A Blueprint for the Milky Way's Stellar Populations. V. 3D Local Dust Extinction

TL;DR

This study constructs a detailed 3D dust extinction map of the Milky Way using Gaia DR3 XP spectra, revealing variations in extinction ratios and validating results against previous maps, with insights into spectral flux calibration issues.

Contribution

It introduces a novel all-sky 3D extinction mapping method using Gaia XP spectra, incorporating metallicity and extinction ratio variations, and assesses spectral calibration accuracy.

Findings

Validated reddening estimates against previous maps outside dense clouds.

Identified systematic changes in the total-to-selective extinction ratio.

Detected flux overestimation at wavelengths below 400 nm in XP spectra.

Abstract

Using a grid of empirically calibrated synthetic spectra developed in our previous study, we construct an all-sky 3D extinction map from the large collection of low-resolution XP spectra in Gaia DR3. Along each line of sight, with an area ranging from $0.2$ to $13.4$ deg$^2$, we determine both the reddening and metallicity of main-sequence stars and model the foreground extinction up to approximately $3$ kpc from the Sun. Furthermore, we explore variations in the total-to-selective extinction ratio in our parameter search and identify its mean systematic change across diverse cloud environments in both hemispheres. In regions outside the densest parts of the clouds, our reddening estimates are validated through comparisons with previous reddening maps. However, a notable discrepancy arises when compared to other independent work based on XP spectra, although our metallicity scale shows reasonable agreement with the high-resolution spectroscopic abundance scale. We also assess the accuracy of the XP spectra by applying our calibrated models, and confirm an increasing trend of flux overestimation at shorter wavelengths below $400$ nm.