Formation and evolution of S0 galaxies: a SAURON case study of NGC 7332
Bacon, Roland; Emsellem, Eric; Peletier, Reynier F.; Cappellari, Michele; Bureau, Martin; Falcón-Barroso, Jesús; Davies, Roger L.; Kuntschner, Harald; Fathi, Kambiz; de Zeeuw, Tim; Copin, Yannick
United Kingdom, Netherlands, France, Germany, United States
Abstract
We present SAURON integral-field observations of the S0 galaxy NGC 7332. Existing broad-band ground-based and Hubble Space Telescope (HST) photometry reveals a double-disc structure and a boxy bulge interpreted as a bar viewed close to edge-on. The SAURON two-dimensional stellar kinematic maps confirm the existence of the bar and inner disc but also uncover the presence of a cold counter-rotating stellar component within the central 250 pc. The Hβ and [O III] emission line maps show that the ionized gas has a complex morphology and kinematics, including both a component counter-rotating with respect to the stars and a fainter corotating one. Analysis of the absorption line-strength maps show that NGC 7332 is young everywhere. The presence of a large-scale bar can explain most of those properties, but the fact that we see a significant amount of unsettled gas, together with a few peculiar features in the maps, suggests that NGC 7332 is still evolving. Interactions as well as bar-driven processes must thus have played an important role in the formation and evolution of NGC 7332, and presumably of S0 galaxies in general.