James Webb Space Telescope Feed Post

Harvard ADS: The JWST Emission Line Survey (JELS): Extending rest-optical narrow-band emission line selection into the Epoch of Reionization

Paper abstract: We present the JWST Emission Line Survey (JELS), a Cycle 1 JWST imaging programme exploiting the wavelength coverage and sensitivity of NIRCam to extend narrow-band rest-optical emission line selection into the epoch of reionization (EoR) for the first time, and to enable unique studies of the resolved ionised gas morphology in individual galaxies across cosmic history. The primary JELS observations comprise ~4.7\mum narrow-band imaging over ~63 arcmin^{2} designed to enable selection of H\alpha emitters at z~6.1, as well as the selection of a host of novel emission-line samples including [OIII] at z~8.3 and Pa \alpha/\beta at z~1.5/2.8. For the prime F466N and F470N narrow-band observations, the emission-line sensitivities achieved are up to ~2\times more sensitive than current slitless spectroscopy surveys (5\sigma limits of 1.1-1.6\times10^{-18}\text{erg s}^{-1}\text{cm}^{-2}), corresponding to unobscured H\alpha star-formation rates (SFRs) of 1-1.6 \text{M}_{\odot}\,\text{yr}^{-1} at z~6.1 and extending emission-line selections in the EoR to fainter populations. Simultaneously, JELS also obtained F200W broadband and F212N narrow-band imaging (H\alpha at z~2.23) that probes SFRs \gtrsim5\times fainter than previous ground-based narrow-band studies (~0.2 \text{M}_{\odot}\text{yr}^{-1}), offering an unprecedented resolved view of star formation at cosmic noon. In this paper we describe the detailed JELS survey design, key data processing steps specific to the survey observations, and demonstrate the exceptional data quality and imaging sensitivity achieved. We then summarise the key scientific goals of JELS and present some early science results, including examples of spectroscopically confirmed H\alpha and [OIII] emitters discovered by JELS that illustrate the novel parameter space probed.