Geometrical parametrization of warps for edge-on galaxies

Abstract

We propose new parameters to describe the geometry of a warped disc when viewed edge-on, a global warp parameter $w$, and a family of three parameters $A$, $B$ and $C$ that describe, independently, the shape of the warp. These parameters are useful to detect some key effects in the understanding of warps. We have also developed software (WIG) which is able to calculate these parameters for a given image of a galaxy in any wavelength and which is described here with some examples, namely ESO 235-53 in the optical, NGC 4013 in 21 cm and NGC 4565 in 1.2 mm continuum.