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University Observatory Munich

Faculty of Physics at the Ludwig-Maximilians-University

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Master’s thesis projects
at the University Observatory

Master’s thesis topics of the Extragalactic Astronomy Group on machine learning, instrumental and observational (Wendelstein) projects, stars and planets, galaxies, gravitational lensing and cosmology can be found →here.

1. Instrumentation and observational projects

C. Gössl (cag@usm.lmu.de), F. Grupp (frank@grupp-astro.de), A. Hess (achim@usm.lmu.de), F. Lang-Bardl (flang@usm.lmu.de), A. Monna (amonna@usm.lmu.de), K. Rozgonyi (Kristof.Rozgonyi@physik.lmu.de), J. Mohr (Joseph.Mohr@physik.lmu.de), A. Riffeser (arri@usm.lmu.de)
Project 1.1: Neuaufbau des 2,4 m Radioteleskops mit präziser Zielausrichung (26.4.2023) (Arno Riffeser, arri@usm.lmu.de)
The radio telescope at the University Observatory is used in the astro-master's practical course to measure the rotation of the Milky Way from the Doppler shift of the 21cm hydrogen line. The new telescope mount should increase the target alignment to 0.1 degrees and recover HI clouds reproducibly. For a large number of measurementsg it shall be be tested if the resolution can be increased by deconvolution of a Gaussian broadening. can be increased. Good Python knowledge is desirable.
Project 1.2: Modelling the “smeared” primary beam for MeerKAT interferometric on-the-fly (OTF) observations (K. Rozgonyi Kristof.Rozgonyi@physik.lmu.de, J. Mohr Joseph.Mohr@physik.lmu.de)
With the upcoming Square Kilometre Array (SKA) and its precursor telescopes, radio astronomy is undergoing a renaissance. New algorithms, data reduction methods and survey modes are actively developed to handle the EB-scale raw data streams produced and to utilise the full potential of these new instruments. As part of a large collaboration, our group at LMU is developing commensal line intensity mapping and interferometric imaging using scanning observations. Such interferometric scanning or on-the-fly (OTF) observations are increasing the survey speed by removing the settle-and-slew overhead while also enabling commensal single-dish intensity mapping, providing a dramatic improvement in data acquisition efficiency. However, the scanning motion of the antennae pointing relative to the delay centre introduces smearing effects that need to be corrected in the imaging process. In particular, the smearing of the primary beam (PB) response introduces flux-density errors in the interferometric images. This project aims to model the smeared PB by measuring the flux-density variation of thousands of sources detected in our pilot MeerKAT OTF observations. The developed PB models and software will be incorporated into our OTF imaging pipeline, which we will use to reduce 100+ hours of MeerKAT OTF data observed in the upcoming year by our collaboration.

2. Stars and planets

T. Preibisch (preibisch@usm.lmu.de), J. Puls (uh101aw@usm.lmu.de), R. Saglia (saglia@mpe.mpg.de), A. Ivlev (ivlev@mpe.mpg.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).

3. Galaxies and AGN

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: Studies of the impact of environment on galaxy and AGN evolution (M. Klein Matthias.Klein@physik.lmu.de, J. Mohr Joseph.Mohr@physik.lmu.de)
Astronomers noticed more than 100 years ago that the galaxy populations within dense galaxy clusters are different from those in the surrounding low-density field, but the underlying reasons remain unclear. Hierarchical structure formation leads dense clusters to form rather late in the Universe and to continue the accretion of surrounding material, including star forming spiral galaxies where through a range of processes they are transformed into ellipticals or S0s. Studies over the past decades have clarified the range of physical processes that are likely contributing to this transformation, and these include ram pressure stripping, mean field tidal stripping and galaxy merging, among others. We are using a new Sunyaev-Zel’dovich effect selected sample of galaxy clusters from SPT that extends to redshift z ~ 2 together with data from the DES, Spitzer, and Herschel to study these galaxy population transitions as a function of cosmic time. The goal of this project is to use the multi-band optical and IR photometry to identify cluster galaxies and study the transition in color and star formation rates as a function of radius from the cluster center as well as a function of cosmic time and cluster mass. Our dataset is uniquely suited for this study, because we have a well understood sample of clusters extending over a broad redshift range and a uniform photometric imaging dataset in the optical and IR over large areas of the sky.
Project 3.3: Exploring the dark side of galaxy formation and evolution using radio continuum data (J. Mohr Joseph.Mohr@physik.lmu.de)
Among the many facets under investigation of the galaxy formation and evolution puzzle, two old and still unanswered questions remain at the core of our incomplete picture:
  1. How do galaxies grow their stellar mass over cosmic time?

    Answering this question has proven difficult mainly because of the uncertainties in estimating the on-going star formation for large, representative galaxy samples. The easily accessible ultra-violet (UV) restframe emission, in principle a direct probe of the young short-lived massive stellar populations, is in fact measuring only the small fraction of that emission that has not been absorbed by the interstellar dust. It thus needs to be corrected by factors that, depending on the intrinsic galaxy properties, can vary by orders of magnitude.

  2. Why does star formation cease at a certain point during the galaxy life?

    In the last decade many studies have agreed in assigning a relevant role to nuclear activity (AGNs, due to massive black hole growth) in affecting the galaxy star formation histories (SFHs). In particular, once a major burst of star formation has eventually exhausted the gas inside the galaxy immediately available for star formation, the so-called “radio-mode feedback” is often invoked as preventing the gas in the outer galaxy halo from cooling and starting star formation again.

    Deep radio surveys, conducted in association with multi-wavelength observations, allow us to probe at the same time dust-unbiased star formation and nuclear activity, and hence have become a fundamental tool in the last decade for studying galaxy evolution. This master project will focus on already available JVLA radio continuum data in the deepest extra galactic fields in order to obtain a dust-unbiased view of star formation over cosmic time and a first-order estimate of radio-AGN feedback to be compared to theoretical model expectations at different redshifts and halo masses.

Project 3.4: Witnessing the last burst of star formation in a galaxy (K. George Koshy.George@physik.lmu.de)
The observed bimodal distribution of local Universe galaxies in star formation properties (from optical color-magnitude and stellar mass-star formation rate diagrams) is due to the process of star formation quenching, making once star forming spiral galaxies to non/little star forming elliptical/S0 galaxies. There are many possible processes responsible for this observed star formation quenching, among which ram-pressure stripping is the dominant mechanism in dense galaxy cluster environment. The hot (107 . . . 108 K) and dense (ne ~ 10−4 . . . 10−2 cm−3) intracluster medium can strip cold gas from the spiral galaxy disk, which eventually truncates star formation as the galaxy moves though the cluster environment. We have acquired ultraviolet data for a sample of galaxies undergoing ram-pressure stripping (with tentacles of star formation along the stripped tails with the galaxy disk resembling a jellyfish) where the ongoing truncation of star formation can be directly studied comparing with emission line diagnostic maps made from MUSE IFU data. This project involves studying the star formation progression in a galaxy undergoing ram-pressure stripping with indications of truncation along the galaxy disk. There are opportunities to collaborate with a larger team involved in multiwavelength analysis of jellyfish galaxies.

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

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., the 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: Mass calibration and cosmological study of X-ray and Sunyaev-Zel’dovich effect selected galaxy clusters using gravitational lensing (S. Bocquet Sebastian.Bocquet@physik.lmu.de, M. Klein Matthias.Klein@physik.lmu.de, J. Mohr Joseph.Mohr@physik.lmu.de)

One of the leading methods for studying the cosmic acceleration, measuring neutrino masses and directly measuring the growth rate of cosmic structures is through studies of the redshift and mass distribution of uniformly selected samples of galaxy clusters. A key element of these studies is constraining the masses of the galaxy clusters using information from weak gravitational lensing.

The goal of this project is to use the available weak gravitational lensing mass information from the Dark Energy Survey within samples of galaxy clusters selected from the South Pole Telescope Sunyaev-Zel’dovich effect survey or the RASS (and soon from eROSITA!) X-ray survey to study the cosmic acceleration, neutrino masses, and the growth rate of cosmic structures.

  • Understand the impact of surrounding large-scale structure and miscentering on the weak-lensing mass estimates of galaxy clusters. Application to real cluster sample with DES shear catalogs to constrain masses.
  • Understand the impact of contaminating impacts due to X-ray and radio AGN on the selection and cosmological analysis of galaxy cluster samples.
  • Measure correlations among cluster observables in the X-ray, SZE, and optical and study their impact on cosmological analyses.
Projects in the Astrophysics, Cosmology, and Artificial Intelligence Group (Daniel Grün et al.)
Projects in the Physical Cosmology Group (Jochen Weller et al.)

5. Computational and theoretical astrophysics

A. Burkert (burkert@usm.lmu.de), B. Ercolano (ercolano@usm.lmu.de), T. Birnstiel (til.birnstiel@lmu.de), K. Dolag (dolag@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 disks, 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 disks.

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 disks, 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.

6. High-energy astrophysics

Gayoung Chon (gchon@usm.lmu.de)
Project 6.1: Probing extreme environments with very-high-energy observations (Gayoung Chon gchon@usm.lmu.de, David Green damgreen@mpp.mpg.de)
Gamma-ray observations allow us to study the most extreme cosmic sources in the Universe. These violent environments, which are not reproducible at Earth-based laboratories, provide opportunities to study processes at the frontier of known physics. Our group tackles a wide range of questions related to astrophysics and fundamental physics, such as probing cosmic-ray acceleration processes and the search for the nature of Dark Matter.

Over 15 years of operations, Fermi-LAT is the preeminent instrument for studying the high-energy universe in the MeV to GeV energy range. It provides a rich data set ripe for discovery of new sources and science. MAGIC is one of the current generation Imaging Atmospheric Telescopes with high sensitivity for extended sources in the Galactic Plane. The prototype of Large Size Telescope (LST) for the Cerenkov Telescope Array (CTA) has completed construction and has started partial scientific operations. Over the next four years, three additional LSTs will be built, providing unprecedented sensitivity to the gamma-ray universe. The combination of three datasets allows for highest sensitivity in studying the extreme environments within our Galaxy.

We seek Master’s students to perform their thesis work with the primary focus on the analysis of Fermi-LAT, MAGIC, and/or LST-1 data on Galactic sources such as Supernova Remnants and Galactic PeVatrons. Although not required, experience in Python and C++ is highly desired.

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