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

Journal article

We present a sample of four emission-line galaxies at z = 6.11–6.35 that were serendipitously discovered using the commissioning data for the James Webb Space Telescope (JWST)/NIRCam wide-field slitless spectroscopy mode. One of them (at z = 6.11) has been reported previously, while the others are new discoveries. These sources are selected by the secure detections of both [O iii] λ5007 and Hα lines with other fainter lines, which were tentatively detected in some cases (e.g., [O ii] λ3727, [O iii] λ4959). In the [O iii]/Hβ–[N ii]/Hα Baldwin–Phillips–Terlevich diagram, these galaxies occupy the same parameter space as that of z ∼ 2 star-forming galaxies, indicating that they have been enriched rapidly to subsolar metallicities (∼0.4 Z⊙), similar to galaxies with comparable stellar masses at much lower redshifts. The detection of strong Hα lines suggests a higher ionizing photon production efficiency within galaxies in the early universe. We find brightening of the [O iii] λ5007 line-luminosity function (LF) from z = 3 to 6, and weak or no redshift evolution of the Hα line LF from z = 2 to 6. Both LFs are underpredicted at z ∼ 6 by a factor of ∼10 in certain cosmological simulations. This further indicates a global Lyα photon escape fraction of 7%–10% at z ∼ 6, which is slightly lower than previous estimates through the comparison of the UV-derived star formation rate density and Lyα luminosity density. Our sample recovers 66 +28 -44 % of z = 6.0–6.6 galaxies in the survey volume with stellar masses greater than 5 × 108M⊙, suggesting the ubiquity of strong Hα and [O iii] line emitters in the Epoch of Reionization, which will be further uncovered in the era of JWST

Authors: Sun, F; Egami, E; Pirzkal, N; Rieke, M; Baum, S

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Astronomical Society
• Journal: The Astrophysical Journal
• Volume: 953
• Issue: 1
• Pages: 53-53
• Publication date: 2023-08-01
• DOI: 10.3847/1538-4357/acd53c
• EISSN: 1538-4357
• ISSN: 0004-637X
• Language: English
• Keywords: Galaxy; Spectral line; Physics; Astrophysics; Astronomy; Emission spectrum; Spectroscopy; Luminosity; Line (geometry)