The History of The Milky Way: The Evolution of Star Formation, Cosmic Rays, Metallicity, and Stellar Dynamics over Cosmic Time

TL;DR

This paper models the Milky Way's evolution over cosmic time, integrating star formation, cosmic rays, metallicity, and dynamics, and predicts an unidentified accretion flow and plasma origins of diffuse X-ray emissions.

Contribution

It presents a comprehensive model of the Milky Way's evolution that reproduces key observed properties and predicts new phenomena like an unidentified accretion flow and plasma origins of X-ray emissions.

Findings

Star formation rate is about half the mass accretion rate.

Reproduces observed star formation, cosmic rays, metals, and rotation curve.

Predicts an unidentified accretion flow and hot plasma from supernova energy.

Abstract

We study the long-term evolution of the Milky Way (MW) over cosmic time by modeling the star formation, cosmic rays, metallicity, stellar dynamics, outflows and inflows of the galactic system to obtain various insights into the galactic evolution. The mass accretion is modeled by the results of cosmological N-body simulations for the cold dark matter. We find that the star formation rate is about half the mass accretion rate of the disk, given the consistency between observed Galactic Diffuse X-ray Emissions (GDXEs) and possible conditions driving the Galactic wind. Our model simultaneously reproduces the quantities of star formation rate, cosmic rays, metals, and the rotation curve of the current MW. The most important predictions of the model are that there is an unidentified accretion flow with a possible number density of $\sim10^{-2}$ cm$^{-3}$ and the part of the GDXEs originates from a hot, diffuse plasma which is formed by consuming about 10 % of supernova explosion energy. The latter is the science case for future X-ray missions; XRISM, Athena, and so on. We also discuss further implications of our results for the planet formation and observations of externalgalaxies in terms of the multimessenger astronomy.