Dust properties of nearby disks: M31 case

TL;DR

This study investigates the dust properties of M31's disk, including opacity, extinction law, and gas-to-dust ratio, using optical and near-infrared photometry of background objects to understand the interstellar medium in M31.

Contribution

It provides new measurements of extinction and gas-to-dust ratio in M31's disk, revealing regional variations and similarities to the Milky Way.

Findings

Extinction in inter-arm regions is consistent with semi-transparent disks (A_v ~ 1).

The total-to-selective extinction ratio R_v is lower than the Galactic average.

Gas-to-dust ratio in M31 is similar to that of the Milky Way and shows no radial dependence.

Abstract

Several properties of the M31 disk, namely: opacity, extinction law and gas-to-dust ratio are studied by means of optical and near-infrared photometry of ten globular clusters and galaxies seen through the disk. The individual extinctions of these objects were estimated with respect to several sets of theoretical spectral energy distributions for globulars and galaxies. Seven targets are consistent with reddened globulars, two - with starburst galaxies and one - with an elliptical. The extinction estimates agree with semi-transparent disk (Av ~ 1) in the inter-arm regions. The total-to-selective extinction ratio in those regions 2.75 is lower on average than the typical Galactic value of Rv=3.1. We also obtained a gas-to-dust ratio, similar to that in the the Milky way. It shows no correlation with the distance from the M31 center.