3D Morphology and Motions of the Canis Major Region from Gaia DR3

TL;DR

This paper combines Gaia DR3 astrometric data with molecular gas observations to reveal the 3D structure and expansion dynamics of the Canis Major region, supporting the hypothesis of multiple supernovae shaping its morphology.

Contribution

It provides the first 3D analysis of the Canis Major region's morphology and dynamics by integrating Gaia data with molecular gas observations, confirming shell expansion and supernova influence.

Findings

Confirmed a 47±11 pc radius shell with 1.6±0.7 km/s expansion velocity.

Estimated an expansion timescale of approximately 4.4 million years.

Suggested at least two supernovae contributed to the shell's formation.

Abstract

The Canis Major (CMa) region is known for its prominent arc-shaped morphology, visible at multiple wavelengths. This study integrates molecular gas data with high-precision astrometric parameters of young stellar objects (YSOs) from Gaia DR3 to provide the first three-dimensional (3D) insights into the dynamical evolution and star formation history of the CMa region. By utilizing the average distances and proper motions of the YSOs as proxies for those of the molecular clouds (MCs), we confirm the presence of a slowly expanding shell-like morphology in the CMa region, with the estimated radius of 47$\pm$11 pc and expansion velocity of 1.6$\pm$0.7 km/s. Further, the dynamical evolution of the shell supports its expansion, with an expansion timescale of $\sim$4.4 Myr obtained by the traceback analysis assuming constant velocities. Finally, a momentum estimate suggests that at least 2 supernova explosions (SNe) are needed to power the observed expanding shell, reinforcing the previous hypothesis of multiple SNe events. This study effectively combines the CO data with the astrometric data of YSOs from Gaia, offering significant support for the future studies on the 3D morphology and kinematics of MCs.