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Astron. Astrophys. 354, 28-34 (2000)

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

V.V. Vlasyuk 1 and O.K. Sil'chenko 2,3

1 Special Astrophysical Observatory, Nizhnij Arkhyz, 357147 Russia
2 Sternberg Astronomical Institute, University av. 13, Moscow 119899, Russia
3 RGO Astronomy Data Centre, Guest Investigator

Received 25 August 1999 / Accepted 12 November 1999

Abstract

By undertaking a spectral and photometric investigation of the central part of the bright elliptical galaxy NGC 759, we have found an optical counterpart for the circumnuclear molecular gas ring with the radius of [FORMULA] ([FORMULA] kpc) which was earlier reported by Wiklind et al. (1997). This counterpart consists of the ionized gas excited by young massive stars and of the dust. The gaseous ring exhibits fast rotation: its projected rotation velocity at [FORMULA] is [FORMULA] km/s. The large projected rotation velocity value together with the asymmetric appearance of the dust ring on the [FORMULA] colour map confirm the hypothesis of Wiklind et al. (1997) about a rather high inclination of the gas rotation plane: our data favours [FORMULA] proposed by them for the molecular gas ring. Meantime the 2D decomposition of the galaxy images both in the V and I bands has revealed an existence of the brightness excess with respect to the de Vaucouleurs' spheroid: this extracomponent is seen in the radius range of 3"-16", its boundaries looking nearly round, and has a radial brightness distribution well-fitted by two exponential laws with different characteristic scales. We argue that two stellar disks are embedded into 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 inner one is inclined by [FORMULA] and so its origin is probably related to the circumnuclear gaseous ring. Within the radius range of their appearance the disks contributes about 10% into the integrated surface brightness.

Key words: galaxies: elliptical and lenticular, cD – galaxies: kinematics and dynamics – galaxies: photometry – galaxies: structure – galaxies: nuclei – galaxies: individual: NGC 759

* Based on observations collected with the 6m telescope of the Special Astrophysical Observatory (SAO) of the Russian Academy of Sciences (RAS) which is operated under the financial support of Science Ministry of Russia (registration number 01-43) and on observations collected with the 1m and 0.6m telescopes of the Special Astrophysical Observatory (SAO) of the Russian Academy of Sciences (RAS).

Send offprint requests to: O.K. Sil'chenko (olga@sai.msu.su)

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© European Southern Observatory (ESO) 2000

Online publication: January 31, 2000
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