ON THE EXTINCTION TOWARDS BAADE WINDOW

An analysis is made on the morphology of the sequences, formed by star s distributed along the line of sight. in (V,V-I) CMDs (Colour Magnitu de Diagram) from Baade's Window (l=1.degrees 0, b=-3.degrees 9). The e xtinction is due Co an absorbing layer with an effective thickness of about 100 pc. A linearly, with distance, increasing extinction up to a maximum value inside the absorbing layer is in first order a good app roximation for the actual extinction present along the line of sight. We show that the morphology of the disc sequence gives a good indicati on of the nearby extinction along the line of sight. The morphology of the bulge/bar red horizontal branch is likely due to a combination of differential reddening and a significant metallicity spread among the horizontal branch stars. This is irrespective of the type of extincti on law adopted. There is in Baade's Window globally no big difference between a Poissonian or a patchy type of extinction, except for substr uctures in the morphology of the sequences for the latter.