Talk abstract

We present the first determination of the luminosity functions of massive young stellar objects (MYSOs) and compact HII (CHII) regions within the Milky Way galaxy. These are determined from the large, well-selected sample of these sources identified by the Red MSX Source (RMS) survey. The MYSO luminosity function shows that there is not a significant population of these objects with a luminosity above $\sim 7\times$10$^{4}$L$_{\odot}$, whilst the luminosity function for CHII regions extends to L~$\sim 6 \times$10$^{5}$L$_{\odot}$ as expected. The lifetimes of these phases are also calculated as a function of luminosity by comparison with the luminosity function for local main sequence OB stars. These indicate that the MYSO phase has a lifetime just over ~10$^{5}$~yrs, whilst the CHII region phase lasts of order 3$\times$10$^{5}$~yrs or about 5\% of the exciting stars main sequence lifetime. The lack of MYSOs above 10$^{5}$L$_{\odot}$ is consistent with the scenario in which objects around 10M$_{\odot}$ are swollen and cool due to high accretion rates, but at higher masses contract rapidly to the main sequence allowing them to ionize their surroundings.