Diffuse interstellar bands in nearby galaxies with MaNGA: environmental trends with metallicity, extinction, ionization, and star-forming activity

Diffuse interstellar bands (DIBs) are absorption features of uncertain origin observed in the optical and near-infrared spectra of stars and galaxies. Although their correlation with dust extinction is well established, the physical conditions governing their strength across different interstellar medium (ISM) environments remain poorly understood. We investigate the environmental dependence of the DIB λ5780 using spatially resolved MaNGA spectroscopy for 837 nearby galaxies spanning a broad range of stellar masses, star-formation rates, and ISM properties. Stellar and nebular parameters are derived via spectral fitting, while DIB absorption is measured from high-signal-to-noise spatially binned residual spectra. We detect the DIB λ5780 in 159 galaxies and report the most distant spatially resolved DIB detection to date, at 232 Mpc. The DIB λ5780 equivalent width correlates positively with both stellar and gas-phase extinction. DIB λ5780 is preferentially detected in regions of high extinction, near- or super-solar metallicity (12 + log (O/H) ≳ 8.5), and moderate specific star-formation rates (−10.5 ≲ log (sSFR/yr−1) ≲ −9). By contrast, it falls below our detection threshold in metal-poor or strongly ionized environments. It is rarely detected in regions with little or no recent star formation, with the few detections in such environments occurring primarily in regions driven by composite ionization. Our results indicate that DIB λ5780 is preferentially detected, within the sensitivity limits of the MaNGA data, in dust-rich, chemically evolved, and moderately ionized environments.