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
Year: 2026
Type: preprint
Abstract: The recent star-formation activity in galaxies can be optimally traced by the H$α$ emission line, with the resulting H$α$ luminosity function (LF) at a given epoch providing a reliable probe of cosmic star formation. We present the first narrow-band determined H$α$ LF into the Epoch of Reionization (EoR) at $z\sim6.1$, using 39 H$α$ 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 H$α$ LF ($-1.79<α_{\rm{Hα}}<-1.62$), but there remains uncertainty in its evolution with redshift. Integrating the JELS dust-corrected H$α$ LFs yields a star-formation rate density of $\log_{10}(ρ_{\rm{SFR_{Hα}}}\,/\,\rm{M_{\odot}\,yr^{-1}\,Mpc^{-3}})=-1.93\,^{+0.14}_{-0.12}$ or $-2.00\,^{+0.16}_{-0.10}$, assuming a continuum-to-line extinction ratios $η_{\rm{dust}}=A_{\rm{cont}}(\rm{6563\,\mathring{A}})/A_{\rm{Hα}}=1$ and 0.44, respectively. Both measurements are consistent within uncertainties with previous results using standard assumptions for the LF integration limit ($L_{\rm{Hα,\,lim}}$) and SFR calibration constant $κ_{\rm{Hα}}$, despite the uncertainties in the dust corrections. We explore the metallicity dependence of $κ_{\rm{Hα}}$ and find $ρ_{\rm{SFR_{Hα}}}$ decreases 0.43 dex compared to the fiducial result and is no longer consistent with UV-determined $ρ_{\rm{SFR}}$ at $z\sim6$. This work highlights the importance of narrow-band surveys in probing the faint H$α$ population and providing new constraints on cosmic star-formation activity into the EoR.
Source: arXiv (Cornell University)
Authors: Pirie, C. A., Duncan, K. J., Best, P. N., McLeod, D. J., Hale, C. L., Cochrane, R. K., Flury, S. R., Stephenson, H. M. O., Arnaudova, M. I., Brinch, M., Dunlop, J. S., Ibar, E., Li, Z, Matthee, J., McLure, R. J., Ossa-Fuentes, L., Patrick, A. L., Selfridge, J., Smail, Ian, Sobral, D., Stott, J. P., Swinbank, A. M.
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Awards: THE INTERSTELLAR PHYSICS OF NORMAL GALAXIES AS REVEALED BY ALMA, An unbiased and resolved view of cosmic star formation, STFC Edinburgh PaA 2021 DTP, G1890539920, TOWARDS A COMPREHENSIVE VIEW OF THE STAR-FORMATION ACTIVITY IN JWST GALAXY SAMPLES AT Z~1.5 (V2), MILLENIUM NUCLEUS FOR GALAXIES, G669014107, Astronomy at Durham 2023-2026, Revealing the hidden early lives of super-massive black holes
OpenAlex ID: W7206156357