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Astronomy and Astrophysics – abstracts
Project Title Author

The entropy floor of galaxy clusters

The free-free emission from galaxies should carry one of the clearest signatures of their star forming activity, but it is notoriously difficult to detect this signal as compared to the much stronger radio (synchrotron) and thermal dust emissions. Our observation and analysis of the 3 millimeter continuum data (obtained from the Plateu de Bure Interferometer) for the nearby starburst galaxy IC 1623 have shown some interesting features. This cannot readily be explained from the known radio emission features in this merging galaxy. The goal of this project is to compare this data will all other publicly available radio and mm/sub-mm data for this galaxy to confirm whether this feature is really caused by the free-free emission, and whether it indicates the primary location of star formation in this merging system.

 

Basu/Bertoldi

Free-free continuum emission in a nearby starburst galaxy

Galaxy clusters contain most of their visible baryonic mass in the form of a diffuse plasma that fills up the space between the galaxies. Studying of this intra-cluster medium is an active field of cosmological research, as it helps us to estimate the mass of the cluster dark matter halos, and to use the clusters as cosmological tools. The entropy of the intra-cluster medium is an excellent tracer of all the heating and cooling processes that have taken place inside the cluster. Our work combining X-ray and millimeter data has opened a new model-independent way to estimate the entropy of this diffuse plasma, and to estimate the "height of the entropy floor", which is essentially a measure of the energy injected into the intra-cluster medium by non-gravitational processes. The goal of this project is to estimate the intra-cluster entropy for one or two clusters, and then compare these values with the predictions from some popular parametric models.

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