Discovery of two neighboring satellites in the Carina constellation with MagLiteS

TL;DR

This paper reports the discovery of two ultra-faint, neighboring satellite galaxies near the Large Magellanic Cloud, using MagLiteS data, and analyzes their properties and potential association with the Magellanic system.

Contribution

It presents the first identification and detailed characterization of Carina II and III satellites, including their stellar populations, distances, and structural differences.

Findings

Carina II is a dwarf galaxy at ~36 kpc with M_V~-4.5 and a 90 pc radius.

Carina III is a more elongated, fainter satellite at ~28 kpc, with M_V~-2.4 and a 30 pc radius.

Both satellites are part of an anisotropic satellite cloud near the Magellanic Clouds.

Abstract

We report the discovery of two ultra-faint satellites in the vicinity of the Large Magellanic Cloud (LMC) in data from the Magellanic Satellites Survey (MagLiteS). Situated 18$^{\circ}$ ($\sim 20$ kpc) from the LMC and separated from each other by only $18^\prime$, Carina~II and III form an intriguing pair. By simultaneously modeling the spatial and the color-magnitude stellar distributions, we find that both Carina~II and Carina~III are likely dwarf galaxies, although this is less clear for Carina~III. There are in fact several obvious differences between the two satellites. While both are well described by an old and metal poor population, Carina~II is located at $\sim 36$ kpc from the Sun, with $M_V\sim-4.5$ and $r_h\sim 90$ pc, and it is further confirmed by the discovery of 3 RR Lyrae at the right distance. In contrast, Carina~III is much more elongated, measured to be fainter ($M_V\sim-2.4$), significantly more compact ($r_h\sim30$ pc), and closer to the Sun, at $\sim 28$ kpc, placing it only 8 kpc away from Car~II. Together with several other systems detected by the Dark Energy Camera, Carina~II and III form a strongly anisotropic cloud of satellites in the vicinity of the Magellanic Clouds.