We thank Dr. J. Bally for kindly providing the CS data and Drs. T.L. Wilson and R. Gaume for critical reading of the manuscript. This work has been partially supported by the Spanish DGICYT under grants PB96-104 and 1FD97-1442. NJR-R has been supported by the Consejería de Educación y Cultura de la Comunidad de Madrid.
© European Southern Observatory (ESO) 2000
Online publication: March 28, 2000