Amongst the most stringent limitations in astronomy and cosmology are the very large uncertainties on galaxy masses and sizes. Yet, this topic is undergoing a revolution due to increasing knowledge of 6D space-velocity data for galaxies in the Local Group. This is driven by Gaia and numerous accompanying surveys that provide an accurate Milky Way rotation curve, detailed orbits of the nearby dwarf galaxies, and first estimates of the motions of dwarf irregulars and in the M31 system. This IAU Symposium has a very focused goal: Determining the mass of galaxies from dwarfs to giant spirals. However, it addresses a very broad range of astronomical fields (from studies of variable stars for estimating distances to dynamical modeling), of wave-lengths to be investigated (from radio and optical for estimating the HI gas and stellar content and their motions, to X-rays for estimating the warm and hot ionized gas), and has major implications for a fundamental question (from the distribution and nature of dark matter to alternative models). Measuring galaxy masses at different scales in the Local Group impacts a broad range of astronomy, from stars, star clusters, to the Milky Way, distant galaxies, and Cosmology.

Telegrafenberg, Potsdam, Germany

The goal of this meeting is to collectively review the advancement in our understanding of solar magnetic fields starting from the fundamental structure size of magnetic fields to global properties of active regions and the Sun as a whole including the heliosphere. This meeting is expected to

• provide a platform to present the latest results from the various research infrastructures available within SOLARNET 2 and beyond, be it ground-based telescopes or space missions;
• contribute to a better understanding of solar features by bringing together high-resolution and synoptic observations, simulations, analytical theory and instrumentation; and
• to discuss the next steps in advancing instrumentation, methods, and theory. To arrive at a cohesive picture of the magnetic Sun, the meeting will be organized according to specific scientific topics and questions, fostering discussions among observers, instrument builders, hosts of data holdings, and theoreticians.

Telegrafenberg, Potsdam, Germany