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Faculty of Physics at the Ludwig-Maximilians-University

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Master’s thesis projects
at the University Observatory

1. Instrumentation and observational projects

U. Hopp (hopp@usm.lmu.de), C. Gössl (cag@usm.lmu.de), A. Riffeser (arri@usm.lmu.de), F. Grupp (fug@usm.lmu.de), A. Hess (achim@usm.lmu.de), F. Lang-Bardl (flang@usm.lmu.de), A. Monna (amonna@usm.lmu.de)

Project 1.1: Development of instrument control systems with Beckhoff SPS for large telescope systems (M. Häuser mhaeuser@usm.lmu.de, A. Hess achim@usm.lmu.de)

Diese Masterarbeit setzt Interesse an elektronischen Steuerungen und Sensorik voraus. Vorkenntnisse in Elektronik (u. U. entsprechende Master- oder Bachelorvorlesungen) und SPS-Technologien im besonderen sind von Vorteil. Im Rahmen des Baus des MICADO-Instruments für das 39-m-EELT-Teleskop in Chile sind diverse Mechanismen und elektronische Steuerungskomponenten zu entwickeln, bauen und zu testen. Mechanismen und Sensorik müssen in einem Test-Kroystat (~80 K) an der USM getestet und von Beckhoff-SPS gesteuert werden. Die Arbeit umfasst die Konzipierung, Durchführung und Dokumentation von Tests diverser Hardware bei Raumtemperatur und bei ~80 K in unserem Kryostaten. Ergebnisse müssen aufbereitet werden um im Rahmen des MICADO-Projekts von anderen internationalen Konsortiumspartnern verwendet zu werden. Als Steuerungselektronik werden Beckhoff-SPS eingesetzt. Zusätzlich kann je nach genauem Thema ein rein astrophysikalisches Beobachtungs- und/oder Datenauswertungsprojekt in Zusammenarbeit mit dem Wendelstein-Observatorium absolviert werden.

2. Stars and planets

T. Preibisch (preibisch@usm.lmu.de), J. Puls (uh101aw@usm.lmu.de), A. W. A. Pauldrach (uh10107@usm.lmu.de), T. Hoffmann (hoffmann@usm.lmu.de)

Project 2.1: Multi-wavelength observations of star formation regions (T. Preibisch preibisch@usm.lmu.de)

Students can carry out investigations as part of an ongoing project, e.g., correlation of object lists in different wavelengths ranges (from X-ray to the sub-mm regime).

Project 2.2: Synthetic infrared spectra of massive stars (J. Puls uh101aw@usm.lmu.de)

The model atmosphere code developed by our working group, “Fastwind”, is one of the world’s most used codes to synthesize the optical and IR spectra of massive stars of spectral types O and B. In recent years, a comprehensive revision of this code has been performed, which among other features also allows to model the ultraviolet range. This new program version, however, has not yet been adapted to calculate the IR range of the spectrum, where just this range is of highest relevance for new and future large telescopes (JWST, ELT). The aim of the suggested Master’s thesis project is, in a first step, to adapt the new “Fastwind” version so that the IR range can be satisfactorily synthesized, including careful tests. A comparison with results from the former program version is mandatory. In a second step, our atomic database shall be extended so that high precision IR spectroscopy of elements different from H and He becomes possible. The work suggested here requires a strong interest in working with and implementing of numerical algorithms.

Project 2.3: Model atmospheres and synthetic spectra for Wolf-Rayet stars (J. Puls uh101aw@usm.lmu.de)

The model atmosphere code “Fastwind”, developed by our group, is one of the world’s most widely used codes for calculating the optical/IR spectra from massive stars of spectral type O and B. The project presented here aims at stepwise extending the code so that the spectra of so-called Wolf-Rayet stars can be synthesized. The main difference of the atmospheres of these Wolf-Rayet (WR) stars in comparison to those of “normal” stars is a significantly higher wind density (practically all optical lines are formed mainly in the wind) and a different chemical composition: in most cases, the helium and nitrogen abundances (products of the CNO cycle) are greatly increased, whilst the hydrogen abundance is dramatically reduced (until zero). The work presented here requires a strong interest in the implementation of numerical methods.

Project 2.4: Period-luminosity relation of long-period variable stars in M31 (J. Snigula snigula@usm.lmu.de, A. Riffeser arri@usm.lmu.de)

Pulsating variable stars are known to follow a relation between the duration of the pulsation, the period, and their mean luminosity. These so-called period-luminosity relations are one of the central tools to get reliable distances of nearby galaxies. Based on theoretical and observational arguments, there has been a long discussion if these relations depends on galactic properties like, e.g., the metallicity of the parent generation of the pulsating stars. Long-period variable stars have, compared with short-period variable stars like Cepheids or RR-Lyrae, been studied only sparsely. Only in the last years a period-luminosity relation was published based on the OGLE data, for the Magellanic clouds (which are very close by and metal poor). The goal of this Master’s thesis project would be to check the long-period variable stars found in the Pandromeda survey of the metal-rich M31 galaxy, and to build using photometry obtained from publicly available data the period-luminosity relation for these stars. Finally these results should be compared with the published results for the Magellanic clouds.

3. Galaxies

H. Lesch (lesch@usm.lmu.de), R. Saglia (saglia@usm.lmu.de), J. Thomas (jthomas@mpe.mpg.de), OPINAS Group (http://www.mpe.mpg.de/1761897/Master-_und_Doktorarbeiten)

Project 3.1: Dynamical modeling of stellar disks (R. Saglia saglia@usm.lmu.de, J. Thomas jthomas@mpe.mpg.de)

Three-dimensional galaxies are often modeled using the Schwarzschild approach. One computes stellar orbits in a given gravitational potential and superposes them to reproduce the available dataset. The modeling of two-dimensional objects like galaxies with stellar disks poses some yet unsolved questions. How well can one compute the gravitational potential using spherical harmonics? What is the optimal amount of regularization? How well can one describe real galaxies? During the thesis project answers to these questions will be tested and implemented.

Project 3.2: Dark Matter in dwarf elliptical galaxies (R. Saglia saglia@usm.lmu.de)

Giant elliptical galaxies are embedded in massive dark matter halos. Not much is known, however, about the dark matter halos of dwarf ellipticals, because their low velocity kinematics are difficult to measure. Thanks to our new high-resolution two-dimensional spectrograph VIRUS-W we were able to obtain high quality spectra for a number of dwarf ellipticals in the Virgo cluster. Goal of the Master’s thesis project is the reduction and analysis of these data, their dynamical modeling and the determination of the dark matter density in these objects.

4. Cosmology, large-scale structure, and gravitational lensing

J. Weller (weller@usm.lmu.de), R. Saglia (saglia@usm.lmu.de), J. Mohr (jmohr@usm.lmu.de), S. Seitz (stella@usm.lmu.de), A. Riffeser (arri@usm.lmu.de), OPINAS Group (http://www.mpe.mpg.de/1761897/Master-_und_Doktorarbeiten)

Project 4.1: Comparing simulated and observed red-sequence clusters (S. Seitz stella@usm.lmu.de, K. Dolag dolag@usm.lmu.de)

The majority of galaxies in clusters are “red” galaxies (S0 or elliptical galaxies), i.e., galaxies with no ongoing star formation. This makes them form a “red sequence” in color-magnitude space. In multi-band photometric surveys (e.g., Dark Energy Survey DES) one sucessfully identifies clusters of galaxies by their red-sequence galaxy population, and estimates the (photometric) redshifts for clusters using the colors of their red galaxies. The number of red galaxies of each cluster is used to define its “richness” (a quantity strongly related to the total mass of the cluster). For many purposes in cosmology one would like to relate the observationally identified “red sequence clusters” to clusters numerically simulated within the framework of structure formation. For example, one would like to know how cluster mass and cluster richness scales, what the scatter is, and how much dark matter is associated with individual red galaxies (as a function of the luminosity and position within the cluster). The goal of this project is to apply the observers’ cluster-finding technique to simulated clusters and to derive a catalog with cluster richness, their red-sequence member galaxies, and dark matter halo masses of individual member galaxies. These findings can then be compared to results from observations or can be used to predict the outcome of ongoing and future observations.

Project 4.2: Cluster mass reconstruction with the weak gravitational lensing effect (S. Seitz stella@usm.lmu.de, T. Varga vargatn@usm.lmu.de)

By their (dark and luminous) matter components clusters of galaxies distort light bundles traversing them. This so called weak gravitational lensing effect alters the shapes of background galaxies and aligns their major axes preferentially tangentially to the foreground clusters centers. One can invert the relevant relations to derive mass maps for galaxy clusters, to measure their projected profiles and “total” masses. We offer projects on this topic, where either data from our own Wendelstein 2-m telescope are taken or where public data, or data from the Dark Energy Survey DES, are used.

Project 4.3: Analyzing the strong lensing effect in HST-clusters (S. Seitz stella@usm.lmu.de, A. Monna amonna@usm.lmu.de)

Towards centers of clusters of galaxies the projected matter density can become large enough that objects in the background of such clusters of galaxies are mapped into multiple images and giant gravitational arcs. The analysis of this so-called strong gravitational lens effect yields the most precise astrophysical mass measurements at cosmological distances. In addition one can constrain the amount of dark matter (i.e., the size of dark matter halos) associated with galaxy cluster members. In this way one can measure the cluster subhalo mass function and the amount of dark matter stripped when galaxies fall into clusters and pass their high density cores.

Project 4.4: Density Split Statistics (S. Seitz stella@usm.lmu.de, O. Friedrich oliverf@usm.lmu.de)

The evolution of the cosmic density field encodes powerful information on the laws of gravity as well as the initial conditions of the universe. So far, most experiments that quantify the large-scale structure of the universe only measured 2-point statistics of the density field. This means that they measured the amplitude of density fluctuations as a function of scale. This provides only a limited view of the large-scale structure and hence limited cosmological information. Within the Dark Energy Survey (DES) Collaboration we established a new method of analyzing the large-scale structure of the universe: Density Split Statistics (DSS). This method closes a major gap in current studies of the large-scale structure: it can disentangle gravitational non-linearities from non-trivial features in the relation between galaxies and matter! The reason for this is that DSS is sensitive to the skewness of density fluctuations (as opposed to only the amplitude). We are looking for a Master student with excellent mathematical skills to complement our work on density split statistics. This student will first familiarize herself/himself with our publications Friedrich & Gruen et al. (arXiv:1710.05162) and Gruen & Friedrich et al. (arXiv:1710.05045). These describe density splits of the gravitational lensing power spectrum. The student will then transfer our formalism to also incorporate density splits of the galaxy power spectrum.

5. Computational and theoretical astrophysics

A. Burkert (burkert@usm.lmu.de), B. Ercolano (ercolano@usm.lmu.de), K. Dolag (dolag@usm.lmu.de), B. Moster (moster@usm.lmu.de)

Research in the Computational Astrophysics Group (CAST) ranges from the theoretical investigation of star and planet formation to studies of processes on cosmological scales. A variety of different, well-known numerical codes (such as Ramses, Gadget, Sauron, Gandalf, Mocassin, and others) are used. Primary investigations regard the formation, the structure, and the evolution of protoplanetary discs, the formation of planetary building blocks and planets, the relation between turbulence and phase transitions in the multiphase interstellar medium (ISM), energetic feedback processes, molecular cloud and star formation in galaxies, as well as cosmological structure and galaxy formation and the interplay between feedback processes, AGN, and galaxy evolution and their imprint on the intergalactic medium (IGM) or the intercluster medium (ICM). Thus, our group studies astrophysical processes on length scales covering more than 14 orders of magnitude, from gigaparsec scales of cosmological structures all the way down to sub-AU scales of dust grains within protoplanetary discs.

astrophysical processes on length scales covering more than 14 orders of magnitude

It is now clear that small-scale processes like the condensation of molecular clouds into stars, magnetic fields and the details of heat transport as well as large-scale processes like gas infall from the cosmic web into galaxies and environment are intimately coupled and have to be investigated in a concerted effort. The various past and ongoing projects within the CAST group cover a link between the various scales and contribute to our understanding of crucial aspects of the formation and evolution of stars and protoplanetary discs, central black holes and AGNs, star-forming regions and the ISM, galaxies and their IGM, galaxy clusters and the ICM as well the large-scale structures in the universe. They also also drive the continuous effort to develop and to apply new numerical methods and the next generation of multi-scale codes within the framework of numerical astrophysics.

Past and ongoing Bachelor’s and Master’s thesis projects were always offered with respect to the individual strengths and interests of the students and cover various areas in the field of computational and theoretical astrophysics:

  • Formation of large-scale cosmological structures (dark-matter halos, galaxies, clusters of galaxies, role of black holes, magnetic fields and non-thermal particles)
  • Evolution and structure of the turbulent interstellar medium (ISM physics, self-regulating star formation, formation of molecular clouds, magnetic fields)
  • Physics of galactic centers (active galactic nuclei, origin and nature of the gas cloud G2 near the Galactic center)
  • Formation of planets, stars, and stellar clusters (stars and their influence on the surrounding protoplanetary disc, interstellar matter, radiative transfer, dynamics of particles and planets in protoplanetary disks)
  • Application and development of numerical tools on parallel CPUs and GPUs and visualization (particle-based SPH/N-body, grid-based, moving-mesh or meshless methods)

More detailed information on ongoing and finished projects as well as more detailed information on ongoing research can be found on the web pages of the Computational Astrophysics Group.

Last updated 2018 April 13 18:39 by Webmaster (webmaster@usm.uni-muenchen.de)