Hydrogen Content of Young Stellar Clusters. IV.Clusters NGC6231, 6383, 6514, and 6531

Abstract

The total amount of hydrogen associated with the young stellar clusters NGC6231, 6383, 6514, and 6531 has been obtained from observations in the continuum at 1410 MHz and in the hydrogen-line emission. NGC6231 contains in its southern part a cloud of neutral hydrogen atoms of density 6 cm- 3 and total mass l00M0 and in its northern part a small ionized cloud of the same density and a mass of ~ 50 M 0. NGC 6383 is embedded in a large neutral hydrogen complex, of which a small part of mass ~450M0 is ionized. The Trifid nebula is ionized by a single 07-type star at nearly twice the accepted distance of NGC6514 and the existence of NGC6514 as a physical cluster appears to be doubtful. The mass of the ionization-bounded Trifid nebula is nearly 5000M0 ? Neither neutral nor ionized hydrogen was found in association with NGC6531.