SISSI: Supernovae in a stratified, shearing interstellar medium

Context . The age of the Local Bubble (LB) constrains the timescale on which the interstellar medium in the solar neighborhood evolves. Previous estimates placed the age of the LB at ≳ 14 Myr, and attributed its expansion to ∼ 15−20 supernovae (SNe), yet a companion paper suggests this age may be overestimated. Aims . We place new constraints on the age of the LB and reevaluate the question of whether its expansion triggered or suppressed local star formation. Methods . We reconstructed the LB’s geometry and momentum using publicly available 3D dust maps and compared them to the high-quality sample of simulated SN remnants in the SISSI project. Independent constraints on the star formation history and SN rate were obtained from a Gaia DR3-based census of nearby star clusters. Results . We find that ∼ 7−59 SNe over ∼ 5.8 Myr to ∼ 2.8 Myr, respectively, are required to explain both the LB’s momentum and size and confirm that such a high SN rate can be sustained by local star clusters. Conclusions . Our analysis yields a substantially smaller LB age than previous estimates, requiring a correspondingly larger number of SNe, driving its expansion. We show that this result is in tension with the conclusion that the LB is powered solely by SNe from the Scorpius-Centaurus OB association, which ceased star formation around the time the LB formed. If our estimates are correct, it follows that the majority of star formation in the solar neighborhood happened before the formation of the LB and was not triggered by its expansion. Instead, the SNe that powered the LB appear to overall have quenched the ongoing star formation process. This does not rule out that star formation in the clouds, located near its current edge, could have been affected by the LB expansion.