Abstract

The physical processes driving the evolution of galaxies across the stellar mass vs. star formation rate plane remain elusive. Through decades of multi-wavelength surveys, we have made tremendous progress in characterising the phenomenological properties of galaxies across redshifts. For instance, it is well established that the local galaxy population is mainly bimodal, with star-forming galaxies on one side and passive systems on the other; that galaxies at earlier epochs were forming stars at higher rates than what is observed today, and that passive and active galaxies show clear differences in their stellar structure. However, understanding the physics behind these relations is challenging, partly because of the difficulty of discriminating between simple correlations and physical causation. An additional level of complication comes from the fact that every physical process invoked to transform a star-forming galaxy into a passive, feature-less one requires at least a few billion years, a time during which even isolated star-forming systems have changed (e.g., grown) significantly. This means that – for example – today’s rotating, star-forming disks cannot be naively assumed to be the progenitors of local passive, dispersion-supported systems. Thus, simply comparing galaxies of different types at fixed redshift and/or at fixed stellar mass is unlikely to provide us with a realistic view of the transformation that they have experienced during their lives. Only by identifying the progenitors of different galaxy populations as a function of time will it be possible to reveal the origin of the heterogeneous population of galaxies that we observe today. This 5-day workshop sponsored by the ARC Centre of Excellence for All Sky Astrophysics in 3D (ASTRO 3D) and the International Centre for Radio Astronomy Research (ICRAR) will focus on 4 key themes (under the general topic of star formation of galaxies across cosmic age), with the aim of summarizing the state of the field, identifying current challenges and discussing ways forward to make significant progress over the life-time of the ASTRO 3D Centre of Excellence.