Complex Small-Scale Structure in the Infrared Extinction toward the Galactic Center

Abstract

A high level of complex structure, or "granularity," has been observed in the distribution of infrared-obscuring material toward the Galactic center (GC), with a characteristic scale of 5″-15″, corresponding to 0.2-0.6 pc at a GC distance of 8.5 kpc. This structure has been observed in ISAAC images, which have a resolution of ∼0″.6, significantly higher than that of previous studies of the GC. We have discovered granularity throughout the GC survey region, which covers an area of 1°6 × 0°8 in longitude and latitude, respectively (300 pc × 120 pc at 8.5 kpc), centered on Sgr A*. This granularity is variable over the whole region, with some areas exhibiting highly structured extinction in one or more wave bands and other areas displaying no structure and a uniform stellar distribution in all wave bands. The granularity does not appear to correspond to longitude, latitude, or radial distance from Sgr A*. We find that regions exhibiting high granularity are strongly associated with high stellar reddening. © 2006. The American Astronomical Society, All rights reserved.