The Co-Evolution of Central Gas Rings and Nuclear Stellar Discs

Nuclear stellar discs have long stayed hidden within the more ambiguous family of (pseudo-)bulges. Only recently they have gotten more attention thanks to high quality observations with the MUSE instrument and they might be much more numerous than we previously thought. At the same time, central gas rings or central molecular zones have been known and investigated for a long time but observational evidence for a direct connection to the stellar component has been scarce. In the project presented in this talk, we use MUSE observations in combination with JWST, HST and ALMA from the PHANGS survey to show that the existence of central gas rings and nuclear stellar discs is directly correlated. The near-perfect match in size and the formation of young star clusters in the ring demonstrate that central gas rings are the outer edge within which nuclear stellar discs are formed. Negative age gradients suggest a co-evolution with an inside-out growing scenario. Only the powerful synergy between these observing facilities made it possible to showcase such clear evidence for this connection.