Previous abstract Next abstract

Session 14 - Milky Way Galaxy.
Display session, Monday, January 15
North Banquet Hall, Convention Center

[14.11] Triaxiality in the Thick Disk and Halo of the Galaxy

J. A. Larsen, R. M. Humphreys (U. Minnesota)

We present results from our searches for triaxiality in the halo and thick disk using the Automated Plate Scanner Catalog of POSS I. Star counts are made in two colors in 16 square degree fields in the direction of the Galactic center and anticenter. Each of the fields has an independent photometric calibration and is chosen to provide systematic coverage of the Galaxy towards the center and anticenter.

The fields have an average completeness limit of 20.5 magnitudes in O and 19.5 magnitudes in E. If the halo is triaxial our magnitude limited sample should show bluer stars (O - E \leq 1.2) on one side of the galactic center to be brighter and more numerous than those on the other side. This signature may be reflected when looking towards the anticenter. We have seen such a signature towards the Galactic center in the same sense as the IRAS AGB bar discovered by Weinberg but 30 degrees above Weinberg's fields. Additional tests for the existence of this feature are discussed. This feature lends support to the idea that the thick disk is triaxial. For many of the fields, sample color-magnitude diagrams and luminosity functions are shown.

Program listing for Monday