An Ultra-Faint Galaxy Candidate Discovered in Early Data from the Magellanic Satellites Survey

TL;DR

A new ultra-faint galaxy candidate, MagLiteS J0644-5953, was discovered in early data from the Magellanic Satellites Survey, showing properties consistent with ultra-faint galaxies and likely associated with the Large Magellanic Cloud.

Contribution

First detection of an ultra-faint galaxy candidate in MagLiteS data, providing insights into satellite systems of the LMC and galaxy formation.

Findings

Discovered a low surface brightness, old, metal-poor stellar system at 45 kpc.

The system's size and luminosity match known ultra-faint galaxies.

Likely gravitationally bound to the Large Magellanic Cloud.

Abstract

We report a new ultra-faint stellar system found in Dark Energy Camera data from the first observing run of the Magellanic Satellites Survey (MagLiteS). MagLiteS J0644-5953 (Pictor II or Pic II) is a low surface brightness ({\mu} = 28.5 mag arcsec$^{-2}$ within its half-light radius) resolved overdensity of old and metal-poor stars located at a heliocentric distance of 45 kpc. The physical size (r$_{1/2}$ = 46 pc) and low luminosity (Mv = -3.2 mag) of this satellite are consistent with the locus of spectroscopically confirmed ultra-faint galaxies. MagLiteS J0644-5953 (Pic II) is located 11.3 kpc from the Large Magellanic Cloud (LMC), and comparisons with simulation results in the literature suggest that this satellite was likely accreted with the LMC. The close proximity of MagLiteS J0644-5953 (Pic II) to the LMC also makes it the most likely ultra-faint galaxy candidate to still be gravitationally bound to the LMC.