A spectroscopic analysis of the ionizing photon production efficiency in JADES and CEERS: implications for the ionizing photon budget

• Published in: arXiv.org
• Main Authors: Pahl, Anthony J, Topping, Michael W, Shapley, Alice, Sanders, Ryan, Reddy, Naveen A, Clarke, Leonardo, Kehoe, Emily, Bento, Trinity, Brammer, Gabe
• Format: Paper
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 03.07.2024
• Subjects: Attenuation; Continuum radiation; Correlation; Dust; Energy distribution; Ionization; James Webb Space Telescope; Median (statistics); Metallicity; Photons; Samples (statistical); Stellar mass
• ISSN: 2331-8422

We have used a combined sample of JADES and CEERS objects in order to constrain ionizing photon production efficiency (\(\xi_{\rm ion}\)) from JWST/NIRSpec and JWST/NIRCam data. We examine 163 objects at 1.06 < z < 6.71 with significant (3\(\sigma\)) spectroscopic detections of H\(\alpha\) and H\(\beta\) in order to constrain intrinsic H\(\alpha\) luminosities corrected from nebular dust attenuation via Balmer decrements. We constrain dust-corrected UV luminosities from best-fit spectral-energy distribution modeling. We find a sample median log\(_{10}\)(\(\xi{\rm ion,0}\)/erg Hz\(^{-1}\)) = \(25.29^{+0.29}_{-0.37}\), assuming f\(_{\rm esc}\)=0 for the escape fraction of Lyman continuum emission. We find significant correlation between \(\xi_{\rm ion,0}\) and z, with 17 objects at z > 4.64 having median log\(_{10}\)(\(\xi_{\rm ion,0}\)/erg Hz\(^{-1}\)) = \(25.38^{+0.38}){-0.38}\), with those below having log\(_{10}\)(\(\xi_{\rm ion,0}\)/erg Hz\(^{-1}\)) = \(25.24^{+0.30}_{-0.33}\). We also find significant, positive correlations between \(\xi_{\rm ion,0}\) and LUV; W{\lambda}([O iii]); [O iii]{\lambda}5007/[O ii]{\lambda}{\lambda}3726, 3729; and inverse correlations with metallicity. In contrast with some previous results, we find no trends between \(\xi_{\rm ion,0}\) and stellar mass, stellar dust attenuation, or UV slope. Applying a multivariate fit to \(\xi_{\rm ion,0}\), z, and MUV to an empirically-motivated model of reionization, and folding in f\(_{\rm esc}\) estimates from direct observations of the Lyman continuum at z ~ 3 from the Keck Lyman Continuum Spectroscopic survey, we find that the number of ionizing photons entering the IGM causes reionization to end at z ~ 5 - 7.