39) Stellar Populations of Nuclear Discs in Barred Galaxies of the TIMER Survey

Abstract: The central molecular zone of the Milky Way is not a unique structure. Similar components are frequently observed in the centres of other galaxies and typically denoted nuclear rings/discs. In this study, we constrain the formation and evolution of these central structures in extragalactic galaxies by deriving mean stellar ages, metallicities and [α/Fe] abundances. To this end, we use observations of unprecedented spatial resolution, obtained with the MUSE integral-field spectrograph for a sample of 21 Milky Way-type galaxies in the local Universe. All nuclear discs in the sample are clearly distinguished based on their stellar population properties. As expected in the picture of bar-driven secular evolution, nuclear discs are younger, more metal-rich, and show lower [α/Fe] enhancements, as compared to their immediate surroundings. Moreover, nuclear discs exhibit well-defined radial gradients, with ages and metallicities decreasing, and [α/Fe] abundances increasing with radius out to the nuclear ring. Often, these gradients show no breaks from the edge of the nuclear disc until the centre, suggesting that these structures extend to the very centres of the galaxies. The results of an accompanying kinematic study characterise nuclear discs as kinematically distinct, rapidly rotating discs with low velocity dispersion, thus again supporting the picture of a bar-driven formation. In addition, we do not find evidence for the presence of large classical bulges in the centres of these galaxies. This chemo-dynamical characterisation of extragalactic nuclear discs provides a crucial benchmark for comparison with the central molecular zone of the Milky Way.

Bio: Final-year PhD student at the European Southern Observatory in Garching, working on secular evolution in disc galaxies