Gas motions in the plane of the spiral galaxy NGC 3631

/ Authors

A.M.Fridman, O.V.Khoruzhii, E.V.Polyachenko, A.V.Zasov, O.K.Sil'chenko, A.V.Moiseev, A.N.Burlak, V.L.Afanasiev, S.N.Dodonov, J. Z. U. O. Science

and 6 more authors

Sternberg Astronomical Institute, Troitsk Institute for Innovation, Thermonuclear Researches, S. A. Observatory, Isaac Newton Group of Telescopes, U. Hertfordshire

/ Abstract

The velocity ﬁeld of the nearly face-on galaxy NGC 3631, derived from observations in the H α line and H i radio line, is analysed to study perturbations related to the spiral structure of the galaxy. We conﬁrm our previous conclusion that the line-of-sight velocity ﬁeld gives evidence of the wave nature of the observed two-armed spiral structure. Fourier analysis of the observed velocity ﬁeld is used to determine the location of corotation of the spiral structure of this galaxy, and the radius of corotation R c is found to be about 42 ′′ , or 3.2 kpc. The vector velocity ﬁeld of the gas in the plane of the disc is restored, and taking into account that we previously investigated vertical motions, we now have a full 3D gaseous velocity ﬁeld of the galaxy. We show clear evidence of the existence of two anticyclonic and four cyclonic vortices near corotation in a frame of reference rotating with the spiral pattern. The centres of the anticyclones lie between the observed spiral arms. The cyclones lie close to the observed spirals, but their centres are shifted from the maxima in brightness.

DOI: 10.1046/j.1365-8711.2001.04218.x