The AURORA Survey: Ionizing Photon Production Efficiency with Minimal Nebular Dust Attenuation Systematics

Abstract We present ionizing photon production efficiencies ( ξ ion ) for 63 z = 1.5–6.9 star-forming galaxies using precise nebular dust attenuation corrections from the JWST Assembly of Ultradeep Rest-optical Observations Revealing Astrophysics (AURORA) survey. A subset of objects within AURORA have individually determined nebular dust attenuation curves, which vary significantly in shape and normalization, resulting in reduced systematic uncertainty when constraining the total attenuation of H α luminosity, and thus the intrinsic ionizing output within our sample. We find evidence for positive correlations between ξ ion and redshift, equivalent width of [O iii ] λ 5007, and O32 = [O iii ] λ 5007/[O ii ] λλ 3726, 3729, and negative correlations between ξ ion and stellar attenuation, UV luminosity ( L UV ), stellar mass, and direct-method metallicity. We test alternate dust prescriptions within this sample, and find that the total attenuation is lower when using the commonly assumed Galactic extinction curve or when assuming that stellar attenuation is equal to nebular attenuation. We also find that assuming either of these alternate dust prescriptions can change the slope of the relationships between ξ ion and galaxy property, notably inducing a flat trend between ξ ion and L UV within AURORA. While the novel nebular dust curves derived from AURORA spectroscopy reveal obscured ionizing photon production within star-forming galaxies at these redshifts, a more complete understanding of stellar attenuation is required to fully reduce the dust systematics on ξ ion for inclusion in reionization models.