Ages, metallicities and structure of stellar clusters in the Magellanic Bridge

TL;DR

This study investigates the ages, metallicities, and structures of 33 stellar clusters in the Magellanic Bridge, revealing their origins, formation epochs, and chemical evolution linked to the Bridge's formation history.

Contribution

It provides the first comprehensive analysis of the structural parameters, ages, metallicities, and masses of Magellanic Bridge clusters, distinguishing between in-situ formation and stripped populations.

Findings

13 clusters likely stripped from the SMC with ages 0.5-6.8 Gyr and low metallicity

15 clusters probably formed in-situ within the last 200 Myr

Detected metallicity dips correspond to Stream and Bridge formation epochs

Abstract

The formation of the Magellanic Bridge during an encounter between the Magellanic Clouds $\sim$200 Myr ago would be imprinted in the chemical evolution and kinematics of its stellar population, with sites of active star formation. Since it contains hundreds of stellar clusters and associations, we combined deep photometry from VISCACHA and SMASH surveys to explore this topic, by deriving structural parameters, age, metallicity, distance and mass for 33 Bridge clusters with robust statistical tools. We identified a group of 13 clusters probably stripped from the Small Magellanic Cloud (0.5$-$6.8 Gyr, $\rm{[Fe/H]} < -0.6$ dex) and another 15 probably formed in-situ ($<$200 Myr, $\rm{[Fe/H]}\sim-0.4$ dex). Two metallicity dips were detected in the age-metallicity relation, coeval to the Stream and Bridge formation epochs. Cluster masses range from 500 to $\sim 10^4 M_\odot$, and a new estimate of $3-5\times 10^5 M_\odot$ is obtained for the Bridge stellar mass.