The Fundamental Physics in Radio Astronomy group of the MPIfR led by Prof. Michael Kramer concentrates on various aspects of fundamental physics, namely the Galactic population of neutron stars, their use for precision tests of general relativity and alternative theories of gravity, the detection of low-frequency gravitational waves and the structure and properties of super-dense matter. To do this we use the largest radio telescopes around the world, including our own 100-m telescope in Effelsberg, the MeerKAT array in South Africa and FAST in China.

We are seeking students for a project on the study of pulsars in globular clusters.

Globular clusters are compact stellar clusters. In their cores, stellar densities can reach millions of stars per cubic parsec. In such dense environments, close stellar encounters can form stellar systems unlike any in the Galactic disk. Among these are exotic types of binary pulsars, which could potentially include millisecond pulsar – black hole binaries.

Pulsars are very compact objects, exhibiting the strongest gravitational fields next to black holes. Acting as cosmic lighthouses and precise cosmic clocks, they can be used to probe gravitational physics under strong-field conditions. High precision timing of pulsars provided the first evidence for the existence of gravitational waves as predicted by Einstein’s theory of gravity (Nobel Prize 1993), and leads to some of the best constraints on alternative gravity theories.

Some of the exotic new binary pulsars now being found in globular clusters with the MeerKAT telescope could be natural laboratories for tests of gravity theories unlike any other system found to date, allowing precise new tests of Einstein’s general relativity but possibly, in addition, tests of some types of alternative gravity theories that could not be carried out until now.

In this project, the student will be hosted at the Fundamental Physics in Radio Astronomy group at the MPIfR. They will mostly be involved in technical and observational aspects, especially related to the follow-up of new binary pulsars discovered in globular clusters. The student will be strongly involved in timing these new binary pulsars, and will be involved in the scientific interpretation and publication of the findings.

The student will also be assisting with pulsar searches in globular clusters carried out with the Giant Metrewave Radio Telescope (GMRT), with the MeerKAT telescope (under the “Transients and Pulsars with meerKAT’’ large science project) and finally the COMPACT project, an ERC starting grant project that is hosted at the Fundamental Physics in Radio Astronomy group at the MPIfR.

The following are the necessary and other desirable criteria that we are looking for in a student. In their application, the prospective students are encouraged to explicitly address how they meet each of the necessary criteria and any other desirable criteria that they fulfill.

Necessary requirements for the project:
• A strong expertise and experience in scripting with high level programming languages like python.
• Strong background in physics, especially general relativity.
• Good proficiency in scientific writing supported by previously written research articles/thesis etc.,

Other desirable criteria:
• Good understanding of linux.
• Experience in radio or pulsar astronomy data acquisition, analysis or inference.
• Experience working with large datasets and/or on large supercomputing systems.
• Experience working with an international, diverse group of collaborators.
• A good TOEFL/IELTS score as a testimony for their language expertise.

Precise measurement of the Galactic foreground emission, that contaminates the faint polarised cosmic microwave background radiation (CMB), is a major challenge for the next-generation of CMB experiments and will impact on the precise measurement of anisotropies in its polarisation states. In particular, the gradient-type E-modes and the curl-type B-modes are highly affected, which enables us to detect primordial gravitational waves and the imprints of the reionisation history of the Universe, that directly impacts on our framework of the inner workings of the Universe.

In order to improve our understanding of the Galactic foreground, dedicated sky surveys are necessary to disentangle the various contributions of the foreground emission, in particular in continuum emission: synchrotron emission from relativistic electrons gyrating in ambient magnetic fields, bremsstrahlung (also referred to as the free–free emission) from thermal electrons scattering off ions, anomalous microwave emission (AME) and emission from thermal dust grains; and in polarised emission: synchrotron and thermal dust emissions. A unique opportunity to measure these contributions will be provided by the 15-m SKAMPI telescope in South Africa (owned by the MPIfR) operating in the frequency range between 1.7 and 3.5 GHz (S-Band) and new analysis techniques. In summary, this will allow for better constraints of the foreground cleaning and thus contribute significantly in the component separation analyses of the CMB foreground and will increase the usable sky area for cosmological analysis of the Planck data, and future mission like e.g. the LiteBIRD experiment. For more information please visit

https://arxiv.org/pdf/1906.04788.pdf

The PhD-Project will cover the full scope of astrophysics and observational cosmology. In particular, observation, development and optimisation of calibration, imaging, and analysis procedures and a compilation of a polarized Southern Sky S-Band survey and modelling of the Galactic foreground will be part of the thesis.

Contact: Dr. Hans-Rainer Klöckner (hkloeckner@mpifr.de), Dr. Gundolf Wieching (wieching@mpifr.de), Prof. Michael Kramer (mkramer@mpifr.de); in collaboration with Dr. A. Basu (Thüringer Landessternwarte) and Prof. D. Schwarz (University of Bielefeld).

Site: Bonn, Max-Planck-Institut für Radioastronomie, Fundamental Physics in Radio Astronomy Group

Understanding gravity using a comprehensive search for fast spinning pulsars and compact binaries” (COMPACT) is an ERC starting grant project that is hosted at the Fundamental Physics in Radio Astronomy group at the MPIfR. The project specifically focuses on targeted searches of the most compact binary pulsar systems and ultra-fast rotating pulsars.

Traditional pulsar searches have been biased against the detection of these systems, mainly owing to the massive computational complexity of the search algorithms needed to find these systems. However, the discovery of these systems have a great potential to contribute to a variety of high profile science ranging from performing fundamental tests of gravity, understanding the internal composition of neutron stars to helping/complementing current and next generation gravitational wave experiments.

With these scientific goals in mind, COMPACT will use some of the most sensitive telescopes in the world: The MeerKAT telescope in South Africa, and the 100-m Effelsberg Telescope in Germany, and use cutting edge algorithms to discover these elusive sources of interest. To perform this, COMPACT will take up the tremendous task of petabyte scale data acquisition and processing with the help of an array of supercomputing systems around the world.  With the MeerKAT telescope, the project will start off as a sub-project of the TRAPUM large science project (www.trapum.org) thereby harnessing scientific and technical expertise from an international collaboration to build up the project.  More information about the project can be found at http://erc-compact.org/

The potential student will take an active role in executing observations, and setting up the data acquisition, analysis and pulsar candidate detection pipelines using state of the art programming and machine learning techniques. With the pulsar discoveries, the student will then perform follow-up observations and use pulsar timing techniques to extract valuable scientific insights. This position offers the chance to contribute to groundbreaking research, working alongside experts in the field and harnessing some of the world’s most advanced radio telescope facilities. The skills the students will acquire during the project are also directly applicable to a number of other scientific and industrial disciplines, thereby providing a solid platform to branch out to a career of their choosing.

The following are the necessary and other desirable criteria that we are looking for in a student. In their application, the prospective students are encouraged to explicitly address how they meet each of the necessary criteria and any other desirable criteria that they fulfill.

Necessary requirements for the project:
• Applicants should indicate how the project matches their profile and research experience.
• A strong expertise and experience in programming with high level programming languages, with a good understanding of object oriented and/or functional programming paradigms. This can be supported with the addition of code samples to the application or links to publicly available code repositories that they have significantly contributed.
• A strong interest in programmatic problem solving, developing/using data analysis pipelines.
• Experience working with large datasets in/outside astronomy in terms of acquisition, processing, analysis or inference.
• A strong background in physics.
• Background knowledge of radio astronomy and cosmology
• A Good proficiency in scientific writing supported by previously written research articles/thesis etc.

Other desirable criteria:
• Experience with or a good understanding of multi-threaded / multi-processing / GPU programming with any high level programming language.
• A Good understanding of linux and networking fundamentals.
• Experience with radio or pulsar astronomy data acquisition, analysis or inference.
• Experience working with machine learning techniques.
• Experience working with large datasets and/or on large supercomputing systems.
• Experience working with an international, diverse group of collaborators.
• A good TOEFL/IELTS score as a testimony for their language expertise.

Contact: Dr. Vivek Venkatraman Krishnan (vkrishnan@mpifr-bonn.mpg.de), Dr. Paulo Freire (pfreire@mpifr-bonn.mpg.de), Prof. Dr. Michael Kramer (mkramer@mpifr-bonn.mpg.de )

Site: Bonn, Max-Planck-Institut für Radioastronomie, Fundamental Physics in Radio Astronomy Group

This project is advertised as a joint project between the Fundamental Physics in Radio Astronomy group led by Prof. Michael Kramer and the Lise Meitner research group led by Dr. Laura Spitler.

Spatial structures in the ionized interstellar medium refract radio waves such that the emission from a radio source propagates along several paths between the source and observer. Some observational consequences of this multi-path propagation are intensity scintillations in the spectrum of compact radio sources and the temporal scattering of pulsed emission. The geometry of the scattering region is encoded in the scintillation and scattering signatures imprinted on a radio burst but extracting the geometry requires detailed modeling.

Historically this work has focused on using pulsars to investigate the structure of the Galactic interstellar medium. But with the ever increasing number of fast radio bursts being discovered, it is now possible to apply these techniques to structures in the interstellar media of distant galaxies.  Fast radio bursts (FRBs) are a new class of astrophysical transients that originate from so-far unidentified extragalactic sources. They propagate through several regimes of ionized media including the intergalactic medium and the interstellar media in their host galaxies and the Milky Way. Observationally they are micro- to millisecond-duration luminous radio flashes with varying spectral bandwidths. A subset of FRB sources repeat, while others appear to be one-off events.

The scattering and scintillation modeling techniques developed for pulsars need to be expanded for FRBs in a number of ways. For example, FRBs pass through the interstellar media of its host galaxy and the Milky Way and are therefore scattered by two screens, which provides additional constraints on the screens’ geometries. FRBs are also cosmological sources occurring in host galaxies with widely different physical properties. Furthermore, scattering has impacts on the detectability of FRBs, which must be understood in order to understand biases in survey samples.

A successful applicant will learn the observational techniques of scintillation and scattering modeling using real data from pulsars and/or FRBs, acquiring new data with the 100-m Effelsberg radio telescope when appropriate. In addition, they will use simulations to model the geometry of scattering screens and use these simulations to predict the impact of scattering and scintillation on the population of FRBs discovered by on-going and future surveys.

Necessary requirements for this project:
Strong proficiency and experience in scripting/programming, in particular in Python
A background knowledge of radio astronomy
An aptitude for learning new mathematical skills and developing new analysis methods
Demonstrate proficiency in scientific writing supported by previously written research articles/thesis, etc.
Applicants should indicate how the project matches their profile and research experience.

Other desirable criteria:
Good understanding of linux
Experience in pulsar or FRB astronomy data acquisition, analysis or inference
Understanding of Fourier-based signal processing methods and/or interferometry
Experience working with an international, diverse group of collaborators.

Contact: Prof. Dr. Michael Kramer (mkramer@mpifr.de), Dr. Laura Spitler (lspitler@mpifr-bonn.mpg.de), Dr. Olaf Wucknitz (wucknitz@mpifr-bonn.mpg.de)

Site: Bonn, Max-Planck-Institut für Radioastronomie, Fundamental Physics in Radio Astronomy Group and Lise Meitner research group

This project is advertised as a joint project between the Fundamental Physics in Radio Astronomy group led by Prof. Michael Kramer and the Lise Meitner research group led by Dr. Laura Spitler.

Fast radio bursts (FRBs) are a new class of astrophysical transients that originate from so-far unidentified extragalactic sources and are characterized by luminous, short-duration radio flashes. Understanding the astrophysical nature of the source that generates FRBs is becoming a major focus of current efforts in observational astronomy. Furthermore, they are also promising new tools that can be applied to a wide range of cosmological and astrophysical applications.

A small fraction of the known fast radio burst sources have been seen to emit multiple bursts, the so-called repeaters. Their repeating nature allows for the possibility of a wide range of observational follow-up including localization post-discovery, regular monitoring in the radio, and simultaneous multi-wavelength campaigns. In addition to being temporally variable, their burst properties are also frequency dependent. Most monitoring observations that have led to large burst samples have been done with observing systems at around 1 GHz with limited bandwidths. Therefore, exploring the frequency-dependent behavior of repeaters over a wide frequency range has required either non-simultaneous observations or coordinating multi-telescope observation campaigns.

This is changing thanks to a new, state-of-the-art receiver on the 100-m Effelsberg radio telescope that records data from 1- 6 GHz simultaneously. Effelsberg is one of the most sensitive radio telescopes in the world, and with this new receiver system we will investigate the polarization, propagation effects, and emission properties over a wider instantaneous bandwidth than previously possible. Detections with this receiver will allow us to better constrain 1) the geometry of the source’s magnetic field, 2) the environment local to the source, and 3) the emission mechanism of repeaters better than ever before. In addition, we can also investigate the broadband nature of potential Galactic repeater analogs, such as magnetars and pulsar giant pulses, and make more robust observational comparisons.

The student will take an active role in planning and conducting observations with the Effelsberg telescope. They will help develop and test a software search pipeline optimized for the new broadband receiver system, potentially using machine learning methods. Analyzing any detections will require that the applicant learn an array of observational techniques such as polarization calibration, burst parameter fitting and extraction, and the reduction of voltage data. In summary, the student will have the opportunity to learn a wide range of observational and computational astronomy techniques and work collaboratively with other members of the group doing complementary research.

Necessary requirements for this project:
• Strong proficiency and experience in scripting/programming, in particular in Python
• A background knowledge of radio astronomy
• Demonstrate proficiency in scientific writing supported by previously written research articles/thesis, etc.
• Applicants should indicate how the project matches their profile and research experience.

Other desirable criteria:
• Good understanding of linux
• Experience working with large datasets and/or on large supercomputing systems
• Experience in pulsar or FRB astronomy data acquisition, analysis or inference
• Experience working with machine learning techniques
• Experience working with an international, diverse group of collaborators.

Contact: Prof. Dr. Michael Kramer (mkramer@mpifr.de), Dr. Laura Spitler (lspitler@mpifr-bonn.mpg.de), Dr. Ramesh Karuppusamy (ramesh@mpifr-bonn.mpg.de)

Site: Bonn, Max-Planck-Institut für Radioastronomie, Fundamental Physics in Radio Astronomy Group and Lise Meitner research group

Prominent jets in active galactic nuclei are believed to be powered by the enormous amount of energy released in the regions surrounding the central supermassive black holes. Understanding the physical mechanism of the generation and transport of this energy is crucial for both building a self-consistent picture of extragalactic relativistic jets and uncovering the ultimate nature of the cosmic black holes. Theoretical explanations relate the production and outward transport of energy to black hole rotation, accretion disks, relativistic plasma jets, and magnetic fields. The latter are also expected to be responsible for the commonly observed edge-brightening of jets. At radio wavelengths, where VLBI observations achieve highest-resolution imaging, one can trace the strongly collimated relativistic jets down to linear scales of a few light days. Observations with the Event Horizon Telescope have now made it possible to image the immediate vicinity of the suspected black holes on event horizon scales. This project will address a major remaining astronomical challenge in the AGN puzzle and potentially the most crucial piece of the unequivocal proof of the very existence of black holes: measuring with sufficient precision the strength and three dimensional structure of the magnetic fields on scales smaller than 1000 gravitational radii from the central black hole in order to answer the questions how jets are launched and powered.  The project will combine (i) high-resolution multi-frequency polarimetric VLBI radio imaging and (ii )opacity measurements for a sample of AGN jets with advanced analytical and numerical modelling of relativistic flows. This combination has the best potential for yielding unprecedented constraints on the theoretical models for cosmic black holes and the production of extragalactic relativistic jets.

Bibliography

• Baczko, A.-K., Schulz, R., Kadler, M., Ros, E., et al.: A highly magnetized twin-jet base pinpoints a supermassive black hole, A&A (2016) 593 47, https://doi.org/10.1051/0004-6361/201527951
• Boccardi, B., Krichbaum, T.P., Ros, E., Zensus, J.A.: Radio observations of active galactic nuclei with mm-VLBI, Astron Astrophys Rev (2017) 25 4, https://doi.org/10.1007/s00159-017-0105-6
• Lobanov, A.P.: Beyond the event horizon or altogether without it? Nature Astronomy (2017) 1 0069, https://doi.org/10.1038/s41550-017-0069
• Janssen, M., Falcke, H., Kadler, M., Ros, E., et al: Event Horizon Telescope observations of the jet launching and collimation in Centaurus A, Nature Astronomy (2021), https://doi.org/10.1038/s41550-021-01417-w
• COMPLETE HERE

Links

M2FINDERS project: www.mpifr-bonn.mpg.de/m2finders

Contact

Prof. Dr. Anton Zensus (azensus@mpifr.de), Prof. Dr. Eduardo Ros (ros@mpifr.de), Dr. Andrei Lobanov (alobanov@mpifr.de),  Dr. Michael Janßen (mjanssen@mpifr-bonn.mpg.de)

Requirements

The candidate is expected to master the English language in the scientific context and have a strong background in astrophysics, physics, and mathematics.  Previous experience in observational astronomy is of advantage, especially in the radio regime; alternatively also experience in numerical and computational astrophysics is desirable.   Programming and scripting skills will be important asset as well.

Site

Bonn, Max-Planck-Institut für Radioastronomie, VLBI Group, in collaboration with the Universitat de València, Spain, the Instituto de Astrofísica de Andalucía, Spain, and the Universität Würzburg, Germany.

Very-long-baseline interferometry (VLBI) is the only method for a direct imaging of  regions in the immediate vicinity of  super-massive cosmic black holes. This includes the shadow around a black hole and its surrounding photon ring (event horizon), and thus tests Einstein’s Theory of General Relativity.

Since the angular resolution of an interferometer increases with decreasing wavelength and with increasing baseline length, millimetre VLBI and space VLBI provide the highest angular resolutions in astronomy (lower than 30 microarcseconds). Since compact radio sources become more transparent with increasing frequency (lower opacity at mm-wavelength),   mm-VLBI  allows us to probe deeper into the self-absorbed regions of AGN, which is not possible at the longer cm-wavelengths.  Our group operates the Global Millimeter VLBI Array (GMVA), which combines up to 14 telescopes into regular 3mm/7mm VLBI observations and is a key partner for the Event Horizon Telescope (EHT), which performes VLBI observations at 1.3mm wavelength.  Both 3.5mm and 1.3mm VLBI observations may include the ALMA telescope.  One of the main goals of this effort is to probe the ‘the black hole shadows’ in the Galactic Centre and in the radio-galaxy M 87. Another important topic is to study the origin of jets and the initial jet acceleration and collimation in more distant radio-galaxies and quasars (AGN) with unprecedented resolution.

The PhD candidate will actively participate in the VLBI imaging of Active Galactic Nuclei (Quasars, BL Lac objects, Radio Galaxies, etc.) with the highest possible  angular and spatial resolution using the available VLBI arrays operating at millimeter wavelength (VLBA, HSA, GMVA, EHT).  The ultimate goal is the study of the polarised fine structure of AGN, to probe the orientation and nature of magnetic fields at the innermost part of their relativistic jets.  The probed scales at high resolution are of a few 10 – 1000 gravitational radii.

Bibliography

• Boccardi, B., Krichbaum, T.P., Ros, E., Zensus, J.A.: Radio observations of active galactic nuclei with mm-VLBI, A&ARv 25 4 (2017), https://doi.org/10.1007/s00159-017-0105-6
• Tilanus, R.P.J., Krichbaum, T.P., Zensus, J.A., et al: Future mmVLBI Research with ALMA: A European vision, arXiv:14060.4650 (2014) https://arxiv.org/abs/1406.4650
• Kim, J.-Y., Krichbaum, T., Lu, R.-S., Ros, E., Bach, U., Bremer, M., de Vicente, P., Lindqvist, M., Zensus, J.A.: The limb-brightened jet of M87 down to the 7 Schwarzschild radii scale, A&A 616, A188 (2018) https://doi.org/10.1051/0004-6361/201832921
• Janssen, M., Falcke, H., Kadler, M., Ros, E., et al: Event Horizon Telescope observations of the jet launching and collimation in Centaurus A, Nature Astronomy (2021), https://doi.org/10.1038/s41550-021-01417-w
• The Event Horizon Telescope Collaboration et al.: First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole, ApJL 875 L4 (2019), https://doi.org/10.3847/2041-8213/ab0e85
• The Event Horizon Telescope Collaboration et al.: First Sagittarius A* Event Horizon Telescope Results. III. Imaging of the Galactic Center Supermassive Black Hole, ApJL 930 L14 (2022), https://doi.org/10.3847/2041-8213/ac6429

Links

M2FINDERS project: www.mpifr-bonn.mpg.de/m2finders

Global mm-VLBI Array: www.mpifr-bonn.mpg.de/div/vlbi/globalmm

Event Horizon Telescope: www.eventhorizontelescope.org

Requirements 

The candidate is expected to master the English language in the scientific context, and have a strong background in astrophysics, physics, and mathematics.  Previous experience in observational astronomy is of advantage, especially in the radio regime.  Programming and scripting skills will be an important asset as well.

Contact

Prof. Dr. J. Anton Zensus (azensus@mpifr.de), Dr. Thomas P. Krichbaum (tkrichbaum@mpifr.de),  Prof. Dr. Eduardo Ros (ros@mpifr.de), Dr. Michael Janßen (mjanssen@mpifr-bonn.mpg.de), Dr. Maciek Wielgus (mwielgus@mpifr.de)

Extragalactic jets are formed in the environments of supermassive black holes (SMBH) in active galactic nuclei (AGN). They are among the most powerful and energetic astrophysical objects. Their relevance is not only due to their role as laboratories of relativistic plasmas, but they also have an important effect in their environments, namely, in the interstellar medium of the host galaxy and the intergalactic medium. Understanding their nature and physics can thus give us key information about the progenitor SMBH and its surroundings, but also about the host galaxy and its history. A combination between detailed VLBI observations and theoretical modelling via numerical simulations has proven to be a very good approach to reach the goal of this research.

At present, we are able to perform numerical simulations in supercomputers, including all the relevant physics of these objects: relativistic gas, magnetic fields, different compositions. We have the tools to convert these models into synthetic data for a direct comparison with observations. VLBI is addressing the innermost radio structure of these objects, and gives the observational input to theoretical studies.  Here we propose to continue an already started line of research, which consists in trying to relate the emitting, non-thermal population of particles, studied through observations, with the thermal gas in the jet and the magnetic fields, responsible for the macroscopic jet dynamics.  The role of magnetic fields and its signature in the polarised emission, which can be simulated for the plasma physics and for the emission processes, is one of the goals of the M2FINDERS project (see below).

Bibliography

• Fromm, C. M., Younsi, Z., Baczko, A.K., Mizuno, Y., Porth, O., Perucho, M., Olivares, H., Nathanail, A., Angelakis, E., Ros, E., Zensus, J.A., Rezzolla, L.: Using evolutionary algorithms to model relativistic jets – Application to NGC 1052, A&A 629 A4 (2019), https://doi.org/10.1051/0004-6361/201834724
• Fromm, C. M., Perucho, M., Porth, O., Younsi, Z., Ros, E,; Mizuno, Y., Zensus, J. A., Rezzolla, L.: Jet-torus connection in radio galaxies. Relativistic hydrodynamics and synthetic emission, A&A (2018) 609 A80, https://doi.org/10.1051/0004-6361/201731048
• Fromm, C. M.; Perucho, M.; Mimica, P.; Ros, E.: Spectral evolution of flaring blazars from numerical simulations, A&A (2016) 588, A101, https://doi.org/10.1051/0004-6361/201731048
• Perucho, M.; Agudo, I.; Gómez, J. L.; Kadler, M.; Ros, E.; Kovalev, Y. Y.: On the nature of an ejection event in the jet of 3C 111, A&A (2009) 489, L59, https://doi.org/10.1051/0004-6361:200810479
• Roelofs, F.; Janssen, M.; Natarajan I.; Deane R.; Davelaar, J.; Olivares, H.; Porth, O.; Paine, S. N.; Bouman, K. L.; Tilanus, R. P. J; van Bemmel, I. M.; Falcke H., et al. (The Event Horizon Telescope Collaboration): SYMBA: An end-to-end VLBI synthetic data generation pipeline. Simulating Event Horizon Telescope observations of M87, A&A (2020) 636, A5, https://doi.org/10.1051/0004-6361/201936622
• MacDonald, N.M., Nishikawa, K.-I.: From electrons to Janskys: Full stokes polarized radiative transfer in 3D relativistic particle-in-cell jet simulations, A&A (2021) 653 A10, https://doi.org/10.1051/0004-6361/201937241
• Kramer, J.A., MacDonald, N.M.: Ray-tracing in relativistic jet simulations: A polarimetric study of magnetic field morphology and electron scaling relations, A&A (2021) 656 A143, https://doi.org/10.1051/0004-6361/202141454

Links

M2FINDERS project: www.mpifr-bonn.mpg.de/m2finders

Requirements 

The candidate is expected to have prior programming experience (e.g., Fortran, C++, Python).  The candidate is expected to master the English language in the scientific context, and have a strong background in astrophysics, physics, and mathematics.

Contact

Prof. Dr. Anton Zensus (azensus@mpifr.de), Prof. Dr. Eduardo Ros (ros@mpifr.de ), Dr. N. MacDonald (nmacdona@mpifr.de), Prof. Dr. Manel Perucho (Univ. València, Spain, perucho@uv.es ), Dr. Christian M. Fromm (Universität Würzburg, cfromm@th.physik.uni-frankfurt.de ),  Dr. Michael Janßen (mjanssen@mpifr-bonn.mpg.de)

Site

Bonn, Max-Planck-Institut für Radioastronomie, VLBI Group in collaboration with the Universitat de València, Spain and the Universität Würzburg

Blazars are active galactic nuclei (AGN) that emit violently variable broadband emission from radio to 𝛾-ray energies. With decreasing luminosity, the peaks of their characteristic double-humped broadband spectra are shifted upwards and the high-energy emission reaches the very-high-energy (VHE) regime at TeV gamma rays. High-peaked BL Lac objects (HBLs) are canonically defined as sources whose primary (synchrotron) emission hump peaks above 1015 Hz. In extreme blazars, the primary emission peak can reach up even higher by up to two orders of magnitude. Blazars are of utmost interest for astroparticle physics as possibly dominant sources of ultrahigh-energy cosmic rays and neutrinos. In particular, HBLs and extreme blazars have been considered in several recent theoretical works as relevant neutrino sources.

The TELAMON program is using the Effelsberg 100-m telescope to monitor the radio spectra of active galactic nuclei (AGN) under scrutiny in astroparticle physics, namely TeV blazars and candidate neutrino-associated AGN. The large Effelsberg dish can yield superior radio data over other programs for very-high-energy (VHE) emitting blazars, which are often faint radio sources.

The project aims to characterize the radio variability of very-high energy emitting AGN jets and trace dynamical processes in the pc-scale jets of blazars related to high-energy flares or neutrino detections.

Bibliography

• Kadler et al. 2021, PoS 974, ICRC 2021: TELAMON: Effelsberg Monitoring of AGN Jets with Very-High-Energy Astroparticle Emissions, arXiv:2108.00383

Contact

Prof. Dr. Anton Zensus (azensus@mpifr.de), Prof. Dr. Matthias Kadler (mkadler@astro.uni-wuerzburg.de), Dr. Alexander Kraus (akraus@mpifr-bonn.mpg.de), Prof. Dr. Eduardo Ros (ros@mpifr.de)

Links

The TELAMON Program: http://telamon.astro.uni-wuerzburg.de

Requirements 

The candidate is expected to have a strong background in physics and mathematics, being able to read, write, and speak English well; advantageous is experience in observational astronomy, especially on radio observations.  Programming and scripting experience is also desired.

Site

Universität Würzburg, Group of Prof. Matthias Kadler or Radio Astronomy/VLBI Department of the MPI für Radioastronomie in Bonn.

The most massive stars, assuming mass loss is not too strong, are thought not to form iron cores, but rather to become unstable due to electron-positron-pair formation before central oxygen burning. The collapsing oxygen-rich core will then ignite oxygen explosively, which may lead to pair-instability supernovae, leaving no compact remnant. While such explosions have been predicted since 50 years ago, they were often assumed to only occur in the early universe. However, very recently, pair- instability supernovae have been found observationally in the local universe. This PhD project aims at constructing the first progenitor and explosion models for local, i.e., finite metallicity pair-instability supernovae, using our most modern hydrodynamic stellar evolution code. The idea is to characterize the observable properties of the progenitor and of the supernovae, and to make predictions for the nucleosynthesis yields of pair-instability, which could well dominate the metal production in their host galaxies.

Requirements:

• Candidates are expected to have attended master level courses on the structure and evolution of stars and on other advanced astronomy topics
• affinity to theoretical astrophysics based on their master thesis work
• experience with the MESA stellar evolution code will be helpful but is not required

Bibliography:

Gal-Yam, A., et al., 2009, Nature, 462, 624

Langer, N., 2009, Nature, 462, 579

Contact: Prof. N. Langer (nlanger@astro.uni-bonn.de)

Site: Bonn, Bonn, Argelander Institute for Astronomy, University of Bonn

Dark energy makes up about 70% of the Universe’s energy content and is responsible for its observed acceleration. A powerful method to constrain this enigmatic component is a precise measurement of the evolution of the most massive objects in the Universe: galaxy clusters. For this purpose, the new X-ray telescope eROSITA has been launched in July 2019. Its mission is the discovery of ~100,000 galaxy clusters, including ALL massive clusters in the entire observable universe. eROSITA will be the first “Stage IV” dark energy probe world-wide. The PhD candidate will enjoy privileged access to the first eROSITA data to study galaxy cluster physics, chemistry, and cosmology.

Requirements:

• Completed master-level courses or a master’s thesis in extragalactic astronomy or cosmology are an advantage.
• Demonstrated expertise in X-ray data reduction and analysis is a plus but not required.
• Browsing through the articles in the bibliography can be useful in connecting your course and research experience with your future plans.

Bibliography:

• Borm et al. (2014, http://adsabs.harvard.edu/abs/2014arXiv1404.5312B)
• Clerc et al. (2018, http://adsabs.harvard.edu/abs/2018arXiv180608652C)
• Hofmann et al. (2017, http://adsabs.harvard.edu/abs/2017A%26A…606A.118H)
• Merloni et al. (2012, http://adsabs.harvard.edu/abs/2012arXiv1209.3114M)
• Pillepich et al. (2012, http://adsabs.harvard.edu/abs/2012MNRAS.422…44P)
• Pillepich et al. (2018, http://adsabs.harvard.edu/doi/10.1093/mnras/sty2240)
• Reiprich et al. (2021, https://ui.adsabs.harvard.edu/abs/2021A%26A…647A…2R/abstract)
• Schellenberger & Reiprich (2017, http://adsabs.harvard.edu/abs/2017MNRAS.471.1370S)
• Zandanel et al. (2018, http://adsabs.harvard.edu/abs/2018MNRAS.480..987Z)

Contact: Prof. Dr. Thomas H. Reiprich (reiprich@astro.uni-bonn.de)

Site: Bonn, Argelander Institute for Astronomy, University of Bonn

Traditional studies of the large-scale structure of the Universe are based on two-point statistics like the power spectrum. However, the galaxy distribution is highly non Gaussian and precious information is stored in its higher-order correlation functions (and their Fourier transforms, the multi-spectra). This project aims to develop theoretical models and statistical methods to extract cosmological information from the analysis of (new and old) higher-order statistics of the galaxy distribution. It involves a combination of numerical simulations and analytical techniques. This project will be conducted within the activities of the Higher-order Statistics work package of the Galaxy Clustering working group of the Euclid consortium.

Literature:

Yankelevich & Porciani “Cosmological information in the redshift-space bispectrum” https://arxiv.org/abs/1807.07076
Oddo et al. “Toward a robust inference method for the galaxy bispectrum: likelihood function and model selection” https://arxiv.org/abs/1908.01774
Kuruvilla & Porciani “The n-point streaming model: how velocities shape correlation functions in redshift space” https://arxiv.org/abs/2005.05331

Contact: Prof. Dr. Cristiano Porciani (porciani@astro.uni-bonn.de)
Site: Bonn, Bonn, Argelander Institute for Astronomy, University of Bonn

Computer simulations play a key role as a complement to observations in astrophysics and cosmology.
Our group is at the forefront of the development and application of innovative numerical techniques. We regularly have access to some of the most powerful HPC facilities. Several Ph.D. projects along different lines of research are available. For instance,
– performing constrained simulations to study the effect of the environment onto structure and galaxy formation;
– modelling molecule and dust formation in simulations of galaxy assembly;
– improving models of stellar feedback in simulations of galaxy formation;
– simulating the epoch of reionisation with hydrodynamic simulations including radiative transfer.

Requirements:

The position requires a strong theoretical background and computer skills. Knowledge of high-level computer languages, preference of Fortran, C, C++, scripting language (Python, bash) and MPI are desirable.

Literature:

Borzyszkowski et al. “ZOMG – I. How the cosmic web inhibits halo growth and generates assembly bias”  https://arxiv.org/abs/1610.04231
Garaldi et al. “The Goldilocks problem of the quasar contribution to reionization” https://arxiv.org/abs/1809.10144
Schäbe et al. “A comparison of H2 formation models at high redshift” https://arxiv.org/abs/2003.04329

Contact: Prof. Dr. Cristiano Porciani (porciani@astro.uni-bonn.de)

Site: Bonn, Bonn, Argelander Institute for Astronomy, University of Bonn

One of the main aims of galaxy cluster surveys is to find the nature of dark energy that is accelerating the expansion of the universe. This is primarily done by counting the number of clusters in mass and redshift bins and compare those with theoretical predictions. In the microwave regime this is done through the measurement of the Sunyaev-Zeldovich (SZ) effect, which is now one of the most efficient methods of finding galaxy clusters out to high redshifts. One variant of this SZ effect, called the kinematic SZ (kSZ) effect, allows a direct measurement of the galaxy cluster momentum, and from that, their local velocities. This kSZ effect is a highly promising tool for cosmological analysis and many new methods are being explored.  The goal of this research project will be to evaluate new and existing methods for extracting the kSZ effect signal from the state-of-the-art CMB survey data from the CCAT observatory. Our group in Bonn is strongly involved in the CCAT project, which will start collecting data from its own telescope in Chile from 2024. Additional goals for this PhD research would be to separate the kSZ effect signal from CMB lensing, where the latter has its own cosmological applications.

Requirements:

A good command of cosmology and radioactive processes
Familiarity with coding in the Python environment and data visualization

References:

1. “CCAT-Prime: science with an ultra-widefield submillimeter observatory on Cerro Chajnantor”, G. Stacey et al. 2018, SPIE proceedings, arXiv:1807.04354

2. “A Space Mission to Map the Entire Observable Universe using the CMB as a Backlight”, K. Basu et al., ESA Voyage 2050 Science Paper, arXiv:1909.01592

Bibliography:

• “A Space Mission to Map the Entire Observable Universe using the CMB as a Backlight”, K. Basu et al., ESA Voyage 2050 Science Paper, arXiv:1909.01592
• “SZ spectroscopy” in the coming decade: Galaxy cluster cosmology and astrophysics in the submillimeter”, K. Basu et al., Astro2020 White Paper, arXiv:1903.04944

Contact: Dr. Kaustuv Basu (kbasu@astro.uni-bonn.de), Prof. Dr. Frank Bertoldi (bertoldi@astro.uni-bonn.de)

Site: Bonn, Argelander Institute for Astronomy, University of Bonn

This PhD project will prepare and conduct sensitive, high-resolution interferometric (ALMA) and single dish (CCAT, GBT, IRAM 30m, LMT) multi-band imaging of galaxy clusters in the Sunyaev-Zeldovich Effect (SZE).

We expect to benefit in particular from using representative subsamples of eROSITA-detected clusters.

Galaxy clusters can be used as powerful probes to constrain cosmological models. They also represent laboratories to study the baryonic physics and its interplay with structure formation. Especially when observed at X-ray or millimeter/sub-mm (SZE) wavelengths, the hot, diffuse intracluster medium (ICM) allows to infer valuable information on the total mass, dynamical structure and evolutionary status of the cluster, as well as on the thermal and chemical properties of the ICM itself. Resolved SZE imaging of galaxy clusters provides important constraints on the cluster baryonic state, e.g. by revealing merger shock fronts and extended regions of shock-heated gas. They can also constrain exotic new physics like dark matter decay via non-thermal SZE. ALMA and single dish SZE imaging put together can resolve all relevant scales of galaxy clusters at all redshifts. This project will start building from several existing data sets (ALMA, IRAM 30m, GBT) of well-known galaxy clusters. It will also support our efforts within the European ALMA regional center (ARC) to investigate methods and develop software for a optimal combination of ALMA interferometer and single dish imaging data.  The PhD student will participate in the transregional collabroative research center TRR 33 “The Dark Universe” and in the activities of the German ARC node.

Requirements:

Basic understanding of radio interferometry and other radio observation techniques
Familiarity with coding in the Python environment and data visualization
Ability to follow and adopt available data analysis software

Reference:

1. “ALMA-SZ Detection of a Galaxy Cluster Merger Shock at Half the Age of the Universe”, K. Basu et al., ApJ 829, 2016, arXiv:1608.05413

2. “SZ spectroscopy” in the coming decade: Galaxy cluster cosmology and astrophysics in the submillimeter”, K. Basu et al., Astro2020 White Paper, arXiv:1903.04944

Contact: Prof. Dr. Frank Bertoldi (bertoldi@astro.uni-bonn.de), Dr. Kaustuv Basu (kbasu@astro.uni-bonn.de)

Site: Argelander-Institute for Astronomy, University of  Bonn

The successful candidate will work on the preparation and execution of (sub-)millimeter continuum surveys with the new FYST/CCAT telescope, which will have first light in late 2024.

The candidate will work on the combination and cross-matching of CCAT and Herschel data (as well as any ancillary information available) for infrared spectral energy distribution analysis of star-forming galaxies in the early universe. The goal of this project is to develop a model of the underlying dusty galaxy population across cosmic history.

The doctoral student will participate in the preparation, observation, and analysis of the deep extragalactic galaxy survey with FYST. The science goal is to trace the star formation history of the universe to unprecedented depth and large spatial scales. For this we will develop novel statistical and ML methods to identify and characterize individual galaxies and constrain population properties.

Required skills:

Experience with programming, e.g., in the python language, telescope data analysis, interferometry, gravitational lens modeling, MCMC-based statistical analysis and/or scientific writing will be regarded as a plus for this position.

The analysis of large data sets requires the application and development of analysis tools that are mostly written in python. Programming skills and a background in astrophysics and statistics are recommended.

Further information:

CCAT Observatory: http://www.ccatobservatory.org

Contact: Prof. Dr. Frank Bertoldi (bertoldi@astro.uni-bonn.de)

Site: Bonn, Argelander Institute for Astronomy, University of Bonn

The doctoral student will participate in the preparation, observation, and analysis of the spectroscopic epoch of reionization galaxy survey with FYST. The science goal is to trace the ionized carbon fine structure line emission and thereby the star formation history at the earliest galaxy formation epoch of the universe. For this we will refine models of the star formation history, of [CII] and CO line emission, and develop tools to separate emission components in the spectral data cube.

Required skills:
The analysis of large data sets requires the application and development of analysis tools that are mostly written in python. Programming skills and a background in astrophysics are required.

Contact: Prof. Dr. Frank Bertoldi (bertoldi@astro.uni-bonn.de)

Site: Bonn, Argelander Institute for Astronomy, University of Bonn

State-of-the-art observational studies of the cosmic histories of star formation, stellar mass, and interstellar gas (i.e. the fuel for star formation) have revealed that galaxies do not contain sufficient cold gas earlier in the universe to explain their stellar mass content today, implying that gas accretion is required to understand galaxy evolution. Yet, the physical properties, timescales, and key mechanisms remain poorly understood.

This project focuses on observational multi-wavelength studies of the physical properties and chemical composition of the interstellar gas and dust involved in the star formation process. Comprehensive new data sets from the Atacama Large (sub-)Millimeter Array (ALMA), the NOrthern Extended Millimeter Array (NOEMA), the Karl G. Jansky Very Large Array (VLA), the James Webb Space Telescope (JWST), and supporting facilities will be used as part of this project to make significant progress in our understanding. The successful candidate will also have the opportunity to participate in large international collaborations as part of their
research efforts.

Requirements:

Experience with

• programming, e.g., in the python language,
• telescope data analysis,
• interferometry,
• gravitational lens modeling,
• MCMC-based statistical analysis
• and/or scientific writing skills

will be regarded as a plus for this position.

Contact: Prof. Dr. Dominik A. Riechers (riechers@ph1.uni-koeln.de)
Site: I. Physikalisches Institut, Universitaet zu Koeln

You will develop SIS mixers up to 1.4 THz to allow the observing astronomers to make use of the highest atmospheric windows that can be reached by the CCAT observatory. You start by familiarizing yourself with designs and results at the higher frequency band (790-820 GHz) of the CHAI instrument (website) and gather hands-on experience by taking part in the testing of  CHAI, to become acquainted with the test methodology. Hopefully well prepared you will then work on designs of ultra-high frequency SIS mixers. Material choices for the SIS junctions as well as for the surrounding circuitry are an important part of the design process and might require pre-tests.  Fabrication will mostly be done by the cleanroom staff, but evaluation of the designs (test set-up) is your task. Initially these mixers are meant to be single pixel mixers, or part of a small ( 4 pixel) focal plane array. Probably starting with a standard double side band design, designs for balanced and/or side band separating configurations are envisaged.

Required skills:
To apply you need a solid background in physics apparent by a BSc and a MSc degree. The latter preferably on a relevant subject for the advertised work. A thorough basic knowledge of solid-state physics and superconductivity is very desirable. Interest in micro fabrication is welcome. Proficiency in English in speech and in writing. As a member of the CHAI instrument team you should be able to work and communicate productively with many different people from professors to engineers and workshop, partly also in German. Practical skills, e.g. in electronics, mechanics, computers will be much valued.

Further information:
https://astro.uni-koeln.de/astrophysical-instrumentation
CCAT observatory: http://www.ccatobservatory.org/
relevant SFB 956 page: https://www.sfb956.de/project/d

Contact: Prof. Dr. Dominik A. Riechers (riechers@ph1.uni-koeln.de), Dr. Netty Honingh (honingh@ph1.uni-koeln.de), Dr. Urs Graf (graf@ph1.uni-koeln.de)
Site: I. Physikalisches Institut, Universitaet zu Koeln

In this project we are aiming to develop a filterbank with a bandwidth of about 200 GHz and a maximum resolution of 1000, using integrated microwave kinetic inductance detectors (MKIDs) as sensitive readout elements. To make a camera we plan to populate the focal plane of the telescope with many of these filterbanks, which requires a compact design and readout.

We are looking for 2 PhD students who each have their independent task, but who need to cooperate well to make a workable single pixel prototype and perform meaningful tests.

One of 2 PhD students (23) will focus on the development of the MKID optimizing its sensitivity and its noise behavior, keeping in mind space limitations, connection to the filterbank and read-out connection. The design and the fabrication technology can significantly influence of the sensitivity of the MKID and a hands-on optimization will be part of the work. This will require that you do micro-fabrication of (pre-)prototypes under the supervision of the cleanroom staff. The existing measurement set-up will mainly be adapted by the other PhD student (24) on this project. Performing the measurements, and evaluating and understanding the physics and the performance of the detector (PhD student 1) and the RF design (PhD student2) is a task for both students.

Required skills:
To apply you must have a solid knowledge of general physics, visible in a BSc and MSc thesis, the latter preferably on relevant subject for these PhD positions. Please include a copy of the (draft of) your Master thesis in your application documents. To come to a working prototype in the course of 3-4 years you must already have knowledge of (microscopic) superconductivity. Experience in cryogenic measurements or micro-fabrication is a significant advantage. A practical attitude is necessary as are decent communication and cooperation skills. As this is a challenging subject perseverance is will be required.

Further information:
https://astro.uni-koeln.de/astrophysical-instrumentation
CCAT observatory: http://www.ccatobservatory.org/
relevant SFB 956 page: https://www.sfb956.de/project/d

Contact: Prof. Dr. Dominik A. Riechers (riechers@ph1.uni-koeln.de), Netty Honingh (honingh@ph1.uni-koeln.de), Urs Graf (graf@ph1.uni-koeln.de), Matthias Justen (justen@ph1.uni-koeln.de)
Site: I. Physikalisches Institut, Universitaet zu Koeln

In this project, we aim to conduct a comprehensive, detailed investigation of the physical and chemical structure of high-feedback, star-forming habitats distributed throughout the Galaxy in the range of different environments. We will do so by combining analysis of both archival and newly acquired high-resolution, multi-frequency observations with the analysis of post-processed synthetic images from existing and new MHD-models.

The topic of the PhD will be the characterisation of the chemical history and cluster evolution, includes producing synthetic maps of various molecular transitions based on chemical post-processing of MHD models,  and comparing, in a statistical way, with observational results.

Experience with

• programming, e.g., in the python language,
• interferometry,
• molecular line data analysis,
• MHD models,
• astrochemical models,
• statistical analysis,
• scientific writing skills,
• good communication skills in English.

will be regarded as a plus for this position.

Contact: Prof. Dr. Peter Schilke (schilke@ph1.uni-koeln.de)
Site: I. Physikalisches Institut, Universitaet zu Koeln