The JWST Emission Line Survey (JELS): A narrow-band determination of the Hα Luminosity Function and Cosmic Star Formation into the Epoch of Reionization
Abstract
The recent star-formation activity in galaxies can be optimally traced by the Hα emission line, with the resulting Hα luminosity function (LF) at a given epoch providing a reliable probe of cosmic star formation. We present the first narrow-band determined Hα LF into the Epoch of Reionization (EoR) at z∼6.1, using 39 Hα emitters selected from the JWST Emission Line Survey (JELS). The observed and dust-corrected LFs are broadly consistent with recent slitless spectroscopic measurements but show notable discrepancies with predictions from cosmological simulations, likely reflecting differences in emission-line and dust modelling. Fits combining multiple LF datasets help constrain the high-redshift faint-end slope of the Hα LF (−1.79<αHα<−1.62), but there remains uncertainty in its evolution with redshift. Integrating the JELS dust-corrected Hα LFs yields a star-formation rate density of log10(ρSFRHα / M⊙ yr−1 Mpc−3)=−1.93 +0.14−0.12 or −2.00 +0.16−0.10, assuming a continuum-to-line extinction ratios ηdust=Acont(6563 mathringA)/AHα=1 and 0.44, respectively. Both measurements are consistent within uncertainties with previous results using standard assumptions for the LF integration limit (LHα, lim) and SFR calibration constant κHα, despite the uncertainties in the dust corrections. We explore the metallicity dependence of κHα and find ρSFRHα decreases 0.43 dex compared to the fiducial result and is no longer consistent with UV-determined ρSFR at z∼6. This work highlights the importance of narrow-band surveys in probing the faint Hα population and providing new constraints on cosmic star-formation activity into the EoR.
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BibTeX
@misc{pirie2026jwst,
title = {{The JWST Emission Line Survey (JELS): A narrow-band determination of the H$α$ Luminosity Function and Cosmic Star Formation into the Epoch of Reionization}},
author = {C. A. Pirie and K. J. Duncan and P. N. Best and D. J. McLeod and C. L. Hale and R. K. Cochrane and S. R. Flury and H. M. O. Stephenson and M. I. Arnaudova and M. Brinch and J. S. Dunlop and E. Ibar and Z Li and J. Matthee and R. J. McLure and L. Ossa-Fuentes and A. L. Patrick and J. Selfridge and Ian Smail and D. Sobral and J. P. Stott and A. M. Swinbank},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.01586},
eprint = {2609.01586},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.01586},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - The JWST Emission Line Survey (JELS): A narrow-band determination of the Hα Luminosity Function and Cosmic Star Formation into the Epoch of Reionization
AU - C. A. Pirie
AU - K. J. Duncan
AU - P. N. Best
AU - D. J. McLeod
AU - C. L. Hale
AU - R. K. Cochrane
AU - S. R. Flury
AU - H. M. O. Stephenson
AU - M. I. Arnaudova
AU - M. Brinch
AU - J. S. Dunlop
AU - E. Ibar
AU - Z Li
AU - J. Matthee
AU - R. J. McLure
AU - L. Ossa-Fuentes
AU - A. L. Patrick
AU - J. Selfridge
AU - Ian Smail
AU - D. Sobral
AU - J. P. Stott
AU - A. M. Swinbank
PY - 2026
DA - 2026/09/01
PB - arXiv
DO - 10.48550/arxiv.2609.01586
UR - https://arxiv.org/abs/2609.01586
AB - The recent star-formation activity in galaxies can be optimally traced by the Hα emission line, with the resulting Hα luminosity function (LF) at a given epoch providing a reliable probe of cosmic star formation. We present the first narrow-band determined Hα LF into the Epoch of Reionization (EoR) at z∼6.1, using 39 Hα emitters selected from the JWST Emission Line Survey (JELS). The observed and dust-corrected LFs are broadly consistent with recent slitless spectroscopic measurements but show notable discrepancies with predictions from cosmological simulations, likely reflecting differences in emission-line and dust modelling. Fits combining multiple LF datasets help constrain the high-redshift faint-end slope of the Hα LF (−1.79<α_Hα<−1.62), but there remains uncertainty in its evolution with redshift. Integrating the JELS dust-corrected Hα LFs yields a star-formation rate density of log_10(ρ_SFR_Hα / M_⊙ yr^−1 Mpc^−3)=−1.93 ^+0.14_−0.12 or −2.00 ^+0.16_−0.10, assuming a continuum-to-line extinction ratios η_dust=A_cont(6563 mathringA)/A_Hα=1 and 0.44, respectively. Both measurements are consistent within uncertainties with previous results using standard assumptions for the LF integration limit (L_Hα, lim) and SFR calibration constant κ_Hα, despite the uncertainties in the dust corrections. We explore the metallicity dependence of κ_Hα and find ρ_SFR_Hα decreases 0.43 dex compared to the fiducial result and is no longer consistent with UV-determined ρ_SFR at z∼6. This work highlights the importance of narrow-band surveys in probing the faint Hα population and providing new constraints on cosmic star-formation activity into the EoR.
ER -