Master- and PhD-Theses

Project 1 (PhD or Master Project in the Dynamics Group):
"Chemodynamical history of the Milky Way"

The Milky Way is the only galaxy whose formation history can be studied star by star. It is currently the focus of extraordinary observational efforts, including both ESA's cornerstone Gaia satellite mission, as well as a multitude of ground-based surveys which are already returning unprecedented data for large numbers of stars. Our group have been at the forefront of clarifying the mass distribution and dynamical structure of the Milky Way's bulge, bar, disk, and dark matter halo from such data.  

We have shown that the Milky Way is a typical barred galaxy and that it has a low dark matter fraction in the bulge.  The logical next step is to understand the chemodynamical structure in the bulge and disk: where do we find the most metal-rich stars in the Galaxy? Where the stars with high alpha-abundances that formed rapidly in the early phases of the Milky Way? We will develop chemodynamical models to determine the orbit distributions of stars with different abundances, and thereby to constrain the processes by which the Milky Way's bulge, bar, and disk were made.

Project 2 (PhD or Master Project in the Dynamics Group):
"Dark matter mass distribution of the Milky Way"

Our current models show that the data prefer a dark matter density profile with a shallow cusp or core in the central few kpc. The goal of this project it to obtain tighter constraints on the slope of the central dark matter cusp and the flattening of the inner dark halo, and thereby constrain the nature of dark matter. This requires including additional survey data in the modelling, as well as some code development in order to constrain the dark halo parameters during the modelling of the data.

Both project 1 and 2 are suitable for candidates who enjoy working with computational models and applying them to modern large data sets. For more information, see the Webpages of the MPE Dynamics Group, Dynamics Group in particular:
* Structure, dynamics, and origin of the Milky Way
* Spiral galaxy bulges                             
* Made-to-measure particle models for galaxies 

Project 3 (PhD or Master Project in the OPINAS Group):
"Dark matter in dwarf elliptical galaxies"

We are performing a systematic 2-dimensional kinematic mapping of the northern nearby dwarf elliptical galaxies with our VIRUS-W instrument at the 2.7m McDonald telescope. Our goal is to measure the stellar kinematics of these objects. This will allow us to constrain the density distribution of the dark matter halos in theseobjects and decide whether a "cusp" (as expected in a Lambda Cold Dark Matter Universe) or a "core" (as suggested by first attempts at these measurements) is present. Moreover, we will investigate the stellar populations by mapping the strength of various absorption line indices: this will allow us to determine the age and metallicity of the galaxies and possibly their gradients. If the galaxies contain ionized gas, we will be able to measure its kinematics too and compare its motions to the stellar ones. The PhD project will involve observation trips at McDonald Observatory, data reduction and analysis and dynamical modeling.

Ralf Bender bender@mpe.mpg.de

Roberto Saglia saglia@mpe.mpg.de

Project 4 (PhD or Master Project in the OPINAS Group):
"The internal kinematics of globular clusters"

Even though they are some of the best studied objects in our nearby universe, many questions around the formation mechanisms of globular clusters remain unanswered. We are performing a systematic 2-dimensional kinematic mapping of the northern largest Milky Way globular clusters with our VIRUS-W instrument at the 2.7m McDonald telescope. Our goal is to constrain the internal kinematics of these objects, quantify the amount of global stellar rotation and possibly set constraints on their dark matter content. Moreover, we will investigate the stellar populations by mapping the strength of various absorption line indices: this will allow us to explore the possible gradients in age and metallicity within the globular clusters. The PhD project will involve observation trips at McDonald Observatory, data reduction and analysis and dynamical modeling.

Ralf Bender bender@mpe.mpg.de

Roberto Saglia saglia@mpe.mpg.de

Project 5 (PhD or Master Project in the OPINAS Group):
"The formation and orbital structure of disks, classical bulges, pseudo bulges and bars"

The Schwarzschild algorithm solves the collisionless Boltzman equation by superposition of orbits, which represent the space of integrals of motion. By solving for the approriate orbital weights, the method allows to determine the masses of the stars, dark matter halos and central black holes together with the distribution of stellar orbits from observed surface brightness profiles and stellar kinematical maps. Schwarzschild models have been calibrated and work well for elliptical galaxies. Disk galaxies have not been studied in detail yet. Their analysis requires extensions to the currently used implementations of Schwarzschild's method: (1) accurate solutions of the Poisson equation for very flattened disks and for bars are needed; (2) an orbit sampling scheme needs to be developed that ensures inclusion of the many more families of orbits supported by these potentials. The project is aimed to expand the existing Schwarzschild code. In a second step, the student can analyse existing observational data for disk galaxies. The main questions are (1) whether the Mbh-sigma scaling relation is different for disk galaxies with pseudo bulges and with classical bulges and (2) what the orbital structure in disk galaxies tells us about the formation history of their various components.

Jens Thomas jthomas@mpe.mpg.de

Roberto Saglia saglia@mpe.mpg.de

Project 6 (PhD or Master Project in the Astrophysics, Cosmology and Artificial Intelligence group ):
"A census of the galaxy population across time"
What do we talk about when we talk about galaxies? Large observational programs like the Dark Energy Survey, the Legacy Survey of Space and Time, Euclid, DESI, and 4MOST, are now and over the next decade gathering data on galaxy samples of unprecedented size. What can we learn about the true underlying distribution of galaxy properties from these photometric and spectroscopic observations? What is the statistical connection of redshifts, masses, biographies, and spectral energy distributions of galaxies? In this project, you will build upon existing artificial intelligence methodology to categorize galaxies to incorporate future survey data and extend and test the modeling of distributions and evolutions of the physical properties of galaxy samples.

Project 7 (PhD or Master Project in the Astrophysics, Cosmology and Artificial Intelligence group ):
"Cosmology with non-Gaussian density fluctuations"
Are the large-scale structures present in the cosmos today, and those present a few billion years ago, consistent with primordial fluctuations that grew under the laws of General Relativity in a Universe filled with mostly vacuum energy and cold dark matter? It turns out this question can be answered much more stringently if we are able to use features of density fluctuations beyond its variance alone, for instance with statistics of the full PDF of matter density. In this project, you will develop techniques to measure and model these non-Gaussian density fluctuations and apply them to the latest data sets from the Dark Energy Survey, the Legacy Survey of Space and Time, Euclid, and spectroscopic surveys.

Project 8 (PhD or Master Project in the Astrophysics, Cosmology and Artificial Intelligence group ):
"Combining Dark Energy Survey with multi-wavelength data"
The whole is sometimes more than the sum of its parts. By statistically combining imaging data, collected by current and soon-to-start astronomical surveys, with information at other wavelengths – from the microwave background to gamma-rays to spectroscopy – we can often gain insights into astrophysical systems and the physics of the cosmos as a whole that no data set on its own would allow. In this project, you will explore connections of the latest imaging data set, the Dark Energy Survey, with such external information, and at the same time help prepare for the next generation of cross-survey discoveries.

Project 9 (PhD or Master Project in the Astrophysics, Cosmology and Artificial Intelligence group ):
"Understanding photometric survey data"
hat's in an image? How do the measurements of faint galaxies we make on their intrinsically noisy, barely resolved images relate to their true features? How can we make statistically powerful and systematically robust statements about the cosmos from analyzing them? In this project, you will go all the way from pixels to cosmology, utilizing a combination of image simulations, state-of-the-art image processing techniques, Bayesian statistics, and artificial intelligence, to underpin the cosmological insights DES, LSST and Euclid are trying to gain from analyzing the largest, deepest, sharpest images of the sky ever taken with a rigorous statistical understanding of the data they collect.

Project 10 (PhD or Master Project in the OPINAS Group/USM Lensing group):
"Measuring weak lensing masses of clusters of galaxies with the Wendelstein 2m telescope"

The student will image SZ, Xray and optically selected clusters with the 30'x30' Wide Field Imager of the 2m telescope on Mt Wendelstein and measure their mass profiles by analyzing the weak lensing effect. The results will be used to constrain the scaling of the mass with the SZ-/Xray/Richness observables. In addition the student is expected to participate in the scientific exploitation of the DES survey regarding cluster and group weak lensing science cases.

Project 11 (PhD or Master Project in the OPINAS Group/USM Lensing group):
"High resolution mapping of the central matter mass distribution in clusters of galaxies with strong lensing"

We will analyse the strong lensing effect of massive CLASH and Frontier Field galaxy clusters having unique HST imaging data in depth and wavelength coverage. The goal is not only to accurately measure the central 2D projected mass distribution but to in particular constrain the depth and extent of dark matter halos of cluster members and to relate their properties to their stellar light and dynamical measures of their central halo depth. By comparing the cluster galaxy members with field galaxies we'll be able to quantify the amount of tidal halo stripping they undergo when orbiting through dense cluster centers. The student will be a member of the CLASH collaboration.

Project 12 (PhD or Master Project in the OPINAS Group):
"Cosmological analysis of anisotropic clustering measurements" 

We will explore the cosmological implications of anisotropic clustering measurements based on galaxy and QSO samples from eBOSS and HETDEX. In particular, we will use measurements of the pattern of baryon acoustic oscillations (BAO) and redshift-space distortions (RSD) to obtain new accurate constraints on the expansion history of the Universe and the growth of density fluctuations. This information offers one of the most powerful routes to constrain the dark energy equation of state parameter, w_DE, and its possible evolution with time, or to detect possible deviations from the predictions of general relativity.

Project 13 (PhD or Master Project in the OPINAS Group):
"Precision cosmology with the Euclid satellite" 

The high-quality data that the Euclid satellite will deliver pose a challenge for our understanding and modeling of LSS observations. As statistical errors become smaller, the control of potential systematic errors becomes essential. The primary uncertainty to compute the likelihood function of Euclid clustering measurements will be to know their associated covariance matrix, C. In most analyses, C is estimated from a set of mock catalogues. However, due to the large volume probed by Euclid this approach might be infeasible. A detailed study of the estimation of C is essential for the success of the mission. We will develop new schemes to minimize the impact of the uncertainties on the covariance matrix as well as theoretical models of C, and use them to compute accurate predictions of the cosmological constraints that can be obtained from Euclid data.

Project 14 (Master Project in the OPINAS Group in collaboration with ESO):
"Rotating open clusters" 

In a recent work Leao et al. have shown that the Hyades cluster rotates with a velocity of about 20 m/sec/Pc. This is the first study demonstrating that open clusters rotate, using both astrometric and spectroscopic radial velocities of Hyades stars. Cluster rotation is possibly a signature of the hierarchical merging formation for open clusters. After becoming familiar with the theory and relevant literature, the master thesis will forllow two phases. During the first one, an available Phython code to compute astrometric radial velocities, clusters' parallaxes and velocity space will be improved to include cluster rotation. In a second phase the GAIA DR2 data of the Hyades will be used together with HARPS radial velocities to recompute the Hyades space motion including rotation and assess the cluster rotation to a much higher degree of confidence.

Roberto Saglia (saglia@mpe.mpg.de),

Luca Pasquini (lpasquin@eso.org)