Star Formation History in the Galactic Thin Disk

TL;DR

This study investigates the star formation history in the Galactic thin disk, revealing a decreasing star formation rate with radius, a negative metallicity gradient, and changes in chemical abundances over billions of years influenced by galactic interactions.

Contribution

It provides new insights into the temporal and spatial variations of star formation and chemical enrichment in the Galactic thin disk, highlighting the impact of galactic interactions.

Findings

Star formation rate decreases with Galactocentric distance.

Metallicity shows a negative radial gradient, while magnesium abundance does not.

Star formation increased around 5 billion years ago, affecting chemical properties.

Abstract

The behavior of the relative magnesium abundances in the thin-disk stars versus their orbital radii suggests that the star formation rate in the thin disk decreases with increasing Galactocentric distance, and there was no star formation for some time outside the solar circle while this process was continuous within the solar circle. The decrease in the star formation rate with increasing Galactocentric distance is responsible for the existence of a negative radial metallicity gradient in the thin disk. At the same time the relative magnesium abundance exhibits no radial gradient. It is in detail considered the influence of selective effects on the form of both age - metallicity and age - relative magnesium abundance diagrams. It is shown that the first several billion years of the formation of the thin disk interstellar medium in it was on the average sufficiently rich in heavy elements (<[Fe/H]> = -0.22), badly mixed (\sigma_[Fe/H] = 0.21), and the average relative magnesium abundance was comparatively high (<[Mg/Fe]> = 0.10). Approximately 5 billion years ago average metallicity began to systematically increase, and its dispersion and the average relative magnesium abundance - to decrease. These properties may be explained by an increase in star formation rate with the simultaneous intensification of the processes of mixing the interstellar medium in the thin disk, provoke possible by interaction the Galaxy with the completely massive by satellite galaxy.