Special Colloquium
Paloma Thevenet	SCHEDULED

Observatoire de Paris

The blazar 3C 66A is known for its optical flux periodicity and complex jet kinematics. Using 22/43 GHz KaVa (KVN and VERA array) observations and 43 GHz VLBA (Very Long Baseline Array) archival data, we have found that its pc-scale jet has a twisted structure and that the inner jet undergoes periodic swings every 11 years. In this talk, we will describe the peculiar characteristics of 3C 66A and delve into possible interpretation scenarios. The multiwavelength flux variability and jet orientation changes hint at a supermassive black hole binary (SMBHB) in which orbital motion and disk-orbit misalignment lead to jet precession. However, combinations of other mechanisms, such as Lense-Thirring disk precession and jet instabilities, could also account for the properties of 3C 66A, underscoring the challenge in robust SMBHB candidate identification.

	Promotionskolloquium
Kartik Rajan Neralwar	SCHEDULED

Max-Planck-Institut für Radioastronomie

The interstellar medium (ISM) is a turbulent, multi-phase medium with a hierarchical structure consisting of molecular clouds (MCs), clumps, and cores. Stars form in dense cores and, over their evolution, inject mass, momentum, and energy back into the ISM through stellar feedback processes. I will present a systematic study of the interactions between stellar feedback and molecular gas structures across different spatial scales and evolutionary stages, using the STARFORGE simulations. These simulations follow the evolution of individual giant molecular clouds, while self-consistently modelling protostellar outflows, stellar winds, radiation and supernovae. I will begin by examining the impact of individual feedback mechanisms on high-resolution gas cores identified in the simulated gas density maps. I will then describe the use synthetic 13CO observations to study the evolution of MCs under the influence of stellar feedback as they would appear in observational surveys such as SEDIGISM. Following this, I will introduce a new pipeline developed to track clumps over time capturing their changes, fragmentation and mergers. Finally, I will present deep-learning based results demonstrating how neural networks trained on synthetic data can identify feedback signatures in real observations. Together, these projects provide a framework for interpreting observed trends in the molecular cloud properties, identifying the observational signatures of stellar feedback in molecular gas, and tracing the time evolution of molecular gas structures in galaxies.

	Special Colloquium
Prof. Roger Deane	SCHEDULED

Inter-University Institute for Data Intensive Astronomy (IDIA), South Africa

I will present an overview and report early science from the MeerKAT-South Pole Telescope (SPT) Survey, a deep UHF-band eXtra Large Project (XLP) legacy project recently approved to map 800 square degrees of the southern sky to a sensitivity of ~10 uJy/beam. Uniquely designed to exploit the synergy between world-leading observatories at ~1 GHz and ~100 GHz, this survey covers the deepest Cosmic Microwave Background fields in existence. In this talk, I’ll focus on early results from the survey’s first stage: a 100 square degree pilot that has already detected ~300,000 radio sources. I will highlight specific results demonstrating the strong synergy between these cm- and mm-wave telescopes, including the identification of high-redshift (z > 6) dusty star-forming galaxies, radio halos in SZ-selected galaxy clusters, and the discovery of rare phenomena like Odd Radio Circles, X-shaped radio galaxies, high-redshift OH megamasers and Long-Period Transients. Ultimately, this survey will serve as a significant pathfinder for SKA-era galaxy evolution and cosmology, with commensal image-domain transient science. Furthermore, it will provide significant radio legacy value to complement upcoming multi-wavelength campaigns with LSST, Euclid, and the Simons Observatory.

	Promotionskolloquium
Shilpa Ranchod	SCHEDULED

MPIfR

Magnetic fields are ubiquitous in the Universe and play a key role in galaxy evolution, influencing star formation, cosmic-ray transport, and feedback. Radio polarisation observations provide a powerful probe of cosmic magnetic fields through Faraday rotation. Large samples of polarised radio galaxies enable rotation measure (RM) grids that trace both extragalactic sources and the magnetised interstellar medium of the Milky Way. As modern interferometers push to µJy sensitivities and dramatically increase RM grid densities, interpreting these measurements requires a better understanding of both foreground Faraday effects and the faint polarised source population. This thesis addresses two key aspects for improving RM grid interpretation: (i) the observational biases and physical origins of Faraday complexity at low Galactic latitudes, and (ii) the nature of the extragalactic polarised source population. Using broadband spectro-polarimetric ATCA observations of polarised extragalactic sources, I show that the observed increase in Faraday complexity toward low Galactic latitudes in the SPASS/ATCA catalogue is largely driven by contamination from diffuse Galactic polarised emission. Our relatively higher-resolution observations allow this contamination to be filtered out, revealing that 42% of sources still show Faraday complexity. We find this complexity to be consistent with turbulent injection scales in the Galactic spiral arms and toward the Galactic centre. In addition, I present the linear polarisation component of the VLA-COSMOS 3 GHz survey, yielding the deepest polarised source counts (2.6 µJy/beam) at this frequency to date. Through these broadband observations, we identify the dominant depolarisation mechanisms in this sample and model the frequency dependence of polarised source counts. Furthermore, these results show that even the µJy polarised sky is dominated by active galactic nuclei, with no detection of star-forming galaxies, implying that significantly deeper observations will be required to probe this population, even at higher frequencies.

	Special Colloquium
Dr. Sasha Plavin	SCHEDULED

Black Hole Initiative, Harvard University

Blazars exhibit dramatic optical variability, but the precise location of these flares — accretion flow, jet base, or extended jet — remains debated. I present a novel approach using Gaia astrometry together with VLBI to localize the flaring regions directly. Among blazars with strong optical emission from extended jets, I demonstrate a universal pattern: optical flares occur very close to the central engine. These measurements use the latest Gaia DR3 and place a typical flare within ~0.5 mas (a few pc) of the VLBI core position, consistent with an origin in the innermost jet or accretion region. Such a direct localization can constrain electron acceleration and seed photon fields, and provide a model-independent anchor for gamma-ray and higher-energy emission zones. The upcoming Gaia DR4 will bring per-epoch astrometry, sharpening these constraints further.