THE PRESENT-DAY STAR FORMATION RATE OF THE MILKY WAY DETERMINED FROM SPITZER-DETECTED YOUNG STELLAR OBJECTS

We present initial results from a population synthesis model aimed at determining the star formation rate (SFR) of the Milky Way. We find that a total SFR of 0.68-1.45 M sun yr-1 is able to reproduce the observed number of young stellar objects (YSOs) in the Spitzer/IRAC GLIMPSE survey of the Galactic plane, assuming simple prescriptions for the three-dimensional Galactic distributions of YSOs and interstellar dust, and using model spectral energy distributions to predict the brightness and color of the synthetic YSOs at different wavelengths. This is the first Galaxy-wide measurement derived from pre-main-sequence objects themselves, rather than global observables such as the total radio continuum, Hα, or FIR flux. The value obtained is slightly lower than, but generally consistent with previously determined values. We will extend this method in the future to fit the brightness, color, and angular distribution of YSOs, and simultaneously make use of multiple surveys, to place constraints on the input assumptions, and reduce uncertainties in the SFR estimate. Ultimately, this will be one of the most accurate methods for determining the Galactic SFR, as it makes use of stars of all masses (limited only by sensitivity) rather than solely massive stars or indirect tracers of massive stars.