One of the key questions in understanding \deleted the \added galaxy formation and evolution \deleted of galaxies is how starbursts affect the assembly of stellar populations in galaxies over time .
We define a burst indicator ( \eta ) , which compares a galaxy ’ s star formation rates on short ( \sim 10 Myr ) and long ( \sim 100 Myr ) timescales .
To estimate \eta , we apply the detailed \deleted temporal luminosity response \added time-luminosity relationship \deleted of \added for H \alpha and near-ultraviolet emission to simulated star formation histories ( SFHs ) from Semi-Analytic Models and the Mufasa hydrodynamical cosmological simulations . \deleted We find that t \added The average \deleted value of \eta is not \deleted itself a good indicator of star formation stochasticity ( burstiness ) ; indeed \added , we show that this average should be close to zero unless the \added galaxy population \deleted being studied has an average SFH \deleted which \added that is rising or falling rapidly .
Instead , \deleted analyzing the width of the \added \eta distribution \deleted of \eta for ensembles of galaxies allows us to characterize \added s the \deleted level of burstiness \deleted in \added of a galaxy population ’ s recent star formation \deleted history .
We find this width to be robust to variations in stellar initial mass function ( IMF ) and metallicity .
We apply realistic noise and selection effects to the models to generate mock HST and JWST galaxy catalogs and compare these catalogs with 3D-HST observations of 956 galaxies at 0.65 < z < 1.5 detected in H \alpha .
Measurements of \eta are unaffected by dust measurement errors under the assumption that E ( B - V ) _ { \mathrm { stars } } = 0.44 E ( B - V ) _ { \mathrm { gas } } ( i.e . Q _ { \mathrm { sg } } = 0.44 ) .
However , setting Q _ { \mathrm { sg } } = 0.8 ^ { +0.1 } _ { -0.2 } removes an unexpected dependence of the average value of \eta upon dust attenuation and stellar mass in the 3D-HST sample while also resolving disagreements in the distribution of star formation rates .
However , even varying the dust law can not resolve all discrepancies between the simulated and the observed galaxies .