Extragalactic Astronomy
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Master thesis topics

Cosmology, large-scale structure, and gravitational lensing

Supervisors: R. Saglia (saglia@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)

  • 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 successfully 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.
  • 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.
  • 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.

Instrumentation and observational projects 

Supervisors: 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)

  • Development of instrument control systems with Beckhoff SPS for large telescope systems
    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.

M31

Supervisors: J. Snigula (snigula@usm.lmu.de), A. Riffeser (arri@usm.lmu.de)

  • 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 depend 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 Andromeda 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.  Supervisors: Jan Snigula snigula@usm.lmu.de, Arno Riffeser arri@usm.lmu.de

Galaxies

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

  • 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.
     
  • 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. The 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.