Astronomy and Astrophysics – abstracts

Project Title	Author
A next-generation galaxy cluster survey with the CCAT-prime telescope Data from wide-area galaxy cluster surveys are one of the main drivers behind the current "golden era" of cosmology. Among the handful of methods that can reliably detect galaxy clusters and infer their masses, the Sunyaev-Zel'dovich, or SZ, effect is a unique one: its signal is practically undiminished by redshift and at frequencies below 220 GHz galaxy clusters produce a negative signal in the microwave sky. At the University of Bonn we are part of a team preparing for a new-generation SZ cluster survey with the CCAT-prime telescope, that will not only improve the raw detection sensitivity of the SZ signal compared to current generation instruments, but will also extend the measurement of the SZ effect in the sub-millimeter domain. Here the SZ signal is positive and gets mixed with contaminating foreground sources. The challenge of this thesis work will be to optimize some of the existing cluster detection methods, and develop new ones, that will yield unbiased cluster SZ measurements in the sub-millimeter wavebands for applications in cosmology and astrophysics.	Basu/Bertoldi
Measuring the cosmic velocity field with galaxy clusters Studying the number count of galaxy clusters is currently one of the leading methods for cosmological studies, particularly for finding out the nature of dark energy. These cluster surveys are primarily conducted in the optical, X-ray, or millimeter wavebands, where the last option make use of the so-called Sunyaev-Zel'dovich (SZ) effect for detecting and characterizing galaxy clusters out to very high redshifts. But the SZ effect measurements also provide additional benefits like inferring the proper motion of galaxy clusters (sometimes called the peculiar velocity) in the comoving cosmological frame. Measuring this velocity field will be a new and much fruitful method for constraining cosmology and particularly the dark energy models. This research project will focus on improving the cluster velocity measurement techniques based on multi-frequency SZ survey data, both from the currently available Planck satellite and also from the upcoming CCAT-prime telescope. Our group at the Bonn University is strongly involved in the latter project whose data will become available starting from 2021.	Basu/Bertoldi
Wide-field imaging Optical imaging surveys of the sky provide one of the major tools for studying the Milky Way and the distribution and properties of galaxies and clusters. Cosmological applications include weak gravitational lensing, which requires superb image quality and data in multiple wave-bands. To cover substantial solid angles, wide-field imaging cameras on large telescopes are used. During this internship, the student will become familiarized with the object contents of wide-field images; using available software, catalogs of objects (galaxies, stars) will be generated and their statistical properties (source counts, clustering properties) investigated. Alternatively, the student can learn how the reduction of these wide-field images proceeds -- how to proceed from noisy single exposures of a field, full of defects (cosmic rays, dead pixels, chip gaps, etc.) to a clean and well-calibrated coadded image.	Erben/Schneider
Molecular gas in redshift galaxies Nearby massive galaxies have experienced some of the most intense episodes of star formation at high redshift. Using the Plateau de Bure Interferometer, we have observed high redshift quasars and starburst galaxies to study molecular line emission. This internship offers the opportunity to reduce millimeter interferometry data and study the interstellar medium of distant starbursts.	Bertoldi
Radioastronomical line observations and data analysis Radioastronomical observations at high spectral resolution, using heterodyne receivers, are a central tool to study the physics and chemistry of interstellar clouds. The observations are affected by the noise and drift characteristics of the detectors, the optical performance of the telescope and receiver, and the atmospheric transmission characteristics. Different observing prodecures and corresponding data analysis tools are in standard use to obtain properly calibrated spectra that allow to derive the physical properties in the interstellar clouds.	Stutzki
Radiative transfer and excitation of interstellar molecules IThe brightness of observable interstellar lines is determined by the abundcance of the carrier molecules or atoms, the physical conditions such as density and temperature, and the radiative transfer within the emission region and on the path towads the observer. One of the standard tools for estimating the physical conditions by comparison with the observed intensities is an "escape probability radiative transfer" model.	Stutzki
Astronomical Survey Data: Data Mining Tools Astronomical data archives containing full sky maps in different wavelength bands are available over the WWW. Multiwavelength images can be extracted from these data bases and get combined with new, dedicated observational results. These image processing methods are an essential tool for any modern astrophysical research.	Stutzki
Development of High Frequency Receivers for Astronomy The opening of the submillimeter and far-infrared spectral regime for astronomical observations, both from the ground and from airborne and spaceborne platforms, is driven largely by the technology development of detectors and receivers. Several new observatories (Herschel, SOFIA, APEX, ALMA, NANTEN2) are becoming operational and heterodyne receivers for these are under development.	Stutzki
Quantum limited heterodyne detectors for astronomy Present day heterodyne receivers operate close to the quantum limit, also up to frequencies in the Terahertz regime. These detectors typically involve superconducting contacts with sub-micron dimensions, fabricated with nanofabrication technologies, e.g. in the KOSMA-Mikrostrukturlabor, and mounted in micro-machined waveguide structures specifically designed using 3-D EM simulation tools.	Stutzki
The Search for Carbon Rich Molecules The intersterstellar medium harbors a rich variety of molecules which are highly reactive and thus unknown to chemistry under terrestrial conditions. Among these species are highly unsaturated carbon chain molecules, like the carbonhydrids CnH, and CnH2, (n=1, 2, 3, â?¦), the cyanopolyynes HCnN (with n=1,3, 5,â?¦11) and the pure carbon chain molecules Cn (n=1,2,3,and 5). We use a supersonic jet combined with laser ablation of graphite to form new carbon containing molecules in a cold molecular beam. A frequency stabilized Terahertz spectrometer records high resolution spectra of new molecular species which are used to characterize the molecular properties and to obtain reliable frequencies for a future detection in space.	Giesen
Deuterium Enrichment in Space and Laboratory Understanding the very large enrichment of molecules containing deuterium rather than hydrogen in space is one of the hot topics in astrophysics. Astronomical observations, chemical modeling and laboratory experiments all disagree by many orders of magnitudes. In this lab course laboratory trapping experiments at temperatures resembling the interstellar medium will be carried out to simulate some of the most important chemical reactions in space. Operating a trap experiment, analyzing the data and interpreting the results are key elements of this course.	Schlemmer
Complex Molecules, building blocks for life ? Rotational spectra of complex molecules present in space will be recorded. Generation and detection of radiation at highest frequencies as well as setting up a laboratory spectrometer are among the practical aspects of this course. Analysis of those spectra will reveal molecular constants and enable predicting spectra in the frequency range of coming observational facilities (SOFIA, Herschel, ALMA).	Lewen
Analysis of near-infrared high resolution imaging High angular resolution imaging allow us to carry out detailed studies of the central stellar cluster of the Milky Way (including its high velocity or dust embedded stars) and the infrared counterpart of the super massive black hole (Sagittaruius A*) at its very center. In addition the nuclei or nearby active galaxies and galactic starforming regions are being performed. These investigations involve modern image processing methods on infrared imaging like deconvolution and spatial filtering techniques.	Eckart
Near-infrared instrumentation for 8m-class telescopes The most recent large telescopes offer the possibility of obtaining highest sensitivity and highest angular resolution in the infrared wavelength regime. This allow us to study the immediate vicinity of e.g. young stars, galactic nuclei, and the center of out own Milky Way. In particular the construction, installation, and usage of the imaging beam combiner LINC/NIRVANA at the Large Binocular Telescope in Arizona as well as the Very Large Telescopes Interferometer (VLTI) in Chile are at the focus of this project.	Eckart
Host galaxies of active galactic nuclei Active galactic nuclei belong to the most powerful and brightest objects in the universe. The mail source of their brightness is the accretion of matter onto a central black hole as well as intense star formation in the central bulges. It is currently unclear how the properties of the galaxies hosting these luminous cores are linked to this central activity. What is the relation between accretion and nuclear star formation and what are the mechanisms that allow matter to be transported into these nuclear regions? The investigations are carried out using infrered (LBT, VLT, VLTI) and mm- and submm-telescopes (IRAM 30m, Plateau de Bure, APEX, ALMA, Herschel, SOFIA)	Eckart
Computer-Simulations on Star-discs systems The central theme of our research are young stars which are surrounded by discs. We study the interplay of these star-disc systems with their cluster environment and investigate how this influences the likelihood of the formation of planetary systems. These investigations require state-of-the art computer simulations of N-body systems.	Pfalzner
X-ray emission of galaxy clusters X-rays are emitted from regions where the Universe is hot and wild.Galaxy clusters, the largest and most massive clearly definedstructures we know, are strong X-ray emitters. Observations ofthese systems require space-based instruments. In this internship,the students will download, reduce, and analyze recent X-ray dataof a galaxy cluster taken with a satellite observatory, usingexisting software in the research group. This will allow them todetermine the intracluster gas mass and temperature, as well as themass of the invisible and dominant component -- dark matter.	Reiprich
Stellar populations and dynamics Internships can be offered for work on topics related to Stellar Populations, Stellar Dynamics, Star clusters, Dwarf Galaxies and Dark Matter. Please consult http://www.astro.uni-bonn.de/~pavel/resea.html for an overview of our research activities.	Kroupa
Study of molecular outflows from young stellar objects Young stellar objects are characterized by event of mass-loss which manifest as powerful "jet-like" molecular outflows. observable in the IR and at the millimeter wavelengths. They are a fundamental aspect of star formation, as they provide a record of the mass-loss history of the system. In this internship, the students will reduce, and analyze spectroscopic data taken with the APEX telescope in Chile using standard software for mm line data. This will allow them to determine the morphology of the emission, and study physical parameters associated to the outflows such as mass, moment, and energy. Comparison between systems of different masses will also be performed, to understand some of the problematics of the process of massive star formation.	Leurini/Menten
Radio-emitting X-ray binaries X-ray binary systems are formed by a normal star and a compact object (neutron star, or black hole). Some of these objects show well collimated radio jets and have been called micro-quasars. The structure of the jets is studied by high resolution interferometric observations. In this internship, the students will reduce with the Difmap software, an interactive program for synthesis imaging, radio interferometric data of a microquasar taken with the Multi-Element Radio Linked Interferometer Network (MERLIN). Aim is to determine if the radio structure is resolved at the given spatial resolution, how the morphology is changing in different epochs and finally how fast the jet is.	Massi
Cosmological N-body simulations (theoretical/numerical project) The formation of the large-scale structure of the universe is usually studied by running high-resolution N-body simulations on supercomputers. During this internship the students will learn how cosmological simulation are performed, familiarize with their outcomes, and compute some statistical properties from a sample output.	Porciani
The cosmic UV background (theoretical/numerical project) The integrated emission from star-forming galaxies and quasars produces the cosmic ultraviolet background which keeps the intergalactic medium ionized at low redshift. The goal of this internship is to develop a computer code that computes the expected energy spectrum of the UV background.	Porciani
The halo model of cosmic structure (phenomenological project) Galaxy clustering can be efficiently described in terms of the halo model that links the galaxy distribution to that of the dark matter. During this internship the students will familiarize with the halo model and use it to derive the mass of the dark-matter halos hosting galaxies from the Sloan Digital Sky Survey.	Porciani
Cosmic shear analysis Numerical simulations of the large-scale structure of the Universe provides the essential tool for predicting the density distribution of matter, given a specified cosmological model. By tracing light rays through the resulting matter distribution, the effects of weak gravitational lensing can be studied quantitatively from these simulations. Based on such ray-tracing, the student will analyze parts of the resulting gravitational shear fields, and study their dependence on the redshift of lensed sources. In addition, the student will get familiarized with the basic concepts of cosmic shear research.	Schneider
Analysis of molecular line data from star forming regions A main research topic of the millimeter & submillimeter astronomy group of the MPIfR are studies of the formation of stars using radio telescopes around the world. The students will participate in the initial data reduction, the analysis of the measured spectral lines and cubes and the modeling of the data.	Wyrowski/Menten
Dust continuum studies of galactic star forming clumps The millimeter & submillimeter astronomy group of the MPIfR is strongly involved in studies of the earliest phases of star formation using the powerful bolometer camera LABOCA at the APEX submillimeter telescope in Chile. A recent highlight is the unbiased cold dust continuum survey of our Milky Way (ATLASGAL). The students will be involved in the analysis and interpretation of the data to learn about Galactic structure, fragmentation in giant molecular clouds and the formation of massive stars in individual dense molecular cloud cores.	Wyrowski/Menten
Simulating supernova progenitors In the context of calculations for the structure and evolution of single and binary stars, we are interested to model the progenitors of various types of supernovae or collapsing objects (accretion induced collapse of white dwarfs and neutron stars, gamma-ray bursts and pair-instability supernovae; cf. http://www.astro.uni-bonn.de/~nlanger/siu_web/research.html). It is the purpose of this project to gain insight into specific observed supernovae by performing simulations which are taylored to those events with our unique numerical codes.	Langer
Simulating the continuum emission from photon-dominated regions The KOSMA-tau numerical model for the physics and chemistry of photon-dominated regions (PDRs) has been recently extended to include the effects of different populations of interstellar dust grains on the structure and emission of those regions. It can simulate the continuum emission from different types of dust. In this project, a data base is to be created that tabulates the spectral energy distribution of the dust emission as a function of different interstellar dust populations, of dust content and other PDR parameters. This data base can be used to select appropriate dust parameters from observed spectra before solving the full chemical problem.	Ossenkopf
The chemical equilibrium in interstellar clouds The KOSMA-tau numerical model for the physics and chemistry of photon-dominated regions (PDRs) has been recently extended to include the effects of different populations of interstellar dust grains on the structure and emission of those regions. It can simulate the continuum emission from different types of dust. In this project, a data base is to be created that tabulates the spectral energy distribution of the dust emission as a function of different interstellar dust populations, of dust content and other PDR parameters. This data base can be used to select appropriate dust parameters from observed spectra before solving the full chemical problem.	Ossenkopf