Magellanic System Stars Identified in SMACS J0723.3-7327 James Webb Space Telescope Early Release Observations Images

TL;DR

This study uses JWST images to identify distant stars likely associated with the Magellanic system, revealing their distribution and properties, and providing insights into the stellar density of the LMC outskirts.

Contribution

First identification of Magellanic system stars in JWST early release images, analyzing their distribution, properties, and implications for the LMC outskirts.

Findings

71 distant stars identified in JWST images.

Stars are likely associated with the Magellanic system.

Stellar density in the LMC outskirts estimated at 740 stars per kpc³.

Abstract

We identify 71 distant stars in JWST/NIRCam ERO images of the field of galaxy cluster SMACS J0723.3-7327 (SMACS 0723). Given the relatively small ($\sim$$10^{\circ}$) angular separation between SMACS 0723 and the Large Magellanic Cloud, it is likely that these stars are associated with the LMC outskirts or Leading Arm. This is further bolstered by a spectral energy distribution analysis, which suggests an excess of stars at a physical distance of $40-100$ kpc, consistent with being associated with or located behind the Magellanic system. In particular, we find that the overall surface density of stars brighter than 27.0 mag in the field of SMACS 0723 is $\sim$2.3 times that of stars in a blank field with similar galactic latitude (the North Ecliptic Pole Time Domain Field), and that the density of stars in the SMACS 0723 field with SED-derived distances consistent with the Magellanic system is $\sim$6.1 times larger than that of the blank field. The candidate stars at these distances are consistent with a stellar population at the same distance modulus with [Fe/H] $= -1.0$ and an age of $\sim$$5.0$ Gyr. On the assumption that all of the 71 stars are associated with the LMC, then the stellar density of the LMC at the location of the SMACS 0723 field is $\sim$$740$ stars kpc$^{-3}$, which helps trace the density of stars in the LMC outskirts.