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We explore the radial variation of star formation histories in dwarf galaxiessimulated with Feedback In Realistic Environments (FIRE) physics. The samplecontains 9 low-mass field dwarfs with M_ star = 10^5 - 10^7 M_sun from previousFIRE results, and a new suite of 17 higher mass field dwarfs with M_star = 10^7- 10^9 M_sun introduced here. We find that age gradients are common in ourdwarfs, with older stars dominant at large radii. The strength of the gradientcorrelates with overall galaxy age such that earlier star formation produces amore pronounced gradient. The relation between formation time and strength ofthe gradient is driven by both mergers and star-formation feedback. Mergers canboth steepen and flatten the age gradient depending on the timing of the mergerand star formation history of the merging galaxy. In galaxies withoutsignificant mergers, early feedback pushes stars to the outskirts at earlytimes. Interestingly, among galaxies without mergers, those with large darkmatter cores have flatter age gradients because these galaxies have morelate-time feedback. If real galaxies have age gradients as we predict, stellarpopulation studies that rely on sampling a limited fraction of a galaxy cangive a biased view of its global star formation history. We show that centralfields can be biased young by a few Gyrs while outer fields are biased old.Fields positioned near the 2D half-light radius will provide the least biasedmeasure of a dwarf galaxy's global star formation history.

A Predicted Correlation Between Age Gradient and Star Formation History in FIRE Dwarf Galaxies