A New Search for HI in the Southern Coalsack

Abstract

Since neutral hydrogen in dust clouds can often be detected from narrow self-absorption dips, two 21 cm profiles with a velocity resolution of 0·2 km s -1 have been obtained in the direction of the Southern Coalsack, in the hope of finding such a self-absorption dip. No neutral hydrogen could be detected. It is likely that most of the hydrogen in the Coalsack is molecular.