The JWST Emission Line Survey (JELS): an untargeted search for H α emission line galaxies at z > 6 and their physical properties

Pirie, C A; Best, P N; Duncan, K J; McLeod, D J; Cochrane, R K; Clausen, M; Dunlop, J S; Flury, S R; Geach, J E; Hale, C L; Ibar, E; Kondapally, R; Li, Zefeng; Matthee, J; McLure, R J; Ossa-Fuentes, L; Patrick, A L; Smail, Ian; Sobral, D; Stephenson, H M O; Stott, J P; Swinbank, A M

Abstract

We present the first results of the JWST Emission Line Survey (JELS). Utilizing the first NIRCam narrow-band imaging at 4.7 m, over 63 arcmin in the PRIMER/COSMOS field, we have identified 609 emission line galaxy candidates. From these, we robustly selected 35 H star-forming galaxies at , with H star-formation rates () of . Combining our unique H sample with the exquisite panchromatic data in the field, we explored their physical properties and star-formation histories, and compared these to a broad-band selected sample at which has offered vital new insights into the nature of high-redshift galaxies. UV-continuum slopes () were considerably redder for our H sample () compared to the broad-band sample (). This was not due to dust attenuation as our H sample was relatively dust-poor (median ); instead, we argue that the reddened slopes could be due to nebular continuum. We compared and the UV-continuum-derived to SED-fitted measurements averaged over canonical time-scales of 10 and 100 Myr ( and ). We found an increase in recent SFR for our sample of H emitters, particularly at lower stellar masses (). We also found that strongly traces SFR averaged over 10 Myr time-scales, whereas the UV-continuum overpredicts SFR on 100 Myr time-scales at low stellar masses. These results point to our H sample undergoing ‘bursty’ star formation. Our F356W sample showed a larger scatter in across all stellar masses, which has highlighted how narrow-band photometric selections of H emitters are key to quantifying the burstiness of star-formation activity.

Citation

Pirie, C. A., Best, P. N., Duncan, K. J., McLeod, D. J., Cochrane, R. K., Clausen, M., Dunlop, J. S., Flury, S. R., Geach, J. E., Hale, C. L., Ibar, E., Kondapally, R., Li, Z., Matthee, J., McLure, R. J., Ossa-Fuentes, L., Patrick, A. L., Smail, I., Sobral, D., …Swinbank, A. M. (2025). The JWST Emission Line Survey (JELS): an untargeted search for H α emission line galaxies at z > 6 and their physical properties. Monthly Notices of the Royal Astronomical Society, 541(2), 1348-1376. https://doi.org/10.1093/mnras/staf1006

• Journal Article Type: Article
• Acceptance Date: Jun 2, 2025
• Online Publication Date: Jun 23, 2025
• Publication Date: 2025-08
• Deposit Date: Sep 22, 2025
• Publicly Available Date: Sep 22, 2025
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 541
• Issue: 2
• Pages: 1348-1376
• DOI: https://doi.org/10.1093/mnras/staf1006
• Keywords: galaxies: high-redshift, surveys, galaxies: emission lines, galaxies: star formation, galaxies: evolution, reionization
• Public URL: https://durham-repository.worktribe.com/output/4264908