We present tentative evidence for the existence of a dissolved star cluster at [ \mathrm { Fe } / \mathrm { H } ] = -2.7 in the Sextans dwarf spheroidal galaxy .
We use the technique of chemical tagging to identify stars that are highly clustered in a multi-dimensional chemical abundance space ( \mathcal { C } -space ) .
In a sample of six stars , three , possibly four , stars are identified as potential cluster stars .
The initial stellar mass of the parent cluster is estimated from two independent observations to M _ { *, \mathrm { init } } = 1.9 ^ { +1.5 } _ { -0.9 } ~ { } ( 1.6 ^ { +1.2 } _ { -0.8 } ) \times 10 ^ { 5 } ~ { } % \mathcal { M _ { \odot } } , assuming a Salpeter ( Kroupa ) initial mass function ( IMF ) .
If corroborated by follow-up spectroscopy , this star cluster is the most metal-poor system identified to date .
Chemical signatures of remnant clusters in dwarf galaxies like Sextans provide us with a very powerful probe to the high-redshift Universe .
From available observational data , we argue that the average star cluster mass in the majority of the newly discovered ultra-faint dwarf galaxies was notably lower than it is in the Galaxy today and possibly lower than in the more luminous , classical dwarf spheroidal galaxies .
Furthermore , the mean cumulative metallicity function of the dwarf spheroidals falls below that of the ultra-faints , which increases with increasing metallicity as predicted from our stochastic chemical evolution model .
These two findings , together with a possible difference in the \langle [ \mathrm { Mg } / \mathrm { Fe } ] \rangle ratio suggest that the ultra-faint dwarf galaxy population , or a significant fraction thereof , and the dwarf spheroidal population , were formed in different environments and would thus be distinct in origin .