Morales, AlexaDave, RomeelFinkelstein, Steven2025-01-212025-01-212024Morales, A.M., Finkelstein, S.L., Leung, G.C., Bagley, M.B., Cleri, N.J., Dave, R., Dickinson, M., Ferguson, H.C., Hathi, N.P., Jones, E. and Koekemoer, A.M., 2024. Rest-frame UV Colors for Faint Galaxies at z∼ 9–16 with the JWST NGDEEP Survey. The Astrophysical Journal Letters, 964(2), p.L24.https://doi.org/10.3847/2041-8213/ad2de4https://hdl.handle.net/10566/19880We present measurements of the rest-frame UV spectral slope, β, for a sample of 36 faint star-forming galaxies at z ∼ 9-16 discovered in one of the deepest JWST NIRCam surveys to date, the Next Generation Deep Extragalactic Exploratory Public Survey. We use robust photometric measurements for UV-faint galaxies (down to M UV ∼ −16), originally published in Leung et al., and measure values of the UV spectral slope via photometric power-law fitting to both the observed photometry and stellar population models obtained through spectral energy distribution (SED) fitting with Bagpipes. We obtain a median and 68% confidence interval for β from photometric power-law fitting of β PL = − 2.7 − 0.5 + 0.5 and from SED fitting, β SED = − 2.3 − 0.1 + 0.2 for the full sample. We show that when only two to three photometric detections are available, SED fitting has a lower scatter and reduced biases than photometric power-law fitting. We quantify this bias and find that after correction the median β SED , corr = − 2.5 − 0.2 + 0.2 . We measure physical properties for our galaxies with Bagpipes and find that our faint ( M UV = − 18.1 − 0.9 + 0.7 ) sample is low in mass ( log [ M * / M ⊙ ] = 7.7 − 0.5 + 0.5 ), fairly dust-poor ( A v = 0.1 − 0.1 + 0.2 mag), and modestly young ( log [ age ] = 7.8 − 0.8 + 0.2 yr) with a median star formation rate of log ( SFR ) = − 0.3 − 0.4 + 0.4 M ⊙ yr − 1 . We find no strong evidence for ultrablue UV spectral slopes (β ∼ −3) within our sample, as would be expected for exotically metal-poor (Z/Z ⊙ < 10−3) stellar populations with very high Lyman continuum escape fractions.enUV spectral slope (β)JWST NIRCamSED fittingStar-forming galaxiesStellar population modelsArticle