Abstract
The origin of the gas in between the Magellanic Clouds (MCs), known as the Magellanic Bridge, has always been the subject of controversy. To shed light into this, we present the results from the MAGellanic Inter-Cloud II (MAGIC II) project aimed at probing the stellar populations in 10 large fields located perpendicular to the main ridge-line of H i in the Inter-Cloud region. We secured these observations of the stellar populations in between the MCs using the WFI (Wide Field Imager) camera on the 2.2 m telescope in La Silla. Using colour–magnitude diagrams, 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 H i gas suggesting that they were either recently stripped from the Small Magellanic Cloud (SMC) or formed in situ. The bulk of intermediate-age stars are located mainly in the Bridge region where the H i 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.
Highlights
A key challenge in modern astrophysics is to understand how galaxies form and evolve
We focus on the stellar content of 10 fields strategically located perpendicular to the MAGIC I field where intermediate-age population was found represented by a purple triangle in Fig. 1
It is striking to note that the bulk of intermediate-age and young(er) stars increase as we move closer to field B2 of MAGIC I located in the vicinity of the Magellanic Bridge (MB) main ridge-line
Summary
A key challenge in modern astrophysics is to understand how galaxies form and evolve. The Magellanic Clouds (MCs) constitute a unique opportunity to study a gas-rich interacting system close-up and to investigate faint outskirts of galaxies Their close proximity (∼50–70 kpc away) enables us to resolve their individual stars, which allows us to directly probe fainter surface brightness levels placing constraints on ages and metallicities without the need to use stellar population synthesis (e.g. Noel et al 2013b). Due to their mutual association over the past few Gyr (as determined from their proper motions: Kallivayalil, van der Marel & Alcock 2006; Besla et al 2007, 2012; Piatek, Pryor & Olszewski 2008; Costa et al 2011; Kallivayalil et al 2013; van der Marel & Kallivayalil 2014; Cioni et al 2014; and numerical simulations: Bekki 2011; Diaz & Bekki 2012; Besla, Hernquist & Loeb 2013). The WFI consists of eight chips covering a field of view of approximately 30 arcmin × 30 arcmin and has a pixel scale of 0.24 arcsec pixel−1
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