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.