Ionizing Photon Production Efficiencies and Chemical Abundances at Cosmic Dawn Revealed by Ultradeep Rest-frame Optical Spectroscopy of JADES-GS-z14-0

JWST has discovered an early period of galaxy formation that was more vigorous than expected, which has challenged our understanding of the early Universe. In this work, we present the longest spectroscopic integration ever acquired by JWST/MIRI (t(obs) approximate to 51 hr). This spectrum covers the brightest rest-frame optical nebular emission lines for the luminous galaxy JADES-GS-z14-0 at z = 14.18. Most notably, we detect [O III]lambda lambda 4959, 5007 at approximate to 14 sigma and H alpha at approximate to 4 sigma with these ultradeep observations. These lines reveal that JADES-GS-z14-0 has low dust attenuation with a recent star formation rate of SFR approximate to 8 +/- 2M(circle dot) yr(-1), star formation rate surface density of Sigma(SFR) approximate to 20 +/- 5M(circle dot) yr(-1) kpc(-2), and ionizing photon production efficiency of xi(ion) approximate to 10(25.3 +/- 0.1) Hz erg(-1). Using standard strong-line diagnostics, we infer a gas-phase oxygen abundance of log(10)(O/H)+12 approximate to 7.5 +/- 0.2 (approximate to 6%Z(circle dot)), carbon-to-oxygen ratio of [C/O] approximate to -0.4 +/- 0.2, ionization parameter of log(10)(U)greater than or similar to-2.4 , and density of nH approximate to 690 +/- 200 cm(-3). Using detailed photoionization modeling, we instead derive log(10)(O/H)+12 approximate to 8.5(-0.4)(+0.4) (approximate to 60%Z(circle dot)), log(10)(U)approximate to-1.4(-0.4)(+0.3) , and n(H)approximate to 540(-320)(+520)cm(-3) . The inferred properties of JADES-GS-z14-0 are similar to those measured for similarly luminous galaxies at z > 10 with previous MIRI/Spectroscopy, such as GHZ2/GLASSz12, GN-z11, and MACS0647-JD1. These results suggest extreme ionization conditions and rapid metal enrichment less than 300 Myr after the Big Bang. Existing simulations are unable to reproduce the empirical and inferred properties of JADES-GS-z14-0. This work demonstrates an important step toward understanding the formation of the first stars and heavy elements in the Universe. Future work will focus on the detection of the rest-frame optical continuum and its interpretation for the stellar population properties of JADES-GS-z14-0.