The Paradigm of SAURON vs. the Ring of NGC 7742 and Other Kinematic Mirages

DIAZ, R.; DOTTORI, H.

San Juan, Argentina

Congreso; Reunion Anual de la AAA; 2008

Asociacion Argentina de Astronomia

In the last ten years several scenarios have been explored toexplain kinematically decoupled cores (KDCs) in early type galaxies.Among them are large fractions of merging events and the subsequentmissing satellite problem, dwarf-spheroidals harassment,giant-ellipticals formation and evolution, and dark matter cuspeffects. We show that the phenomenon of core counter rotation canalso be explained by a warping of the equatorial plane defined bythe observed stellar rotation. Once an instability has led to awarped inner disk core, the perturbed orbits can maintain a commonorientation due to rigid body-like rotation at the central region.We found that warp angles not larger than 30 degrees could explainfast and low rotators of the "Sauron paradigm" in a unified scenariorequiring the smallest angular momentum difference between the outerdisk and its KDC, including the paradigmatic case of thecounter-rotating ring of NGC 7742.  We propose that these "kinematicmirages" cannot be neglected and therefore caution should be takenwhen considering the KDC statistics under the galaxy formation andevolution scenarios.