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 \sim 3 magnitudes deeper than the discovery data , providing improved determinations of 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 ( \sim 13.5 Gyr ) and metal-poor ( [ Fe/H ] \lesssim - 2.2 ) .
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 other three satellites land directly on the locus defined by Milky Way ultra-faint dwarf galaxies of similar luminosity .
Ret II is the most elongated nearby dwarf galaxy currently known for its luminosity range .
Our structural parameters for Phe II and Tuc III suggest that they are both dwarf galaxies .
Tuc III is known to be associated with a stellar stream , which is clearly visible in our matched-filter stellar density map .
The other satellites do not show any clear evidence of tidal stripping in the form of extensions or distortions .
Finally , we also use archival HI data to place limits on the gas content of each object .