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

We present the first results of the JWST Emission Line Survey (JELS). Utilising the first NIRCam narrow-band imaging at 4.7\(\mu\)m, over 63 arcmin\(^{2}\) in the PRIMER/COSMOS field, we identified 609 emission line galaxy candidates. From these, we robustly selected 35 H\(\alpha\) star-forming galaxies at \(z \sim 6.1\), with H\(\alpha\) star-formation rates (\(\rm{SFR_{H\alpha}}\)) \(\sim0.9-15\ \rm{M_{\odot} \ yr^{-1}}\). Combining our unique H\(\alpha\) 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 \(z\sim 6\) which offered vital new insights into the nature of high-redshift galaxies. UV-continuum slopes (\(\beta\)) were considerably redder for our H\(\alpha\) sample (\(\langle\beta\rangle\sim-1.92\)) compared to the broad-band sample (\(\langle\beta\rangle\sim-2.35\)). This was not due to dust attenuation as our H\(\alpha\) sample was relatively dust-poor (median \(A_V=0.23\)); instead, we argued the reddened slopes could be due to nebular continuum. We compared \(\rm{SFR_{H\alpha}}\) and the UV-continuum-derived \(\rm{SFR_{UV}}\) to SED-fitted measurements averaged over canonical timescales of 10 and 100 Myr (\(\rm{SFR_{10}}\) and \(\rm{SFR_{100}}\)). We found an increase in recent SFR for our sample of H\(\alpha\) emitters, particularly at lower stellar masses (\(