NGC 759 : A giant elliptical with a just-forming decoupled nucleus

By undertaking a spectral and photometric investigation of the central part of the bright elliptical galaxy NGC 759, we have found an optical counterp art for the circumnuclear molecular gas ring with the radius of similar to 3 " (similar to 1 kpc) which was earlier reported by Winklind et al. (1997) . This counterpart consists of the ionized gas excited by young massive sta rs and of the dust. The gaseous ring exhibits fast rotation: its projected rotation velocity at R approximate to 3 " is similar to 220 km/s. The large projected rotation velocity value together with the asymmetric appearance of the dust ring on the (V - I) colour map confirm the hypothesis of Wiklin d et al. (1997) about a rather high inclination of the gas rotation plane: our data favours i approximate to 40 degrees proposed by them for the molec ular gas ring. Meantime the 2D decomposition of the galaxy images both in t he V and I bands has revealed an existence of the brightness excess with re spect to the de Vaucouleurs' spheroid: this extracomponent is seen in the r adius range of 3 "-16 ", its boundaries looking nearly round, and has a rad ial brightness distribution well-fitted by two exponential laws with differ ent characteristic scales. We argue that two stellar disks are embedded int o the bright elliptical galaxy: the outer one is seen nearly face-on and so its origin is probably related to that of the main galactic body, the inne r one is inclined by i approximate to 40 degrees and so its origin is proba bly related to the circumnuclear gaseous ring. Within the radius range of t heir appearance the disks contributes about 10% into the integrated surface brightness.