Optical absorption from the Magellanic Stream in the spectrum of Fairall-9

As part of a program to study visual absorption lines arising in interstellar material (disk and possible halo) in the lines of sight to extragalactic objects, absorption from known high-velocity H I clouds has been sought in the spectra of three globular-cluster cores and the core of the Seyfert galaxy, Fairall-9. A positive detection of absorption by gas in the Magellanic Stream in the spectrum of Fairall-9 is reported. From considerations of calcium and sodium ionization equilibria, limits are placed on the metallicity, Z, of the Stream gas of log 2/Z (cosmic) in the range -2-0.25. These limits are not stringent enough to differentiate between a primordial or a Magellanic Clouds origin for the Stream, but any depletion of calcium would increase the value of Z and favor a Cloud origin.