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Astron. Astrophys. 318, L39-L42 (1997)

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Letter to the Editor

A counter-rotating tilted gas disc in the peanut galaxy NGC 128 *

Eric Emsellem 1 and Robin Arsenault 2

1 European Southern Observatory, Karl-Schwarschild Strasse 2, D-85748 Garching b. München, Germany
2 Canada-France-Hawaii Corporation, P.O. Box 1597, Kamuela, HI 96743, USA

Received 14 November 1996 / Accepted 7 January 1997


We have obtained V, [FORMULA], [FORMULA] HRCAM images and TIGER spectrography of the central region of the peanut galaxy NGC 128. The colour images reveal the presence of a red disc tilted by about 26 degres with respect to the major-axis of the galaxy. This tilted disc is made of dust and gas, as revealed by the 2D TIGER map of the ionized gas distribution. The TIGER stellar and gas velocity fields show that the angular momentum vectors of the stellar and gaseous components are reversed. We therefore suggest that the gas orbits belong to the so-called anomalous family, which is evidence for a tumbling triaxial potential (a bar) associated with the peanut morphology. The bar formation has very probably been triggered through the interaction with its nearby companion NGC 127, from which the dissipative component is being accreted along retrograde orbits.

Key words: ISM: kinematics and dynamics – galaxies: NGC 128 – galaxies: interactions – galaxies: kinematic and dynamics – galaxies: nuclei

* Based on observations taken with the Canada-France-Hawaii Telescope, operated by the National Research Council of Canada, the Centre National de la Recherche Scientifique of France, and the University of Hawaii

Send offprint requests to: E. Emsellem (email: eemselle@eso.org)

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© European Southern Observatory (ESO) 1997

Online publication: July 8, 1998