Main Colloquium
Dr. Neco Kriel	ORATED

Australian National University

Small-scale dynamos are thought to explain how weak magnetic fields in the early universe were amplified to the strengths we observe in galaxies today. While this process is usually associated with the early stages of galaxy formation, mergers between mature galaxies can trigger bursts of turbulence that reignite dynamo activity. A key question is how quickly the magnetic energy grows during these events. Seminal theories suggest this process could be too slow to matter – taking longer than the age of the universe – because growth is limited by slow diffusion. However, recent works have begun to challenge this idea. In this talk, I will present new simulations that explore this question and offer insight into the processes that regulate magnetic growth in galaxies.

	Special Colloquium
Dr. Sasha Plavin	ORATED

Black Hole Initiative, Harvard University

Interstellar scattering enlarges the apparent size of compact radio quasars, and VLBI resolution lets us measure this broadening over the whole sky. By analysing thousands of archival VLBI observations, we have compiled an all-sky catalogue of quasar scattering sizes and produced a corresponding Galactic scattering map. Complementary deep, multi-band campaigns on a few highly scattered sources are under way, already revealing individual screens and constraining their locations, turbulence spectra, and inner scales. I will present the latest results from the all-sky VLBI mapping of the Milky Way, and discuss the ongoing deep follow-ups, placing the VLBI view in the context of other tracers of the ionised interstellar medium.

	Master Colloquium
Prathamesh Ingale	ORATED

MPIfR

Active galactic nuclei are some of the most powerful sources in the cosmos and M81*, a nearby low-luminosity AGN, offers a unique window into their jet dynamics. In this thesis, we explore compelling evidence of jet precession and flaring variability in M81* using over 60 high-resolution VLBI observations (VLBA, EVN) and complementary multi-frequency monitoring with the Effelsberg radio telescope. Our analysis traces the jet's evolving orientation and disentangles its variability across time and frequency, providing new insights into AGN behavior in the sub-Eddington regime.

	Special Colloquium
Dr. Callum Lynn	ORATED

Australian National University

Observations of neutral hydrogen (HI) within galaxies are an important tracer to probe the evolution of complex physical processes that occur within the interstellar medium (ISM). With its close proximity, the gas of the Milky Way provides us the ideal laboratory to investigate these processes and the eventual formation of molecular clouds at scales beyond the sub-grid resolution of most numerical ISM simulations. Observations of this calibre are vital to test our current theoretical understanding of the turbulent cascade and formation of cold gas. The SKA precursor, ASKAP, has observed the Milky Way foreground towards the Magellanic System in unprecedented detail, with its current spatial resolution and unbiased detection manner cataloguing hundreds of Milky Way HI absorption sources within a relatively small field of view, rivalling the combined catalogue of previous detections across the entire sky. I will present recent work done by the GASKAP-HI Collaboration using these latest advancements in source density made by the GASKAP-HI survey. More specifically I will discuss the unique prospect of calculating the structure function of optical depth and other HI properties across a filamentary region, to better understand the spatial structure of the cold neutral medium and its formation. I will also discuss the correlation between HI and dust and how the increased background source density has enabled the ability to detect higher temperature phases of gas through stacking spectra to improve the signal-to-noise beyond the current observational sensitivity of ASKAP.

	Main Colloquium
Dr. Antonia Rowlinson	ORATED

University of Amsterdam and ASTRON

Binary neutron star mergers are exciting high energy phenomena in our Universe, leading to gravitational wave events, gamma-ray bursts and kilonovae. We know the majority of gold and other heavy elements are produced by these events. However, a key outstanding question is: What is the remnant formed by these mergers? A black hole or an even more massive neutron star? If it is a neutron star, it will be spinning at near break-up velocities with a huge magnetic field – a newborn magnetar. By studying emission in X-rays and optical following these mergers, there are hints that we have seen the formation of magnetars. The newly formed magnetar is predicted to give bright, short duration, flashes of coherent radio emission soon after its formation. I am using LOFAR to chase these coherent signals following binary mergers and, excitingly, we have our first candidate detection. To firmly associate candidates with poorly localised binary mergers, we also require deep transient surveys with LOFAR. In this colloquium, I will describe the magnetar central engine model for binary neutron star mergers and outline the key results from our fast transient surveys in the image plane with LOFAR. Looking towards LOFAR2.0, I will describe our efforts to fully automate fast transient image plane searches to find coherent radio transients from multiple progenitor systems. Finally, I will introduce the upcoming AARTFAAC2.0 and outline the exciting results we hope to obtain from it.

	Special Colloquium
Dr. Abhisek Mohapatra	ORATED

University of Cape Town

One of the fundamental questions in astrophysics is how galaxies form and evolve across cosmic time. At the heart of this lies neutral hydrogen (HI) — the raw material for star formation and a key component of the baryon cycle. With powerful new radio telescopes like MeerKAT, we can now push the frontier beyond the local Universe. In this talk, I’ll introduce the LADUMA survey — Looking at the Distant Universe with the MeerKAT Array — the deepest HI survey from the MeerKAT. LADUMA focuses on a single field, with 300 hours of L-band observations (probing HI to z < 0.6) and a planned 3000 hours in UHF-band (extending to z ~ 1.4). From our first 127 hours of L-band data, we have detected HI in about 240 galaxies out to redshift ~0.5. These direct detections allow us to trace the distribution and evolution of HI in galaxies over time. By combining LADUMA’s deep HI data with rich multi-wavelength surveys, we’re beginning to piece together how galaxies acquire, retain, and deplete their gas. I’ll share some of our initial results and discuss what they reveal about the role of HI in galaxy evolution, and how LADUMA is poised to transform our view of the distant Universe.

	Master Colloquium
Sanket Bangar	ORATED

MPIfR

Pulsars are highly magnetized, rapidly rotating neutron stars that emit beams of electromagnetic radiation. The evolution of the average emission widths with frequency provides valuable insights into the magnetospheric structure and emission physics of pulsars. Traditional width metrics, such as W50 and W10, often fail to capture the true extent of the emission region, especially in profiles with low-intensity wings or multiple components. To address this, we have developed a novel algorithm, \texttt{PsrWid}, designed to systematically determine emission widths across a wide frequency range. The algorithm utilizes Gaussian Process Regression to model the pulse profile without assuming a predefined functional form, allowing for a clean separation of signal and noise. The on-pulse region is then identified using the Kneedle algorithm, which locates the knee point in the cumulative distribution of log-intensity, providing a robust thresholding mechanism. We applied PsrWid to pulse profiles of 1271 pulsars observed with MeerKAT as part of the Thousand-Pulsar-Array (TPA) program, conducting a statistical analysis of pulse widths and their correlation with pulsar properties, particularly spin period and magnetic field strength. As a case study, we investigate PSR B0355+54, analyzing its pulse profile evolution over a wide frequency range (102 MHz - 72 GHz) using new observations from the Effelsberg 100-m radio telescope alongside archival data from the European Pulsar Network (EPN). In addition, polarization analysis reveals that while the integrated position angle (PPA) swing deviates from the Rotating Vector Model (RVM), averaging only highly linearly polarized single pulses recovers the expected S-shaped swing, offering insight into the underlying emission geometry.

	Master Colloquium
Rishi Kumar	ORATED

MPIfR

Pulsar timing is a powerful tool in modern astrophysics, enabling high precision investigations of fundamental physics. Accurate timing measurements of neutron stars enable precise pulsar mass determination, stringent tests of general relativity, constraints on the equation of state of dense matter, and, through pulsar timing arrays (PTAs), a pathway to detecting low-frequency gravitational waves from supermassive black hole mergers. However, the presence of radio frequency interference (RFI) continues to limit the precision of such measurements. In an increasingly crowded radio environment and with telescopes operating across wider bandwidths, traditional statistical thresholding methods for RFI excision often prove inadequate. Therefore, a machine learning based approach is essential to handle the complexity of modern RFI. In this work, we develop a neural network–based technique for RFI flagging in averaged pulsar data and evaluate its performance against conventional statistics-based methods implemented in the pulsar analysis software PSRCHIVE. We then perform narrow-band and wide-band timing analysis of the millisecond pulsar PSR J0740+6620 using data processed through both RFI mitigation strategies, and we derive the mass of the pulsar to be $2.140\pm0.030 M_{\odot}$, consistent with previously published values within $1\sigma$. This study demonstrates the potential of neural networks in enhancing the robustness of pulsar timing pipelines, particularly in preparation for next-generation radio observatories.

	Main Colloquium
Dr. Amit Seta	ORATED

ARC DECRA fellow at the Australian National University

Even though the interstellar medium (ISM) of star-forming galaxies has been known to have a multiphase structure (broadly hot, warm, and cold phases) since the 1970s, how magnetic fields differ between the ISM phases is still unknown. Using a combination of theory, simulations, and observations, this talk explores how the multiphase nature of the ISM shapes magnetic fields. In particular, using Zeeman magnetic field measurements and pulsar observations, the relationship between the turbulent kinetic and magnetic energy densities will be established. The findings from these studies will enhance our understanding of the role of magnetic fields in star formation and galaxy evolution, and also prepare us to harness the upcoming wealth of radio polarisation data from the SKA.

	Special Colloquium
Dr. Hao Ding	ORATED

Mizusawa VLBI Observatory, NAOJ, Japan

With spin periods of as short as a few milliseconds, millisecond pulsars (MSPs) have been extensively observed for testing gravitational theories and directly detecting the stochastic gravitational-wave background. While most properties of MSPs are constrained with the pulsar timing technique that times and models of the pulse arrivals, the astrometric parameters of MSPs (especially the parallaxes) can be more precisely determined in the image domain with very long baseline interferometry (VLBI) in a time-efficient manner. Precise astrometric determinations for MSPs in binary/trinary systems are known to be essential for sharpening tests on gravitational theories. In this talk, I will highlight three emerging scientific prospects of MSP astrometry, including 1) probing the MSP formation channels, 2) sharpening the localizing capability of pulsar timing arrays, and 3) connecting the reference systems used by VLBI and pulsar timing. I will introduce the latest status of VLBI astrometry of MSPs with a special focus on innovative observing/data-reduction techniques, and discuss the future of precision low-frequency astrometry.

	Special Colloquium
Dr. Víctor Manuel Patiño Álvarez	ORATED

INAOE-MPIfR Max Planck Partner Group Leader, Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE), México

I present some of the results obtained during the last few years by myself and the INAOE AGN Group / Max Planck Partner Group, including the work of the Master and PhD students. Regarding the multiwavelength variability studies. We find that sources like 3C 279 and 3C 454.3 have activity periods in which the gamma-rays can be dominated by either synchrotron self-Compton (which was previously though not possible for this type of blazars), or external inverse Compton. In the sources 3C 279, 3C 454.3, CTA 102, and B2 1633+382 we discovered the location of at least one gamma-ray emission region within the jet, at 42 pc, 9 pc, 25 pc and 41 pc, respectively, from the central engine. For 3C 279 and 3C 454.3 we find evidence of there being multiple gamma-ray emission regions, and in the case of the former, we can even pinpoint one of them to a moving VLBI component. We also found evidence of the existence of broad line emitting material that is being ionized by the jet in the sources 3C 454.3 and CTA 102; this has important implications on the calculation of black hole masses. Also, preliminary results from our research show that over half of the blazar population presents this additional broad line region.

	Main Colloquium
Prof. Jan Forbrich	ORATED

University of Hertfordshire

What do young stars in Orion and giant molecular clouds in Andromeda have in common? They are now both revealed in unprecedented detail thanks to the transformative power of wideband upgrades to radio interferometry. Starting with the VLA and VLBA upgrades and the advent of ALMA, radio astronomy has entered a new era - soon to be propelled even further by the SKA and ngVLA, and initiatives like ALMA2040. A key driver of this progress is the development of wideband radio receivers, dramatically enhancing continuum sensitivity and enabling simultaneous spectral line observations. In this talk, I will showcase two examples of how these advances are reshaping star formation science. First, focusing on nearby star formation, I will present the Orion Radio All-Stars, illustrating how the upgraded VLA, VLBA, and ALMA are revolutionizing our view of young radio stars in the Orion Nebula Cluster - the closest region of high-mass star formation. For the first time, we have detailed information on radio emission mechanisms and variability across a large sample of young stellar objects. These observations provide critical new constraints on high-energy irradiation in protostellar environments, with implications for planet formation. Switching to nearby galaxies, I will highlight the SMA Andromeda Dust and Molecular Gas Survey (SMA ADAMS), leveraging the wideband upgrade of the Submillimeter Array to observe the Andromeda Galaxy - the nearest large spiral galaxy. Dust continuum observations are essential for characterizing molecular clouds, and for the first time, we can now detect thermal dust emission from resolved individual Giant Molecular Clouds in Andromeda - alongside their CO isotopologue emission. These results are helping to bridge the gap between Galactic and extragalactic star formation studies, placing our detailed view of local Galactic star formation in a wider context.

	Special Colloquium
Dr. Hendrik Müller	ORATED

National Radio Astronomy Observatory, Socorro NM, USA

Next-generation radio interferometers like ngVLA will operate at much higher data rates and sensitivities challenging current interferometric data processing pipelines. Scalability to the Petaflops regime per second may be necessary. These developments are supported by the ongoing push towards science ready data products (SRDP), calling for high performance, and automatized batch processing of huge data sets. NRAO is actively preparing for this era of big-data processing and is laying out the algorithmic and pipeline-heuristical foundations already now. In this talk, I will review recent approaches to data processing by NRAO to scale algorithms towards its next generation of flagship instruments. These include a novel software infrastructure envisioned to replace CASA, especially developed for scalable deployment on GPUs. Calibration, and particularly RFI flagging, is expected to supersede the deconvolution as the limiting factor for the images dynamic range and needs to be performed iteratively with the imaging deploying the same GPU architecture. Imaging-wise, while imaging with CLEAN was the to-go method for decades, in view of increased sensitivity and dynamic range, the assumption inherent to CLEAN saturate the performance unacceptably. The development of efficient, scalable and fast wide-band and wide-field multiscale deconvolution algorithms is paramount. Much anticipated convergence acceleration is achieved by clustering components informed by Bayesian heuristics, applying concepts and ideas of convex optimization to the CLEAN framework, and the utilization of AI for efficient compressing among the spatial and spectral domain. Finally, I will discuss pathways to automatization of pipelines and some computing logistics to streamline the downstream analysis.

	Main Colloquium
Dr. Stella Ocker	ORATED

Carnegie-Caltech Brinson Fellow

The time has come for a new electron density model of the Milky Way. Galactic electron density models describe the multi-component, multi-scale structure of the ionized interstellar medium (ISM). These models are routinely used to predict the distances of radio sources lacking independent distance measures, in addition to forward modeling the dispersion and scattering of pulsars, fast radio bursts (FRBs), active galactic nuclei, and masers. In this talk I will discuss the developments motivating construction of a new electron density model, and some key puzzles that face our understanding of multi-scale electron density structure in our Galaxy. Unlike previous models, large-scale surveys of the ionized ISM are being actively folded into the model construction. Specific case studies will be discussed to demonstrate how characterization of the Galactic electron density affects our understanding of extragalactic FRBs and their use as cosmic probes.

	Special Colloquium
Dr. Efthalia Traianou	ORATED

Instituto de Astrofísica de Andalucía-CSIC, Granada

OJ 287 is one of the most fascinating blazars, believed to host a binary supermassive black hole system and known for its rich history of multi-wavelength variability. In this talk, I will present high-resolution 22 GHz space VLBI observations of OJ 287 from RadioAstron (April 2016), offering a unique view of its jet structure and magnetic field topology at sub-milliarcsecond scales. Our imaging reveals a bent jet morphology, significantly more extended than seen in previous years. Using regularized maximum-likelihood imaging and polarimetric analysis, we observe a transition in the magnetic field from a toroidal-dominated core to a helical structure downstream, indicating an evolving jet. Additionally, model-fitting suggests the emergence of a new component, likely linked to the December 2015 optical outburst and the secondary black hole's passage through the primary's accretion disk.

	Special Colloquium
Dr. Shafqat Riaz	ORATED

University of Tuebingen

Cancelled -- Cancelled -- Cancelled

	SFB Colloquium
Prof. Robin Garrod	ORATED

University of Virginia

The interstellar medium provides an enormous laboratory for the exploration of chemistry of various kinds. Some of the most molecule-rich interstellar objects - known as "hot molecular cores" - are accretions of warm gas and dust that surround young protostars, which ultimately evolve into high-mass stellar systems. Along with their low-mass (solar-type) analogs, "hot corinos", they are characterized by rich rotational emission spectra that exhibit a wealth of organic molecules of varying degrees of complexity. But the formation of these "hot" (>100 K), gas-phase molecules is closely related to an earlier stage of chemistry that occurs on the surfaces of microscopic dust grains at much lower temperatures. Recent observational, experimental and modeling evidence indicates that some of the most complex molecules that we detect in highly evolved protostellar systems may have a much earlier origin than previously thought. Here I will present new modeling treatments that allow us to trace the continuum of hot and cold chemistry involving interstellar organics. I will also demonstrate some initial results from new coupled radiation hydrodynamics and gas-grain chemical modeling of hot core/corino systems, and our efforts to simulate observations of their molecular line emission.

	Special Colloquium
Dr. Eric Rohr	ORATED

Max Planck Institute for Astronomy, Heidelberg

The intracluster medium (ICM) today is comprised largely of hot, X-ray emitting gas at approximately the virial temperature of the cluster, where smaller cool gas clouds of unknown origin and lifespan are scattered throughout it. Using the collection of 352 cosmological zoom-in magneto-hydrodynamic simulations of massive clusters (M_200c(z=0) ~ 10^14.3-15.4 M_sun) in the TNG-Cluster simulation, which employs the highly successful TNG galaxy formation model, I quantify the evolution of the cool (T ~ 10^4-4.5 K) ICM across cluster-centric distance, gravitational origin, and cosmic epoch, where the cluster progenitors unambiguously had more cool halo gas than their descendants. Importantly, I demonstrate that in TNG-Cluster, a majority of the cool cluster gas today is found in satellite galaxies and the cluster centers for cool-core clusters. Moreover, the kinetic mode of SMBH feedback, which is primarily responsible for quenching massive galaxies in the TNG simulations, drives the evolution of the thermodynamic properties of the "smooth" (i.e., gas not bound to satellite galaxies) multiphase ICM out to $\sim$Mpc scales. As the multiphase ICM depends on the implemented baryonic physics and feedback, comparisons across models and with observations can be used to guide the next generation of cosmological simulations, and I make the first such comparison here using recent eBOSS and DESI observations of MgII absorption features in background quasars.

	Promotionskolloquium
Manali Jeste	ORATED

Max-Planck-Institut für Radioastronomie

Asymptotic giant branch (AGB) stars are low- to intermediate-mass stars at the end of their life. At this stage of the stellar evolution, these objects shed large amounts of matter in the form of gas and dust, forming a circumstellar envelope around them and enriching the interstellar medium. In this talk, I will present my thesis work where we probe these envelopes using carbon-bearing species, the C atom, and various molecules, with observations from different single-dish telescopes. We use the rotational lines of the HCN molecule, arising from its ground and vibrationally excited states, to study the inner and hotter parts of the envelope, whereas fine-structure lines of atomic and ionised carbon (C 0 and C + ) are used to constrain their distribution in the envelope of the archetypal star, IRC +10216. Furthermore, we focus on AGB stars as a population and analyse 445 stars as part of the Nearby Evolved Stars Survey (NESS) collaboration. We observed transitions of the CO molecule from multiple rotational states to derive their physical parameters along with mass-loss rates. I will explore the statistical distributions of the inferred stellar parameters and demonstrate how the statistical analysis of a stellar population confirms and extends our understanding of its contribution to the cosmic cycle of matter.

	Main Colloquium
Dr. Reza Ayromlou	ORATED

University of Bonn

In this talk, I will present an overview of my research into the interplay between galaxy evolution and large-scale structure. I'll delve into the effects of both intrinsic physical processes, such as Supernova and AGN feedback, and external environmental effects on the evolution of galaxies and gas, with a focus on large-scales. This includes theoretical studies based on simulations like L-Galaxies, IllustrisTNG, EAGLE, and SIMBA, alongside observational data from SDSS, DESI, and XMM-Newton, among others. A central aspect will be understanding how feedback processes not only regulate star formation within galaxies but also drive the redistribution of gas within and beyond dark matter halos, reaching a newly identified characteristic scale called the Closure Radius. Additionally, I will explore how environmental processes influence galaxy and gas properties across various spatial scales. Finally, I will discuss how the interplay between intrinsic and external processes can induce correlations in galaxy properties from kiloparsec (kpc) to several megaparsec (Mpc) scales, significantly exceeding the virial radii of even the largest galaxy clusters—a phenomenon known as galactic conformity. Finally, I highlight critical pathways for future theoretical and observational studies aimed at unraveling the physical of galaxy formation and evolution across different scales.

	Main Colloquium
Dr. Lauren Rhodes	ORATED

McGill

The deaths of massive stars are sometimes accompanied by the launch of highly relativistic and collimated jets identified as gamma-ray bursts (GRBs). GRB 221009A has been dubbed the BOAT or brightest of all time for its record-breaking gamma-ray brightness. In this talk, I will present a summary of the observations conducted by my collaborators and I (Bright & Rhodes et al 2023, Fulton et al 2023, Rhodes et al 2024), resulting in comprehensive multi-wavelength coverage including the most detailed radio study of any GRB to date. At radio frequencies, it is also the brightest radio counterpart detected to date and our campaign spanned over three orders of magnitude in frequency space starting a few hours post burst and continuing to this day (over 900 days later). I will discuss the importance of such coverage for theoretical modelling and our understanding of jet geometry for all manner of jetted transients from tidal disruption events to x-ray binaries. Finally, I will present a brief overview of our plans to continue monitoring this fascinating object.

	Promotionskolloquium
Davit Alkhanishvili	ORATED

AIfA, Bonn

The Lambda-CDM model is the standard in cosmology, with large-scale structure clustering measurements playing a key role in parameter constraints. Next-generation galaxy surveys highlight the growing importance of higher-order statistics like the bispectrum, which offers improved constraints but introduces computational challenges. This thesis focuses on modeling the bispectrum using perturbation theory to enhance its role in extracting cosmological information. First, we test next-to-leading order perturbation theory expansions using N-body simulations, finding that effective field theory (EFT) provides the most accurate small-scale predictions. We also assess the impact of systematic and statistical errors. Next, we demonstrate how deep neural networks can be employed to model survey geometry effects on the power spectrum and bispectrum, achieving high accuracy with efficient computation. Lastly, we evaluate a third-order galaxy bias expansion against synthetic Eucilid-like survey catalogues, demonstrating that combining the power spectrum and bispectrum allows accurate cosmological parameter extraction up to mildly non-linear scales, improving constraints by a factor of 2-5 over the power spectrum alone.

	Main Colloquium
Patrick Reichherzer	ORATED

University of Oxford

Galaxy clusters host a zoo of radio morphologies—from compact bubbles and extended halos to sausages, bridges, and relics—all generated by cosmic rays (CRs) interacting with magnetic fields. The transport of these CRs across galaxy clusters reflects a reciprocal interaction across plasma scales. Large-scale processes (≳kpc) typically influence microscale behavior (~npc), but we show that microscale fluctuations—inherently patchy and intermittent in nature—shape large-scale radio morphologies in galaxy clusters by mediating CR propagation. This patchiness creates a heterogeneous medium where various plasma microinstabilities collectively affect CR transport. Our multi-scale simulations (kinetic to MHD) show a scale-dependent diffusion coefficient, with a transition at ~1–10 kpc: diffusion dominates below this scale, while advection takes over above it. This interplay shapes radio morphologies, revealing that microscale physics significantly affects macroscopic CR transport. We reveal that microscale physics isn't just driven—it actively sculpts the radio sky, offering testable predictions for next-generation observations.

	Special Colloquium
Dr. Yuh Tsunetoe	ORATED

Harvard University

Very long baseline interferometry (VLBI) observations reveal that relativistic jets like the one in M87 have a limb-brightened, double-edged structure. Meanwhile, analytic and numerical models struggle to reproduce this limb-brightening. We propose a model in which we invoke anisotropy in the distribution function of synchrotron-emitting nonthermal electrons such that electron velocities are preferentially directed parallel to magnetic field lines, as suggested by recent particle-in-cell simulations. We implement our emission model in both general relativistic magnetohydrodynamic (GRMHD) simulations and axisymmetric force-free electrodynamic (GRFFE) jet models and produce simulated jet images at multiple scales and frequencies using polarized general relativistic radiative transfer. We find that the synchrotron emission is concentrated parallel to the local helical magnetic field and that this feature produces limb-brightened jet images on scales ranging from tens of microarcseconds to hundreds of milliarcseconds in M87. We also present theoretical predictions for horizon-scale images that can be tested with next generationinstruments. Due to the scale-invariance of the GRMHD and GRFFE models, our emission prescription can be applied to other targets and serve as a foundation for a unified description of limb-brightened images of extragalactic jets.

	Master Colloquium
Kamalpreet Kaur	ORATED

MPIfR/Bonn

Recent radio observations of the Galactic Center (GC) have revealed a significant population of point sources, including potential pulsars and other compact objects. Detecting pulsars in the GC is challenging due to scattering effects that smear pulsed signals. However, image-based search techniques can overcome this limitation and identify potential pulsar candidates. Additionally, under certain conditions, the supermassive black hole Sagittarius A* (Sgr A*) can also be treated as a point source. It exhibits variability across the electromagnetic spectrum, with short-time variability at low radio frequencies (< 3 GHz) still largely unexplored. This work has two main objectives. Firstly, we identify potential pulsar candidates using the S4 band (2.62-3.50 GHz) of the MeerKAT Radio Telescope. We discovered 13 new unresolved sources by applying image-based techniques and proposed three potential pulsar candidates based on their spectral index. This highlights the importance of image-based search in identifying potential pulsar candidates in the scattering-dominated GC. Secondly, from the observation conducted on 21st March 2024, we report on the flux variability of Sgr A* with a modulation index of 5.38% at 2.79 GHz. This is done for the first time using the MeerKAT Radio Telescope, offering access to previously uncharted parameter space, which will help better understand variability and emission processes in Sgr A*.

	Main Colloquium
Prof. Naomi Ota	ORATED

Nara Women’s University

The XRISM satellite, launched in 2023, is the successor to Hitomi and marks a major step forward in high-resolution X-ray spectroscopy. Equipped with the microcalorimeter spectrometer Resolve, XRISM enables precise measurements of gas motions and turbulence in galaxy clusters. In this talk, I will present the initial results from XRISM observations of the A2029 galaxy cluster, highlighting gas dynamics in the cluster core and the role of non-thermal pressure in the outer regions. I will also discuss future prospects, including upcoming observational strategies and implications for galaxy cluster studies.

	SFB Colloquium
Dr. Nick Indriolo	ORATED

Johns Hopkins University, Baltimore

Chemical complexity in the molecular interstellar medium (ISM) is driven by fast ion-molecule reactions. This network of chemical reactions requires a source of ionization, and as molecular gas is generally well-shielded from ionizing UV photons, cosmic rays provide the dominant source of ionization in such environments. The impact of cosmic rays on atomic and molecular hydrogen is parameterized as the cosmic-ray ionization rate (CRIR; number of ionizations per atom/molecule per unit time), which serves as an important input variable in astrochemical modeling. Our understanding of cosmic rays in both diffuse and dense gas has vastly improved over the past decade as more detailed chemical models have been developed, and as more sensitive observations of molecules that respond to the CRIR have been made. The recent creation of 3D dust maps using Gaia differential extinction measurements allows, for the first time, ionization rates inferred from observations of molecular absorption lines to be assigned to a physical location in the nearby Galaxy. By combining this information we are beginning to build the first map of the CRIR in the solar neighborhood. I will discuss our ongoing work on this project, and how we can use such a map to better understand cosmic-ray acceleration and propagation.

	Special Colloquium
Julian Ruestig	ORATED

DZA

Strong gravitational lensing, a consequence of general relativity, magnifies distant background sources and transforms them into complex shapes when passing behind massive foreground objects. This powerful phenomenon offers a unique view into the distant cosmos by probing directly the distribution of dark matter and providing independent constraints on the Hubble constant. These research objectives call for the utmost precision in the estimation of the distributions of the lens mass and the source surface brightness. Fortunately, we stand at the threshold of a new era - recent and future strides in radio telescope technology, such as SKA and DSA 2000, promise to provide an abundance of observations of unprecedented quality. Realizing the full potential of these advancements hinges on achieving the highest reconstruction fidelity. In this talk, I will introduce LensCharm, a novel Bayesian approach for strong-lensing signal reconstruction that can be connected to Bayesian imaging algorithms such as resolve, allowing for non-parametric reconstruction of both source brightness and lens mass distribution along with their uncertainties.

	Master Colloquium
Lynn Hansen	ORATED

MPIfR/AIfA

The SKAMPI telescope is a new 15-m single-dish prototype telescope operated by the MPG as a stand-alone observatory and is currently undergoing system performance and science verification analyses. It is located on the South African SKA-mid site and equipped with an S-band and a Ku-band receiver. Utilizing SKAMPI, an S-band All Southern Sky Survey in total intensity covering 1.75-3.5GHz has been performed, which serves as a pathfinder to explore observation strategies for upcoming all sky surveys. This work presents an evaluation of SKAMPI's antenna pointing model, which accounts for systematic effects due to collimation errors, encoder offset, nonorthogonality of axes, axis plane tilt, and possible gravitational effects acting on the telescope dish. Additionally, a first version of the Ku-band pointing model has been estimated. The impact of the individual model parameters is tested and an optimised pointing model reducing the number of model parameters from 9 to 5 is proposed, thereby minimizing systematic pointing effects that would propagate into future surveys. A power spectrum analysis has been used to investigate the impact on the overall structure of the Galactic foreground and its scientific impact on CMB studies. We find that the change in the pointing model impacts various angular scales and can be associated with the primary beam properties of the telescope.

	Master Colloquium
Survi Kumari	ORATED

MPIfR/AIfA

Massive stars (≥8M⊙) are essential for the evolution of galaxies as they influence the surrounding medium and the subsequent star formation activity. They are much rarer than their lower-mass counterparts and are known to be formed in dense molecular clumps. Moreover, high-mass star forming clumps evolve on shorter timescales, within dynamic and complex environments and are still deeply embedded in their parent molecular cloud during the earliest phases, making it difficult to study the initial conditions involved. This makes the study of high-mass star forming regions extremely important and challenging. In these early stages, the gas temperature is low, allowing the environments to be probed by molecules whose rotational lines lie in the sub-millimeter wavelength range. Ammonia is a key tracer of dense gas and in dense, pre-stellar cores, reactions with deuterated ions (such as H2D+) convert it into its deuterated isotopologues NH2D, NHD2, and ND3. The abundance of deuterium bound in molecules (with respect to its parent species) is orders of magnitude higher in cold molecular clouds than the primordial [D]/[H] ratio (∼ 10e−5, Oliveira et al. 2003). The variation in deuterium fractionation has been used as a tracer of the evolutionary phases in low-mass star formation, therefore in my master’s thesis I investigate if the same can be done for the high-mass regime.

	Special Colloquium
Mr. Ezequiel Albentosa-Ruiz	ORATED

Universitat de València, Spain

The Galactic Center supermassive black hole, Sagittarius A* (Sgr A*), provides a unique laboratory for studying astrophysical variability across wavelengths. Using high-cadence, full-polarization light curves from ALMA observations during the 2018 Event Horizon Telescope (EHT) campaign (April 21–25), we analyze Sgr A*'s variability and polarization properties with standard time-series analysis tools. Comparing these results with the April 2017 light curves offers insights into the variability and consistency of Sgr A*'s behavior across both observational campaigns. We also take a closer look at April 24, 2018, when Chandra detected a notable X-ray flare, to investigate the time delay between high-energy and mm-wavelength peaks. Finally, we compare the observed variability in our light curves with predictions from GRMHD simulations, evaluating accretion models near Sgr A* under extreme conditions. The results presented in this talk provide new insights into Sgr A*'s accretion dynamics and multi-wavelength emission.

	Master Colloquium
Pranav Limaye	ORATED

AIfA/MPIfR

Fast Radio Bursts (FRBs) are extremely bright, coherent, short-duration flashes of radio light with an extragalactic origin. While some FRBs are known to repeat, a significant fraction have only been detected as one-off events. The underlying progenitor responsible for these intense, extragalactic radio bursts remains an open question. Although the coherent emission from these objects is observed over a very narrow bandwidth, different bursts from the same source can span a broad range of frequencies, making detection challenging for radio telescopes with limited bandwidth. This work presents an observational study of the active repeating FRB, FRB 20240114A, using the Effelsberg 100-m Radio Telescope. The newly installed Ultra BroadBand receiver on the telescope enables the study of FRBs over a wide frequency range of 1.3–6 GHz. Conducting FRB observations with this receiver allowed for the collection of a rich broadband sample of bursts from FRB 20240114A. Various statistical analyses were performed on this sample, comparing results with existing FRB studies and exploring potential connections to neutron stars, which are among the most widely favored FRB progenitor models.

	Main Colloquium
Dr. Michal Zajaček	ORATED

Department of Theoretical physics and Astrophysics, Faculty of Science, Masaryk University, Brno, Czech Republic

I will describe the detection of quasiperiodic ultrafast outflow in the system ASASSN-20qc at z=0.056 (Pasham et al., 2024). The outflow is revealed in the X-ray spectra as an absorption feature, which is periodically enhanced every ~8.5 days. The periodic nature of the ultrafast outflow is best explained by an orbiting perturber that is inclined with respect to the accretion flow. In this way, the orbiting body pushes the disc gas into the outflow funnel, where it is then accelerated by the ordered magnetic field (Sukova et al. 2021). The observed period of 8.5 days, in combination with the inferred SMBH mass of 10^7-10^8 Msun, indicates a semi-major axis of ~100 gravitational radii. The observed outflow rate to inflow rate ratio puts constraints on the influence radius of the perturber. For ASASSN-20qc, the influence radius of 3 gravitational radii suggests the presence of a massive perturber in the intermediate-mass black hole (IMBH) mass range. Quasiperiodic ultrafast outflows (QPOuts) are thus a novel phenomenon that can reveal new EMRI/IMRI candidates that otherwise do not exhibit significant periodic changes in the continuum flux density (or the accretion rate).

	Special Colloquium
Dr. Frederic Jaron	ORATED

TU Vienna

Long-term flux monitoring of astrophysical sources enables detailed analysis of the timing characteristics of their emission. This can be a powerful tool to investigate the physical processes at work in these systems. The TeV-emitting binary star LS I +61°303 has been observed in radio monitoring programs since 1977. It has also been the target for monitoring at higher energies and is included in the search for neutrinos. Periodic signals in the radio emission from this source have been observed to be present and remain stable over decades. Modulation patterns are systematically related across the electromagnetic spectrum. I will discuss these findings in a scenario of periodic accretion onto a compact object and different emission regions within a precessing jet.

	Special Colloquium
Dr. Paola Domínguez Fernández	CANCELED

Center for Astrophysics | Harvard & Smithsonian

TBD

	Special Colloquium
Dr. Martina Scialpi	ORATED

INAF

A large population of AGN pairs residing in the same galaxy—the so-called dual AGN—is predicted to exist at redshifts z > 0.5. These systems constitute the parent population of merging black holes (BHs), making their number and properties a key starting point for theoretical predictions on the level of the gravitational wave (GW) background and the event rate investigated in pulsar timing array (PTA) experiments and by the future LISA mission. Until recently, only a handful of dual AGN had been identified at sub-arcsec separations. In this talk, I will present the first statistically significant sample of these systems with separations ranging from 0.15" to 0.8" (~ kpc at z>0.5), selected using the innovative Gaia multi-peak (GMP) technique. However, follow-up observations are needed to confirm the nature of these objects and distinguish true dual AGN from gravitationally lensed systems. I will showcase spatially resolved optical and near-IR spectroscopy data of approximately 50 systems at cosmic noon, obtained with ground-based AO-assisted instruments including Keck, VLT, and LBT. Additionally, I will present how combining low-frequency and VLBI radio data with optical/IR observations enables us to confirm optically-selected objects and identify strong radio-selected dual AGN/lens candidates. Building on the classification of these systems, I will also present the first study of dual AGN properties, including the luminosity and the mass functions, their separation distributions, their fraction within the total AGN population, and how these characteristics evolve with redshift.

	Main Colloquium
Dr. Taro Shimizu	ORATED

MPE

Near-infrared interferometry is a unique tool to study the inner sub-parsec structure of AGN which is inaccessible with current single dish telescopes. With VLTI/GRAVITY, we can now spatially resolve not just the hot dust continuum on milliarcsecond scales through imaging but also the broad-line region on microarcsecond scales through spectro-astrometry. In this talk, I will review the latest results from our observations of local AGN with GRAVITY where we have mapped the kinematics of the BLR in seven nearby AGN, measured sizes of the hot dust for sixteen AGN, and reconstructed images for two AGN. BLR kinematics have allowed us to independently measure the BLR size and supermassive black hole mass where we begin to find a departure from the radius-luminosity relation at high luminosity. I will give an overview of the GRAVITY+ upgrades that will allow for direct black hole mass measurements out to high redshift and therefore a precise tracing of supermassive black hole-galaxy coevolution through cosmic time. With the addition of wide-angle off-axis fringe tracking and a state-of-the-art AO system, we have already pushed observations out to cosmic noon and beyond and I will show the first results and sample from this program.

	Master Colloquium
Jannick Schulze	ORATED

MPIfR

The SKAMPI telescope is a new single-dish prototype telescope, located on the South African SKA-mid site, which is currently undergoing science commissioning. The telescope stores metadata on the state of the telescope and environmental conditions for each observation. This metadata can be used to investigate potential systematic errors by studying telescope behaviour under changing conditions over time. A workflow has been developed to validate and characterise sensor data, using two different types of Machine Learning approaches that generate models fully describing SKAMPI. These models have been evaluated and learned relations have been extracted from the trained models to validate results and investigate dependencies. A difference in azimuth- and elevation-dependency of exceeding ADC-input saturation of the receiver system is shown. Overall the developed workflow provides first insights into the systematics of SKAMPI and, over a longer time span of operation, could be used to investigate time-dependencies of said relations. In addition it is shown that an ISS downlink emitter, or similar satellite-based emitters, can be successfully used to image SKAMPIs antenna pattern up to the 4th sidelobe.

	Main Colloquium
Dr. Javier R. Goicoechea	ORATED

IFF-CSIC

The earliest stages of (exo)planet formation takes place in protoplanetary disks of gas and dust around young stars. It has become evident that the majority of these disks originate within a cluster of stars, subjecting them to intense ultraviolet (UV) radiation. Despite its relevance to planet formation theories (our proto-Solar System disk formed in a cluster) little is known about the role of this external UV radiation in the formation, evolution, and chemical composition of embryonic planetary systems. The unprecedented capabilities of JWST combined to ground based observatories such as ALMA now enables us to characterize protoplanetary disks irradiated by UV from the cluster.

	Main Colloquium
Dr. Hannah Uebler	ORATED

MPE

One of the most surprising results coming out of the first two years of science operations with JWST is the unexpectedly high abundance of actively accreting black holes in the early Universe. Compared to the local population, many of these early black holes appear to differ in various aspects, such as their relation to their host galaxies or their multi-wavelength properties. These observational findings challenge our understanding of the past evolution of present-day supermassive black holes, and provide new ways to constrain theoretical models of black hole formation and growth. I will give an overview of recent observational results on massive black holes in the first few billion years and how they fit into current models, largely driven by the unprecedented capabilities of JWST to explore cosmic dawn, and with a focus on results from the NIRSpec GTO surveys JADES and GA-NIFS.

	Special Colloquium
Prof. Dr. Jongho Park	ORATED

KyungHee University

Very Long Baseline Interferometry (VLBI) achieves ultrahigh angular resolution by utilizing widely separated radio telescopes. The quality of VLBI images improves with more participating telescopes, a principle realized by the Global VLBI Alliance (GVA). In this talk, I will present recent advances in AGN jet studies enabled by the GVA. 1. We identified a dense, cold ambient medium near the core of the 3C 84 jet, which guides its propagation on parsec scales and significantly influences its overall shape. 2. Our observations of NGC 315 reveal that its jet, previously known for a center-brightened morphology at parsec scales, is actually edge-brightened—a feature unresolved in earlier VLBI studies. I will discuss the physical implications of these findings and explore future research opportunities with the GVA and the Global Millimeter VLBI Array (GMVA).

	Special Colloquium
Dr. Guang-Xing Li	ORATED

SWIFAR, Kunming

Modern Astronomical Observations provide high-fidelity images that might contain complex structures. The effective approaches to analyzing these structures remain missing. Here, I present a method, which can extract information from these maps by analyzing the relationship between measurement values from adjacent pixels. The method can reveal regularities in the parameter space, which is hard to obtain otherwise, and can provide optimal ways to divide a region into patches of heterogeneous properties. I provide examples where the method has been used to analyze astronomical, medical, agricultural, and climate images.

	Main Colloquium
Dr. Frank Rieger	ORATED

IPP

Accreting supermassive black holes are believed to drive the energy output in the form of radiation and relativistic plasma outflows (jets) seen in active galactic nuclei (AGN). As the most powerful, persistent sources in the Universe, AGN provide a unique possibility to explore the realm of extreme physics. I will highlight some recent advances in the high-energy plasma diagnostics of these objects, ranging from magnetospheric processes in the vicinity of supermassive black holes to the physical characteristics of their large-scale jets. On black-hole horizon scales, for example, gap-type particle acceleration is a likely mechanism behind the rapidly variable gamma-ray emission observed in sources such as M87, and may supply the plasma necessary for continuous jet formation. On larger scales, a combination of first and second-order Fermi-type acceleration processes presumably plays a key role in shaping the non-thermal emission properties of AGN jets. I will give an introduction to these scenarios, comment on their potential role for ultra-high energy cosmic-ray production, and address some of the key challenges currently facing this field.