Abstract
Abstract
We aim to characterize nebular and stellar reddening in star-forming galaxies as a function of global galaxy properties (stellar mass, star formation rate (SFR), and metallicity) at 2.7 z
E
(
B
−
V
)
star
to
E
(
B
−
V
)
gas
when direct measurements of nebular reddening are unavailable. Our results are based on JWST/NIRSpec measurements of both individual spectra, with a sample of 293 galaxies, and composite spectra, including a larger sample of 327 galaxies. We estimate nebular reddening using the Balmer decrement (H
α
/H
β
) above 10
8.5
M
⊙
, where the sample is representative. Stellar reddening and SFRs are derived through
Prospector
SED fitting, while gas-phase metallicities are estimated from strong emission-line ratios. At fixed stellar mass, Balmer decrements remain consistent within uncertainties across our redshift range, indicating that stellar mass primarily determines the overall dust column even by
z
∼ 7. We find that differential reddening (Δ
E
(
B
−
V
) ≡
E
(
B
−
V
)
gas
−
E
(
B
−
V
)
star
) scales linearly with mass and SFR at
z
∼ 2.7−4.0, but shows no mass or SFR dependence above
z
∼ 4.0. We find evidence for smaller Δ
E
(
B
−
V
) above
z
∼ 5.0, suggesting that nebular emission and stellar continuum probe increasingly similar dust columns towards higher redshift. Finally, we find that nebular reddening correlates strongly with metallicity out to
z
∼ 5, whereas the correlation between stellar reddening and metallicity is weaker or absent. Together, these results suggest that both dust mass and geometry play a significant role in shaping the observed reddening of high-redshift galaxies.