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

August 2023 • 2023ApJ...953...53S

Authors • Sun, Fengwu • Egami, Eiichi • Pirzkal, Nor • Rieke, Marcia • Baum, Stefi • Boyer, Martha • Boyett, Kristan • Bunker, Andrew J. • Cameron, Alex J. • Curti, Mirko • Eisenstein, Daniel J. • Gennaro, Mario • Greene, Thomas P. • Jaffe, Daniel • Kelly, Doug • Koekemoer, Anton M. • Kumari, Nimisha • Maiolino, Roberto • Maseda, Michael • Perna, Michele • Rest, Armin • Robertson, Brant E. • Schlawin, Everett • Smit, Renske • Stansberry, John • Sunnquist, Ben • Tacchella, Sandro • Williams, Christina C. • Willmer, Christopher N. A.

Abstract • 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 ${66}_{-44}^{+128}$ % of z = 6.0-6.6 galaxies in the survey volume with stellar masses greater than 5 × 10⁸ M _☉, 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.

Links

• PREPRINT http://arxiv.org/abs/2209.03374
• NED https://ned.ipac.caltech.edu/uri/NED::InRefcode/2023ApJ...953...53S
• ELECTR https://doi.org/10.3847/1538-4357/acd53c
• SIMBAD https://simbad.u-strasbg.fr/simbad/sim-ref?querymethod=bib&simbo=on&submit=submit+bibcode&bibcode=2023ApJ...953...53S
• PDF https://iopscience.iop.org/article/10.3847/1538-4357/acd53c/pdf
• DATA https://archive.stsci.edu/mastbibref.php?bibcode=2023ApJ...953...53S
• DATA https://doi.org/10.17909/f8p1-e696