Three-Dimensional Structure of the Central Molecular Zone

TL;DR

This paper provides a detailed 3D structural analysis of the Central Molecular Zone in the Galactic Center, revealing its embedding in the HI disc, associated arms, and a warping star-forming ring, based on multi-wavelength data and proper motion measurements.

Contribution

It offers the first comprehensive 3D model of the CMZ, combining HI, CO, and proper motion data to elucidate the spatial and velocity structure of the Galactic Center region.

Findings

CMZ embedded in a central HI disc of radius ~320 pc

Identification of a warping star-forming ring parallel to molecular arms

Determination of the 3D positions of Sgr B2 and Sgr C relative to Sgr A*

Abstract

A detailed comparison of HI and CO line cube data of the Galactic Center (GC) region from the archives is obtained. The central molecular zone (CMZ) is shown to be embedded in the HI disc (central HI zone, CHZ) of radius $\sim 320$ pc and vertical scale height $\sim 70$ pc. A radio continuum belt is shown to run parallel to molecular Arms I and II. The belt draws a double-infinity shape on the sky, connecting Sgr E ($l\sim -1^\circ.2)$, C, B1, B2 and Sgr D ($+1^\circ.2$), and is interpreted as a warping star-forming ring. The molecular Arms are closely associated with the HI arms on the longitude-velocity diagram (LVD), showing coherent rigid-body ridges. Due to the close relationship between HI and CO, the HI line absorption can be used to determine the Arms' position relative to Sgr A, B1, B2 and C.Combining the trigonometric data of proper motions of Sgr A$^*$ and maser sources of Sgr B2 as well as radial velocities, the 3D velocity vector of Sgr B2 is determined. From these analyses, the molecular Arm I with Sgr B2 is shown to be located in the near side of Sgr A$^*$, and Arm II with Sgr C in the other side, both composing a pair of symmetrical Arms around the GC. We present a possible 3D view of Sgr A through E and Arms I and II along with a parameter list.