2026/07/12 by Ruonan Guo, Cheng Li, Tao Jing +3
#astro-ph.GA
We combine the SwiMv4.2 Swift/UVOT+MaNGA catalog with 2MASS Ks imaging to map the 2175Å attenuation bump at kiloparsec scales in nearby galaxies. We use two complementary estimators: an ultraviolet-to-near-infrared attenuation-curve method, yielding AbumpUOIR and B for 2487 high-continuum-S/N spaxels, and the NUV-only method of Battisti et al. (2025), yielding AbumpNUV and kbump for 7934 spaxels. The two absolute bump estimates agree well where they overlap. We compare bump strength with local stellar-population, emission-line, attenuation-curve, and geometric diagnostics after separating star-forming (SF) and non-SF regions. The strongest bumps occur at low specific Hα surface brightness, ΣHα/Σ_∗, especially in non-SF regions, where this ratio traces ionized-gas emission per unit stellar mass rather than sSFR. The bump also weakens with EW(Hα) and strengthens with Dn4000 and stellar age. In contrast, metallicity, inclination, galactocentric radius, AV, and optical attenuation-curve slope are secondary predictors. The absolute strength AbumpNUV increases with ΣHα and Σ_∗, while the relative strengths kbump and B do not, indicating that absolute bump amplitude partly follows dust column whereas normalized strengths better trace effective bump prominence. These results support local radiation-field processing of the 2175Å carriers.