A detailed Galaxy model and the derived theoretical star distribution is very important for interpreting observational data and detecting unexpected phenomena. Bahcall and Soneira constructed a model for the disk and spheroid components of the Galaxy (1980, ApJS, 44 , 73). In selected sky areas at galactic latitudes above 20 degrees , it has shown good agreement with available star counts of up to 10**5 stars. On the other hand, the HST Guide Star Catalog (GSC), with data on over 10**7 stellar objects up to 15--16 magnitudes , provides an excellent opportunity to test the model on much larger sky areas and data sets. A complete comparison with the GSC, which we intend to carry out, should improve our estimates of the galactic structure parameters, and allow other corrections and extensions to the model. We have developed software for the detailed statistical analysis of the GSC data versus the B-S model, and used it to process selected areas uniformly distributed over the whole sky. In the paper, we will discuss our preliminary results, and examine future prospects of the project, possible pitfalls, and potential problems.
Astronomical Data Analysis Software and Systems III
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