Paper detail

Bar-Driven Evolution and 2D Spectroscopy of Bulges

A multi-faceted approach is described to constrain the importance of bar-driven evolution in disk galaxies, particularly bulge formation. N-body simulations are used to construct stellar kinematic bar diagnostics for edge-on systems and to quantify the expected vertical structure of bars, and they are compared to observations of 30 edge-on spirals, most with a boxy bulge. Long-slit spectra of the galaxies show characteristic double-hump rotation curves, dispersion profiles with secondary peaks and/or flat maxima, and correlated h3 and V profiles, indicating that most of them harbor edge-on bars. The presence of cold, quasi-axisymmetric central stellar disks is also suggested, presumably formed through bar-driven gaseous inflow and star formation. K-band imaging of the same galaxies spectacularly highlights radial variations of the bars' scaleheights, as expected from vertical disk instabilities. The light profiles also vary radially in shape but never approach a classic de Vaucouleurs law. Filtering of the images further isolates the specific orbit families at the origin of the boxy structure, which can be directly related to periodic orbit calculations in 3D barred potentials. Bars are thus shown to contribute substantially to the formation of both large-scale triaxial bulges and embedded central disks. Relevant results from the SAURON survey of the stellar/ionized-gas kinematics and stellar populations of spheroids are also described. Examples are used to illustrate the potential of coupling stellar kinematics and linestrengths (age and metallicity), here specifically to unravel the dynamical evolution and related chemical enrichment history of bars and bulges. [Abridged]