A 100-parsec elliptical and twisted ring of cold and dense molecular clouds revealed by Herschel around the Galactic Center

TL;DR

This paper reveals a large, elliptical, and twisted ring of cold molecular clouds around the Galactic Center, traced by Herschel data, consistent with theoretical models of barred galaxy potentials.

Contribution

It identifies and characterizes a 100-parsec elliptical ring of dense clouds around the Galactic Center, linking observations with galactic potential models.

Findings

The ring has a semi-major axis of 100 parsecs and is inclined by 40 degrees.

The ring's morphology aligns with stable x_2 orbits in a barred potential.

Displacement of Sgr A* suggests asymmetries in the Galactic Center structure.

Abstract

Thermal images of cold dust in the Central Molecular Zone of the Milky Way, obtained with the far-infrared cameras on-board the Herschel satellite, reveal a 3x10^7 solar masses ring of dense and cold clouds orbiting the Galactic Center. Using a simple toy-model, an elliptical shape having semi-major axes of 100 and 60 parsecs is deduced. The major axis of this 100-pc ring is inclined by about 40 degrees with respect to the plane-of-the-sky and is oriented perpendicular to the major axes of the Galactic Bar. The 100-pc ring appears to trace the system of stable x_2 orbits predicted for the barred Galactic potential. Sgr A* is displaced with respect to the geometrical center of symmetry of the ring. The ring is twisted and its morphology suggests a flattening-ratio of 2 for the Galactic potential, which is in good agreement with the bulge flattening ratio derived from the 2MASS data.