Quantifying the anisotropic density structure of the Central Molecular Zone – a 2D correlation function approach

The Central Molecular Zone (CMZ) is a ring-like structure sitting at the center of the Milky Way. Using the 870 mu m continuum map from the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL), we study anisotropy in the density structure of gas in the CMZ utilizing the 2D correlation function. To quantify the spatial anisotropy, we define the critical angle theta(half), as well as the anisotropy parameter A pi/4 theta(half) - 1. We find that the density structure is strongly anisotropic at a large scale (similar to 100 pc), and the degree of spatial anisotropy decreases with decreasing scale. At the scale of similar to 10 pc, the structure is still mildly anisotropic. In our analyses, we provide a quantitative description of the anisotropic density structure of gas in the CMZ, and the formalism can be applied to different regions to study their differences.