Direct evidence for a bar at the Galactic center

Abstract

The bar at the center of the Milky Way, long postulated from a number of different studies, is unambiguously detected in the 24 microns observations of the Galactic center of Matsumoto et al. (1982). The emission from a triaxial stellar bar is modeled and its distinctive signature is described. This signature is found in the data. The near side of the bar is in the Galactic quadrant and the bar is tilted with respect to the Galactic plane in a sense consistent with the work of Sinha (1979) and of Liszt and Burton (1980), who first proposed a tilted bar to explain the kinematics of the H I and CO at the Galactic center. The small extinction that is observed at latitudes greater than 3 deg at 2.4 microns cannot account for the asymmetries observed in the distribution of the infrared emission. The bar is distinct from the triaxial spheroid postulated by Blitz and Spergel (1991) as the source of the asymmetries in the H I distribution in the outer Galaxy.