High-resolution Reddening Map in the Direction of the Stellar System Terzan 5

We have used optical images acquired with the Hubble Space Telescope to construct the first high-resolution extinction map in the direction of Terzan 5, a peculiar stellar system in the inner bulge of our Galaxy. The map has a spatial resolution of 8″ × 8″, over a total field of view of 200″ × 200″. The absorption clouds show a patchy structure on a typical scale of 20″ and extinction variations as large as δE(B - V) ∼0.67mag, especially in the direction of the center of the system. These correspond to an absolute color excess ranging from E(B - V) = 2.15mag up to 2.82mag. After the correction for differential reddening, two distinct red giant branches become clearly visible in the color-magnitude diagram of Terzan 5 and they correspond well to the two sub-populations with different iron abundances recently discovered in this system. © © 2012. The American Astronomical Society. All rights reserved.