Beyond the Solar Circle − Trends in Massive Star Formation Between the Inner and Outer Galaxy

We have compiled the most complete compact and ultracompact H II region catalogue to date via multiwavelength inspection of survey data. We utilize data from the recently available SASSy 850 μm survey to identify massive star-forming clumps in the outer Galaxy (RGC > 8.5 kpc) and cross-match with infrared and radio data of known UC H II regions from the RMS database. For the inner Galaxy sample (RGC < 8.5 kpc), we adopt the compact H II regions from previous works that used similar methods to cross-match ATLASGAL with either CORNISH or RMS, depending on the location within the Galactic plane. We present a new UC H II region catalogue that more than doubles the original sample size of previous work, totalling 536 embedded H II regions and 445 host clumps. We examine the distance independent values of NLy/M and Lbol/M as proxies for massive star formation efficiency and overall star formation efficiency, respectively. We find a significant trend showing that Lbol/M decreases with increasing RGC, suggesting that the overall star formation per unit mass is less in the outer Galaxy.