Mapping the reddening plane in the Galactic disk through interstellar extinction of open clusters

TL;DR

This study maps the distribution of interstellar dust in the Galactic disk using open clusters, revealing a sinusoidally varying reddening plane, asymmetries, and the Sun's position relative to this dust layer.

Contribution

It introduces a detailed mapping of the Galactic reddening plane using a large sample of open clusters, highlighting its sinusoidal variation and asymmetries.

Findings

Reddening plane varies sinusoidally with Galactic longitude.

The Sun is located approximately 15.7 pc above the reddening plane.

The dust layer has an average thickness of about 201 pc.

Abstract

As thousands of new open clusters in the Galaxy have recently been reported with reddening or extinction information, we map the distribution and properties of the Galaxy's interstellar material in the Galactic disk as traced by these open clusters. By analyzing the distribution of interstellar extinction for 6215 open clusters located at low Galactic latitude b <= 6 deg, corresponding to the thin Galactic disk, we identify a reddening plane characterized by a dust layer whose thickness varies with Galactic longitude. By splitting the open clusters sample into several sub-regions of Galactic longitude, we observe that the reddening plane is not perfectly aligned with the formal Galactic plane, but instead varies sinusoidally around the Galactic mid-plane. The maximum and minimum interstellar absorption occur at approximately 42 deg and 222 deg, respectively, along the Galactic longitude. Our analysis reveals a noticeable north-south asymmetry in the distribution of interstellar absorption, with a higher proportion of interstellar material below the Galactic plane. We also find that the Sun is located 15.7 +/- 7.3 pc above the reddening plane. The scale height of the open clusters from the reddening plane is estimated to be z_h = 87.3 +/- 1.8 pc. The mean thickness of the absorbing material in the reddening plane, which represents the average extent of the dust layer responsible for interstellar extinction, is found to be about 201 +/- 20 pc. Our findings provide insights into the distribution of interstellar dust, its relationship with the Galactic thin disk, and its implications for the Galactic structure.