Investigating the Intrinsic Correlations between Hα Equivalent Width and Stellar Mass from z ~ 0.4 to 2: Implications on Episodic Star Formation Histories

In this talk, I present a new methodology of modeling intrinsic Hα Equivalent Width (EW) distributions constrained by observations drawn from narrowband surveys (LAGER, HiZELS, and DAWN) between z ~ 0.4 and 2.2, investigate its intrinsic, selection-corrected correlation with stellar mass, and discuss the implications it has on star-formation histories. The Hα EW is an observational proxy of the specific star formation rate (sSFR) and a tracer of episodic star-formation activity. Past studies find Hα EW anti-correlates with stellar mass and increases with redshift; however, selection effects may bias the underlying results. We find EW and stellar mass intrinsically correlate within ~ 5σ–7σ significance from null. The correlation steepens with increasing redshift suggesting higher EW emitters at low stellar masses. Low-mass galaxies are also found to have higher fractions of sSFR outliers compared to high-mass galaxies indicative of bursty SF activity. The intrinsic correlation between EW and stellar mass is found to reproduce the EW distribution, Hα luminosity function, and stellar mass function at all redshifts, which suggests it is shaped by physical processes associated with star formation rather than a byproduct of selection effects.