Title: Physical properties and star formation efficiency for Galactic High-mass star forming regions 

Abstract: Massive star formation occurs in the interior of Giant Molecular Clouds (GMC) 
and proceeds through many stages, each involving different physical scales. Intermediate 
scales, represented by coherent structures of gravitationally bound material, are difficult 
to study, mainly due to observational biases which characterize ground-based instruments. 

In this talk I will review the physical properties (dust temperature, mass, luminosity)  
derived for a complete sample of Massive Young Stellar Objects (MYSOs) and Ultra Compact 
HII (UCHII) regions selected from the Red MSX Source (RMS) survey data base and 
investigated using Planck and IRAS/IRIS data. 

Using the distance-independent L/M ratio, we study the star formation efficiency as a 
function of Galactocentric radius. We find that the star formation efficiency is fairly 
constant out to R ~ 14 kpc, which we argue may correspond to the transition radius between 
hydrogen and molecular gas, following the prediction of Leroy et al. for a sample of spiral galaxies.