Testing Intermittency of the Galactic Star Formation History along with the Infall Model

Abstract

We analyze the star formation history (SFH) of the Galactic disk by using an infall model. Based on the observed SFH of the Galactic disk, we first determine the timescales of the gas infall into the Galactic disk ($t_{\mathrm{in}}$) and that of the gas consumption to form stars ($t_{\mathrm{sf}}$). Since each of the two timescales does not prove to be determined independently from the SFH, we first fix $t_{\mathrm{sf}}$. Then, $t_{\mathrm{in}}$ is determined so that we minimize ${\chi }^2$. Consequently, we choose three parameter sets: ($t_{\mathrm{sf}}$ [Gyr], $t_{\mathrm{in}}$ [Gyr]) = (6.0, 23), (11, 12), and (15, 9.0), where we set the Galactic age as 15 Gyr. All of the three cases predict almost identical star formation history. Next, we test the intermittency (or variability) of the star formation rate (SFR) along with the smooth SFH suggested from the infall model. The large value of the ${\chi }^2$ statistic supports the violent time-variation of the SFH. If we interpret the observed SFH with smooth and variable components, the amplitude of the variable component is comparable to the smooth component. Thus, intermittent SFH of the Galactic disk is strongly suggested. We also examined the metallicity distribution of G-dwarfs. We found that the true parameter set lies between ($t_{\mathrm{sf}}$ [Gyr], $t_{\mathrm{in}}$ [Gyr]) = (6, 23) and (11, 12), though we should need a more sophisticated model including the process of metal enrichment within the Galactic halo.

arXiv comment19 pages LaTeX, to appear in ApJ

References in corpus (7)

• The Global Schmidt Law in Star Forming Galaxies
• Dust-to-gas Ratio and Metal Abundance in Dwarf Galaxies
• The metallicity distribution of G dwarfs in the solar neighbourhood
• An Intermittent Star Formation History in a 'Normal' Disk Galaxy: The Milky Way
• Global Law for Dust-to-gas Ratio of Spiral Galaxies
• A Variation of the Present Star Formation Activity of Spiral Galaxies
• Metal Enrichment in the Early Galactic Halo

Cited by in corpus (6)

• Evolution of Dust-to-Metal Ratio in Galaxies
• The origin of dust in galaxies revisited: the mechanism determining dust content
• Hydrodynamical simulations of Galactic fountains II: evolution of multiple fountains
• Hydrodynamical simulations of Galactic fountains I: evolution of single fountains
• Emission from Dust in Galaxies: Metallicity Dependence
• Chemical Evolution of the Galaxy Based on the Oscillatory Star Formation History