EIGER. II. First Spectroscopic Characterization of the Young Stars and Ionized Gas Associated with Strong Hβ and [O iii] Line Emission in Galaxies at z = 5–7 with JWST

Abstract

We present emission-line measurements and physical interpretations for a sample of 117 [O iii] emitting galaxies at z = 5.33–6.93, using the first deep JWST/NIRCam wide-field slitless spectroscopic observations. Our 9.7 hr integration is centered upon the z = 6.3 quasar J0100+2802—the first of six fields targeted by the EIGER survey—and covers λ = 3–4 μm. We detect 133 [O iii] doublets, but close pairs motivated by their small scale clustering excess. The galaxies are characterized by a UV luminosity M UV ∼ −19.6 (−17.7 to −22.3), stellar mass ∼108 (106.8−10.1) M ⊙, Hβ and [O iii]4960+5008 EWs ≈ 850 Å (up to 3000 Å), young ages, a highly excited interstellar medium, and low dust attenuations. These high EWs are very rare in the local universe, but we show they are ubiquitous at z ∼ 6 based on the measured number densities. The stacked spectrum reveals Hγ and [O iii]4364, which shows that the galaxies are typically dust- and metal-poor (E (B − V) = 0.1, 12 + log ( O / H ) = 7.4 ) with a high electron temperature (2 × 104 K) and a production efficiency of ionizing photons (ξ ion = 1025.3 Hz erg−1). We further show the existence of a strong mass–metallicity relation. The properties of the stars and gas in z ∼ 6 galaxies conspire to maximize the [O iii] output from galaxies, yielding an [O iii] luminosity density at z ≈ 6 that is significantly higher than that at z ≈ 2. Thus, [O iii] emission-line surveys with JWST prove a highly efficient method to trace the galaxy density in the Epoch of Reionization.

First Sample of Hα+[O iii]λ5007 Line Emitters at z > 6 Through JWST/NIRCam Slitless Spectroscopy: Physical Properties and Line-luminosity Functions

“…Our [O III] LF measurement is also higher than the z ∼ 8 estimate in De Barros et al (2019) by a factor of ∼2. From χ 2 statistics, these [O III] LF determinations at z ∼ 6.2 and ∼8 may be consistent with each other (p-value = 0.3; see also Matthee et al 2023 for most recent results).…”

EIGER. III. JWST/NIRCam Observations of the Ultraluminous High-redshift Quasar J0100+2802

“…Simultaneously, we obtain direct imaging observations in two short wavelengths filters, i.e., F115W and F200W (see Section 2.3). The observational setup as well as the data reduction process are described in detail Kashino et al (2023) and Matthee et al (2023). We will summarize the main steps briefly below.…”

JWST/NIRSpec Measurements of Extremely Low Metallicities in High Equivalent Width Lyα Emitters

“…Here, we target some of the highest-EW LAEs with JWST/NIRSpec in order to detect these rest-frame optical emission lines. The observed strengths and ratios of emission lines can be used to determine numerous physical quantities in these galaxies such as their star formation rates (SFRs), gasphase metallic abundances, and ionization properties, as has already been shown with cycle 1 data from JWST (e.g., Matthee et al 2023;Roberts-Borsani et al 2023;Schaerer et al 2022;Taylor et al 2022;Wang et al 2022;Brinchmann 2023;Cameron et al 2023;Fujimoto et al 2023;Nakajima et al 2023;Sanders et al 2023a). In this first paper, we focus on the ratio of [O III] λ5007 to Hβ λ4861, with supplementary information provided by the ratio of [N II] λ6584 to Hα λ6563.…”