Classical Cepheids in the Galactic outer ring R1R2'

TL;DR

This study uses the distribution and kinematics of classical Cepheids within 3 kpc of the Sun to support the existence of the Galactic outer ring R1R2', determining the Sun's position angle relative to the Galactic bar and explaining extinction features.

Contribution

It provides evidence for the outer ring R1R2' in the Galaxy and estimates the Sun's position angle with respect to the Galactic bar based on Cepheid data.

Findings

Optimal solar position angle theta_b=37 +/- 13 degrees.

Cepheid kinematics align with the outer ring R2.

Extinction rise explained by the outer ring R1.

Abstract

The kinematics and distribution of classical Cepheids within ~3 kpc from the Sun suggest the existence of the outer ring R1R2' in the Galaxy. The optimum value of the solar position angle with respect to the major axis of the bar, theta_b, providing the best agreement between the distribution of Cepheids and model particles is theta_b=37 +/- 13 degrees. The kinematical features obtained for Cepheids with negative Galactocentric radial velocity VR are consistent with the solar location near the descending segment of the outer ring R2. The sharp rise of extinction toward of the Galactic center can be explained by the presence of the outer ring R1 near the Sun.