Atlas and catalog of dark clouds based on digitized sky survey I

We present a quantitative atlas and catalog of dark clouds derived by using the optical database Digitized Sky Survey I. Applying a traditional star-count technique to 1043 plates contained in the database, we produced an A(V) map covering the entire region in the galactic latitude range vertical bar b vertical bar < 40 degrees. The map was drawn at two different angular resolutions of 6' and 18', and is shown in detail in a series of figures in this paper. Based on the A(V) map, we identified 2448 dark clouds and 2841 clumps located inside them. Some physical parameters, such as the position, extent, and optical extinction, were measured for each of the clouds and clumps. We also searched for counterparts among already known dark clouds in the literature. The catalog of dark clouds presented in this paper lists the cloud parameters as well as the counterparts.