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Astron. Astrophys. 337, 9-16 (1998)

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Statistics of optical warps in spiral disks

Vladimir Reshetnikov 1, 2 and Françoise Combes 2

1 Astronomical Institute of St.Petersburg State University, 198904 St.Petersburg, Russia
2 DEMIRM, Observatoire de Paris, 61 Av. de l'Observatoire, F-75014 Paris, France

Received 7 April 1998 / Accepted 8 June 1998


We present a statistical study of optical warps in a sample of 540 galaxies, about five times larger than previous samples. About 40% of all late-type galaxies reveal S-shaped warping of their planes in the outer parts. Given the geometrical parameters and detection sensitivity, this result suggests that at least half of all galaxy disks might be warped. We demonstrate through geometrical simulations that some apparent warps could be due to spiral arms in a highly inclined galaxy. The simulations of non warped galaxies give an amount of false warps of [FORMULA] 15%, while simulations of warped galaxies suggest that no more than 20% of the warps are missed. We find a strong positive correlation of observed warps with environment, suggesting that tidal interactions have a large influence in creating or re-enforcing warped deformations.

Key words: galaxies: evolution – galaxies: interactions – galaxies: spiral – galaxies: structure

Send offprint requests to: F. Combes, (bottaro@obspm.fr)

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© European Southern Observatory (ESO) 1998

Online publication: August 6, 1998