Broadband cavity enhanced absorption spectroscopy and the secret of the diffuse interstellar bands.

In the Sackler Laboratory for Astrophysics we have a BO project available for a student A, N or A/N to use a running setup ('BB-DIB') to search for carriers of the so called diffuse interstellar bands. The research involves the use of vacuum technology, plasma expansions, and broad band optical spectroscopy. The students job is to help in recording spectra and to compare results with the known DIB positions.

Polarimetric upgrade of a hyperspectral imaging instrument

Commercial remote-sensing instruments often only measure (part of) the spectral information for a given scene, while also the polarization of the collected light contains crucial information. You will work with us and a consortium of industrial partners to develop a polarimetric upgrade to a state-of-the-art hyperspectral imaging system. You will design and test the optomechanical system, perform calibrations, develop data reduction routines, and perform the first hyperspectropolarimetric imaging measurements ever of various scenes, particularly in the context of Crime Scene Investigation.

Lieke van Son

Robbie Brooijmans

The size of z~8 Galaxies

z~8 is only a few hundred million years after the big bang, yet already galaxies have formed and may have the typical maximum luminosity of galaxies for the next few billion years. The project is to measure the sizes of z~8 galaxies (selected based on their colors) and determine their sizes. Only a brief cosmic time later (z~7), we see a distribution of sizes tailing off to large (>kpc) galaxies. The goal is to see if this is true at z~8.

Achromatic liquid crystal polarization modulation

Dr. Frans Snik/ Prof. Christoph Keller

Quantitative spectroscopy with the iSPEX smartphone add-on.

The iSPEX add-on for smartphones has been developed to enable citizen science measurements of atmospheric aerosol properties through polarimetric observations of the blue sky. The unique implementation of the iSPEX optics makes that it is also a spectrograph. It will be your job to calibrate the iSPEX add-on and the smartphone to enable quantitative spectroscopy, much in the same way as the calibration of major spectroscopic instruments at large telescopes. The end goal is to show the applicabilty of spectroscopic iSPEX measurements for a multitude of interesting applications; e.g. color measurements of lamps, paint, water, etc.

Low frequency radio observations of a galaxy cluster.

Radio emission from the intracluster medium was recently discovered in the galaxy cluster Abell 1550. This type of emission very rare and is thought to be caused by shocks and turbulence accelerating intracluster electrons to produce substantial synchrotron emission. In this project we will conduct the first study of the very low frequency radio emission from this cluster. Our aims will be to a) learn the aspects of radio astronomy that are required for challenging low frequency radio observations; b) refine the procedure used to produce high quality radio images; c) interpret the observed cluster radio emission.

Louis Cheung

Hiddo Algera

ALMA observations of HL Tau

Newly formed stars are surrounded by disks of gas and dust. Inside these disks, planetyary systems are thought to form. The Atacama Large Millimeter / submillimeter Array (ALMA) is ideally suited to study the cold gas and dust for signatures of planet formation. In this project the students will calibrate an ALMA data set of one or more protoplanetary disks, reconstruct the image cube, and analyse the continuum emission from the dust and the line emission from the gas. We will look at the structure and kinematics of the disk, and compare this to theoretical expectations.

Isabel van Vledder

Dieuwertje van der Vlugt

Measuring the Milky Way in Brown Dwarfs

Deep near-infrared surveys with the Hubble Space Telescope have found small brown dwarf stars far out into the outer reaches of our Milky Way. The project is to model the disk of the Milky Way using the MCMC fit program to determine the size and thickness of the brown dwarf disk of the Milky Way.

Searching for minor Solar System bodies in KiDS

Study of the KiDS data set to characterize known and discover new asteroids and comets, and improve their orbital parameters.

Accreting matter around black holes

Solve differential equations numerical and add drag force mimicking the presence of an ambient gas between BH and ring of matter around BH. Look at effects on the accretion rate.

Magnetic Nanoparticles

A more realistic view of the feasibility of using magnetic particles for enhancing MRFM and studying Ferritin with MRFM.

The variability of Centaurus A at radio frequencies

The aim of this project is to investigate the known variability of the supermassive black hole nucleus of the nearest radio galaxy Centaurus A at high radio frequencies (20 - 400 GHz), and its effect on the spectral index - an important clue to its nature. Practical work involves reduction and analysis of five sets of short observations with the Australia Telescope (ATCA) on five frequencies (20-100 GHz), using both the AIPS and MIRIAD reduction packages.

Design a dispersion corrector for a MATISSE Fringe Tracker

To remove atmospheric fluctuations from interferometric observations we to correct the chromatic effects in refraction.. The project will study the chromatic effects of different atmospheric components, and propose hardware solutions to remove them.

The sizes and abundance of ultra-faint galaxies in MUSE datacubes

The MUSE instrument on the VLT has just entered operations and will be used in part to observe ultra-faint galaxies out to z~6.5. In particular the 30 hour exposure we have on the Hubble Deep Field South gives us an unprecedented view of the very faint and distant galaxy population and it allows us to see extended emission around galaxies - this is light coming from emission lines that extend further than the stellar light of the galaxies. The main goal of this project is to determine what fraction of galaxies show this extended emission and how this correlates with basic properties of the galaxies. Are these halos of extended emission associated with starburst galaxies, or maybe post-starburst galaxies? To do this it is necessary to find the objects so to test and possibly develop/improve methods to find objects in the MUSE data cubes and thereafter to measure the extent and estimate the basic physical parameters of the galaxies (if not available from other sources).

Search for strong lensing by the BCG in low redshift galaxy clusters.

Strong gravitational lensing provides a direct measurement of the enclosed mass on the scales probed by the lensed images. For low redshift clusters these images probe small physical scales. As a consequence the brightest cluster galaxy (BCG) complicates finding the strong lensing cases, but with high-quality data the light from the BCG can be subtracted. We have collected data for a large sample of nearby clusters and the aim of this BO project is to model the BCG light and find strong lensing cases. These can then be used to select the best candidates for follow-up and detailed modelling.

Discovering galaxy groups and clusters in the KiDS data

In this project the student will look for galaxy groups and clusters using mainly optical images from the Kilo Degree Survey. The primary goals will be to confirm small groups candidates already identified using spectra from the GAMA survey and to find more systems at higher redshifts. Some preliminary cluster catalogues will be available at the time the project will start. If time will allow it, the student will also be to measure the luminosity and the stellar mass content of the groups/clusters and their masses using weak gravitational lensing.

Photometric redshifts

The accelerated expansion of the universe is an open question, which potentially can be caused by dark energy, modified gravity or another form of unknown physics. To understand the expansion observers perform large galaxy surveys, probing the properties of dark energy and dark matter through galaxy clustering, redshift space distortions (RSD) and weak lensing (WL). The KiDS galaxy survey (Pi K. Kuijken, Leiden) is an ongoing lensing surveys with a large contribution from the Leiden cosmology group. To extract cosmological information, one need to determine the galaxy distance. Because the number of galaxies required for a lensing survey, spectroscopy is infeasible. Instead lensing surveys rely on measuring the galaxies in multiple broad band and estimate low resolution distances using algorithmic techniques (photo-z). The student is expected to work on photo-z, focusing on improving the performance and understanding of the distance determination on KiDS data.

Searching for extended Lya haloes in KiDS

In this project, the student will search for Lyman alpha haloes at redshifts z~2-3 using broadband ugr data from the KiDS survey. Lyman alpha (Lya) haloes are among the largest individual structures in the Universe, the largest being ~100 kpc, and are also very luminous (~10^44 erg/s). The nature of these haloes is enigmatic and it is still uncertain what is the powering source, which could be either AGN, high star formation or even large gas inflows. Lya haloes are detected around high redshift radio galaxies, but are also blindly found using narrow-band surveys. A major limitation is the current sample size, which originates from the limited probed volume by narrow-band surveys. Because the Lya haloes are so bright, they are even visible as blue, extended sources in broadband data. By using the optimal combination of survey depth and area provided by KiDS, this project will be a major step forward in terms of probed volume and can lead to discoveries of new Lya haloes.

Suitability of the material KBr as a instrument/cryostat window

Cryostats for astronomical instruments need windows to allow the signal to enter the instrument optics inside the vacuum vessel. However, the transmission of most materials is limited to a relatively small wavelength range. The instrument METIS for the E-ELT requires a window which transmits from 1 - 22 microns. One material with the proper transmission peroperties is KBr, which is, however, very hygroscopic. Manufacturers have claimed that the crystal can be protected against dissolution by coating layers but this has never been demonstrated. This project requires a test setup for a series of measurements of the transmission, reflection, and homogenity of the KBr and possible changes with time (humidity). The measurements have to be done within the NOVA O/IR group in Dwingeloo and should be done by a single student (not a team of two).

The measured efficiency of the X-Shooter instrument on the VLT.

There appears to be a mismatch between the measured efficiency of the X-Shooter instrument on the VLT and the sum of the efficiencies of all of its optical components as given by the manufacturers. This discrepancy could be due to non optimal performance of the coatings at cryogenic temperature, but also due to polarization effects. A setup to measure polarisation (could be a simple polarizer or wire grid) has to be developed to derive the transmission properties of witness samples at low temperatureto measure. The measurements have to be done within the NOVA O/IR group in Dwingeloo and should be done by a single student (not a team of two).