One Phd project
with Dr Elena Maria
Rossi on Hypervelocity star theoryi, catalogue searches and data modelling.
Hypervelocity stars are stars which travel at an enormous speed
through our halo, and they are thought to originate from the Galactic
Centre. The relativistic potential of the central black hole, SgrA*,
is indeed the only possibility to impart such a phenomenal kick to a
star. The project aims to develop a model for formation of
Hypervelocity stars and predict observables (such as velocity
distributions) that will be compared with upcoming GAIA data. GAIA
sample of hypervelocity stars will be of extraordinary quality and
quantity. Comparing data with models will allow us to put
unprecedented constraints on the Milky Way Galactic Potential and the
star population in the Galactic Bulge. This information is vital to
understand galaxy formation in general.
- Structure formation in a warm dark matter universe:
Although hot dark matter (e.g. the standard model neutrinos) is
disfavored by cosmological observations, warm dark matter
(e.g. sterile neutrinos) is compatible with all observations and may
in fact be required to explain the structure and abundance of dwarf
galaxies. While the difference between warm and cold dark matter is
small from a cosmological point of view, it is of crucial importance
for particle physics, as it could imply a huge difference in the
properties of the corresponding particle and could have impact on some
very fundamental questions. Sterile neutrinos are strongly motivated
from a particle physics point of view and astronomical constraints on
their properties allow a systematic experimental program including
accelerator and other direct searches.
As part of the framework of the de Sitter program in cosmology, Alexey Boyarsky and Joop Schaye are working on numerical modeling of structure formation in a universe with decaying dark matter particles that have significant primordial velocities with a non-thermal spectrum, as is expected for sterile neutrinos. The overall aim is to produce reliable predictions that can be checked with the data of upcoming weak lensing surveys, quasar absorption line data, and other tracers of structure formation on intermediate scales.
- Observational Studies of Distant Galaxies: Marijn Franx
will have a PhD position to study the evolution of galaxies using the
Hubble Space Telescope. We have obtained 240 orbits of observing time
to study galaxies with the Wide Field Camera 3 in grism mode. We will
study galaxies spectroscopically, and derive the evolution of the red
sequence of galaxies from z=2 to z=0, and the buildup of star forming
galaxies. The goal is to also compare the results to theorical
simulations.
- Observations of Faint Galaxies in the Early Universe: The faintest,
lowest luminosity galaxies in the early universe likely play the dominant
role in both the production of metals and the reionization of the universe
and likely contain the bulk of the stellar mass. However, their properties
remain somewhat poorly constrained. We should be able to greatly improve
our characterization of faint galaxies in the early universe using
ultra-deep spectroscopic observations -- which we will obtain using a
powerful new spectrograph MUSE to be commissioned on the Very
Large Telescope in Chile -- in combination with deep Hubble+Spitzer
observations over the Hubble Ultra Deep Field and over cluster fields
where one can benefit from the lensing magnification of the faint high-redshift
universe. The new MUSE observations should allow for order of magnitude
gains over existing studies and benefit from the substantial time allocation
appropriated to the MUSE GTO team. There will be an opening for a new
PhD student in the group of Rychard
Bouwens to take advantage of these observations to obtain a much improved
understanding of this important population of faint galaxies in the early universe.
- Studying chemical enrichment through clusters of galaxies:
The chemical elements are synthesized in different types of progenitors,
predominantly different classes of supernovae and AGB stars. Even within a class
of sources differences in structure or model calculations may lead to
significant differences in the resulting elemental abundances. Also other
factors such as initial mass function and spatial redistribution processes play
a role. Because clusters of galaxies retain most of the produced elements in the
hot intracluster medium, they are the best objects to study nucleosynthesis on a
cosmic scale. In this research we will study the X-ray spectra of a large sample
of clusters observed with the XMM-Newton telescope. Both data from the RGS and
EPIC instruments will be used. Depending on the source properties, abundances of
the ten most abundant elements will be measured and compared to different
combinations of models for stellar nucleosynthesis. Starting from 2015 also data
from Astro-H with its high-resolution spectrometer SXS will be used to obtain
abundances for rare elements with large diagnostic power such as Na, Co, Cr and
Mn. This work with Jelle Kaastra is done together with SRON in Utrecht.
- Galaxy halo masses, shapes, and sizes from KiDS+VIKING+GAMA:
Koen Kuijken's's research centers on the distribution of dark matter in galaxies and the universe, using gravitational lensing and dynamics.
Cosmological observations indicate that over 80% of the matter in the universe is 'dark', of a form that is not part of standard particle physics. Nevertheless the dark matter is crucial for the formation of galaxies, and for understanding their properties today.
The purpose of this PhD project is to establish the properties of dark haloes around galaxies as function of their baryon properties (morhology, type, stellar mass, shape) and their environment, out to several hundred kpc. The measurements will be done using the technique of weak gravitational lensing. Such fundamental measurements are direct tests of the galaxy formation paradigm, and will provide essential qualitative information with which to test galaxy formation models and simulations. The principal datasets that will be used are the GAMA spectroscopic survey, which is now nearly complete over three 48-square degree patches, the near-IR imaging survey VIKING on VISTA, and the optical imaging survey KiDS, and they will allow a unique catalogue of morphological parameters, redshifts, luminosities, stellar masses, spectroscopic environment densities, and weak lensing masses to be constructed.
- Project on Interstellar dust studied through X-rays, with supervisor Dr
Elisa Costantini (SRON-Utrecht, www.sron.nl/~elisa ) and Xander Tielens (Leiden Univ.):
In recent years it has become clear that the X-rays are a powerful tool to study the interstellar medium.
Studying the absorption and the scattering of X-ray radiation by dust particles allows
us to access to the physical and chemical properties of dust. X-rays provide complementary information, with respect to
the longer wavelengths studies, which can help in solving fundamental still open issues in the field, such as iron and
oxygen inclusion in dust grains. The X-ray background sources used to reveal the intervening dust are bright X-ray binaries,
mostly located in the Galactic plane. X-rays are sensitive to a wide range of interstellar matter column densities, therefore
dust in the X-rays can be studied in every direction in the Milky Way,
allowing for a complete mapping of dust environments, characterized by different extinction
and possibly dust formation history.
This project is focussed on the study of X-ray high-resolution spectra of brigh sources which are modified by the effect of dust absorption. Mostly data from the X-ray observatory Chandra and XMM-Newton will be used. Data of the same dust environments from the Spitzer infrared space telescope, will be also be analysed. The student will deal with the analysis and interpretation of both X-ray and infra-red data of a sample of interesting lines of sight. He/she will be involved also with the implementation of newly acquired laboratory measurements of dust into the astronomical model. The aim is to define an X-ray view of the chemical composition of dust in our Galaxy and implement it in existing dust models.