Hydrogen Content of Young Stellar Clusters. V. Clusters NGC6604, 6611, and 6823

Abstract

Measurements of the total amount of hydrogen gas associated with the O-type clusters NGC 6604, 6611, and 6823 are reported. Only a small part of the large visible nebula in which NGC 6604 appears to be embedded is associated with the cluster. The small ionized nebula associated with NGC6604 has a mass of ~600Mo and is part of a larger neutral cloud. The mass of the ionized nebula associated with NGC 6611 is ~ 5000 M 0, while a neutral hydrogen shell with a total mass of ~ 105 M 0 probably surrounds the ionized nebula. The cluster NGC 6823 is embedded in a bright nebula of mass ~ 1800 Mo. A neutral hydrogen shell of mass ~ 2000 M 0 surrounds the ionized nebula, so that the total mass of hydrogen associated with NGC 6823 is ~ 4000 Mo.