Validity of local stellar–nebular differential reddening at high redshift

Determine whether the differential reddening relationship between stellar continuum and nebular line attenuation established for local starburst galaxies—quantified by the ratio f = E(B−V)star / E(B−V)neb ≈ 0.44–0.47 (e.g., Calzetti 2000; Kreckel et al. 2013)—holds for high-redshift star-forming galaxies.

Background

In nearby star-forming systems, nebular emission lines are observed to suffer greater dust attenuation than the stellar continuum, a difference commonly described by a two-component dust geometry. This has been quantified by relations such as f = E(B−V)star / E(B−V)neb ≈ 0.44 for local starbursts (Calzetti 2000) and f ≈ 0.47 in star-forming regions of local galaxies (Kreckel et al. 2013).

Whether these locally calibrated relations apply to high-redshift galaxies is uncertain due to potential evolution in star-formation activity, dust geometry, and clumpiness, as well as observational challenges in measuring Balmer decrements at z ≳ 2.5. Establishing the applicability of the local f relation at high redshift is important for accurate dust corrections of emission lines and continuum, and thus for deriving intrinsic galaxy properties and cosmic star-formation histories.

References

However, the validity of these relationships at high redshift remains an open question.

— The ALPINE-CRISTAL-JWST Survey: Stellar and nebular dust attenuation of main-sequence galaxies at z~4-6  (2510.18248 - Tsujita et al., 21 Oct 2025) in Introduction (Section 1)

This factor remains uncertain for galaxies in the early Universe.

— RIOJA. Environmental Effects on Stellar Populations and Ionized Gas in a Protocluster at $z=7.88$  (2608.16343 - Osone et al., 17 Aug 2026) in Section 5.1, “Correction For Dust Attenuation”