Special Colloquium
Prof. Dr. Steven Tingay	SCHEDULED

Curtin Institute of Radio Astronomy (CIRA), Australia

I will provide an update on the Murchison Widefield Array (MWA), on behalf of the six nation partnership that supports the operation of this facility. The MWA is an SKA precursor and I will briefly summarise recent MWA science results of significance, the recent completion of the Phase III upgrade of the MWA facility (describing new capabilities, new observing modes, and new science opportunities), and the path to transition from the MWA to the SKA-Low facility toward the end of this decade. This transition offers unique opportunities for joint science between the MWA and SKA-Low during the transition period, in particular as the SKA-Low moves through the Array Assembly 2 (AA2) phase. I will describe these opportunities.

	Special Colloquium
Dr Minghui Xu	SCHEDULED

GFZ Potsdam

Absolute astrometric catalogs are widely used to define celestial reference frames for many astronomical applications. However, the correspondence between a specific feature in a radio image and its cataloged absolute astrometric position is ambiguous because existing catalogs are generally constructed using point-source models. Significant progress has been made toward addressing this issue by using 15 years of MOJAVE observations to model the source structure of AGN jets. We use images aligned with respect to the identified radio “core,” which naturally serves as the reference point for determining a more stable astrometric position for each AGN after source-structure modeling. Interestingly, the physical interpretation of the resulting position remains uncertain. Does the improved absolute astrometric position correspond to the identified radio core, or does it trace the physical base of the jet? This talk will examine that unresolved connection between astrometry and the underlying astrophysical structure.

	Main Colloquium
Prof. Dr. Dan Homan	SCHEDULED

Denison University, USA

Quasars, and their extreme variety "Blazars", are the brightest examples of Active Galactic Nuclei (AGN) which are powered by supermassive black holes that are voraciously feeding on material flowing into the center of the galaxy. In addition to their tremendous output of light across the electromagnetic spectrum, some AGN also have collimated outflows of highly energetic plasma which stream away from the center of the galaxy at apparent speeds greater than the speed of light. These highly relativistic jets have recently been shown to be associated with neutrino sources detected by IceCube as well as ultrahigh energy cosmic rays. The MOJAVE program uses NRAO’s Very Long Baseline Array to image and monitor these jets very near their origin in the supermassive black hole, accretion disk system. Our goal is to better understand the structure of these jets, how they are accelerated and collimated, as well as their magnetic and particle properties. This work involves disentangling the effects of relativistic motion, observed projected in two-dimensions with the true jet direction aligning close to our line of sight, to uncover the underlying properties of the jet itself. I will discuss some recent results of the MOJAVE program that are rooted in our decades long monitoring. Our very long *time* baselines and large sample statistics provide unique information that allow us to begin to separate intrinsic properties from apparent behavior that can often be transitory and confusing.

	Special Colloquium
Daniel Maschmann	SCHEDULED

University of Wyoming, USA

Compact star clusters are gravitationally bound systems that preserve the properties of the interstellar medium where they formed. This makes them ideal probes of past star-formation activities and the mass-assembly history of their host galaxy. With high resolution HST and JWST observations we can identify the star cluster population in nearby galaxies (5-23 Mpc) providing an alternative gateway to study stellar populations. I will present the publicly available PHANGS-HST star cluster catalog consisting of ~100,000 star clusters and compact stellar associations identified in 38 nearby galaxies. I will further discuss their observational and physical properties and include new JWST observations. With this statistical power we were able to find a direct link​ between the star cluster population properties and the host galaxy’s position relative to the main sequence of star-forming galaxies. This confirms that small-scale stellar populations provide a unique window into the global evolution of their hosts. Star cluster samples selected from HST observations are biased towards more evolved star clusters that are no longer deeply dust embedded. New JWST observations including the NIR and MIR at comparable resolution reveal that we are missing a significant amount of ongoing still dusty star formation which is a crucial aspect of the Baryonic Cycle. Furthermore, were we able to identify ongoing dust production in young massive star clusters with JWST that points towards mass-dependent feedback mechanisms. Finally, I would like to discuss future efforts to combine our knowledge of individual aspects of the Baryonic Cycle, including phase transition in the earliest star formation stages and further discuss star-formation triggering.