Segue 1 is the current best candidate for a “ first galaxy ” , a system which experienced only a single short burst of star formation and has since remained unchanged .
Here we present possible star formation scenarios which can explain its unique metallicity distribution .
While the majority of stars in all other ultra-faint dwarfs ( UFDs ) are within 0.5 dex of the mean [ Fe/H ] for the galaxy , 5 of the 7 stars in Segue 1 have a spread of \Delta [ Fe/H ] > 0.8 dex .
We show that this distribution of metallicities canot be explained by a gradual build-up of stars , but instead requires clustered star formation .
Chemical tagging allows the separate unresolved delta functions in abundance space to be associated with discrete events in space and time .
This provides an opportunity to put the enrichment events into a time sequence and unravel the history of the system .
We investigate two possible scenarios for the star formation history of Segue 1 using Fyris Alpha simulations of gas in a 10 ^ { 7 } M _ { \odot } dark matter halo .
The lack of stars with intermediate metallicities -3 < [ Fe/H ] < -2 can be explained either by a pause in star formation caused by supernova feedback , or by the spread of metallicities resulting from one or two supernovae in a low-mass dark matter halo .
Either possibility can reproduce the metallicity distribution function ( MDF ) , as well as the other observed elemental abundances .
The unusual MDF and the low luminosity of Segue 1 can be explained by it being a first galaxy that originated with M _ { vir } \sim 10 ^ { 7 } M _ { \odot } at z \sim 10 .