Scylla V: Constraints on the spatial and temporal distribution of bursts and the interaction history of the Magellanic Clouds from their resolved stellar populations

TL;DR

This study uses deep Hubble data to analyze star formation histories in the Magellanic Clouds, identifying burst events and their correlation with galaxy interactions, revealing insights into their interaction history and stellar population distribution.

Contribution

It introduces a standardized framework for burst identification in the Magellanic Clouds and links star formation bursts to their dynamical interaction history.

Findings

Identified multiple global and local star formation bursts in SMC and LMC.

Found that bursts correlate with interaction events predicted by dynamical models.

Discovered similarities in stellar populations between SMC Wing/Bridge and LMC southwestern regions.

Abstract

We measure the star formation histories (SFHs) from the Scylla survey in approximately 98,000 pc^2 and 75,000 pc^2 of the SMC and LMC, respectively, using deep Hubble Space Telescope imaging (80% complete to more than 1 mag below the ancient main-sequence turnoff, 25.1 and 26.0 mag in F475W and F814W) from 74 pointings. We group the fields into eight sub-regions in the SMC and seven in the LMC. We use the birth rate parameter to identify bursts of star formation and measure their properties in each sub-region. Our methodology provides a standardized framework for burst identification and reveals both broad and fine burst characteristics. We identify global and local bursts, defined as those occurring in at least half or less than half of a galaxy's sub-regions, respectively. In the SMC we find two global (about 5 and 1.5 Gyr ago) and one local burst (about 3 Gyr ago). In the LMC we find one global burst (about 3 Gyr ago). Comparing these findings with dynamical models of the LMC and SMC orbital histories, we find that when models predict a shared dynamical trigger for bursts across both galaxies, the burst begins earlier in the SMC with a greater enhancement in star formation rate than in the LMC. Finally, using age-metallicity relations (AMRs) and cumulative SFHs, we report that the Wing/Bridge region in the SMC resembles the southwestern LMC both chemically and in stellar mass assembly over the last about 7 Gyr, possibly due to stellar material stripped from the LMC during their last interaction.