Radial distribution of stars, gas and dust in SINGS galaxies. II. Derived dust properties

TL;DR

This study analyzes the radial distribution of dust, gas, and stars in SINGS galaxies, revealing how dust properties and PAH abundance vary with metallicity, star formation history, and galaxy type, with implications for galaxy evolution.

Contribution

It provides detailed radial profiles of dust properties and their relation to metallicity, star formation history, and galaxy morphology, expanding understanding of dust distribution in galaxies.

Findings

Dust profiles are exponential with constant scale-lengths across galaxy types.

PAH abundance correlates with metallicity, flattening or reversing at high metallicity.

Dust-to-gas ratio decreases with galactocentric radius and metallicity.

Abstract

We present a detailed analysis of the radial distribution of dust properties in the SINGS sample, performed on a set of UV, IR and HI surface brightness profiles, combined with published molecular gas profiles and metallicity gradients. The internal extinction, derived from the TIR-to-FUV luminosity ratio, decreases with radius, and is larger in Sb-Sbc galaxies. The TIR-to-FUV ratio correlates with the UV spectral slope beta, following a sequence shifted to redder UV colors with respect to that of starbursts. The star formation history (SFH) is identified as the main driver of this departure. We have also derived radial profiles of the total dust mass surface density, the fraction of the dust mass contributed by PAHs, the fraction of the dust mass heated by very intense starlight and the intensity of the radiation field heating the grains. The dust profiles are exponential, their radial scale-length being constant from Sb to Sd galaxies (only ~10% larger than the stellar scale-length). Many S0/a-Sab galaxies have central depressions in their dust radial distributions. The PAH abundance increases with metallicity for 12+\log(O/H)<9, and at larger metallicities the trend flattens and even reverses, with the SFH being a plausible underlying driver for this behavior. The dust-to-gas ratio is also well correlated with metallicity and therefore decreases with galactocentric radius.