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. Show more
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https://doi.org/10.3929/ethz-b-000618850Publication status
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Journal / series
The Astrophysical JournalVolume
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Publisher
American Institute of PhysicsOrganisational unit
03613 - Lilly, Simon (emeritus) / Lilly, Simon (emeritus)
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