Testing intermittence of the galactic star formation history along with the infall model

We analyze the star formation history (SFH) of the Galactic disk by using a n infall model. Based on the observed SFH of the Galactic disk, we first de termine the timescale of the gas infall into the Galactic disk (ti,) and th at of the gas consumption to form stars (t(sf)). Since each of the two time scales does not prove to be determined independently from the SFH, we first fix t(sf). Then, t(in) is determined so that we minimize chi(2). Consequen tly, we choose three parameter sets: [t(sf) (Gyr), t(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 t est the intermittence (or variability) of the star formation rate (SFR) alo ng 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 amplitu de of the variable component is comparable to the smooth component. Thus, i ntermittent SFH of the Galactic disk is strongly suggested. We also examine d the metallicity distribution of G dwarfs. We found that the true paramete r set lies between [t(sf) (Gyr), t(in) (Gyr)] = (6, 23) and (11, 12), thoug h we need a more sophisticated model including the process of metal enrichm ent within the Galactic halo.