Despite being abundant across the Universe, dwarf galaxies (by which we mean here galaxies with stellar masses less than a billion solar masses) remain a challenge to study and understand in detail. Their low optical brightnesses make them difficult to detect beyond the local Universe in anything but the deepest observations.  And when it comes to studying their interstellar medium, the problem is exacerbated by their their very low metal and dust contents, making them a challenge to detect and study using standard methods. Our understanding of all the components of the baryon cycle (gas in- and outflows, formation of ISM structures, and star formation) remains incomplete for all galaxies, but in particular for dwarf galaxies due to these additional challenges.  At the same time, the need to improve this understanding is greater now than ever, with facilities such as JWST and soon SKA putting the spotlight on low mass galaxies and their role in reionising and chemically-enriching the early Universe.

In this PhD project, you will combine information from across the electromagnetic spectrum to extend our understanding of star formation and galaxy evolution in low mass galaxies.  The discovery of vast numbers of faint, low mass galaxies in new optical and radio surveys provides us with the opportunity to expand galaxy scaling relations into the dwarf galaxy regime and model them to better understand the relative roles of gas inflows, star formation and feedback in regulating galaxy growth. In particular, you will take part in the analysis of new data from the APEX telescope which allow us to supplement existing datasets with crucial information about the molecular interstellar medium.  Follow-up high-resolution work with facilities such as IRAM-NOEMA, ALMA and MeerKAT is also expected to zoom in on key objects and processes.

Necessary requirements:

• Strong background in physics and astronomy and relevant degree.
• Good proficiency in scientific coding with Python
• Good proficiency in scientific writing supported by previously written research articles/thesis etc.
• Ability to work as part of a large, international team.

Other desirable criteria:

• Experience with commonly-used software for submm/radio data analysis (in particular CASA and GILDAS).
• Experience working with large datasets.
• Previous research experience in the general areas of interstellar medium studies, star formation, or galaxy evolution.

Detailed studies of molecular gas in large galaxy samples have revealed that star formation is not a completely universal process: at fixed molecular gas surface density, the output of the star formation process can vary by an order of magnitude, depending on the local properties of the gas and the large scale galactic environment. Understanding what exactly regulates the efficiency of the star formation process, and what are the dominant factors responsible for suppressing or enhancing it is however still work in progress.  The challenge lies in the need to measure gas, star formation, and both the local and global properties of the galaxies in large enough samples to probe a wide range of conditions and get the full picture, while also having enough spatial resolution to zoom in on the sites of star formation and disentangle the many possible mechanisms at play.

In this PhD project, you will get to explore these questions by analysing data from a new survey, KILOGAS, which has this exact aim of combining sample size (and broad parameter space coverage) with spatial resolution.  KILOGAS is a high-priority ALMA Cycle 11 project which will deliver kpc-scale CO(2-1) maps for an unprecedentedly large sample of 500 galaxies (order of magnitude increase on previous samples).  All the galaxies also have resolution-matched optical integral field spectroscopic observations from the SAMI and MaNGA surveys.  This will allow us to tackle a broad range of science questions, including for example the factors that trigger and regulate star formation and those responsible for quenching, to the impact of galaxy dynamics and stellar potentials on the ISM, and the connection between the ISM of galaxies and the larger scale gaseous environments.  Depending on the specific science questions tackled in the thesis work, the project may be supplemented with additional data from relevant (sub)mm/radio facilities such as IRAM, APEX and MeerKAT.

Necessary requirements:

• Strong background in physics and astronomy and relevant degree.
• Good proficiency in scientific coding with Python
• Good proficiency in scientific writing supported by previously written research articles/thesis etc.
• Ability to work as part of a large, international team.

Other desirable criteria:

• Experience with commonly-used software for submm/radio data analysis (in particular CASA and GILDAS).
• Experience working with large datasets.
• Previous research experience in the general areas of interstellar medium studies, star formation, or galaxy evolution.

Over the past year alone, the Dark Energy Spectroscopic Instrument (DESI) has collected more optical spectra of galaxies than astronomers had over the past century.  This rate of increase in the size of spectroscopic samples will only increase with the upcoming arrival of several other instruments such as 4MOST on the VISTA telescope and MOONS on the VLT.   These enormous datasets open up new areas of investigations, but also pose significant data analysis challenges that require novel methods.

In this PhD project, you will develop new methods to exploit these rich spectroscopic datasets in order to measure the physical properties of galaxies (masses, star formation rate, chemical enrichment, outflow properties, etc.) and address open questions in the field of galaxy evolution, making use of data from DESI and 4MOST-WAVES.  Possible topics include for example the connection between galaxy properties and those of their dark matter halos,  the impact of cosmic web structures on galaxy evolution, and the chemical evolution of galaxies.  Depending on the specific question to be explored, the project will challenge you to explore novel methods such as emulators for spectrophotometric modelling, likelihood-free inference and Bayesian forward modelling.   In addition to the optical spectroscopic datasets, the project may rely on the use of data from large-scale radio surveys to include additional information about gas and star formation.

Necessary requirements:
Strong background in physics and astronomy and relevant degree.
Good proficiency in scientific coding with Python
Good proficiency in scientific writing supported by previously written research articles/thesis etc.
Ability to work as part of a large, international team.

Other desirable criteria:
Experience with galaxy spectral energy distribution fitting and/or the measurement of galaxy properties (masses, star formation rates, metallicity, etc.) from optical datasets.
Experience working with large datasets.
Familiarity with Bayesian statistics and/or machine learning methods.
Previous research experience in the general area of galaxy evolution.

Massive stars form in dense clumps within giant molecular clouds.  This evolutionary sequence, from diffuse clouds, to dense cores and ultimately stars, depends on the galactic environment and the conditions in the interstellar medium.   Understanding this in detail is a challenge, as it requires large-scale mapping of the gas and dust in a broad range of environments. In recent years, much progress has been made in sensitive, high-resolution mapping of our Milky Way at (sub) millimeter wavelengths, both in the dust continuum and in molecular line emission. The APEX 12m submm telescope has contributed to this significantly, with both the ATLASGAL dust continuum survey at 870 micron and the SEDIGISM survey of the southern Galactic plane in the 13CO and C18O (2-1) lines.

These surveys are now being complemented by (1) new APEX CO (2-1) and dust observations in the outer Milky Way towards lower metallicities and dust-to-gas ratios, and (2) higher excitation and angular resolution observations of CO (3-2) line and 350 micron dust imaging of giant molecular cloud complexes in the inner Milky Way.  For the dust observations, the new APEX A-MKID dual color camera with ~3500 pixels at 870 and ~20000 pixels at 350 micron will be used.

In this PhD project, you will join the observations of these new Galactic Plane surveys and work on the data reduction and the combined analysis of the datasets to analyse how the physical conditions, as well as the fragmentation of clumps within clouds, vary in different Galactic environments and evolutionary stages. Furthermore, with the high spatial resolution and sensitivity that can only be obtained in our own Galaxy, the surveys will be used as a “local truth” for the reliable interpretation of gas and dust observations in distant galaxies.

Necessary requirements:
Strong background in physics and astronomy and relevant degree.
Experience working with large datasets.
Ability to work as part of a large, international team.

Other desirable criteria:
Experience with commonly-used software for submm/radio data analysis (in particular CASA and GILDAS).
Previous research experience in the general areas of star formation or interstellar medium studies.

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 the following research areas:

a) Searching for pulsars and transient radio sources
The discovery of new pulsars frequently leads to new scientific results depending on the pulsar’s properties. With recent advancements in receivers and computing we are able to probe deeper into the Galaxy than ever before. Radio astronomy also offers a unique chance to explore the dynamic sky as many energetic processes are expected to be visible in this part of the electromagnetic spectrum.

b) Pulsars as probes of gravity
Pulsars are very compact objects, exhibiting the strongest gravitational fields next to black holes. Acting as cosmic lighthouses and precise cosmic clocks, pulsars 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. Our research in that field of experimental gravity is driven by improvements in instrumentation and new pulsar discoveries.

c) Pulsar as detectors for low frequency gravitational waves
The direct detection of gravitational waves from merging black holes with LIGO has opened up a completely new window to the Universe: the gravitational wave sky. In 2023 Pulsar Timing Arrays published the first evidence for low frequency gravitational waves. Pulsar Timing Arrays use a number of high-precision millisecond pulsars that are timed extremely precisely. This complements the observations of ground-based gravitational wave detectors like LIGO and VIRGO. To make such a detection a European collaboration, the European Pulsar Timing Array, uses the largest radio telescopes in Europe, including the 100-m radio telescope in Effelsberg.

d) Pulsars as probes of super-dense matter and stellar evolution
Neutron stars represent the most extreme state of matter in the observable Universe. We can study the properties of this super-dense matter when we observe neutron stars in the form of radio pulsars, e.g. mass measurements in binary pulsars offer some of the best constraints for the “equation-of-state”. These mass measurements also offer clues for understanding the birth mass distribution of neutron stars and for the evolution of different types of binary pulsars

Necessary requirements for the project:

• Strong background in physics or astronomy.
• Good proficiency in scientific writing supported by previously written research articles/thesis etc.

Other desirable criteria:

• Good understanding of Linux.
• Experience in scripting with high level programming languages like Python.
• Experience working with large datasets.
• Experience working with an international, diverse group of collaborators.
• A good TOEFL/IELTS score as a testimony for their language expertise.

Contact:
Prof. Dr. Michael Kramer (mkramer@mpifr.de), Dr. David Champion (champion@mpifr-bonn.mpg.de), Dr. Vivek Venkatraman Krishnan (vkrishnan@mpifr-bonn.mpg.de), Dr. Laura Spitler (lspitler@mpifr-bonn.mpg.de)

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

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, optimisation of calibration, imaging, and analysis procedures and a compilation of a polarized Southern Sky S-Band survey and modeling of the Galactic foreground will be part of the thesis.

Necessary requirements:

• Applicants should indicate how the project matches their profile and research experience.
• Demonstrate high level programming experience, applicant should be comfortable with scripting and/or programming, especially Python and databases (e.g. mysql).
• A strong interest in programmatic problem solving, developing/using data analysis pipelines/workflows.
• Background knowledge of radio astronomy techniques, polarisation, Galactic foreground and cosmology.
• The applicant should be proficient in scientific writing, supported by previously written research articles/thesis.

Other desirable criteria:

• Experience in telescope observations, willingness to meta-data analysis and data quality assessment.
• Knowledge of polarisation calibration (e.g. Mueller Matrix)
• Experience working with an international, diverse group of collaborators.

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

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

The 3000-hour MPIfR MeerKAT Galactic Plane Survey (MMPGS) survey is a commensal survey enabling both time-domain and imaging-domain sciences. The continuum and polarization data from the MMGPS survey offer one of the deepest views of the southern Galactic plane, with the broadest frequency coverage (0.544-2.844 GHz) in the pre-SKA era at high angular resolution. We seek candidates who will construct high-fidelity polarization products from these exquisite observations: a broadband rotation measure catalog of extragalactic polarized sources and spatially resolved Faraday depth cubes for diffuse polarized synchrotron emission from the Galaxy. Possible PhD topics include:

(1) Uncovering new features of the Galactic-scale magnetic field

(2) Characterizing the turbulent magneto-ionic medium over a wide range of physical scales

(3) Identifying and probing magnetized gas of individual spatially resolved Galactic objects (e.g., such as supernova remnants and HII regions, etc.)

(4) Detailed characterization and modeling of the ultra-broadband polarization properties of extragalactic radio sources.

Necessary requirements for the project:

• Strong background in physics or astronomy.
• Good proficiency in scientific writing supported by previously written research articles/thesis etc.
• Proficiency in scripting/programming with high level programming languages like Python.
• Background knowledge of radio astronomy techniques,interferometry, polarization
• Applicants should indicate how the project matches their profile, research interest and experience

Other desirable criteria:

• Good understanding of Linux.
• Experience working with broadband polarization data
• Experience working with large datasets.
• Experience working with an international, diverse group of collaborators

Contact: Dr. Sui Ann Mao (mao@mpifr-bonn.mpg.de), Dr. Hans-Rainer Klöckner (hkloeckner@mpifr-bonn.mpg.de), Prof. Michael Kramer (mkramer@mpifr.de)

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

The MuSES (Multi-messenger Studies of Extragalactic Super-colliders) project, led by Prof. Yuri Kovalev, within his advanced ERC grant, aims to understand the physical processes near supermassive black holes responsible for launching and propagating relativistic jets in active galactic nuclei (AGN). The project studies the relationship between black holes, accretion disks, and the surrounding medium, with particular emphasis on jet acceleration, collimation, and the conversion of electromagnetic energy into plasma kinetic energy. A key focus is on proton acceleration and neutrino production mechanisms. The project has two main objectives:

1. Observational Studies of AGN Jet Geometry, Collimation, and Acceleration:

•    Measuring jet shapes using parsec-scale images.
•    Conducting multi-year kinematic analysis to probe plasma acceleration in jets.
•    Developing new automated algorithms for VLBI model-fitting and kinematic measurements.

2. Probing Neutrino Production Mechanisms in Blazars:

•    Studying parsec-scale properties of neutrino-selected blazars through regular VLBI observations and neutrino-triggered experiments.
•    Reconstructing physical conditions in AGN jets related to high-energy neutrino events.
•    Analyzing radio-to-gamma-ray variations in connection to neutrino events.

Techniques include multi-messenger radio-to-gamma-ray and neutrino observations, multi-frequency very-long-baseline interferometry (VLBI) polarization observations, leveraging data from the ongoing MOJAVE project and other dedicated VLBA experiments.

We are seeking up to three students for projects on reducing and analyzing VLBI data and/or analyzing multi-band electromagnetic and neutrino data, including AGN jet simulations.

Necessary requirements for the project:

• Strong background in mathematics, particularly data analysis methods, as well as physics, especially high energy radiative processes.
• A strong expertise and experience in scripting with high level programming languages like python.
• Good proficiency in scientific writing supported by previously written research articles/thesis etc.

Other desirable criteria:

• Good understanding of linux.
• Experience in radio astronomy data acquisition, analysis, or radio interferometry techniques and VLBI
• Experience in modern methods of statistical data analysis, including multi-messenger approach, or AGN jet simulations
• 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.

Bibliography

• IceCube Collaboration: Multimessenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A, Science 361, eaat1378 (2018); https://www.science.org/doi/10.1126/science.aat1378
• Blandford, Meier, Readhead: Relativistic Jets from Active Galactic Nuclei, Annual Review of Astronomy and Astrophysics, 57, 467-509 (2019); https://doi.org/10.1146/annurev-astro-081817-051948
• Kovalev et al.: A transition from parabolic to conical shape as a common effect in nearby AGN jets, MNRAS 495, 3576-3591 (2020); https://doi.org/10.1093/mnras/staa1121
• Lister et al.: MOJAVE. XVII. Jet Kinematics and Parent Population Properties of Relativistically Beamed Radio-loud Blazars, ApJ 784, 43 (2021); https://doi.org/10.3847/1538-4357/ab86bd
• Plavin, Kovalev, et al.: Growing evidence for high-energy neutrinos originating in radio blazars, MNRAS, 523, 1799-1808 (2023); https://doi.org/10.1093/mnras/stad1467

Links
MuSES project: https://www.mpifr-bonn.mpg.de/muses

Contact

Prof. Dr. Yuri Kovalev (ykovalev@mpifr-bonn.mpg.de), Prof. Dr. Anton Zensus

Site

Bonn, Max-Planck-Institut für Radioastronomie, Very Long Baseline Interferometry Group

Interferometric imaging and analysis are going through an exciting phase of rapid development, inspired by the successes of the Event Horizon Telescope and the advent of new powerful instruments such as ALMA, MeerKAT, and ngVLA. The dramatic improvement of sensitivity, fidelity, and sheer amount of data expected from these instruments call for development of automatized, unsupervised techniques for reconstruction and analysis of images made from radio interferometric data. This will be the main focus of the project, building upon the foundations provided by the earlier developments in the group, including the method for wavelet-based image decomposition (WISE; Mertens & Lobanov 2015, 2016) and new imaging methods based on forward modelling and Bayesian approaches. The main aim of the project is to combine these imaging and analysis methods into the first unified framework that would comprise automated, unsupervised image reconstruction, objective structure decomposition and classification, and effective analysis of structural variability. This framework would be applied to the data from large VLBI surveys and monitoring programs, including the VLBA monitoring program MOJAVE, the observations made as part of the M2FINDERS projects, and to the data from state-of-the-art observations with the Global Millimeter VLBI Array at 86 GHz and the Event Horizon Telescope at 230 and 345 GHz.

Requirements:
The candidate is expected to master the English language in the scientific context and have a strong background in astrophysics/physics and mathematics.  Experience and skills in computational optimization techniques and observational astronomy is of advantage.

Bibliography

• J.-S. Kim, H. Mueller, A.S. Nikonov, R.-S. Lu, J. Knollmueller, T.A. Ensslin, M. Wielgus, A.P. Lobanov, “Imaging the black hole shadow and extended jet of M87”, 2024, arXiv:2409.00540. https://doi.org/10.48550/arXiv.2409.00540

• J.-S. Kim, A.S. Nikonov, J. Roth, T.A. Ensslin, M. Janssen, P. Arras, H. Mueller, A.P. Lobanov,
  “Bayesian self-calibration and imaging in Very Long Baseline Interferometry”, 2024, arXiv:2407.14873. https://doi.org/10.48550/arXiv.2407.14873

• H. Mueller, A.P. Lobanov, “DoG-HiT: A novel VLBI multiscale imaging approach”, 2022, A&A, 666, 137. https://doi.org/10.1051/0004-6361/202243244

• F. Mertens, A.P. Lobanov, “Detection of multiple velocity components in partially overlapping emitting regions”, 2016, A&A, 587, 52. https://doi.org/10.1051/0004-6361/201527791

• F. Mertens, A.P. Lobanov, “Wavelet-based decomposition and analysis of structural patterns in astronomical images”, 2015, A&A, 574, 67. https://doi.org/10.1051/0004-6361/201424566

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

Contact

Prof. Dr. Anton Zensus (azensus@mpifr.de), Dr. Andrei Lobanov (alobanov@mpifr.de).

Site

Bonn, Max-Planck-Institut für Radioastronomie, Very Long Baseline Interferometry Group

1. Imaging the innermost regions of AGN: Using millimetre VLBI techniques to obtain high-resolution images of AGN jets, focusing on the regions closest to the central black hole.
2. Measure the magnetic field structure: Analyse the polarisation properties of the observed radio emission to determine the strength, orientation and structure of the magnetic fields within these jets.
3. Constrain Theoretical Models: Compare the observational results with theoretical models of AGN jets and black hole accretion disks, providing critical constraints on their physical processes.
4. Understanding Jet Launching and Powering: Investigate the role of magnetic fields in launching and powering relativistic jets, potentially shedding light on the enigmatic nature of supermassive black holes.

• VLBI observations: Using the Global Millimeter VLBI Array (GMVA) and the Event Horizon Telescope (EHT) to make high-resolution observations of a sample of AGN jets at millimetre wavelengths.
• Polarimetric Analysis: Analysis of the polarisation properties of the observed radio emission to extract information about the magnetic field structure.
• Theoretical Modelling: Develop and apply advanced analytical and numerical models of relativistic flows to interpret the observational data and constrain theoretical parameters.
• Multi-frequency approach: Combining VLBI observations at multiple frequencies to study the opacity and spectral properties of the jets, providing additional constraints on their physical conditions.

• Eppel, F., Hessdörfer, J., Kadler, M., Benke, P., et al., TELAMON: Effelsberg monitoring of AGN jets with very-high-energy astroparticle emission. I. Program description and sample characterization – A&A (2024)  684, A11, http://doi.org/10.1051/0004-6361/202348262
• Ros, E., Kadler, M., Perucho, M., et al., Apparent superluminal core expansion and limb brightening in the candidate neutrino blazar TXS 0506+056, A&A (2020) 633, L1, https://doi.org/10.1051/0004-6361/201937206
• Fuhrmann, L., Angelakis, E., Zensus, J.A., et al., The F-GAMMA programme: multi-frequency study of active galactic nuclei in the Fermi era. Programme description and the first 2.5 years of monitoring, A&A (2016) 596, A45 – https://doi.org/10.1051/0004-6361/201528034

Research objectives

1. Plasma dynamics in curved space time: Performing
   general relativistic magneto-hydrodynamic (GRMHD)
   simulations of accreting black holes to investigate the
   plasma dynamics
2. Radiative transfer in curved space time: Develop a
   understanding of the emission processes around SMBH
   and their dependence on the plasma properties.
3. Synthetic data generation: Generate synthetic
   observations from the theoretical models investigating and
   understanding the limitations of observations
4. Constrain Theoretical Models: Compare the observational
   results with theoretical models throughout the
   electromagnetic spectrum with special focus on EHT
   (radio) and GRAVITY (NIR) observations

Methodology:

• Conduct GRMHD simulations of accreting black holes using standard and non-standard initial conditions.
• Compute the radiative signatures of the GRMHD simulations from the radio to the x-ray regime.
• Interdisciplinary approach: Combine observations in the radio, NIR and x-ray regime with numerical simulations to
  obtain a comprehensive understanding of SgrA* and its flaring behaviour

Expected results:

• Advanced models for the plasma and emission dynamics using advanced GRMHD simulations
• Insights into the plasma processes in the direct vicinity of black holes and their relationship to high-energy emission.
• Constraints on theoretical models for black hole flares and variability.

• EHT collaboration SgrA* paper I, ApJL 930, L12 (2022)
  https://ui.adsabs.harvard.edu/abs/2022ApJ…930L..12E/abstract
• EHT collaboration SgrA* paper V, ApJL 930, L16 (2022)
  https://ui.adsabs.harvard.edu/abs/2022ApJ…930L..16E/abstract
• GRAVITY collaboration, A&A 635, A143 (2020)
  https://ui.adsabs.harvard.edu/abs/2020A%26A…635A.143G/abstract
• Nathanail A., Fromm C., et al MNRAS 495, 1549 (2020)
  https://ui.adsabs.harvard.edu/abs2020MNRAS.495.1549N/abstract

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, Argelander Institute for Astronomy, University of Bonn

More than 99% of the baryonic matter of the modern Universe is in a plasma state, making cosmic flows susceptible to the influence of magnetic fields. Magnetic fields have been detected in a variety of astrophysical environments, including planets, stars, the Milky Way, other star-forming galaxies, and even in the intracluster medium of galaxy clusters. Since the magnetic diffusion timescale is typically shorter than the age of the Universe, amplification mechanisms are required to explain the persistence of these fields.
The most well-established amplification processes are magnetohydrodynamic (MHD) dynamos. In classical MHD, dynamos are processes that convert kinetic energy from large-scale flows or turbulence into magnetic energy, resulting in an exponential growth of magnetic field strength over time.
This PhD project focuses on modeling different types of dynamos, using both semi-analytical approaches and numerical simulations, to explore the origin and evolution of magnetic fields in various astrophysical environments, such as the interstellar and intergalactic medium. Part of the research will also involve modeling the radio emission signatures produced by cosmic rays that propagate in magnetized cosmic plasma. By comparing theoretical predictions with observed radio continuum emissions, we aim to distinguish between various dynamo models and understand their contributions to cosmic magnetism.

Requirements:

The position requires a strong theoretical background, preferentially in astrophysics, and/or fluid dynamics and plasma physics, and computer skills. Experience in high-level programming languages, particularly Fortran and scripting languages such as Python and Bash, is highly desirable.

Bibliography:

• Schober, Schleicher, & Klessen (2013): “Magnetic field amplification in young galaxies” (Astronomy & Astrophysics, https://ui.adsabs.harvard.edu/abs/2013A%26A…560A..87S/abstract)
• Rappaz & Schober (2024): “The effect of pressure-anisotropy-driven kinetic instabilities on magnetic field amplification in galaxy clusters” (Astronomy & Astrophysics, https://ui.adsabs.harvard.edu/abs/2024A%26A…683A..35R/abstract)
• Brandenburg, Rogachevskii, & Schober (2023): “Dissipative magnetic structures and scales in small-scale dynamos” (Monthly Notices of the Royal Astronomical Society, https://ui.adsabs.harvard.edu/abs/2023MNRAS.518.6367B/abstract)
• Federrath, Chabrier, Schober, Banerjee, Klessen, & Schleicher (2011):
“The Mach number dependence of the turbulent dynamo: Solenoidal versus compressive flows”
(Physical Review Letters, https://ui.adsabs.harvard.edu/abs/2011PhRvL.107k4504F/abstract)
• Schober, Sargent, Klessen, & Schleicher (2023): “A model for the infrared-radio correlation of main-sequence galaxies at GHz frequencies and its dependence on redshift and stellar mass” (Astronomy & Astrophysics, https://ui.adsabs.harvard.edu/abs/2022arXiv221007919S/abstract)
• Carteret, Bendre, & Schober (2023): “Observational Signatures of Galactic Turbulent Dynamos” (Monthly Notices of the Royal Astronomical Society, https://ui.adsabs.harvard.edu/abs/2023MNRAS.518.4330C/abstract)

Contact: Prof. Dr. Jennifer Schober (Schober.Jen@gmail.com)

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  and astrophysical information from the analysis of (new and old) statistics of the galaxy distribution and other probes (e.g. line intensity mapping and the Ly-alpha forest). It involves a combination of numerical simulations and analytical techniques. Involvement in the activities of the Euclid Consortium is possible and recommended.

Requirements:

A strong theoretical background in Cosmology and statistics.

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), Dr. Emilio Romano-Diaz (emiliord@astro.uni-bonn.de)

Site: 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;
– BH/AGN feedback and their role in simulations of galaxy formation;
– simulating the epoch of reionisation with hydrodynamic simulations including radiative transfer.

Requirements:

The position requires a strong theoretical background in astrophysics 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
• Khatri et al. “HYACINTH: HYdrogen And Carbon chemistry in the INTerstellar medium in Hydro simulations” https://ui.adsabs.harvard.edu/abs/2024A%26A…688A.194K/abstract
• Fichtner et al. “Connecting stellar and galactic scales: Energetic feedback from stellar wind bubbles to supernova remnants”
  https://ui.adsabs.harvard.edu/abs/2024arXiv240211008F/abstract

Contact: Prof. Dr. Cristiano Porciani (porciani@astro.uni-bonn.de), Dr. Emilio Romano-Diaz (emiliord@uni-bonn.de)

Site: Bonn, 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

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 a PhD student who has an independent task, but who needs to cooperate well to make a workable single pixel prototype and perform meaningful tests.

The PhD student 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. Performing the measurements, and evaluating and understanding the physics and the performance of the detector and the RF design is as well a task for the student.

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 this PhD position. 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, University of Cologne

Planet formation in young stellar systems is nowadays a clearly identified evolutionary path in the cycle of matter from large to small scales. Such processes seem to occur predominantly in the circumstellar disks surrounding pre-main sequence stars much younger than 10 Myr. Multi-wavelength and multi-technique approaches involving high-spectral and high-angular resolution observations are required for a comprehensive understanding of planet formation in disks. As part of this comprehensive approach, the exploration of the inner astronomical units of protoplanetary disks requires observations using VLTI infrared interferometry.

As a follow-up of the GRAVITY YSO Survey (https://sites.google.com/view/lucas-labadie/research?authuser=0), the topic of this PhD will focus on the exploitation of existing high-resolution data from GRAVITY and MATISSE, as well as from GRAVITY(+), to constrain the ejection/accretion processes driving the star-disk interactions and to exploit the temporal baseline of our observations to probe to the temporal variability of the highly dynamic inner regions of the disk.

Ideally, experience with

• long-baseline (infrared and/or sub-millimeter) interferometry
• radiative transfer models
• programming in Python or comparable language
• exploitation in reduction of astronomical observational data (spectroscopy/imaging)
• statistical analysis of data
• good communication skills in oral and written English

will be considered as an asset for this position.

Contact: Prof. Dr. Lucas Labadie (labadie@ph1.uni-koeln.de)

Site: I. Physikalisches Institut, University of Cologne