Mapping dust attenuation and the 2175 {\AA} bump at kpc scales in nearby galaxies

TL;DR

This study introduces a new method to measure dust attenuation properties, including the 2175 Å bump, at kpc scales in nearby galaxies, revealing correlations with star formation activity and dust opacity.

Contribution

A novel, model-independent approach to derive dust attenuation curves and the 2175 Å bump from observed spectra, calibrated with NIR photometry, applied to spatially resolved galaxy data.

Findings

Attenuation curve slope is shallower at higher optical opacity.

The 2175 Å bump correlates negatively with specific star formation rate.

Variations in the 2175 Å bump are linked to star formation processes.

Abstract

We develop a novel approach to measure dust attenuation properties of galaxies, including the dust opacity, shape of the attenuation curve and the strength of the 2175{\AA} absorption feature. From an observed spectrum, the method uses a model-independent approach to derive a relative attenuation curve, with absolute amplitude calibrated using NIR photometry. The dust-corrected spectrum is fitted with stellar population models to derive the dust-free model spectrum, which is compared with the observed SED/spectrum from NUV to NIR to determine dust attenuation properties. We apply this method to investigate dust attenuation on kpc scales, using a sample of 134 galaxies with integral field spectroscopy from MaNGA, NIR imaging from 2MASS, and NUV imaging from Swift/UVOT. We find the attenuation curve slope and the 2175{\AA} bump in both optical and NUV span a wide range at kpc scales. The slope is shallower at higher optical opacity, regardless of the specific star formation rate (sSFR), minor-to-major axis ratio (b/a) of galaxies and the location of spaxels within individual galaxies. The 2175{\AA} bump presents a strong negative correlation with the sSFR, while the correlations with the optical opacity, b/a and the location within individual galaxies are all weak. All these trends appear to be independent of the stellar mass of galaxies. Our results support the scenario that the variation of the 2175{\AA} bump is driven predominantly by processes related to star formation, such as the destruction of small dust grains by UV radiation in star-forming regions.