Journal Article

Rest-frame UV Colors for Faint Galaxies at z ∼ 9–16 with the JWST NGDEEP Survey

Leung, Gene C. K, Wilkins, Stephen M, Finkelstein, Steven L, Yung, L. Y. Aaron, Bagley, Micaela B, Cleri, Nikko J, Hathi, Nimish P, Ferguson, Henry C, Pirzkal, Nor, Dickinson, Mark, Smith, Britton, Jones, Ewan, Morales, Alexa M, Dave, Romeel, Papovich, Casey, Koekemoer, Anton M, Pérez-González, Pablo G

2024

Overview

We 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 βPL=−2.7−0.5+0.5 and from SED fitting, βSED=−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 βSED,corr=−2.5−0.2+0.2 . We measure physical properties for our galaxies with Bagpipes and find that our faint ( MUV=−18.1−0.9+0.7 ) sample is low in mass ( log[M*/M⊙]=7.7−0.5+0.5 ), fairly dust-poor ( Av=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+0.4M⊙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. Our observations are consistent with model predictions that galaxies of these stellar masses at z ∼ 9–16 should have only modestly low metallicities (Z/Z ⊙ ∼ 0.1–0.2).

• Publisher: IOP Publishing
• Subject: Bias / Confidence intervals / Galaxies / James Webb Space Telescope / Photometry / Physical properties / Power law / Spectral energy distribution / Star & galaxy formation / Star formation / Star formation rate / Stellar models / Stellar populations