Fundamental parameters of the highly reddened young open clusters Westerlund 1 and 2

We study the compact open clus- ters Westerlund 1 (BH 197) and Westerlund 2. We present CCD integrated spectroscopy for both clusters, and CCD imaging in the V and I bands for the former one. So far, Westerlund 1 is possibly the most reddened open cluster studied in detail (Av 13:0). It has an age of 8 3M yr and a distance from the Sun of d 1:0 0: 4k pc. For Westerlund 2 we derive a visual absorptionAV 5:0 mag, an age of 2 3M yr, and d =5 : 7 0 :3 kpc. From luminosity and structural arguments we conclude that Westerlund 1, although young and compact, it is a massive cluster, in contrast to Westerlund 2.