Stellar Populations in the Outskirts of the Small Magellanic Cloud: No Outer Edge Yet

TL;DR

This study finds that the Small Magellanic Cloud's stellar disk extends at least 6.5 kpc without truncation, indicating it is larger than previously believed and dominated by disk stars over a halo.

Contribution

It provides new evidence that the SMC's stellar disk extends beyond 6.5 kpc without truncation, challenging prior assumptions about its size and structure.

Findings

SMC contains intermediate-age and old stars at 6.5 kpc from center

Surface brightness profile follows exponential law out to 6.5 kpc

No evidence of a stellar halo or truncation at observed radii

Abstract

We report the detection of intermediate-age and old stars belonging to the SMC at 6.5 kpc from the SMC center in the southern direction. We show, from the analysis of three high quality 34\arcmin $\times$ 33\arcmin CMDs, that the age composition of the stellar population is similar at galactocentric distances of $\thicksim$4.7 kpc, $\thicksim$5.6 kpc, and $\thicksim$6.5 kpc. The surface brightness profile of the SMC follows an exponential law, with no evidence of truncation, all the way out to 6.5 kpc. These results, taken together, suggest that the SMC `disk' population is dominating over a possible old Milky Way-like stellar halo, and that the SMC may be significantly larger than previously thought.