Connecting Telescopes, Connecting Minds – Perspectives for Global Radio Astronomy and Global Science

Jul 21, 2026, 1:30 AM → Jul 22, 2026, 10:00 PM Europe/Berlin

Universitätsclub Bonn

Andrei Lobanov (Max-Planck-Institut für Radioastronomie, Bonn), Anton Zensus, Eduardo Ros

A Scientific Symposium in Honor of J. Anton Zensus

July 21–22 | Universitätsclub Bonn  | Participation by invitation only

In July 2026, leading scientists and long-standing collaborators will convene in Bonn to celebrate—and continue—the scientific legacy of Prof. J. Anton Zensus, who served as Director at the Max Planck Institute for Radio Astronomy from 1997 until January 2026 and now continues his engagement with the institute as Emeritus Director.

Over nearly three decades in Bonn—and during earlier appointments at the National Radio Astronomy Observatory in Charlottesville and Socorro, as well as at the California Institute of Technology—Anton Zensus has shaped modern radio astronomy. His scientific vision and leadership have influenced generations of researchers and advanced our understanding of the most energetic phenomena in the Universe.

Equally defining has been his role as a mentor to dozens of early-career scientists and as an architect of international collaborations that transcend institutional and national boundaries. This meeting is both a celebration and a conversation—an invitation to reflect on where radio astronomy has come from, and where, together, we can take it next.

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Rationale and Structure of the Meeting

The event is conceived in two complementary parts, reflecting both the scientific depth and the broader human and institutional dimensions of Anton Zensus’ career.

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Part I: Scientific Meeting - Sharpening the View — VLBI at the Frontier    

Day 1 and until noon of Day 2 — 75 invited participants

The first part is designed as a focused scientific workshop highlighting the key research themes that have defined Anton Zensus’ work. Central to this legacy is the study of active galactic nuclei (AGN), their relativistic jets, and the physics of their central supermassive black holes.

A hallmark of this research has been the development and application of very-long-baseline interferometry (VLBI) at the highest angular resolutions. Observations with space-borne antennas, the Global mm-VLBI Array, and the Event Horizon Telescope have enabled transformative insights into jet formation, collimation, and black hole environments—complemented by single-dish observations and multi-wavelength and multi-messenger studies across the electromagnetic spectrum and beyond.

The workshop aims to provide forward-looking scientific perspectives inspired by these achievements. By bringing together leading experts and long-standing collaborators, it will highlight current challenges, emerging methodologies, and future opportunities in high-resolution astrophysics and black hole research.

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Part II: Symposium on Science Policy and Academic Culture:  Making the Invisible Visible — Celebrating Five Decades of VLBI at the MPIfR

Afternoon and Evening of Day 2 — 100 invited guests — followed by reception

How does transformative science actually happen? What conditions allow individuals and institutions to build knowledge across borders, nurture talent, and shape the scientific culture of an entire field?

This symposium steps back from the telescope and asks these broader questions. Drawing on the experience and reflections of Anton Zensus and his peers, it will explore:

• Science as a collaborative and international endeavor
• Mentorship and the development of scientific talent
• Leadership in large research infrastructures and global collaborations
• The role of research institutes in shaping science policy and public engagement
  
  

These themes reflect Anton Zensus’ long-standing commitment not only to scientific excellence, but also to building communities, fostering international partnerships, and promoting knowledge across institutional and national boundaries.

The symposium will conclude with a reception, offering participants an opportunity for informal exchange and shared celebration

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This two-part event honors a career that has combined scientific innovation, institutional leadership, and dedication to mentoring. By connecting cutting-edge astrophysics with reflections on science policy and academic culture, the meeting celebrates not only past achievements but also the continuing vitality of the scientific enterprise that Prof. Zensus has helped to shape.

This meeting is both a celebration and a conversation—an invitation to reflect on where radio astronomy has come from, and where, together, we can take it next.

Tue, July 21

Sharpening the View — VLBI at the Frontier: I. AGN and jets in broader astrophysical context

1 AGN in broader context

to be completed

Speaker: Prof. Wolfgang Duschl (Universität Kiel)

2 From Compact Jets to Event Horizons: High-Resolution VLBI of Supermassive Black Holes

to be completed

Speaker: Dr Rusen Lu (Shanghai Astronomical Observatory - Chinese Academy of Sciences)

3 Multi-band and multimessenger studies of AGN

High-resolution radio interferometry has been instrumental in revealing the physics of relativistic jets in active galactic nuclei. Recent years have witnessed the emergence of a new population of high-energy emitting radio galaxies, extending well beyond the classical blazar paradigm. Fermi-LAT detections now include not only FR I and FR II sources, but also the abundant low-power FR 0s, young Compact Symmetric Objects (CSOs), and even Giant Radio Galaxies (GRGs). These misaligned systems demonstrate that efficient particle acceleration to GeV (and occasionally TeV) energies occurs across the full radio-loud AGN sequence. Broadband modelling shows that the high-energy emission is predominantly leptonic — synchrotron self-Compton in compact jets and inverse-Compton scattering of CMB, EBL and host-galaxy photon fields in the extended lobes — while hadronic contributions remain possible in dense nuclear environments.
Hard X-ray and optical studies indicate that both radiatively efficient (HERG-like) and inefficient (LERG-like) accretion modes can power these high-energy sources, with the jet duty cycle and restarting activity appearing largely independent of the instantaneous accretion state. Recent associations of radio galaxies such as 3C 403 and 3C 120 with high-energy neutrinos further highlight the multimessenger potential of this population, suggesting that neutrino production may occur either in magnetized coronae or through transient interactions in structured (spine-sheath) jets.
Looking ahead, NewAthena will provide high-resolution X-ray spectroscopy of coronae, accretion flows and lobe IC emission, while CTAO will extend the SED to the VHE regime. The IceCube Upgrade and future IceCube-Gen2 will deliver larger neutrino samples with improved angular resolution, enabling us to test coronal versus jet-origin scenarios in misaligned AGN. In this context, the SKA — and in particular SKA-VLBI — will play a central role by connecting parsec- to kiloparsec-scale structures and pinpointing the exact sites of high-energy dissipation, from compact jet bases to extended lobes. These multi-band and multi-messenger synergies will deliver the first spatially resolved view of particle acceleration and energy release in misaligned AGN, directly building on the international collaborative framework fostered by Anton Zensus.

Speaker: Dr Gabriele Bruni (INAF - IAPS)

4 Studies of dark matter using AGN lensing

The approach used by the Search for MIlli-LEnses (SMILE) project makes use of strong gravitational lens systems in the milliarcsecond regime, where the lens is a compact object with mass between ~ 10^6 and 10^9 solar masses. This mass range is crucial for the widely accepted ΛCDM cosmological model, which predicts the existence of many more DM sub-galactic halos (< 10^11 solar masses), than the currently observed number. To explore such small angular scales, high-resolution VLBI radio data are used. Searching for milli-lenses in a catalog of ~ 5000 radio loud sources will allow us to detect lenses in this mass range, or, failing that, to tighten significantly our constraints on the number of sub-galactic halos and consequently discard some viable DM models.

Speaker: Dr Carolina Casadio (Institute of Astrophysics - FORTH (Crete))

Sharpening the View — VLBI at the Frontier: II. AGN and jets in broader astrophysical context

5 AGN physics with VLBI from ground and space

Anton Zensus was one of the founders of the 2 cm VLBA Survey, which evolved into the MOJAVE program -- a decades-long VLBA monitoring effort that has transformed our understanding of relativistic jet kinematics, brightness temperatures, and polarization in AGN, and their connection to high-energy emission. Anton's vision also extended into space VLBI: as a member of the RadioAstron International Science Council, he was a cornerstone of MPIfR's support for this ambitious mission, which achieved space-ground baselines up to 350,000 km and delivered unprecedented angular resolution, revealing extreme brightness temperatures and new details of jet microphysics near supermassive black holes.
In this talk, I will touch upon historic aspects and highlight selected results from the 2cm VLBA/MOJAVE and RadioAstron programs, celebrating Anton Zensus's foundational role in establishing and sustaining these transformative projects for AGN science, and their legacy for future VLBI efforts.

Speaker: Prof. Yuri Kovalev (MPI für Radioastronomie)

6 VLBI studies of relativistic outflows

to be completed

Speaker: Dr Tuomas K. Savolainen (Metsähovi Radio Observatory)

7 Numerical modelling of relativistic jets

The Ole Miss Blazar Group has recently been established at The University of Mississippi (UM). Our group is actively involved in both theoretical modelling and observation of relativistic Blazar jets. The group is a part of UM's Center for Multimessenger Astrophysics (UMCMA). In this talk, I will summarize three of the group's student led projects: (i) GPU Enabled Simulations of Jet Propagation using the gPLUTO Code, (ii) Polarized Radiative Transfer Calculations of Jet Synchrotron Emission using the RADMC-3D Code, and (iii) Modeling Blazar Orphan Gamma-ray Flares using the BLAZE Code. The Ole Miss Blazar Group has been awarded a National Science Foundation (NSF) grant (Award #: 2429473) to establish a partnership between the UM and BU Blazar Groups. In particular, we are working to extend BU's optical polarimetric monitoring of a sample of Gamma-ray bright Blazars targeted by NASA's Imaging X-ray Polarimetry Explorer (IXPE). Our group is now conducting monthly optical polarimetric Blazar observations at the Perkins Telescope Observatory (PTO) in Flagstaff, Arizona. The linearly and circularly polarized synchrotron emission from Blazar jets carry imprints of both the strength and orientation of the jet's collimating magnetic field as well as the plasma content of the jet environment. Our relativistic jet simulations yield synchrotron polarization estimates that can be used to interpret both Very Long Baseline Interferometric (VLBI) jet observations and single dish light curves of jet variability. By attempting to bridge the gap between theoretical modelling and observation, we aim to advance our understanding of the intrinsic plasma nature of relativistic Blazar jets in 3D.

Speaker: Nicholas MacDonald (The University of Mississippi)

8 The evolution of AGN and their Jets

Since their discovery, active galactic nuclei have frequently been in the focus of astronomical observations. Radio interferometers have transformed our understanding of this activity phase, including relativistic jets, and its role in the evolution of galaxies. In my talk, I will provide an overview on what VLBI observations during the last few decades have taught us about the physics of AGN and their jets. I will also discuss the future of this research field, which looks especially bright thanks to new instrumentation such as the SKA and ngVLA. Finally, I will reflect on my personal journey, which is closely tied to the MPIfR.

Speaker: Dr Anne-Kathrin Baczko

Sharpening the View — VLBI at the Frontier: III. Supermassive black holes and their vicinity

9 Black Holes and the Event Horizon Telescope

To be completed

Speaker: Prof. Mariafelicia De Laurentis (Università Federico II Napoli)

10 Numerical Simulations of Black Hole Environs: A Multi-scale View

Event Horizon Telescope (EHT) observations now resolve black hole environments on horizon scales, directly probing the physics of black hole accretion and jet launching. I will show how modern two-fluid general relativistic magnetohydrodynamic (GRMHD) simulations, coupled with anisotropic emission models, provide a unified framework to interpret these data, from the polarised structure at EHT scales to emission across multiple wavebands. This approach enables a seamless connection to very long baseline interferometry (VLBI) observations at longer wavelengths, as will be provided by the next-generation VLA (ngVLA), where jets emerge, collimate, and accelerate, and further to the large-scale structures that will be probed by the Square Kilometre Array (SKA). By linking these regimes, we can trace the evolution of relativistic jets across many orders of magnitude in scale within a single physical model. Finally, I will highlight how physics-informed neural networks (PINNs) are beginning to transform both simulation and inference, opening new pathways to constrain black hole and jet physics directly from observations.

Speaker: Dr Christian M. Fromm (Universität Würzburg)

11 EHT polarimetry of black holes

to be completed

Speaker: Dr Joana A. Kramer (Universiteit van Amsterdam)

12 EHT studies of the inner jets

To be completed

Speaker: Prof. Mikhail Lisakov (Pontificia Universidad de Chile - Valparaíso)

Sharpening the View — VLBI at the Frontier: IV. Supermassive black holes and their vicinity

13 Magnetic field probes of black hole physics

The most compelling evidence for existence of cosmic black holes comes from the LIGO/VIRGO detections of gravitational waves, the GRAVITY tracking of relativistic stellar and accretion disk motions in the Galactic Centre, and the EHT imaging of the strong gravitational lensing on scales down to several gravitational radii in M87 and Sgr A*. At the same time, these observations can be still reconciled with a range of hypothetical horizonless objects such as wormholes, gravastars, and naked singularities. While very similar to the canonical black holes in most of the observable manifestations, the horizonless objects are expected to feature dipole magnetic fields of more than 10 billion Gauss in strength – which is at least five orders of magnitude stronger than the maximum field strength that can supported by accretion of matter onto a black hole. The difference between these two possibilities can be efficiently probed on scales below about ten thousand gravitational radii with multifrequency polarimetric VLBI observations. Such observations can yield robust estimates of magnetic field from the broadband spectrum and opacity of the synchrotron emission, its brightness temperature and Faraday rotation. These magnetic field indicators have been employed in several recent studies, including the project M2FINDERS solely focused on making magnetic field measurements on smallest linear scales, down to the event horizon. Results of these measurements present growing indications of magnetic fields stronger than ten thousand Gauss, making some of these measurements difficult to be reconciled with the canonical black hole scenario. A review of these results will be presented here and further discussed in context of perspective developments of this line of research.

Speaker: Dr Andrei Lobanov (MPIfür Radioastronomie, Bonn)

14 Electric fields near black hole horizon

Magnetic fields play a central role in black hole astrophysics. They are routinely included in theoretical models and numerical simulations, and are well constrained observationally through synchrotron emission and polarization measurements. By contrast, the electric fields induced by black hole rotation in an external magnetic field remain much less directly accessible. These fields are essential ingredients in many scenarios of particle acceleration, pair production, and relativistic jet launching, yet their very presence near astrophysical black holes is still debated because of plasma screening and rapid charge neutralization.

In this talk I will discuss the structure of electromagnetic fields near the event horizon of Kerr black holes. I will begin with a self-consistent analytical treatment of a rotating black hole immersed in an external magnetic field, showing how frame dragging naturally induces electric fields and drives charge separation in a plasma. I will then present recent fully general-relativistic particle-in-cell simulations that confirm these theoretical predictions. The simulations show that a black hole can accumulate a non-zero electric charge from surrounding plasma and sustain an unscreened electric field, at least within the ergosphere. Finally, I will discuss prospects for detecting these effects with future VLBI observations, including Event Horizon Telescope observations.

Speaker: Dr Arman Tursunov (Institute of Physics, Czech Academy of Sciences, Prague)

15 Advanced imaging algorithms for black hole studies

Horizon-scale imaging of black holes using millimeter very long baseline interferometry has moved rapidly beyond traditional CLEAN deconvolution toward a new generation of forward modeling methods, such as regularized maximum likelihood and Bayesian imaging. Achieving the extremely high resolution required for horizon-scale imaging means contending with sparse and noisy data, and novel calibration and imaging approaches have been developed to address these challenges. I will discuss this evolving imaging landscape, covering closure imaging, polarization calibration, dynamic imaging, and multi-frequency imaging. I will also discuss future directions, including the application of GPU-based gridders and AI methods to techniques enabled by new instrumentation, such as frequency phase transfer with multi-band receivers, and their relevance to next-generation arrays like the ngVLA and ngEHT.

Speaker: Jongseo Kim (MPIfR)

16 Simultaneous Multi‑frequency VLBI and Frequency Phase Transfer at Millimeter Wavelengths

Recent advances in multi‑frequency receivers are transforming mm‑VLBI, with Frequency Phase Transfer (FPT) emerging as a key technique for high‑frequency observations. By mitigating turbulent tropospheric phase fluctuations, FPT extends phase coherence times and significantly improves sensitivity.
In this talk, we review recent progress in dual‑ and triple‑band VLBI capabilities across the global mm‑VLBI community. First, a global VLBI array equipped with triple‑band receivers operating at 22/43/86 GHz is rapidly maturing. Pilot studies have delivered high‑fidelity imaging and high‑precision core‑shift measurements, which are critical for probing magnetic field structures in AGN jets.
Furthermore, recent test observations have demonstrated the feasibility of extending FPT to even higher frequencies, reaching 258 GHz with APEX and the IRAM 30‑m telescope. Future additions of facilities such as NOEMA and JCMT are expected to enable transformative improvements in black hole imaging and studies of ultracompact regions.

Speaker: Dr Guang-Yao Zhao (MPI für Radioastronomie)

Wed, July 22

Sharpening the View — VLBI at the Frontier: V. High resolution radio interferometry

17 Millimetre VLBI, from CMVA to EHT and beyond

To be completed

Speaker: Prof. Eduardo Ros (MPI für Radioastronomie)

18 IRAM and Submillimeter wavelength interferometry

To be completed

Speaker: Dr Karl Friedrich Schuster (IRAM Grenoble)

19 ALMA & ASTRON developments

To be completed

Speaker: Dr Violette C.M. Impellizzeri (ASTRON)

20 AMT & EHT/ngEHT developments

to be completed

Speaker: Dr Michael Janßen (Radboud Universiteit Nijmegen)

Sharpening the View — VLBI at the Frontier: VI. High resolution radio interferometry

21 EVN and Global VLBI

to be added

Speaker: Dr Agnieszka Słowikowsa (JIVE)

22 German Perspectives for Next-Generation High-Frequency VLBI

Germany is one of the world's leading nations in high-frequency VLBI, a position closely associated with the scientific legacy of Anton Zensus and reflected in major contributions to European and global VLBI networks from centimeter to millimeter wavelengths. Looking ahead, existing national facilities, most notably the 100-m Effelsberg telescope, will continue to form the backbone of German participation in global VLBI networks. They will be complemented by the planned Wetterstein Millimeter Telescope (WMT), a new facility for next-generation high-frequency VLBI in Germany. At the same time, the international landscape is entering a new era. Germany is expanding its role in the Square Kilometre Array (SKA), whose unprecedented sensitivity will transform VLBI observations up to 15 GHz through SKA-VLBI in combination with compatible European stations. The ngVLA will extend comparable advances into the millimeter regime up to approximately 120 GHz. The WMT provides a natural European link between these facilities, strengthening current VLBI arrays while enabling future SKA-VLBI and ngVLA very-long-baseline observations. Looking further ahead, these developments naturally motivate LEVERAGE, a European concept for a distributed network of next-generation VLBI antenna clusters designed to complement both SKA-VLBI and the ngVLA. Building on decades of expertise in instrumentation, telescope development, and high-frequency VLBI, Germany is well placed to play a leading role in LEVERAGE and the next generation of global very-long-baseline astronomy.

Speaker: Matthias Kadler (JMU Würzburg)

23 ngVLA and VLBI developments at the NRAO

The next-generation Very Large Array Project is designing a new instrument capable of sensitive high-resolution observations from 1-115 GHz. An international collaboration (including Germany) is working on ngVLA design, building on successful technical and scientific collaborations between US and German radio astronomers over the past several decades, particularly for long-baseline science. In this talk we will discuss the status of ngVLA, including new developments in the coming year which will accelerate the project and create new VLBI opportunities.

Speaker: Dr Anthony Beasley (NRAO)

24 The Role of U.S. FFRDCs In Transformative Science – Past and Future

The Federally Funded Research and Development Center (FFRDC) model was established in the U.S. to focus on high risk, long-term R&D needed by the government that was of a scale and complexity that would not be pursued by industry or academia without government funding. The model emerged after World War II, building on the Manhattan Project and other R&D efforts pursued during the War, and paralleling effort in Europe. Associated Universities, Inc. (AUI) was formed in 1946 to pursue an early implementation of the FFRDC model, and ten years later founded the National Radio Astronomy Observatory (NRAO), an FFRDC AUI manages for the U.S. National Science Foundation (NSF). This talk will discuss some of the history in the U.S. that drove the establishment of the Model and what unique value this Model still provides in scientific R&D, including in shaping science policy, supporting global collaborations, and driving world-leading infrastructure forward.

Speakers: Dr Adam Cohen (AUI), Anthony Beasley (NRAO)

25 Radioastronomie: Looking Back – Looking Ahead

I will discuss the circumstances leading to the many transformational discoveries made by radio astronomers over the past century since Karl Jansky’s pioneering work and the development of the new techniques, such as VLBI, that made these discoveries possible. I then speculate on the prospects for further discoveries from the next generation of new radio telescopes currently planned or under development.

Speaker: Dr Kenneth Kellermann (NRAO)

Making the Invisible Visible — Celebrating Five Decades of VLBI at the MPIfR

26 Welcome Address

Speaker: Dr Marlene Weiß (Süddeutsche Zeitung)

27 Einstein to Black Holes: Big Science and International Collaboration

Speaker: Prof. Jürgen Renn (MPI für Geoanthropologie, Jena)

28 Five Decades of VLBI at MPIfR

Speaker: Prof. Antxon Alberdi (Instituto de Astrofísica de Andalucía-CSIC, Granada)

29 Science Outlooks

Speakers: Dr Aleksei Nikonov (MPI für Radioastronomie), Ms Lena C. Debbrecht (MPI für Radioastronomie), Dr Saurabh (MPI für Radioastronomie)

30 Panel Discussion

Speakers: Dr Agnieszka Słowikowsa (JIVE), Dr Kenneth I. Kellermann (NRAO Charlottesville), Mr Lutz Stenvers (mtex antenna technology), Prof. Mariafelicia De Laurentis (Università Federico II Napoli)