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 broad-band photometry from NIRCam with Prospector, using both spatially integrated emission and $\sim 0.6$ kpc pixel-by-pixel measurements. We derive the stellar-to-nebular dust attenuation ratio ($f=E(B-V{)}_{\mathrm{star}}/E(B-V{)}_{\mathrm{neb}}$) from the SED fits and the Balmer decrement with H$\hat{I}\pm$ and H${\hat{I}}^2$. 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 $E(B-V{)}_{\mathrm{star}}=0.009-0.15$ mag for in our sample, assuming $f=1$ (often adopted in high-redshift studies) instead of $f=0.51$ underestimate line luminosities and ionizing photon production efficiency $\hat{I}{¾}_{\text{ion}}$ by $\sim 3-36\%$ and $\sim 4-46\%$, respectively. We also find that the total stellar masses estimated from spatially-integrated SED fits with a delayed-$\ddot{I}„$ star-formation histories are systematically smaller than the sum of pixel-by-pixel SED fits, with a median offset of $\sim 0.26$ dex, likely because the integrated fits are biased toward luminous young stellar populations.

Accepted for publication in ApJ. 23 pages and 7 figures. See also the companion "The ALPINE-CRISTAL-JWST Survey" papers by Faisst et al. and Fujimoto et al