SDSS+JWST Census of Stellar and Nebular Dust Attenuation at $z \sim 0$-7: Mass Dependence and Redshift Evolution

We present the demography of dust attenuation, including its mass dependence and redshift evolution, using spectroscopic samples of 34,182 SDSS galaxies at $z\sim0.1$ and 863 JWST/JADES galaxies at $z\sim1.5$--$7$. We find that, on average, ${\rm H\alpha}/{\rm H\beta}$ ratios are comparable to the Case B recombination value at $M_\ast \lesssim 10^9 M_\odot$, and increase beyond $M_\ast \sim 10^9 M_\odot$ both at $z\sim0.1$ and $1.5$--$7$. We derive the nebular attenuation $A_{\rm V, nebular}$ from Balmer decrements and the stellar attenuation $A_{\rm V, stellar}$ from rest-frame UV--optical spectra with supplementary \textit{GALEX} data, via comparisons with stellar-population models and multiple attenuation curves in a consistent manner across cosmic time. We find no significant redshift evolution of $A_{\rm V, nebular}$ and $A_{\rm V, stellar}$ at fixed $M_\ast$ over $z\sim0$--$7$, forming a universal extinction relation, and both rise from $0.2$--$0.4$ at $M_\ast \lesssim 10^9 M_\odot$ to $\sim1$ at $M_\ast \sim 10^{11} M_\odot$. Interestingly, at $M_\ast \gtrsim 10^9 M_\odot$, $A_{\rm V, nebular}$ rises more steeply than $A_{\rm V, stellar}$. This correlation holds within an uncertainty of $\sim\pm0.2$ for various combinations of attenuation curves (Calzetti, SMC, and Milky Way). These results indicate that $M_\ast \sim 10^9 M_\odot$ is a transition mass in dust attenuation, whose low-mass behavior reflects dust widely distributed by feedbacks. These mass-dependent extinction results address the long-standing issue of appropriate choice of the stellar-to-nebular color excess ratio, $f\equiv E(B-V)_{\rm stellar}/E(B-V)_{\rm nebular}=1.0$ or $0.44$, and suggest that galaxy $M_\ast$ determines $f$ from $\sim1.0$ to $\sim0.44$ across low- to high-mass galaxies.