# Revealing the dust attenuation properties on resolved scales in NGC628 with SWIFT UVOT data

## TL;DR

This study investigates dust attenuation laws in NGC628 at 325 pc resolution using multi-wavelength data and advanced SED fitting, revealing spatial variations in the attenuation curve and insights into dust properties.

## Contribution

It provides the first detailed resolved-scale analysis of dust attenuation law variations within a galaxy using SWIFT UVOT data and the CIGALE SED fitting code.

## Key findings

- The median attenuation curve in NGC628 is steep but less so than the SMC curve.
- Regions with high dust extinction have shallower attenuation curves.
- No correlation was found between bump strength and 8.0 micron emission.

## Abstract

Understanding how dust attenuation laws vary between and within galaxies is a key question if we want to reliably measure the physical properties of galaxies at both global and local scales. To shed new light on this question, we present a detailed study of the slope and bump strength of the attenuation law in the nearby spiral galaxy NGC628 at the resolved spatial scale of 325 pc. To do so, we have modelled a broad multi-wavelength dataset from the ultraviolet (UV) to the infrared (IR) with the state-of-the-art SED fitting code CIGALE, including SWIFT UVOT data for which we have developed a new optimized reduction pipeline. We find that the median dust attenuation curve of NGC628 is fairly steep, but not as steep as the SMC curve, and has a sub-MW-type UV bump. We observe intriguing variations within the galaxy, with regions of high $A_V$ exhibiting a shallower attenuation curve. We argue that the flattening of the curve is due to a dominance of absorption-over-scattering events at higher $A_V$. No trend between the bump strength and the IRAC 8.0 micron emission was found. However, this does not necessarily rule out PAHs as the main contributors to the UV bump.