The Magellanic Inter-Cloud Project (MAGIC) II: Slicing up the Bridge

TL;DR

This study investigates the stellar populations in the Magellanic Bridge using optical observations, revealing distinct spatial distributions of stars of different ages and supporting the tidal stripping origin of the gas and stars.

Contribution

It provides new observational evidence on the ages and distributions of stars in the Magellanic Bridge, clarifying their origins and the structure of the stellar populations.

Findings

Young stars correlate with HI gas, suggesting recent stripping or in-situ formation.

Intermediate-age stars are mainly in the bridge, likely tidally stripped from the SMC.

Old stars extend up to 8 Kpc from the SMC, indicating a large stellar halo.

Abstract

The origin of the gas in between the Magellanic Clouds (MCs), known as the Magellanic Bridge (MB), has always been the subject of controversy. To shed light into this, we present the results from the MAGIC II project aimed at probing the stellar populations in ten large fields located perpendicular to the main ridge-line of HI in the Inter-Cloud region. We secured these observations of the stellar populations in between the MCs using the WFI camera on the 2.2 m telescope in La Silla. Using colour-magnitude diagrams (CMDs), we trace stellar populations across the Inter-Cloud region. In good agreement with MAGIC I, we find significant intermediate-age stars in the Inter-Cloud region as well as young stars of a similar age to the last pericentre passage in between the MCs (~200 Myr ago). We show here that the young, intermediate-age and old stars have distinct spatial distributions. The young stars correlate well with the HI gas suggesting that they were either recently stripped from the SMC or formed in-situ. The bulk of intermediate-age stars are located mainly in the bridge region where the HI column density is higher, but they are more spread out than the young stars. They have very similar properties to stars located ~2 Kpc from the SMC centre, suggesting that they were tidally stripped from this region. Finally, the old stars extend to some 8 Kpc from the SMC supporting the idea that all galaxies have a large extended metal poor stellar halo.