Astronomisches Institut

Lehrstuhl für Astronomie

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• INTERNAL

Diffuse emission of ionized gas in our Milky Way contains a significant amount of information about stellar feedback, galaxy evolution and the structure of the interstellar and intergalactic medium. The low surface brightness of this emission presents a considerable technical challenge and can be problematic for the data reduction. The goal of this project is the observation and data reduction of select sky regions with wide field telescopes. Observations on the roof of the NA building, as well as traveling to Italy and doing further observations there, are part of this project. A data reduction pipeline has already been developed. Interest in nightly observations and technical details are essential.

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During the early stages of the formation of galaxies, gas flows into the galaxy on one hand, while young massive stars and Supernovae push gas out of the galaxies as a galactic wind on the other hand. As a result of this, these proto-galaxies should be surrounded by large hulls of gas. While there is some direct evidence of this, the structures in the early universe are still heavily debated. The goal of this project is to search for these gas halos, and to confirm if the low luminosity of these structures can be compensated by image processing methods such as stacking and filtering. Due to this, a possible candidate should be interested in complex astronomical image processing.

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Observations on galaxies at redshift z~2 imply that these galaxies are not starburst galaxies, but that their high star formation is due to clumpy structures and high turbulence in their gas rich disks. The existence of these turbulent clumps of star formation poses the question if this is a general, until now overlooked mode of star formation. The goal of this project is the analysis of the kinematics and morphology of nearby galaxies with a high star formation rate to look for these clumpy modes of star formation and to then analyze their properties in terms of thermal and non-thermal radio emission to get an idea about the importance of magnetic fields in these galaxies. Candidates should be interested in more complex astronomical image processing and radio astronomy.

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Despite the success of the theory of dark matter in many branches of astrophysics, some points remain that can't be fully explained within the paradigm of cold dark matter. One of those issues is the “too big to fail” problem: There should be more SMC-like galaxies within the Halo of our Milky Way than are observed. These galaxies are too large to end as just a DM Halo without gas and stars (too big to fail), as would be possible for very low mass objects. One way out of this predicament is, that our galaxy is not actually a typical objects for the entire universe. This project will analyze the connection between stellar matter and dark matter by means of H-Alpha kinematics of a sample of far away galaxies in order to check if there actually is a global “too big to fail” problem. The required work for this project includes the analysis of Fabry-Perot data cubes as a technical aspect, for which software has already been developed at our working group, as well as the photometry of galaxies.

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Spectra from Quasars that are spatially close to galaxies on the sky are extremely valuable, as they contain information about the gas in the Halo of foreground galaxies. The combination of spectra and Faraday Rotation of radio-loud Quasars delivers additional information about the magnetic fields in the Halo of these galaxies. This project will analyze the properties of the Halo gas and the magnetic field of star forming galaxies. As this data was collected in surveys, only the analysis of the already reduced data has to be done, for which software is readily available (in the CALIFA consortium).

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As shown by X-Ray emission measurements, hot gas with a temperature of millions of degrees exists as a thin plasma in the Halos of galaxies. Unfortunately, it has so far not been possible to measure the kinematics of this gas, as the spectral resolution of X-Ray satellites has been insufficient. Due to this, many physical processes in this gas are not understood so far. A detection of the (unfortunately very weak) highly ionized iron lines in the visual spectral range would be a breakthrough for this area of research. This project will use the large database of the Sloan Digital Sky Survey to search for an integral signal in the spectra of Quasars. Ability and willingness to program simple scripts would be useful to efficiently analyze the more than one million spectra.

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In addition to the well-known optical and near-infrared images of the Hubble Ultra Deep Field, there are also UV images with similar depth. With this data, and the conventional Lyman Break method, Lyman-Break galaxies with medium redshift can be found as well. The high sensitivity of the Hubble images allow for the detection of very low mass objects as well. The project is the search for low-mass Lyman-Break galaxies at low redshift, the determination of their properties on the basis of HST photometry and structural analysis, and the comparison with galaxies in the early universe.

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Many processes in the interior of stars, including those responsible for pulsations and eruptions, change with decreasing metallicity. The mechanisms for sudden outbursts (transients) are not very well known, and especially at low metallicities completely unclear. This is a big problem, as it means that we don't really understand stellar evolution in the early universe. In this project, data from photometric surveys in Arizona, California, Australia and with the robotic MONET 1.2m telscope (and other telescope) will be used to find and analyse light curves of stellar transients in metal-poor galaxies.

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M31 and M33, the spiral galaxies nearest to our Milky Way, contain a significant number of very massive stars, part of which are in their Luminous Blue Variable (LBV) phase. As large areas of both galaxies are currently being mapped by the Hubble Space Telescope, there is the chance to look at the properties and surroundings of many LBVs. By means of photometry, spectroscopy and comparison with the latest stellar evolution models, the aim of this project is determining the mass of the LBVs and the stars in their surroundings.

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For some time now, our group has regularly observed M33, M31 and other nearby galaxies to study long-term variability of massive stars in order to learn more about their structure and internal instabilities. Joining this new CCD-based photometry data with recently digitized historical photo plates allow for the analysis of variability over more than 100 years time, a so far unexplored time frame. The goal of this project is to create and analyse light curves of very massive stars to search for trends, periodic variations and outbursts.

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Contrary to the „old“ textbook knowledge, it has been shown in recent years, that many globular clusters contain more than one population of stars. The aim of this project is to look for sub-populations in the massive globular clusers M33 and NGC 4833 with means of ground-based wide-field photometry and supporting datasets from the Hubble Space Telescope.

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When and how galaxies grow due to the accretion of smaller galaxies and which structures are created in massive galaxies by this process is an elementary question of galaxy evolution. The photometric surveys that are currently running are producing data that, with the assistance of advanced data reduction techniques, can be used for the search of very weak structues around nearby galaxies. Our group has shown, that this is even possible with data from the Sloan Digital Sky Survey, while the more recent survey open even more possibilities.c

• Project #1: Search for dissolving satellite galaxies in selected samples
• Project #2: Developing an automatic search/classification method for these very weak structures around galaxies (in cooperation with the AIP Potsdam)
• Project #3: Determining age and composition of the brightest objects with spectroscopy (within the CALIFA consortium) and/or own spectra

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The contribution of galaxies with low surface brightness (LSB galaxies) to the local baryon density has not yet been concluded. The large photometric surveys that are currently running allow for the search for LSB galaxies for the first time.

• Project #1: In this project, as a pilot project, the most sensitive part of the Sloak Digital Sky Survey („stripe 82“) should be searched for these LSB galaxies
• Project #2: The search for LSB galaies in HST deep fields.

Important prerequisites for this project include ability and motivation for computer usage and script programming (most suitably in Python).

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