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Cosmic Evolution Early Release Science Survey (CEERS): Multi-classing Galactic Dwarf Stars in the deep JWST/NIRCam Published: 9/12/2023 12:33:30 AM Updated: 9/12/2023 12:33:30 AM

Paper abstract: Low mass (sub)stellar objects represent the low end of the initial massfunction, the transition to free-floating planets and a prominent interloperpopulation in the search for high-redshift galaxies. Without proper motions orspectroscopy, can one identify these objects photometrically? JWST/NIRCam hasseveral advantages over HST/WFC3 NIR: more filters, a greater wavelength range,and greater spatial resolution. Here, we present a catalogue of (sub)stellardwarfs identified in the Cosmic Evolution Early Release Science Survey (CEERS).We identify 518 stellar objects down to m_F200W ~ 28 using half-lightradius, a full three magnitudes deeper than typical HST/WFC3 images. A kNNnearest neighbour algorithm identifies and types these sources, using fourHST/WFC3 and four NIRCam filters, trained on SpeX spectra of nearby browndwarfs. The kNN with four neighbors classifies well within two subtypes: e.gM2\pm2 or T4\pm2, achieving ~95% precision and recall. More granulartyping results in worse metrics. In CEERS, we find 9 M8\pm2, 2 L6\pm2, 1T4\pm2, and 15 T8\pm2. We compare the observed long wavelength NIRCamcolours -- not used in the kNN -- to those expected for brown dwarf atmosphericmodels. The NIRCam F356W-F444W and F410M-F444W colours are redder by amagnitude for the type assigned by the kNN, hinting at a wider variety ofatmospheres for these objects. We find a 300-350pc scale-height for M6\pm2dwarfs plus a second structural component and a 150-200pc scale-height forT6\pm2 type dwarfs, consistent with literature values.