The ALPINE-CRISTAL-JWST Survey: Stellar and Nebular Dust Attenuation of Main-sequence Galaxies at z ∼ 4–6

Abstract

Characterizing dust attenuation is crucial for revealing the intrinsic physical properties of galaxies. We present an analysis of dust attenuation in 18 spectroscopically confirmed star-forming main-sequence galaxies at z = 4.4−5.7 observed with JWST/NIRSpec IFU and NIRCam, selected from the ALPINE and CRISTAL ALMA large programs. We fit the emission-line fluxes from NIRSpec and the broadband photometry from NIRCam with Prospector, using both spatially integrated emission and ∼0.6 kpc pixel-by-pixel measurements. We derive the stellar-to-nebular dust attenuation ratio (f = E(B − V)star/E(B − V)neb) from the SED fits and the Balmer decrement with Hα and Hβ. Although individual galaxies show large scatter, the best-fit value is f=0.51−0.03+0.04 , slightly higher than that measured for local starburst galaxies. We find weak correlations of f with galaxy properties, increasing with higher specific star formation rates, younger stellar ages, and more recent star formation. For the range of E(B − V)star = 0.009−0.15 mag for in our sample, assuming f = 1 (often adopted in high-redshift studies) instead of f = 0.51 leads to the underestimation of line luminosities and ionizing photon production efficiency ξion by ∼3%−36% and ∼4 %−46%, respectively. Finally, total stellar masses estimated from spatially integrated SED fits with delayed-τ star formation histories are systematically smaller than the sums of pixel-by-pixel SED fits by a median of ∼0.26 dex, likely because the integrated fits are biased toward luminous young stellar populations.