The MAGPI Survey: Evidence for Non-Universal Resolved Dust Attenuation Relations Beyond the Local Universe

Abstract

We study the spatially resolved relation between dust attenuation ($A_V$) and star formation rate surface density ($\hat{I}{\pounds }_{\mathrm{SFR}}$) in galaxies from the MAGPI survey ($0.25<z<0.42$). Using Balmer-decrement-based attenuation maps for 178 galaxies, we investigate whether the locally calibrated resolved $A_V$--$\hat{I}{\pounds }_{\mathrm{SFR}}$ relation remains valid at intermediate redshift by comparing MAGPI with the local relation measured from MaNGA. We find a clear positive correlation between $A_V$ and $\hat{I}{\pounds }_{\mathrm{SFR}}$ in MAGPI, with systematically higher attenuation than in MaNGA at fixed $\hat{I}{\pounds }_{\mathrm{SFR}}$. After matching galaxies in stellar mass ($M_{\ast }$) and offset from the star-forming main sequence ($\hat{I}”$SFMS), MAGPI galaxies remain more attenuated than MaNGA galaxies at fixed $\hat{I}{\pounds }_{\mathrm{SFR}}$. The attenuation excess is strongest for galaxies below the SFMS ($\hat{I}”A_V\sim 0.40$ mag), weaker for galaxies on the SFMS ($\hat{I}”A_V\sim 0.28$ mag), and minimal for galaxies above the SFMS ($\hat{I}”A_V\sim 0.07$ mag). The dependence of the offset on $\hat{I}”$SFMS suggests that nebular attenuation on kpc scales is regulated not only by local star formation activity, but also by the global evolutionary state of the host galaxy. Together, these results indicate that the resolved $A_V$--$\hat{I}{\pounds }_{\mathrm{SFR}}$ relation is not universal, and that locally calibrated attenuation relations may not fully describe galaxies at intermediate redshift. This highlights the need for attenuation calibrations that account for galaxy population and redshift when interpreting spatially resolved galaxy properties.