Abstract

The epoch in which galaxies transition from merger-driven to secular-driven evolution is tightly related to the epoch of disc settling. While the timing of this transition is of fundamental importance to theories of galaxy formation and evolution, it is still poorly constrained. Once discs settle, they are able to form stellar bars, which cause gas inflow to the central regions of galaxies. This gas inflow builds, in a short time-scale, rotationally-supported central structures, called nuclear discs. Thus, timing the formation of nuclear discs allows us to time the bar formation epoch and the disc settling. However, such a task is not trivial, since the observed light combines overlapping information from both the old main disc and the younger structure. In this work, we present a novel methodology for disentangling the light of the nuclear structure from the main disc, deriving isolated star formation histories, which enable us to determine the moment of bar formation. We applied this methodology to four nearby Milky Way-like galaxies observed with MUSE@VLT, successfully estimating the bar formation epoch. This is the first methodology to date focused on timing bar formation that can be broadly applied to galaxies with IFS data. We plan to use it for the TIMER-MUSE survey in the future, shedding light on the disc-settling epoch for a larger data set.

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