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Literature
Date: 10/31/2024

Arxiv: The JWST Emission Line Survey (JELS): An untargeted search for Hα emission line galaxies at z > 6 and their physical properties Published: 10/15/2024 8:35:19 PM Updated: 10/30/2024 4:58:16 PM

Paper abstract: We present the first results of the JWST Emission Line Survey (JELS).Utilising the first NIRCam narrow-band imaging at 4.7\mum, over 63arcmin^{2} in the PRIMER/COSMOS field, we identified 609 emission line galaxycandidates. From these, we robustly selected 35 H\alpha star-forming galaxiesat z ~ 6.1, with H\alpha star-formation rates (\rm{SFR_{H\alpha}})~0.9-15\ \rm{M_{\odot} \ yr^{-1}}. Combining our unique H\alpha samplewith the exquisite panchromatic data in the field, we explored their physicalproperties and star-formation histories, and compared these to a broad-bandselected sample at z~ 6 which offered vital new insights into the natureof high-redshift galaxies. UV-continuum slopes (\beta) were considerablyredder for our H\alpha sample (\langle\beta\rangle~-1.92) compared tothe broad-band sample (\langle\beta\rangle~-2.35). This was not due todust attenuation as our H\alpha sample was relatively dust-poor (medianA_V=0.23); instead, we argued the reddened slopes could be due to nebularcontinuum. We compared \rm{SFR_{H\alpha}} and the UV-continuum-derived\rm{SFR_{UV}} to SED-fitted measurements averaged over canonical timescalesof 10 and 100 Myr (\rm{SFR_{10}} and \rm{SFR_{100}}). We found an increasein recent SFR for our sample of H\alpha emitters, particularly at lowerstellar masses (<10^9 \ \rm{M_{\odot}}). We also found \rm{SFR_{H\alpha}}strongly traced SFR averaged over 10 Myr timescales, whereas the UV-continuumover-predicts SFR on 100 Myr timescales at low stellar masses. These resultspoint to our H\alpha sample undergoing `bursty' star formation. Our F356W z~ 6 sample showed a larger scatter in \rm{SFR_{10}/SFR_{100}} across allstellar masses, which highlighted how narrow-band photometric selections ofH\alpha emitters are key to quantifying the burstiness of star-formationactivity.