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PhD positions

The Kapteyn Astronomical Institute of the University of Groningen invites applications for at least 5 PhD positions. We seek excellent students with strong backgrounds in the physical sciences who desire obtaining a PhD degree from a top European university. A successful candidate must hold a Masters degree or equivalent by the starting date of the position. Previous research experience and skills will be important criteria for the selection. The PhD positions are not restricted by nationality. Kapteyn PhD students are funded for four years, are paid as civil servants, earn competitive salaries (the current annual gross salary, including allowances, increases from about EUR 28,000 in year 1 to about EUR 36,000 in year 4), and are eligible for both social security and retirement benefits. Applicants should send a CV, transcripts of study records (with grades), and a brief statement of past research and research interests to application@astro.rug.nl. They should also arrange for two reference letters to be sent to this address by the application deadline. Informal enquiries about these positions are welcome and should be sent to the address provided above. Starting dates are negotiable. Complete applications received by 1 September 2013 will receive full consideration. Candidates who submit complete applications before that date may be contacted earlier. Selections of candidates will continue until all positions are filled.

1. Unveiling the Low-Mass End of the Initial Mass Function in Distant Galaxies

Promotors: Scott Trager and Leon Koopmans (Kapteyn Institute)

The number of stars formed at a given mass - the initial mass function (IMF) - in a galaxy is crucial information for our understanding of the evolution of galaxies and the Universe. We propose to directly measure the low-mass end of the IMF in distant galaxies more accurately and precisely than ever before. This will allow us to probe the possible change of IMF slope and/or shape over a wide variety of galaxy masses. The IMF has long been assumed to be universal, simply because it has been nearly impossible to measure outside the Local Group. A variation of IMF shape and/or slope with galaxy mass, hinted at in previous work by our group and others, will directly impact our measurements of the baryon mass budget of the Universe, the dark matter content of galaxies, and our limited understanding of low-mass star formation in different environments. The student will build new, flexible stellar population models to characterize the low-mass end of the stellar mass function using a new stellar spectral library, XSL (the X-Shooter Spectral Library) led by Scott Trager, and compare these with existing and forthcoming galaxy spectra to understand the stellar and dark matter budgets in galaxies.

2. Using LOFAR for detailed studies of AGN and AGN physics

Promotor: Raffaella Morganti (ASTRON, Kapteyn Institute)

The physical conditions, dynamics and evolution of radio-loud active galaxies have been important topics of research since the earliest days of radio interferometry. This subject has recently gained new relevance as a result of advances in our understanding of the evolution of galaxies and large-scale structure, which have revealed the important role of energy input from radio-loud AGN in this process. This project will make use of the new data obtained with LOFAR in order to make a major step forward in this field. LOFAR (LOw Frequency ARray) is a new innovative radio telescope that is conducting observations in the, essentially unexplored, 100-250 MHz wavelength regime. With these data, the selected candidate will study the life cycle of nearby (radio-loud) AGN, the relevant physical parameters (in relation to their stage in life) of such AGN and connect all this to the energy released and feedback by targeting a number of nearby AGN. The select student will join the group supported by the ERC Advanced grant "Exploiting new radio telescopes to understand the role of AGN in galaxy evolution" led by R. Morganti.

3. Characterisation and Visualisation of HI in galaxies

Promotor: Thijs van der Hulst (Kapteyn Institute), co-supervisor: Paolo Serra (ASTRON/ATNF)

The new APERTIF focal plane array system on the WSRT will soon provide observations of the HI on many thousands of galaxies. In preparation to this we have secured WSRT HI observations of the Coma cluster and its environs which will be used in combination with ancillary data to study the structure and evolutionary state of galaxies in dense environments. These data will also serve as a test bed for automated procedures that are being developed for characterising HI properties in WSRT data cubes. The PhD student will join the APERTIF science group led by Thijs van der Hulst, Marc Verheijen and Tom Oosterloo.

4. Measuring the (dark-matter) mass power-spectrum of early-type galaxies on 1-10 kpc scales

Promotor: Leon Koopmans (Kapteyn Institute)

5. Disk structure and planet formation across spectral types

Promotor: Inga Kamp (Kapteyn Institute)

With new instruments pushing for higher sensitivity, interesting differences in the architecture of planetary systems as a function of spectral type is emerging: More massive stars have a higher frequency of more massive planets. In addition, the recent results from the Kepler mission show that the frequency of planetary systems is very high, implying that the success rate of a disk to make planets must be very high as well. We want to understand to which extent the diversity in planetary systems is rooted in the difference of protoplanetary disk structure around M dwarfs and more massive stars. The aim is to use advanced thermo-chemical disk models to study the physical and chemical structure as a function of spectral type. These models in connection with Spitzer, Herschel and submm (e.g. ALMA) observations will provide insight into the mass distribution, temperature structure and chemical composition of disks as a function of the spectral type of the central star. In addition, the models will provide predictions for the chemical diversity of the inner disk that could be addressed through JWST/MIRI GT observations. The PhD student will join the disk group led by Inga Kamp in Groningen and will have the opportunity to participate in the FP7 project "Disk Analysis" (PI: Peter Woitke).

6. Massive star formation -- from Herschel to ALMA

Promotor: Floris van der Tak (SRON and Kapteyn Institute)

The ALMA telescope is a great opportunity to study long-standing questions in high-mass star formation in novel ways. In particular, its high sensitivity and angular resolution allow us to trace the flow of matter from cores via disks onto protostars and into jets and outflows with unprecedented precision. In this project, a PhD student will perform ALMA observations of high-mass star-forming regions. Specific science goals are the accretion mechanisms (monolithic vs competitive), the kinematics of circumstellar disks (solid-body vs Keplerian; as a function of mass and age) and the onset of bipolar outflows (stellar wind vs disk wind). A major new step will be the use of continuum observations to probe low-mass companions to young high-mass stars, which addresses the origin of stellar multiplicity, but also takes existing work on the protostellar core mass function to the stellar scale, thus directly addressing the origin of the IMF. Multi-wavelength observations will be essential to disentangle the contributions of free-free and dust emission to the observed continuum. A special role in this project is played by observations of H2O and H2O-18 lines in ALMA Band 5 (built by NOVA Groningen). Multi-line observations with Herschel-HIFI have shown large H2O abundance variations within star-forming regions, suggesting that H2O is highly localized where gas is accelerated. The proposed ALMA observations are essential to understand the origin of the H2O seen with Herschel, and its destiny. Other lines of common tracers of kinematics and physical conditions such as CO, CS and CH3CN will be observed simultaneously with the multi-band continuum. Sources will be drawn from the Herschel key project on water, and other surveys.

Kapteyn Astronomical Institute related projects

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