Faking Kinematic ``Warps'' with Radial Oscillatory Motions

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Session 6 -- Normal Galaxies: Structure and Dynamics
Display presentation, Monday, 9:20-6:30, Pauley Room

[6.14] Faking Kinematic ``Warps'' with Radial Oscillatory Motions

G. R. Roelofs, R. H. Miller (University of Chicago)

Velocity maps of disk galaxies almost never look like purely planar, circular flows; other velocity components tend to disturb the symmetries expected of such an idealized system. Traditionally many of these distortions have been interpreted in terms of warped disks, both because of an historical bias against steady-state radial galactic motions and because of the indisputable fact that many disk galaxies are indeed warped---the evidence from edge-on observations alone is sufficient proof of this. Recent studies, however, including both numerical models and observations, indicate that galaxies oscillate in radial normal modes of relatively large amplitude. Given this and the fact that such radial motions produce velocity signatures similar to those of warped disks, it is reasonable to investigate the extent to which kinematic observations of disk galaxies can be interpreted in terms of planar disks with a radial flow component, rather than warped disks with purely circular flows. We report preliminary results for some radial-flow fits of kinematic data and compare with ``standard'' fits based on tilted-ring models.

Monday program listing