The simulation of molecular clouds formation in the Milky Way

TL;DR

This paper uses advanced 3D hydrodynamic simulations to model the formation and properties of molecular clouds in the Milky Way, incorporating detailed physics and gravitational effects, and compares results with observations.

Contribution

It presents a comprehensive simulation of molecular cloud formation in the Galaxy, including detailed physics and gravitational influences, and reproduces observed properties and structures.

Findings

Simulated clouds form in spiral arms due to instabilities.

Cloud properties match observed mass spectra and velocity dispersions.

Synthetic galactic longitude-velocity diagrams resemble observed structures.

Abstract

Using 3D hydrodynamic calculations we simulate formation of molecular clouds in the Galaxy. The simulations take into account molecular hydrogen chemical kinetics, cooling and heating processes. Comprehensive gravitational potential accounts for contributions from the stellar bulge, two and four armed spiral structure, stellar disk, dark halo and takes into account self-gravitation of the gaseous component. Gas clouds in our model form in the spiral arms due to shear and wiggle instabilities and turn into molecular clouds after $t\simgt 100$ Myr. At the times $t\sim 100 - 300$ Myr the clouds form hierarchical structures and agglomerations with the sizes of 100 pc and greater. We analyze physical properties of the simulated clouds and find that synthetic statistical distributions like mass spectrum, "mass-size" relation and velocity dispersion are close to those observed in the Galaxy. The synthetic $l-v$ (galactic longitude - radial velocity) diagram of the simulated molecular gas distribution resembles observed one and displays a structure with appearance similar to Molecular Ring of the Galaxy. Existence of this structure in our modelling can be explained by superposition of emission from the galactic bar and the spiral arms at $\sim$3-4 kpc.