A Deeper Look at the New Milky Way Satellites: Sagittarius II, Reticulum II, Phoenix II, and Tucana III
Bur\c{c}in Mutlu-Pakdil, David J. Sand, Jeffrey L. Carlin and, Kristine Spekkens, Nelson Caldwell, Denija Crnojevi\'c, Allison K., Hughes, Beth Willman, Dennis Zaritsky

TL;DR
This study provides deep photometric analysis of four faint Milky Way satellites, revealing their ages, metallicities, structural properties, and possible classifications, with implications for understanding their origins and evolution.
Contribution
It offers the first detailed deep photometry of these satellites, clarifies their nature and classifications, and investigates signs of tidal disturbance and gas content.
Findings
Sgr II is likely a globular cluster, the most extended in its luminosity range.
Reticulum II is a highly elongated ultra-faint dwarf galaxy.
Tucana III is confirmed as a dwarf galaxy associated with a stellar stream.
Abstract
We present deep Magellan/Megacam stellar photometry of four recently discovered faint Milky Way satellites: Sagittarius II (Sgr II), Reticulum II (Ret II), Phoenix II (Phe II), and Tucana III (Tuc III). Our photometry reaches ~2-3 magnitudes deeper than the discovery data, allowing us to revisit the properties of these new objects (e.g., distance, structural properties, luminosity measurements, and signs of tidal disturbance). The satellite color-magnitude diagrams show that they are all old (~13.5 Gyr) and metal-poor ([Fe/H]). Sgr II is particularly interesting as it sits in an intermediate position between the loci of dwarf galaxies and globular clusters in the size-luminosity plane. The ensemble of its structural parameters is more consistent with a globular cluster classification, indicating that Sgr II is the most extended globular cluster in its luminosity range. The…
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