Outer rings in non-barred galaxies

An interesting issue is to understand the origin of outer rings in non-barred galaxies. These rings are usually observed in barred disk galaxies, and are associated to the main dynamical resonances. Our analysis combined for the first time the study of the stellar and gaseous component using a multispectral approach: HI, CCD multiband photometry and Hα spectroscopy of a sample of 4 non-barred galaxies with outer rings. A bidimensional velocity field is requiered to be combined with long-slit data, for a precise determination of the main dynamical resonances.

The studied galaxies

Rings in non-barred galaxies Rings in non-barred galaxies
Rings in non-barred galaxies Rings in non-barred galaxies
Top-left : B-R image of the 3-ringed galaxy  NGC 7217 (Verdes-Montenegro et al 1995).

Top-right: Map of the HI column density distribution in NGC 6015. The dashed line corresponds to the ring fitted to the optical B-I image (Verdes-Montenegro et al 1997).

Bottom-left: Map of the HI column density distribution in NGC 3344 (Verdes-Montenegro et al 2000).

Bottom-right: Contour map of the HI column density distribution in NGC 3642 overlapped on the R image (Verdes-Montenegro et al 2002).

Papers

PDF File The three rings of the isolated galaxy NGC 7217
VERDES-MONTENEGRO, L., BOSMA, A., ATHANASSOULA, E.
Astron. Astr. 300, 65-77 (1995)
PDF File The ringed, warped and isolated galaxy NGC 6015.
VERDES-MONTENEGRO, L., BOSMA, A., \& ATHANASSOULA, E.
Astron. Astrop. 321, 754-764 (1997)
PDF File A detailed study of the ringed galaxy NGC 3344
VERDES-MONTENEGRO, L., BOSMA, A., ATHANASSOULA, E.
Astronomy and Astrophysics 356, 827 (2000)
PDF File Star formation in the outskirts of the ringed galaxy NGC 3642
VERDES-MONTENEGRO, L., BOSMA, A., ATHANASSOULA, E.
Astronomy and Astrophysics, 389, 825. (2002)