Establishing the Connection between Peanut-shaped Bulges and Galactic Bars

It has been suggested that the peanut-shaped bulges seen in some edge-on disk galaxies are due to the presence of a central bar. Although bars cannot be detected photometrically in edge-on galaxies, we show that barred potentials produce a strong kinematic signature in the form of double-peaked line-of-sight velocity distributions with a characteristic “figure-ofeight” variation with radius. We have obtained spectroscopic observations of two edge-on galaxies with peanut-shaped bulges (NGC 5746 and NGC 5965), and they reveal exactly such line-of-sight velocity distributions in both their gaseous (emission line) and their stellar (absorption line) components. These observations provide strong observational evidence that peanut-shaped bulges are a by-product of bar formation. Subject headings: galaxies: spiral — galaxies: kinematics and dynamics — galaxies: structure — galaxies: individual (NGC 5746, NGC 5965) 1 present address: Kapteyn Instituut, PO Box 800, 9700 AV Groningen, the Netherlands