SF-03-0007

3D CMZ: Distinguishing Near vs. Far Distances in the Galactic Center Using Spitzer and Herschel

Dani R. Lipman

A comprehensive 3D model of the central 300pc of the Milky Way, the Central Molecular Zone, (CMZ), is fundamental to understanding energy cycles in galactic nuclei. Current observational constraints are insufficient to distinguish existing 3D models. We determine probabilistic near/far locations for all clouds in the CMZ using Spitzer 8um dust extinction and Herschel dust emission. High column densities in the CMZ lead to all clouds being optically thick at 8um. Thus, typical dust extinction methods cannot be used for clouds of interest in the CMZ. We developed two independent dust extinction methods using a simplistic model of CMZ background emission and Spitzer 8um maps: 1) a flux ratio of the Spitzer emission to the model background, and 2) a flux difference between a corrected foreground and background. The likely near/far locations are determined for each cloud in the CMZ, and are compared to four different orbital models for the geometry of the CMZ. Our results show good agreement between the two methods, as well as good agreement with results from absorption feature analysis. Future work will utilize our results, combined with complementary constraints from absorption features, to further constrain 3D models of the CMZ.