DETECTION OF NEUTRAL GAS IN THE CENTRAL GALAXY OF THE CENTAURUS CLUSTER

We describe the detection of neutral gas within the central galaxy of the Centaurus cluster of galaxies, NGC 4696. The detection is in the f orm of sodium D absorption, against the background stellar emission. T he gas is clearly associated with the compact emission filament system and dust lane in the central 20 '' of the galaxy; it shares the same velocity field as the emission-line gas, the absorption line strength correlates with the amount of extinction due to dust, and the equivale nt width of narrow absorption features is related to the emission-line strength. The quantitative relationship between absorption line stren gth and extinction is compared with Galactic ratios. The strength of s odium absorption is large for the typical E(B-V) observed, although si milar to what is found in external spiral galaxies. Several possibilit ies may account for this, including larger internal random motions tha n are present in the Galactic ISM, higher gas-to-dust ratio than Galac tic, or a higher neutral fraction of sodium in NGC 4696. The observati ons imply a common origin for the warm and neutral components, which m ay be a merger.